Evaluation of the Accuracy of NaviDent,

a Novel Dynamic Computer-Guided

Navigation System for Placing Dental

Implants

by

Eszter Somogyi-Ganss

A thesis submitted in conformity with the requirements for the degree of Master of Science

Graduate Department of Prosthodontics University of Toronto

© Copyright by Dr. Eszter Somogyi-Ganss (2013)

ii

Abstract

Evaluation of the Accuracy of NaviDent, a Novel Dynamic Computer-Guided

Navigation System for Placing Dental Implants

Degree of Master of Science

2013

Eszter Somogyi-Ganss DMD, PhD

Graduate Department of Prosthodontics

University of Toronto

Objectives: To evaluate and compare an experimental surgical navigation system (ESNS) in implant

placement accuracy to static planning and transfer systems. Material and Methods: Partially

edentulous, surgical typodonts were used to simulate prosthetically-driven osteotomies in preclinical

setting. After cbCT acquisition the DICOM files were used to reverse plan and fabricate surgical guides.

Manual placement, three static guiding systems and ESNS were compared. Eight osteotomies per jaw

were transferred to 10 typodonts in five series, resulting in 400 osteotomies by 3 operators, each

modality. Lateral, vertical, total and angular deviations were measured and compared. Results:

Computer-assisted systems were comparable and provided superior precision laterally and in

angulation, but not vertically; implants placed in free-end positions were less accurate. Conclusions: All

computer-aided methods showed less than 2 mm or 5 degrees error on average, which needs to be

considered in clinical practice.

iii

We will either find a way, or make one.

Hannibal

iv

Acknowledgements

There are several people who contributed to my work on this thesis that I’d like to thank:

First and foremost my supervisor Dr. Asbjørn Jokstad for his example of relentless

pursuit of truth in science and his help with this work.

This thesis would not have been the same without the constructive criticism of my two

committee members Dr. Ernest W. N. Lam and Dr. Howard I. Holmes.

Sincere thanks to my dear colleagues Dr. Brent P. C. L. Winnett and Dr. Waad Kheder,

who (almost) voluntarily disappeared in the dust cloud and helped with the

experimental part.

Doron Dekel and Arish Quazi for the development of the experimental surgical

navigation system and all the troubleshooting.

I gratefully acknowledge Charles Victor helping me with statistics.

Dr. Romeo Paculanan for his help with the initial laboratory steps.

Slawek Bilko for his help with construction of the surgical guides.

The very accommodating staff at the Radiology department who were always willing to

take ‘just one more’ cbCT.

This project was supported by: Claron Technology Inc., Toronto, Canada and Nobel Biocare

Research Fellowship, Prosthodontics

v

Table of Contents Abstract ........................................................................................................................................................ ii

Acknowledgements ..................................................................................................................................... iv

List of Tables .............................................................................................................................................. viii

List of Figures .............................................................................................................................................. xi

Introduction ................................................................................................................................................. 1

Significance of implant dentistry .............................................................................................................. 1

Implant-retained prostheses .................................................................................................................... 1

Therapy plan requirements .................................................................................................................. 2

Radiographic diagnostics ...................................................................................................................... 2

Planning implant positions based on diagnostic imaging .................................................................... 6

Operational surgical implant positioning strategies ................................................................................ 7

Historical development of dynamic systems ....................................................................................... 7

Freehand implant placement ............................................................................................................... 8

Laboratory fabricated surgical guides .................................................................................................. 9

Computer-assisted static systems ......................................................................................................10

Surgical guides produced by computerized additive or subtractive manufacturing .........................11

Dynamic computer-assisted dental implant surgery systems ...........................................................13

Accuracy of computer-assisted implant placement in the literature ................................................15

Study rationale ...........................................................................................................................................18

Study objectives .........................................................................................................................................18

Hypothesis ..................................................................................................................................................19

Materials and methods ..............................................................................................................................20

Pre-surgical and surgical preparation ....................................................................................................20

a) Acrylic, laboratory made surgical template ...............................................................................23

vi

b) Simplant and SurgiGuide ............................................................................................................24

c) Straumann Guided Surgery (coDiagnostiX and gonyX) ..............................................................26

d) NobelGuide surgical template (NobelClinician) .........................................................................29

e) Surgical Experimental Navigation System ..................................................................................31

Accuracy estimation ...............................................................................................................................37

Statistics .................................................................................................................................................41

Results ........................................................................................................................................................42

Power calculations .................................................................................................................................42

Descriptive statistics – Summary of means and standard deviations ....................................................43

Descriptive statistics – Box plots of different outcomes in the mandible .............................................44

Descriptive statistics – Box plots of different outcomes in the maxilla .................................................50

Descriptive statistics – Box plots of different outcomes in both jaws combined ..................................55

Overall statistical comparison of surgical methods ...............................................................................60

Pairwise comparison of methods for different outcomes .....................................................................60

Overall measurements .......................................................................................................................60

Jaw type ..............................................................................................................................................64

Typodont jaw models .........................................................................................................................64

P-values for pairwise comparisons of models for different outcomes ..................................................65

Overall comparison of osteotomy positions for different outcomes ....................................................68

P-values for pairwise comparisons of teeth for different outcomes in the mandible ...........................69

P-values for pairwise comparisons of teeth for different outcomes in the maxilla ..............................73

Intra- and inter-rater agreement ...........................................................................................................75

Discussion ...................................................................................................................................................76

Image processing....................................................................................................................................76

Virtual planning ......................................................................................................................................77

Technical fabrication of a surgical stent ................................................................................................77

Surgery ...................................................................................................................................................78

vii

Clinical relevance....................................................................................................................................82

Summary ....................................................................................................................................................85

Conclusions ................................................................................................................................................86

References ..................................................................................................................................................87

viii

List of Tables

Table 1. Effective dose from dental imaging techniques (µSv) .................................................................... 3

Table 2. Advantages and limitations of cone beam computed tomography ............................................... 6

Table 3. Commercially available implant planning softwares ....................................................................11

Table 4. Possible errors in computer-assisted dental implant placement surgery ....................................13

Table 5. Technology used in commercial computer-assisted implant placement tools ............................15

Table 6. Accuracy data for computer-assisted implant planning and placement .....................................16

Table 7. Accuracy data for computer-assisted implant planning and placement (continued) ..................17

Table 8. Lateral deviation of entry and apex (Figure 22 A and B) ..............................................................43

Table 9. Vertical deviation of apex (Figure 22 C) .......................................................................................43

Table 10. Total deviation of apex (Figure 22 D) .........................................................................................43

Table 11. Angular deviation of apex (Figure 22 E) .....................................................................................44

Table 12. Box plots of total deviation of apex in the mandible (Figure 22 E) ............................................45

Table 13. Box plots of vertical deviation of apex in the mandible (Figure 22 C) .......................................46

Table 14. Box plots of lateral deviation of apex in the mandible (Figure 22 B) .........................................47

Table 15. Box plots of lateral deviation of entry in the mandible (Figure 22 A) ........................................48

Table 16. Box plots of angular deviation of apex in the mandible (Figure 22 D) .......................................49

Table 17. Box plots of total deviation of apex in the maxilla (Figure 22 E) ................................................50

Table 18. Box plots of vertical deviation of the apex in the maxilla (Figure 22 C) .....................................51

Table 19. Box plots of lateral deviation of apex in the maxilla (Figure 22 B) .............................................52

Table 20. Box plots of lateral deviation of entry in the maxilla (Figure 22 A) ............................................53

Table 21. Box plots of angular deviation of apex in the maxilla (Figure 22 D) ...........................................54

Table 22. Box plots of total deviation of apex in both jaws combined (Figure 22 E) .................................55

Table 23. Vertical deviation of apex in both jaws combined (Figure 22 C) ................................................56

Table 24. Lateral deviation of apex in both jaws combined (Figure 22 B) .................................................57

Table 25. Lateral deviation of entry in both jaws combined (Figure 22 A) ................................................58

Table 26. Angular deviation of apex in both jaws combined (Figure 22 D) ...............................................59

Table 27. Overall comparison of surgical methods ....................................................................................60

Table 28. Pairwise comparison of methods for total deviation of apex (difference in mm) .....................61

Table 29. Pairwise comparison of methods for lateral deviation of apex (difference in mm) ..................61

Table 30. Pairwise comparison of methods for vertical deviation of apex (difference in mm) .................62

Table 31. Pairwise comparison of methods for lateral deviation of entry (difference in mm) .................63

ix

Table 32. Pairwise comparison of methods for angular deviation of apex (difference in degrees) ..........63

Table 33. Comparison of outcomes between jaw types (mm and degree) ...............................................64

Table 34. Overall comparison of five slave typodont models (mm and degree) .......................................64

Table 35. P-values for pairwise comparisons of models for total deviation of apex (difference in mm) ..65

Table 36. P-values for pairwise comparisons of models for lateral deviation of apex (difference in mm)

....................................................................................................................................................................65

Table 37. P-values for pairwise comparisons of models for vertical deviation of apex (difference in mm)

....................................................................................................................................................................66

Table 38. P-values for pairwise comparisons of models for lateral deviation of entry (difference in mm)

....................................................................................................................................................................66

Table 39. P-values for pairwise comparisons of models for angular deviation of apex (difference in

degrees) ......................................................................................................................................................67

Table 40. Overall comparison of osteotomy positions in the mandible for different outcomes (mm and

degree) .......................................................................................................................................................68

Table 41 P-values for pairwise comparisons of teeth for total deviation of apex in the mandible

(differences in mm) ....................................................................................................................................69

Table 42. P-values for pairwise comparisons of teeth for lateral deviation of apex in the mandible

(differences in mm) ....................................................................................................................................70

Table 43. P-values for pairwise comparisons of teeth for vertical deviation of apex in the mandible

(differences in mm) ....................................................................................................................................70

Table 44. P-values for pairwise comparisons of teeth for lateral deviation of entry in the mandible

(differences in mm) ....................................................................................................................................71

Table 45. P-values for pairwise comparisons of teeth for angular deviation of apex in the mandible

(differences in degrees) .............................................................................................................................71

Table 46. Overall comparison of osteotomy positions by tooth number in the maxilla for different

outcomes (mm and degree) .......................................................................................................................72

Table 47. P-values for pairwise comparisons of teeth for total deviation of apex in the maxilla

(differences in mm) ....................................................................................................................................73

Table 48. P-values for pairwise comparisons of teeth for lateral deviation of apex in the maxilla

(differences in mm) ....................................................................................................................................73

Table 49. P-values for pairwise comparisons of teeth for vertical deviation of apex in the maxilla

(differences in mm) ....................................................................................................................................74

x

Table 50. P-values for pairwise comparisons of teeth for lateral deviation of entry in the maxilla

(differences in mm) ....................................................................................................................................74

Table 51. P-values for pairwise comparisons of teeth for angular deviation of apex in the maxilla

(differences in degrees) .............................................................................................................................75

Table 52. Intra- and inter-rater agreement................................................................................................75

xi

List of Figures

Figure 1. Duplication of typodonts and articulation of casts .....................................................................20

Figure 2. Tooth setup and fabrication of radiographic guides ...................................................................21

Figure 3. cbCT images of typodonts with radiographic guides ..................................................................22

Figure 4. cbCT images of master typodonts with osteotomies..................................................................23

Figure 5. Acrylic, laboratory made surgical template ................................................................................24

Figure 6. Implant surgical positions planned with the Simplant software (mandible, maxilla) .................25

Figure 7. Safe SurgiGuides from Simplant (maxilla, mandible) ..................................................................26

Figure 8. Straumann radiographic guides with TempliX plates (maxilla, mandible)..................................26

Figure 9. Implant surgical positions planned with the CoDiagnostiX software (mandible, maxilla) .........27

Figure 10. Transfer of planned CoDiagnostiX parameters to Straumann SurgiGuide in the laboratory ...28

Figure 11. Straumann Guided Surgery templates (maxilla, mandible) ......................................................29

Figure 12. Radiographic guides for NobelClinician and NobelGuide .........................................................29

Figure 13. Implant surgical positions planned with the NobelClinician software (mandible, maxilla) ......30

Figure 14. NobelGuide surgical templates .................................................................................................30

Figure 15. Jaw tracker of the experimental surgical navigation system ....................................................32

Figure 16. Drill tracker of the experimental surgical navigation system ..................................................32

Figure 17. Planning and guidance interface of experimental surgical navigation system .........................33

Figure 18. Moulded JawRefs of the experimental surgical navigation system ..........................................34

Figure 19. Clinical setup of experimental surgical navigation system .......................................................35

Figure 20. Diagram of tooth numbers on typodont ...................................................................................37

Figure 21. Accuracy estimation jigs to secure master and slave typodonts ..............................................38

Figure 22. Accuracy estimation software for evaluation of osteotomy positions .....................................39

Figure 23. Measurements adopted from Brief et al.[24] ...........................................................................39

Figure 24. Statistical power of effect sizes .................................................................................................42

1

Introduction

Significance of implant dentistry

To replace edentulous spaces, implant-retained prostheses have evolved from a questionable

treatment modality to an evidence-based option with a highly predictable outcome in the last

30 years [1]. A significant part of this advance is the evolution of radiographic diagnostic and

therapy planning tools. Today, the clinician may choose between periapical radiographs,

orthopantomograms, slice computed tomography technology and cone beam computed

tomography. New computed technologies enable three-dimensional image reconstructions

and interactive therapy planning softwares; the latter leading to fabrication of computed

tomography-derived surgical guides and computer guided surgery. Computed tomography

scans and computer-aided surgery are tools to achieve consistently accurate prosthetically

driven surgical procedures, functional as well as aesthetic prostheses [2].

Implant-retained prostheses

In modern dentistry the patient should be restored to normal contour, function, comfort,

esthetics, speech and health. The advantage of implant dentistry is the ability to achieve this

regardless of atrophy, disease or injury of the masticatory system. Therefore there is an

increased demand for implant-related treatments, due to several factors, such as an aging

population and a higher life expectancy, tooth loss related to age, consequences of failed fixed

and removable dental prostheses, the effects of edentulism on the stomatognathic system,

patient compliance with removable dental prostheses, psychological aspects of tooth loss with

increased esthetic and social pressure, predictable long-term results of implant supported

prostheses and advantages of implant-retained prostheses over other conventional solutions.

Several treatment objectives are better obtained using implant-retained prostheses

versus conventional removable dental prostheses, such as help maintain alveolar bone levels,

restore and maintain vertical dimension of occlusion, maintain muscle tone (facial esthetics),

2

provide esthetic improvement with tooth positioning, improved phonetics, occlusion and

masticatory performance, reduced size of prostheses (elimination of major connectors and

flanges), improved stability and retention of removable prostheses, eliminate the need to alter

adjacent teeth, offer a more permanent replacement and improve psychological health [1, 3-

8].

Therapy plan requirements

Dental implants can be used to restore edentulous or partially edentulous jaws in several ways.

If sufficient number of implants can be placed, and the vertical and horizontal relationships of

the jaws are satisfactory, an implant supported-fixed dental prosthesis can be planned. If the

conditions are not so favourable, a removable denture can be delivered. Both options differ in

esthetic possibilities, ease of access for dental hygiene and cost effectiveness. The choices are

influenced by many factors and warrant careful consideration. Therefore the clinician should

first perform an initial examination, leading to a review of treatment options and a preliminary

treatment plan. The following specific treatment plan should be made reflecting the patients’

preferences to achieve a satisfactory implant-prosthetic design [9].

Radiographic diagnostics

It is important to obtain correct information about the planned artificial tooth, the implant

insertion area and the critical anatomical structures of the jaws prior to dental implant

placement. Practitioners today have the benefit of multiple options to choose from with

respect to pre-implant radiographic assessment, such as intra-oral radiography, tomography,

computed tomography (CT) and cone beam computed tomography (cbCT) with very diverse

radiation doses (Table 1) [10].

3

Table 1. Effective dose from dental imaging techniques (µSv)

Intraoral radiographs (F-speed film) <1.5

Orthopantomograms 2.7 – 24.3

Cephalometric radiographs <6

Multislice computed tomograms 280 - 1410

Adopted from Evidence Based Guidelines from the European Commission [11]

Considering the rapid development and widespread availability of cbCT it is imperative to

establish safety guidelines even if dental exposure only forms a few percent of the population’s

total medical exposure to avoid overtreatment, especially with 3D imaging [12]. According to

the latest evidence based guidelines issued by the European Commission, cbCT imaging is of

value for pre-operative planning, especially in cases with proximity of vital anatomical

structures or clinical doubt about shape of alveolar ridge, but should not routinely be used for

post-operative follow up examinations [11].

Intraoral radiographs

Conventional images, captured on x-ray film or digital sensors, offer relatively limited

applicability for dental implant planning purposes. However, such periapical, bitewing and

occlusal intra-oral radiographs are the most basic and often only imaging techniques used in

general dentistry. Since these images are produced without intensifying screens, they have a

relatively high spatial resolution but also subject the patients to a rather high radiation dose

for their small size [13]. If this method is used, the long cone paralleling technique should be

chosen for the following reasons: reduced skin dose; minimal distortion; less magnification;

demonstration of a true relationship between the bone height and adjacent teeth; no

superimposition of the zygoma over the upper molar region and reproducibility if specific

aiming devices or stents are used. Regarding their use in implant dentistry, periapical and

bitewing radiographs are often used to assess the jaws post-implant placement, whereas

occlusal radiographs have limited use. However cross-sectional occlusal radiographs might

provide information about the bucco-lingual dimension of the mandible [10]. The main

limitations of this technique are its two-dimensional nature and the resulting overlapping

anatomical structures [14].

4

Orthopantomogram (OPG) / Panorex

Rotational panoramic tomography is a specialized extra-oral imaging technique to produce a

flat representation of the curved surfaces of the jaws and larger craniofacial complex [14]. The

technique is relatively widely utilized due to its low cost and small radiation dose and its

availability to provide an excellent overview of both jaws and dentition; however it is also

subject to considerable and unpredictable geometric distortion, non-uniform densities and

relatively low spatial resolution compared to intra-oral radiographs [13]. For the purpose of

pre-and post-implant assessment, the limitations of the method are distortion in the horizontal

plane, an unknown magnification in the vertical plane, true relationships are not demonstrated

well and the image is only two-dimensional, just like the intra-oral radiographs. The accuracy of

the picture is operator dependent and reproducibility is limited due to distortions as a result of

patient positioning, as well as the location of critical anatomical structures, such as the alveolar

inferior canal or the maxillary sinus. Other problems with OPGs include superimposition of

airway shadows, soft tissue shadows and ghost images, all of which can render interpretation

of the radiograph challenging and potentially misleading [10].

Computed Tomography (CT)

Current multislice computed tomography scanners produce three-dimensional images of an

object by taking series of two-dimensional images, with a widened fan shaped beam and a

two-dimensional array detector, which produces faster scan times and reduced radiation

exposure compared to the earlier models [15]. Moreover, distortion factors in early devices

were mostly eliminated through CT scan imaging techniques, consequently CT scans have

developed to be a very valuable tool to assess accurate bone height, width, density (Hounsfield

units), identify soft and hard tissue pathology and localize anatomical structures such as the

alveolar inferior canal or maxillary sinus [16, 17]. Therefore this technique has long been the

gold standard for pre-implant assessment of the jaws, since examination times are very short

and isotropic images can be reformatted in any plane, it eliminates anatomical noise and

provides high contrast resolution, allowing differentiation of tissues with less than 1% physical

density difference as opposed to 10% in conventional radiographs [18]. Its limitations include a

relatively high radiation dose compared to other imaging modalities, beam hardening artefacts

or scatter from metal restorations, the relatively high cost of examination and the

5

inconvenience that it has to be coordinated with medical radiology practices and that patients

have to leave the dental office [10].

Cone Beam Computed Tomography (cbCT)

In cbCT technology the fan-shaped x-ray beam used in conventional CT has been substituted by

a cone-shaped x-ray beam to acquire projection data via a flat detector during a single 180˚ or

360˚ rotation, from which a volumetric data set is reconstructed [15]. Its major advantage is

that due to less powerful x-ray tubes, rapid scan times, pulsed x-ray beams and sophisticated

image receptor sensors the method subjects the patients to a lower radiation dose than

conventional CT, by one order of magnitude or more [19]. On the other hand, this causes a

significant image noise and lower contrast resolution, meaning unattainable soft tissue

assessment [14]. Scanning time is similar to modern conventional CT machines (10-70

seconds), the acquired data set can be used to create multiplanar and three-dimensional

reconstructions too, but cbCTs can create a higher spatial resolution (75-400 µm) with isotropic

voxels, as well as replicate upright positioning of patients as with orthopantomograms and are

in general cheaper and can be used in the dental office [13]. cbCT often include software

packages with helpful tools, for example panoramic simulation with oblique reslicing and

automated arch detection or implant assessment modules with cross sectional imaging for

planning, integrated implant databases for dynamic on-screen placement simulation [14].

Furthermore, the volumetric data can be exported in DICOM format and viewed with

numerous third party programs that are freely available [10]. Because of inadequate low

contrast detail of the technique, acrylic restorations cannot be distinguished, but adding

radiopaque markers may help in planning implants for the axis of the restorations [14]. Further

limitations of the technique are the system-dependent wide range of fields of views, which

might create partial volume artefacts, as well as the different algorithms to reconstruct the

data, resulting in a great variation of image quality and radiation dose and also different

exposure parameters, which heavily influence image quality (Table 2) [20].

6

Table 2. Advantages and limitations of cone beam computed tomography

Modified from Benavides et al. and De Vos et al. [20, 21]

Depending on the cbCT equipment used, the effective dose can range from 11-674 µSv for

small and medium field of view and 30-1073 µSv for large field of view acquisitions [11].

Moreover, due to the rapid development of the technique, there are currently no clear

guidelines for optimal scanning parameters to produce the best image quality with the lowest

radiation dose for the patient [10].

Planning implant positions based on diagnostic imaging

Proper planning of dental implant position and its exact transfer to the operation site in the

oral cavity can be considered as one of the most important factors for the long-term success of

implant supported prosthetic restorations [22]. Once the treatment plan has been defined,

radiographic imaging has the potential to facilitate precise surgical planning, including the

choice of implant shape (cylindrical or tapered), diameter and in cases where bone atrophy is

present, the length and type of horizontal or vertical bone augmentation [9]. Since poor

implant positioning compromises esthetics and function, as well as increases the risk to

implant failure due to biomechanical overload, computer-aided (static) and computer-guided

Advantages Limitations

Multiplanar reconstruction Soft tissue visualization limited

Significantly less radiation than spiral CTs, but

still high resolution

Depending on brand and settings, some cbCT machines

produce higher radiation doses in comparison to

orthopantomograms

Available in dental office Bone density may be difficult to evaluate

Facilitates interactive treatment planning Metal objects create artifacts

Enables three dimensional bone volume

assessment Higher cost

Potential for generating all 2D images Low contrast range (dependent on type of detector)

Computer aided surgery is an option Computer-aided surgical softwares are an additional

expense

Real size data, isotropic voxel size Increased noise from scatter radiation and loss of contrast resolution

Less disturbance from metal artifacts and reduced cost in comparison to spiral CTs

Movement artefacts affect the whole dataset

Cannot be used for estimation of Hounsfield units

7

(dynamic) surgical systems are the latest tools to achieve optimal results [23]. Based on

conventional stone casts or advanced digital imaging systems, surgical templates have been

developed to establish a continuity between diagnosis, prosthetic planning and surgical

phases, to guide the operating surgeon to improve accuracy and safety of dental implant

placement [24].

Operational surgical implant positioning strategies

Historical development of dynamic systems

Planning data was first used intraoperatively with a stereotactic system, based on x-ray

pictures by Horlsey and Clarke [25]. Several other stereotactic systems appeared later [26, 27],

with several disadvantages. They worked punctually, the point of interest could only be

approached along a linear path, there needed to be a rigid linkage between the localization

frames fixed to the skull and there was no feedback of movements of surgical instruments. In

the beginning of the 90’s, a new stereotactic system, the Viewing Wand got FDA approval,

originating from Missisauga, Canada [28]. The system operated with a multi-joint arm with

potentiometers reaching 60 cm and exhibited 1±0.25 mm error per the manufacturer and 2-4

mm by an independent study [29]. Calibration of the system was cumbersome, required

touching 40-50 surface points on the patients’ head for maximum accuracy, or the installation

of three titanium mini screws. Since the arm-guided systems had a restricted reach, satellite

navigation systems were developed, operated by light, ultrasound or electromagnetism, such

as the 3-Space R digitizer (Polhemus Navigation systems), Flashpoint-3D-Localizer (Pixsys,

Boulder, CO, USA) or an infrared-based positioning system [30]. The latter system was used for

bone segment navigation in maxillofacial surgery and performed with an error of 0.1 mm in

experimental conditions but 2-4 mm during surgery. Currently, ultrasound navigation systems

are stated to be in the range of 2-5 mm, but exhibit accuracy problems because of

temperature variations and air movement in the operatory. Magnetic field based navigation

systems are sensitive to electromagnetic interferences and moving metal objects in the

operatory. In other words, the electromagnetic tracker of the navigation system may be

8

disturbed by the surgical motor, so the surgical drill can’t be visualized on the computer screen

to correct for any errors. The accuracy reported for magnetic field systems is similar to that of

the ultrasound systems, but these setups are less expensive. Infrared light based navigation

systems have also been developed and show higher technical precision and are not sensitive to

interferences, but need a free line of sight though [29]. For instance the Surgical Segment

Navigator developed at the University of Regensburg used infrared positioning devices and

reported 0.1 mm error in cadavers and 0.3-1.1 mm error during surgery in 95% of the cases

[31].

The advent of new and faster microprocessors in the mid-nineties prompted the

developments of the first generation of computer-aided guidance in a dentistry context; one

group reported implementation of virtual implant planning and a surgical stent [32], one

attempted using electromagnetic navigation in implant dentistry [33] and another developed a

computer program to plan in 3D and segmented planes [34]. Following these advances in

imaging techniques and their analysis, several other softwares were created to further

precision of computer navigation. The Virtual Patient System attempted to combine

electromagnetic and optical tracking to circumvent the disadvantages in each, but the method

has not been widely accepted [35]. A further software development shortened the preparation

and set up time, as well as let the system track up to four surgical tools with LEDs [36]. Today,

the commercially available systems use videooptical navigation, since they provide high

technical precision (less than 1 mm error), convenient handling and easy sterilization.

However, one still needs constant visual contact with the trackers, the technical expertise

necessary are considerable and the systems are very costly [29] .

Freehand implant placement

During a manual freehand implant placement procedure, the basis of the implant positioning is

usually a conventional stone cast and an orthopantomogram. With this approach it is difficult

to assess bone width or quality, the true path of the inferior mandibular nerve, the spatial

location of the nasal floor or sinus volume and the documented imaging distortion factors. To

facilitate planning, a radiopaque radiographic guide can be fabricated with position markers of

9

a definite size, which makes it possible to calculate the amount of distortion on the x-ray

image. This method can be supplemented by bone mapping as a diagnostic tool to define the

bucco-lingual dimension of the available alveolar ridge [37].

Freehand implant surgery places a big responsibility on the surgical dexterity and

experience of the clinical surgeon. During implant surgery the implant axis should ideally be

parallel to the crowns of the neighbouring teeth. To achieve this, bony structures obtained by

palpation of the edentulous alveolar ridge or exploratory surgery serve as landmarks, and also

help avoid damage to critical structures, such as nerves and vessels. After drilling the pilot

hole, intraoperative x-rays can be taken to further aid orientation and correct for any possible

angulation or spatial problems before proceeding with the osteotomy [38]. The correct

transfer from planning to actual implant position is often difficult to achieve, because human

visual perception is limited and it is difficult to correlate two-dimensional imaging data to

three-dimensional surgical sites intraoperatively [39]. The vestibule-oral and mesio-distal

temporal deviation of experienced implant surgeons using the freehand technique has been

reported to be in the range of 5 to 15 degrees [40].

Laboratory fabricated surgical guides

The need for high accuracy in surgical placement of dental implants has led to the

development of numerous surgical template concepts. After analysis of the clinical and

radiological findings, as well as the study model, the laboratory will fabricate a diagnostic tooth

set up or use a copy of the patient’s existing prosthesis to fabricate a surgical guide on dental

stone cast. Possible guide designs include the labial or lingual outline surgical guide based on

the proposed definitive restoration. A clear vacuum-formed matrix duplicate of the existing or

ideal temporary restoration, and by vacuum-formed matrix filled with clear acrylic resin [41]. A

further refinement is to have a guide channel prepared by drilling a hole through the clear

acrylic resin of the same diameter as the pilot drill, or by embedding titanium sleeves as drill

guidance for implant placement [42]. The latter technique allows for correct initial positioning,

but not for correct inclination at implant placement; the implant cannot be placed with the

guide after the initial preparation due to insufficient diameter for the larger pilot drill or twist

drill to pass through the channel prepared within the guide. Laboratory-fabricated surgical

10

guides facilitate prosthetically driven implant planning but allow for relatively few

intraoperative modifications based on anatomical structures or other adjustments [39].

Although laboratory-fabricated guide techniques offer fast and cheap transfer of the

prosthetic plan, it depends on a critical minimum intraoral stability of the surgical guides,

which are placed on a few remaining teeth or directly on the mucosa or the crest of the bone.

Placement of the implants in the posterior zone can also present a problem since the opposing

dentition might limit the space to insert and use the surgical guides. Implant placement with a

laboratory fabricated acrylic surgical guide with sleeve inserts has been reported to result in

an average distance between the planned implant and the actual osteotomy of 1.5 mm at the

entrance and 2.1 mm at the apex [43].

Computer-assisted static systems

With the advancement of CT and cbCT technology in the last two decades, dental clinicians

have access to more accurate three-dimensional images of implant placement sites, which

enables them to visualize jaw anatomy, bone height, width, density and position of anatomical

structures on a whole new level. Further developments of computer hardware and software

have permitted the invention of surgery planning tools that allow the user to visualize and

manipulate axial, cross-sectional and panoramic images together with treatment planning

capabilities and bone density assessment necessary for dental implant planning. A virtual

schematic implant replica can be placed in a software environment based on the final

prosthodontic plan [17]. There are different approaches to transfer the planned digital

information to the clinical situation: A surgical template can be converted from the CT

radiological template that was used by utilizing a mechanical positioning device and drilling

machine, or generated by computer-aided design/computer-aided manufacture (CAD/CAM)

additive or subtractive manufacturing technology [44]. Advantages of the static approach over

current dynamic methods are uncomplicated intra-operative handling of surgical templates,

and relatively easy co-ordination of procedures between template planning, manufacturing

and surgical application without the need for additional expensive equipment. [22]. Accuracy

of the static systems has been found to have an overall mean error at the entry point of 0.74

mm [45].

11

Table 3. Commercially available implant planning softwares

Software platform (former names)

Available software modification

Manufacturer Used in # of accuracy studies

3D-Doctor Able Software, USA

10 DR implant 10 DR Seoul, South Korea

Artma virtual implant EuroDoc, Vienna, Austria 3

Blue Sky Plan Blue Sky Bio, Grayslake, IL, USA

coDiagnostiX CoDiagnostiX SkyPlanX

IVS Solutions, Chemnitz, Germany Bredent, Senden, Germany

1

CTV (PraxisSoft) M + K Dental, Kahla, Germany

DenX Image Guided Implantology (IGI) Image Navigation, Jerusalem, Israel 5

DentalVox (Era Scientific) Bisofera, Rimini, Italy 1

DentalSlice Bioparts, Brasília, Brazil

DDent Plus I AlloVision, Greenville, SC, USA

DigiGuide MDI Imtec, Ardmore, OK, USA

Easy Guide (CAD Implant, Praxim)

Keystone Dental, Drillington, MA, USA 2

Implant Location System Tactile Technologies, Rehovot, Israel

InVivo Dental Anatomage, San Jose, CA, USA 1

Implant 3D (Stent CAD) Implant 3D Impla 3D Navi

Media Lab, La Spezia, Italy Schütz Dental, Rosbach, Germany

Implanner Dolphin Imaging, Chatsworth, CA, USA

Implant 3D (Med 3D) Implant 3D CeHa Implant IGS Monitor

Med3D, Heidelberg, Germany C. Hafner, Pforzheim, Germany 2ingis, Brussels, Belgium

3

Implametric 3dent, Valencia, Spain

Mona dent (Med3D) Mona-X, Dortmund, Germany

Nobel Guide Nobel Biocare, Zürich, Switzerland 4

PHANToM Geomagic, Wlimington, MA, USA 1

Robodent RoboDent, Garching, Germany 2

Simplant (Surgicase) Simplant/SurgiGuide Facilitate ExpertEase

Materialize, Leuven, Belgium AstraTech, Mölndal, Sweden Dentsply Friadent, Mannheim, Germany

3

Scan2guide Scan2Guide ImplantMaster

Ident, Foster, CA, USA Various

Stryker Navigation Cart Stryker, Kalamazoo, MI, USA 1

Sicat Implant Sicat Implant Galileos Implant

Sicat, Bonn, Germany Sirona, Bensheim, Germany

1

Treon Medtronic, Minneapolis, MN, USA 4

Vector Vision BrainLab AG, Feldkirchen, Germany 1

Virtual Implant Placement (Implant Logic)

BioHorizons, Birmingham, AL, USA

Visit Research Project, University of Vienna 5

Modified from Neugebauer et al. [46]

Surgical guides produced by computerized additive or subtractive manufacturing

Manufacturing a surgical template with CAD/CAM technology commences with virtual

planning and placement of implants with dedicated software. The dentist then transfers the

planned data file to a manufacturer for production of a surgical template. Both additive and

subtractive manufacturing techniques have been described in the literature. In the subtractive

12

technique, a computer numerically controlled (CNC) milling machine mills the surgical guide

relative to the therapy plan. Metal sleeves or series of metal sleeves with incremental

diameters can be added for an ideal guidance of surgical drills. These sleeves result in a more

precise implant placement than laboratory made acrylic surgical templates. The surgical

template concept allows converting the guide into a provisional restoration for immediate

loading situations [47]. The disadvantages compared to the laboratory-fabricated guides are

higher cost and radiological exposure for the patients.

Stereolithography is a computer-aided additive manufacturing process to obtain three-

dimensional models by curing a liquid UV-curable polymer layer by layer with a computer-

driven UV laser, stacking and polymerizing cross-section patterns [48]. After a section has been

traced, solidified and added to the layer below, the stereolithographic platform descends by a

single layer thickness, typically 0.05 mm to 0.15 mm. After the complete model is formed, it is

cleaned of excess resin by immersion in a chemical bath and then cured in a UV oven. Another

method is selective laser sintering, where the laser used is carbon dioxide, which fuses layers

of fine polyamide powder together. The advantage of the latter is that it does not require

support structures, since the unsintered powder provides sufficient support during model

fabrication [49]. For dental implant surgery, both technologies are based on CT derived image

data. A prosthetically driven virtual implant placement is completed by the clinician. Either a

single surgical guide is made or a surgical template with a series of keys or multiple guides with

different diameter cylinders for the manufacturer-specific sequential burs of the osteotomy

[50]. The accuracy of the stereolithographic method depends on the quality of the CT scanner

and the thresholding method (i.e. the process how the computer distinguishes and calculates

soft tissue and hard tissue values). Previous studies have shown a dimensional stability of rapid

prototyping models in the range of 0.6 mm [48]. The main advantage of the system is the

capacity to fabricate complex three-dimensional models for bone-, mucosa- or teeth-

supported templates that are otherwise difficult or impossible to create [48]. Disadvantages of

this system are indistinct stereolithographic layer outlines when teeth or metal restorations

are present due to their higher radiopacity and scattering [47].

13

Dynamic computer-assisted dental implant surgery systems

A relatively recent emerging field in dental implantology is dynamic computer-assisted dental

implant surgery. For the accurate transfer, registration of the patient’s prosthetic outcome is

necessary with trackers or superficial markers, after which a navigation system allows the

surgeon to guide the instrument freely, as in conventional treatment. Orientation of the drill

and the patient is calculated in space using position recognizing sensors [39]. Dynamic tracking

can be performed using electromechanical, glass fibre, ultrasound, electromagnetic, optical or

combined techniques. Owing to as yet unsolved technical problems with these systems, only

optical infrared tracking is of clinical relevance today [23]. The patient’s position is

continuously tracked and registered during the surgical procedure with fiducial markers placed

in close proximity to the operation field integrated with the cbCT images. Fiducial markers can

be applied using anatomical landmarks or by surface matching, which later will be recorded by

tracking systems, together with position sensors mounted on the surgical instrument to allow

co-visualization in real time [51].

Table 4. Possible errors in computer-assisted dental implant placement surgery

Static systems Dynamic systems

Errors during digital processing

Image data resolution Image data resolution

Image data processing

(enlargement, reduction, distortion)

Image data processing

(enlargement, reduction, distortion)

Planning software Planning software

Manufacturing of the template Registration errors

Computer algorithm inaccuracies Computer algorithm inaccuracies

Tracking errors

Errors during surgical execution of plan

Positioning and/or movement of template

intraoperatively

Positioning and/or movement of trackers

intraoperatively

Deviation between displayed and manually achieved

implant position

Changes of the patient’s anatomy by the procedure,

e.g. removal of bone, reflection of flap

14

Several commercial optical navigation systems are available at present: e.g., NaviBase,

NaviDoc and NaviPad (www.robodent.com), Treon (medical, commercially not available –

www.medtronicnavigation.com) , IGI (formerly DenX - www.image-navigation.com) and VISIT

(not commercially available) [44].

A recent systematic review concludes that dynamic systems provide greater accuracy

than static systems [45]. A tentative reason may be that most static systems have been

measured in vivo, while accuracy of dynamic systems has been measured mostly in vitro. A

current disadvantage of some dynamic techniques is the time-consuming pre-surgical set up

and that their intraoperative application can be significantly longer than with the static

method, partly due to setting up the navigation device, as well as high purchase and

maintenance costs of the systems [22].

There are still deficiencies regarding the application of dynamic surgical navigation

systems. Most of them exhibit acceptable in vivo accuracy, but there are still no reliable details

referring to the actual accuracy during surgery. The set up procedures can be time consuming,

the software operating needs to be well integrated into the operation procedure, and the

external monitors have to be well-adapted to the surgeon’s view [52].

15

Table 5. Technology used in commercial computer-assisted implant placement tools

Brand Fabrication Technology

Artma Local Optical tracking (infrared)

Blue Sky Plan Central/Local 3D-printing

CoDiagnostiX Local Mechanical

DenX IGI Local Optical tracking (infrared)

DentalVox Central CAM-milling

DentalSlice Central Stereolithography

DDent plus I Local Mechanical

Easy Guide Central CAM-milling

Implant Location System Central CAM temperature-forming

Implametric Central Stereolithography

Implant3D Local Mechanical

Implant3D (Med3D) Local Mechanical Optical tracking (infrared)

NobelGuide Central Stereolithography

Robodent Local Optical tracking (infrared)

Scan2guide Central Rapid manufacturing technology

Sicat Implant Central CAM-milling

Simplant Central Stereolithography

Treon Local Optical tracking (not commercially available)

VISIT Local Optical tracking (infrared)

VIP Pilog Compu-Guide Central CAM-milling

Modified from Neugebauer et al. [46]

Accuracy of computer-assisted implant placement in the literature

Since the 1960’s more than 3000 papers were published on computer-assisted implant

placement, but it is challenging to compile the data and draw interferences. There is a wide

variation of study designs, evaluation methods and outcome criteria. The most recent articles

and their relevant results are collected in Tables 5 and 6.

16

Table 6. Accuracy data for computer-assisted implant planning and placement

Error entry (mm) Error apex (mm) Error angle (mm) Vertical error (mm)

Study Year System Principle Study design Positioning

Method

Sites

(n)

Direction Mean SD Max Mean SD Max Mean SD Max Mean SD Max

D’Haese et al [53] 2012 Facilitate Guide Human Implant 78 0.91 0.44 2.45 1.13 0.52 3.01 2.60 1.61 8.86 - - -

Di Giacomo et al [49] 2012 Implantviewer Rhino

Human Implant 60 1.35 0.65 2.69 1.79 1.01 4.00 6.53 4.31 18.64 - - -

Behneke et al [54] 2012 Med3D Navigation Human Implant 132 0.32 0.23 0.97 0.49 0.29 1.38 2.10 1.31 6.26 0 0.41 1.47

Petersson et al [55] 2012 NobelGuide Guide Human Implant 90 0.85 - 2.68 1.07 - 2.63 2.00 - 6.96 -0.09 - 2.05

Kühl et al [56] 2012 coDiagnostiX Guide Manual

Cadaver Implant 19 19

1.52 1.56

- 3.54 3.43

1.54 1.84

- 3.64 3.22

1.83 1.90

1.00 1.08

3.48 3.63

Nokar et al [57] 2011 Guide Model Bore 32 Mesiodist Buccoling

0.88 0.22

0.38 0.17

- -

- - - 1.2 0.08 - 0.11 0.05 -

Arisan et al [58] 2010 Aytasarim Simplant

Guide Guide

Human Implant 279 1.31 0.81

0.33 0.51

2.90 1.60

1.62 1.01

0.54 0.40

3.40 1.72

3.50 3.39

1.38 0.84

5.90 4.60

- -

- -

- -

Nickenig et al [59] 2010 CoDiagnostiX Guide Human Implant 23 Med-lat Ant-post

0.90 0.90

1.06 1.22

3.70 4.50

0.60 0.90

0.57 0.94

2.70 3.40

4.20 3.04 10.0 - -

- -

- -

Petersson et al [60] 2010 NobelGuide Guide Cadaver Implant 67 78

Mandible Maxilla

1.05 0.83

0.47 0.57

3.13 2.78

1.24 0.96

0.58 0.50

3.63 2.43

2.46 2.02

0.67 0.66

7.44 5.38

0.48 0.10

0.52 0.60

1.46 1.61

Van Assche et al [61] 2010 NobelGuide Guide Human Implant 21 0.60 0.30 1.4 0.90 0.40 1.8 2.20 1.10 4.0 -0.10 0.5 0.8

Widmann et al [62] 2010 StealthStation Navigation Model Bore 104 0.46 0.34 1.51 0.88 0.65 4.24 0.83 0.60 2.51 - - -

Widmann et al [63] 2010 Guide Cadaver Implant 51 0.69 0.46 1.96 0.89 0.68 3.06 2.81 2.17 9.16 - - -

Dreiseidler et al [64] 2009 SICAT Guide Model Implant 60 0.22 0.10 0.38 0.34 0.15 0.62 1.09 0.51 2.00 0.25 0.21 0.8

Ozan et al [65] 2009 Guide Human Implant 110 1.11 0.70 - 1.41 0.90 - 4.10 2.30 - - - -

Valente et al [66] 2009 Simplant Guide Human Implant 108 1.40 1.30 6.50 1.60 1.20 6.90 7.90 4.70 24.9 1.00 1.00 4.20

Casap et al [67] 2008 IGI DenX LandmarX

Navigation Navigation

Human Human

Landmark Landmark

- -

0.5 3-4

- -

- -

- -

- -

- -

- -

- -

- -

- -

- -

- -

Elian et al [68] 2008 IGI DenX Navigation Human Implant 14 0.89 0.53 - 0.96 0.50 - 3.78 2.76 - - - -

Ersoy et al [69] 2008 Guide Human Implant 48 46

Maxilla Mandible

1.04 1.42

0.56 1.05

- -

1.57 1.44

0.97 1.03

- -

5.31 4.44

0.36 0.31

- -

- -

- -

- -

Ruppin et al [23] 2008 Simplant Robodent

Artma

Guide Navigation Navigation

Cadaver Implant 40 40 40

1.50 1.00 1.20

0.80 0.50 0.60

- - -

- - -

- - -

- - -

7.90 8.10 8.10

5.00 4.60 4.90

- - -

0.60 0.60 0.80

0.40 0.30 0.70

- - -

Wittwer et al [70] 2007 VISIT

Treon

Navigation

Navigation

Human

Human

Implant

Implant

32

32

Buccal Lingual Buccal Lingual

1.00 0.70 1.00 1.20

0.50 0.30 0.50 0.80

2.00 1.20 2.40 3.40

0.60 0.70 0.80 0.70

0.20 0.30 0.60 0.50

0.90 1.00 2.00 1.60

- - - -

- - - -

- - - -

- - - -

- - - -

- - - -

17

Table 7. Accuracy data for computer-assisted implant planning and placement (continued) Error entry (mm) Error apex (mm) Error angle (mm) Vertical error (mm)

Study Year System Principle Study design Positioning Method

Sites (n)

Direction Mean SD Max Mean SD Max Mean SD Max Mean SD Max

Widmann et al [71] 2007 Treon Guide Guide

Navigation

Model Bore Bore Bore

56 56 56

- - -

- - -

- - -

0.50 0.60 0.40

0.30 0.30 0.30

1.20 1.40 1.00

- - -

- - -

- - -

- - -

- - -

- - -

Van Assche et al [72] 2007 Nobel Guide Cadaver Implant 12 1.10 0.70 2.30 1.20 0.70 2.40 1.80 0.80 4.00 - - -

Wittwer et al [73] 2006 Treon Navigation Human Implant 80 1.20 0.80 3.40 0.80 0.60 2.00 - - - - - -

Chiu et al [74] 2006 IGI DenX Navigation Model Bore 80 0.43 0.56 2.23 - - - 4.00 3.50 13.60 0.37 0.28 1.04

Kusumoto et al [75] 2006 PHANToM Navigation Model Bore 6 x-axis y-axis

0.12 0.20

0.06 0.18

- -

- -

- -

- -

- -

- -

- -

- -

- -

- -

Kramer et al [76] 2005 IGI DenX Navigation Model Implant 40 - - 0.30 - - - - - 4.00 - - 0.30

Di Giacomo et al [77] 2005 SimPlant Guide Human Implant 21 1.45 1.42 4.50 2.99 1.77 7.10 7.25 2.67 12.2 - - -

Hoffmann et al [78] 2005 Vector Vision Navigation Model Bore 240 0.95 0.25 - - - - 1.35 0.42 - 0.97 0.34 -

Brief et al [24] 2005 RoboDent IGI DenX

Navigation Navigation

Model Model

Bore Bore

15 15

0.35 0.65

0.17 0.58

0.75 2.37

0.47 0.68

0.18 0.31

0.72 1.22

2.12 4.21

0.78 4.76

3.64 20.43

0.32 0.61

0.21 0.36

0.71 1.43

Widmann et al [79] 2005 Treon Navigation Model Bore 112 0.42 0.26 1.00 - - - - - - 0.25 0.12 0.60

Sarment et al [43] 2003 SimPlant Guide Guide

Model Model

Bore Bore

50 50

1.50 0.90

0.70 0.50

1.80 1.20

2.10 1.00

0.97 0.60

3.70 1.60

8.00 4.50

4.50 2.00

8.70 5.40

- -

- -

- -

Wagner et al [80] 2003 VISIT Navigation Human Implant 32 Buccal Lingual

0.80 1.00

0.30 0.50

2.10 2.60

1.10 1.30

0.90 0.90

3.40 3.50

6.40 -

- -

17.40 -

- -

- -

- -

Wanschitz et al [81] 2002 VISIT Navigation Cadaver Implant 20 Buccal Lingual

0.55 0.49

0.31 0.38

1.50 1.40

1.44 1.36

0.79 0.70

3.50 3.20

- -

- -

- -

- -

- -

- -

Wanschitz et al [82] 2002 VISIT Navigation Cadaver Implant 15 Buccal Lingual

0.58 0.57

0.40 0.49

1.40 1.80

0.79 0.77

0.71 0.63

3.10 2.90

3.55 -

2.07 -

10.40 -

- -

- -

- -

Van Steenberghe et al [83]

2002 Nobel Guide Cadaver Implant 16 0.80 0.30 - 0.90 0.30 - 1.80 1.0 - - - 1.10

Gaggl et al [84] 2002 SNM Navigation Navigation

Model Model

Bore Implant

60 60

0.20 0.20

- -

- -

- -

- -

- -

- -

- -

- -

0.11 0.25

0.22 0.26

0.60 0.90

Brief et al [85] 2001 IGI DenX Navigation

Navigation

Model

Model

Bore

Bore

38

8

x-axis y-axis x-axis y-axis

0.50 0.30 0.30 0.20

- - - -

1.10 0.90 0.60 0.50

0.60 0.30 0.20 0.60

- - - -

1.10 1.00 0.30 1.20

- - - -

- - - -

- - - -

0.20 0.20 0.20 0.20

- - - -

0.70 0.70 0.50 0.50

Gaggl et al [86] 2001 SNM Navigation Model Bore 100 - - - - - - - - - 0.14 0.05 0.23

Modified from Jung et al. [44]

18

Study rationale

The primary purpose of this study project is to appraise a new surgical navigation system that

can provide dentists with CT-based real-time visual guidance in the placement of dental

implants. The accuracy of implant socket drilling using the surgical navigation system should be

no worse than that provided by stereo-lithographic drill guides (the current standard of

practice). After an initial usability confirmation phase, the project will concentrate on

validating that the experimental surgical navigation system accuracy in a simulated clinical

setting is acceptable.

Study objectives

To implement the experimental surgical navigation system and determine implant transfer

and placement accuracy in typodonts in a near clinical setting.

To determine implant transfer and placement accuracy in typodonts in a near clinical

setting in four commercially available static planning and transfer systems.

To compare the results obtained with the experimental surgical navigation system with

those four commercially available static planning and transfer systems.

To define the discrepancies in accuracy between the upper and lower jaw and their

different sextants.

To delineate the extent of the initial learning curve with the different planning and transfer

systems.

Specifically, the objectives are to establish the accuracy of an experimental surgical

navigation system in comparison with drill guide surgical stent procedures made from cbCT

scans and also provide usability feedback.

19

Hypothesis

The null hypothesis is that the accuracy of an experimental surgical navigation system is not

better than commonly used methods for surgical positioning of dental implants.

The alternative hypothesis is that the experimental surgical navigation system facilitates

accurate placement of dental implants.

20

Materials and methods

Pre-surgical and surgical preparation

1. Partially edentulous, patient-equivalent typodonts (maxilla- A-J F OK K, mandible- A-J F UK

K, Frasaco GmbH, Tettnang, Germany) and mannequin (P-6/5 TS, Frasaco GmbH, Tettnang,

Germany) with silicone lining and accurate surgical anatomy were used. Both the maxillas

and mandibles had three teeth, 13, 23, 27 and 37, 33 and 43. The models were duplicated

in reversible hydrocolloid (Dupli-Coe-Loid, GC America Inc. Alsip, IL, USA), poured up in

dental stone (Microstone, Whip Mix Corp, Louisville, KY, USA) and the resulting casts were

articulated in a KaVo Protar 5 articulator (KaVo Dental, Charlotte, NC, USA)(Figure 1).

Figure 1. Duplication of typodonts and articulation of casts

(a) typodont mandible and duplicated cast, (b) typodont maxilla and duplicated cast,

(c) articulated casts in articulator, (d) articulated typodonts in mannequin

2. Acrylic denture teeth (Classic Trubyte, moulds 266, 46 and F33 in shade 62C) were

selected and set up in wax on the stone casts to mimic ideal occlusion. The finished set ups

21

were duplicated with irreversible hydrocolloid (Jeltrate Plus, Dentsply International,

Milford, DE, USA) and poured up in dental stone (Microstone, Whip Mix, Louisville, KY).

Following that a vacuum foil (Sta-Vac sheet resin 0.020, Buffalo Dental Canada, Cambridge,

ON) was adapted to the resulting cast with a vacuum forming machine (Biostar, Perma

Laboratories, Brunswick, OH) and maxillary and mandibular radiographic guides were

prepared with radiopaque acrylic material (BiocrylX, Great Lakes Orthodontics Ltd., New

York, NY)(Figure 2).

Figure 2. Tooth setup and fabrication of radiographic guides

(a-c) tooth setup on articulated casts, (d-f) duplicated radiopaque teeth in vacuform matrix on

casts, (g-i) duplicated radiopaque teeth in vacuform matrix on typodonts

22

3. The radiographic guides were duplicated with a laboratory putty matrix (Zetalabor,

Zhermack, Badia Polesine, Italy) and surgical guides were fabricated in clear acrylic

(ProBase Cold, Ivoclar Vivadent, Schaan, Liechtenstein) to transfer the final prosthetic

solution to the typodonts.

4. The maxillary and mandibular radiographic guides were placed on the master typodonts

and volume data of the region of interest was acquired by cbCT on the CB MercuRay

(Hitachi Medical Systems, Tokyo, Japan) in I mode (FOV = 10 cm), 100 kV and 10 mA

(Figure 3).

Figure 3. cbCT images of typodonts with radiographic guides

(a) maxilla, (b) mandible

5. Following this, the acrylic laboratory-fabricated surgical guides were used to prepare eight

parallel implant osteotomies on the mandibular and maxillary master typodont models in

the regions of missing teeth (3 posterior left, 3 posterior right, 2 anterior). The

osteotomies were made in optimized locations relative to the planned tooth location

dictated by the radiographic stent, in the depth of 10 mm with a diameter of 4 mm. The

master typodonts models with the resulting osteotomies were scanned with a cbCT

machine CB MercuRay in I-mode, with settings of 100 kV and 10 mA according to the

instructions pertaining to each individual modality (described below) (Figure 4).

23

Figure 4. cbCT images of master typodonts with osteotomies

(a) maxilla (b) mandible

6. The resulting DICOM files from the cbCT were used for five different planning transfer

modalities for implant placement, using an (a) acrylic, laboratory made surgical template,

(b) Simplant SurgiGuide, (c) Straumann Guided surgery, (d) NobelGuide and an (e)

experimental surgical navigation system.

7. The five modalities were next compared with regard to accuracy:

a) Acrylic, laboratory made surgical template

The radiographic guides were duplicated with a laboratory putty matrix (Zetalabor,

Zhermack, Badia Polesine, Italy) and fabricated in clear acrylic (ProBase Cold, Ivoclar

Vivadent, Schaan, Liechtenstein) to transfer the final prosthetic solution to the typodonts.

Bore-holes were made in the two replicated tooth set ups and used as a surgical template.

The same surgical guides were used later with the pilot drill to initiate the osteotomies on

the slave typodonts, then the surgical guides were set aside and the osteotomies were

continued without template guidance (Figure 5). The operators used guiding pins during

the surgical procedure to establish parallelism of osteotomies.

24

Figure 5. Acrylic, laboratory made surgical template

(a) surgical guides on casts, (b) surgical guides

b) Simplant and SurgiGuide

The DICOM files from the cbCT scan were converted to SimPlant planner format by the

Radiology Department at the University of Toronto and opened with the SimPlant

software (Materialise Dental, Leuven, Belgium). The master boreholes were located and 8

implants were placed virtually per jaw in the previous osteotomies, visible on the

reformatted CT images (Figure 6).

25

Figure 6. Implant surgical positions planned with the Simplant software

(a) frontal, horizontal, panoramic view and 3D reconstruction of mandible, (b)

magnification of panoramic view of mandible , (c) frontal, horizontal, panoramic view and

3D reconstruction of maxilla, (d) magnification of panoramic view of maxilla

The surgical plan and duplicate casts were sent to the manufacturing facility and four

tooth-supported Safe SurgiGuides were ordered for the maxilla and the mandible to be

used with the Straumann guided surgical drills (Ø2.8, 3.2, 3.5, 4.2) (Straumann USA,

Andover, USA). After delivery, the fit of the surgical template was checked on the

typodonts, disinfected and placed in the mannequin (Figure 7). A flapless procedure was

performed with the Safe SurgiGuides, ensuring fixed implant position and angulation, with

a vertical physical stop according to the manufacturer’s instructions.

26

Figure 7. Safe SurgiGuides from Simplant

(a) four surgical guides to accommodate each drill size for the maxilla

(b) four surgical guides to accommodate each drill size for the mandible

c) Straumann Guided Surgery (coDiagnostiX and gonyX)

The scan templates for the maxilla and mandible were manufactured in a local laboratory

based on the prepared radiographic guide and the master cast. The radiographic guide

was connected to the Straumann TempliX plate with the three reference pins, for both

maxilla and mandible (Figure 8).

Figure 8. Straumann radiographic guides with TempliX plates

.

(a) radiographic guide on maxillary cast (b) radiographic guide on mandibular cast

The master typodonts were scanned with the scanning guides on a CB MercuRay unit in I

mode with 100 kV and 10 mA settings. The DICOM files from the cbCT scan were imported

to the coDiagnostiX software. The master osteotomies were located and 8 implants placed

in them virtually per jaw (Figure 9).

27

Figure 9. Implant surgical positions planned with the CoDiagnostiX software

(a) frontal, sagittal, horizontal section, panoramic view and anterior view of 3D

reconstruction of maxilla, (b) frontal, sagittal, horizontal section, panoramic view and

occlusal view of 3D reconstruction of maxilla, (c) frontal, sagittal, horizontal section,

panoramic view and anterior view of 3D reconstruction of mandible, (d) frontal, sagittal,

horizontal section, panoramic view and occlusal view of 3D reconstruction of mandible

A tooth-supported surgical template was ordered from the local laboratory based on the

GonyX settings and a duplicate cast (Figure 10).

28

Figure 10. Transfer of planned CoDiagnostiX parameters to Straumann SurgiGuide in

the laboratory

(a) gonyX template plan for #24, (b) gonyX verification form for mandible, (c) articulated

cast with surgical guide in gonyX machine, (d) verification of titanium sleeve position with

verification form, (e) placement of titanium sleeves with gonyX device, (f) verification of

adequate spacing for titanium sleeves

After delivery, fit of the surgical template was checked on the cast and the typodonts. The

guide was placed in the mannequin (Figure 11) A flapless procedure was performed with

the template utilizing the Straumann Guided surgery system per the manufacturer’s

instructions, ensuring fixed implant position and angulation, with a physical stop.

29

Figure 11. Straumann Guided Surgery templates (maxilla, mandible)

(a) surgical guides on casts, (b) surgical guides

d) NobelGuide surgical template (NobelClinician)

The previously optimized tooth setup was duplicated in a local laboratory to produce a

radiographic guide. Radiopaque (guttapercha) markers were positioned in the guide for

software recognition (Figure 12). Following the double scan protocol the guides were

scanned both on the typodonts and by themselves to facilitate automatic segmentation of

the radiographic guides.

Figure 12. Radiographic guides for NobelClinician and NobelGuide

(a) radiographic guide on mandibular cast with radiopaque markers,

(b) radiographic guide on maxillary cast with radiopaque markers

30

The resulting DICOM files from the cbCT scans were imported to the NobelClinican

software. The master osteotomies were located and 8 implants placed in them virtually

per jaw (Figure 13).

Figure 13. Implant surgical positions planned with the NobelClinician software

(a) panoramic, frontal section and 3D rendering of mandible with planned surgical guide

(b) panoramic, frontal section and 3D rendering of maxilla with planned surgical guide

Tooth-supported surgical templates with

three guiding pins each were ordered from

Nobel Biocare. After delivery, the fit of the

surgical template was checked on the cast

and corrected (Figure 14). The guide was

placed in the mannequin and the holes

drilled for the guiding pins. After

stabilization with the pins, a flapless

procedure was performed with the

template, ensuring fixed osteotomy position

and angulation, with a physical stop.

maxilla and mandible

Figure 14. NobelGuide

surgical templates

31

e) Surgical Experimental Navigation System

Concept

The experimental surgical navigation system includes an optical tracking system and

trackers for the hand piece and the jaws. The jaw tracking appliance is minimally intrusive

and the software is designed to facilitate the automation and simplification of key tasks

such as CT-patient registration, drill calibration and panoramic curve drawing, also

containing a very simple, self-explanatory, planning and guidance user interface.

Hardware components

Computer: a standard tablet computer

Optical tracking camera: MicronTracker (Claron, Inc.) model Hx40. To evaluate

accuracy of the camera, Root Mean Squared Error was used. RMSE is the most

frequently used measure of spatial measurement accuracy, calculated by averaging the

squares of the individual error values, then taking the square root of the average. If all

the errors have the same magnitude, RMSE generates the same value as the average

error. When some of the errors are larger than others, however, they are given more

weight, resulting in the RMSE being larger than the average. In the many experiments

conducted to measure the accuracy of MicronTracker products the ratios between

RMSE and 95% confidence interval were found to be very similar across experiments,

95%CI » 1.85 x RMSE, which amounts to a 0.20 mm RMS error average of 20,000

positions in the field of measurement (http://www.clarontech.com/microntracker-

specifications.php)

Mount: Holds the tracking camera and computer screen at dental surgeon’s eye level

JawRef: A thin thermoplastic shell designed to be easily moulded to the lower or

upper jaw (after a 40 sec dip in hot water), attached to an aluminum skeleton at

its front buccal position. The skeleton provides an anchor for the jaw tracker and

is designed to allow automatic jaw-CT registration.

Jaw tracker: A solid, lightweight part designed to be attached to the JawRef

skeleton that carries an arrangement of circular black/white regions (XPoints)

called a marker, whose pose in 3D space can be precisely tracked by the camera.

32

Part of the jaw tracker is designed to allow calibration of the relationship

between the drill tip and the drill tracker (Figure 15).

Figure 15. Jaw tracker of the experimental surgical navigation system

Jaw tracker attaching to the stent on the dentition with black and white fiducial

markers

Drill tracker: A marker-carrier part that clamps to the drill (handpiece) handle

such that it maintains a rigid spatial relationship with the head holding the drill bit

(Figure 16).

Figure 16. Drill tracker of the experimental surgical navigation system

(a) drill tracker attaching to the stent on the dentition with black and white

fiducial markers

33

Software components

An integrated planning and guidance application with a straightforward planning user

interface, which is optional (guidance can work even without planning) (Figure 17).

Guidance set up and interaction requires no keyboard/mouse input - the system will

configure itself and respond based only on drill motions relatively to the jaw tracker.

Figure 17. Planning and guidance interface of experimental surgical navigation system

The screenshot shows the user interface with the tools in the left upper corner, the

calibration and navigation feedback panel in the left lower corner, the navigation panel in

the middle (crosshair of horizontal position on top and angulation in the bottom) and the

cbCT slices with planned implant

Thermoplastic material (Polyform, Patterson Medical, Mississauga, Canada) was heated

for 40 seconds in boiling water and used to mould the JawRef surgical guide (Figure 18)

over the cast and radio-opaque provisional teeth prior to the CT scan.

34

Figure 18. Moulded JawRefs of the experimental surgical navigation system

Jaw reference stents with metal tags

The DICOM files from the cbCT were imported into the NaviDent software and the

planning of implant placements were done with the planning software. After that, JawRef

sections were removed, where drilling was to be done. The drill tracker was attached to

the hand piece and calibrated using jaw tracker by the stereoscopic camera navigation

system. The jaw tracker in turn was attached to the JawRef and mounted on the maxillary

or mandibular typodont in the mannequin, after which the bur was installed and

calibrated by touching its point tip on the jaw tracker to detect the position of the

typodont and the drill (See clinical setup on Figures 19-21). Following this registration

procedure, the position of the bur tip was identified in reality – the software recognized

the position and orientation of the patient’s jaw together with the bur tip and displayed

them simultaneously on the screen. The correct position, orientation and path for the

movement were indicated in real time, using specific signals.

35

Figure 19. Clinical setup of experimental surgical navigation system

36

(a) Operator and mannequin in clinical setting with experimental surgical navigation

system, (b) positioning of additional light, camera and screen in relation to mannequin and

operator during clinical procedure, (c) positioning of the jaw tracker and drill tracker

during surgical procedure

8. Guided by the respective module of each of the five planning concepts, the osteotomies

for the eight implants on each jaw were made on a Frasaco mannequin in near clinical

conditions (Figure 20). The experimental setup gave us an accurate simulation of clinical

conditions in a preclinical setting with typodonts that mimic human bone density,

hardness and radiopacity. The experimental setting resulted in ten typodonts with a total

of 80 osteotomies with any of the five systems, designated as one series of experiments.

Three series were carried out by one investigator, then to avoid personal bias, one series

each was repeated by two independent investigators. Consequently, 5 series with a total

of 400 osteotomies was analyzed for each implant surgical transfer modality.

37

Figure 20. Diagram of tooth numbers on typodont

9. 12 surgical typodonts were used (6 maxillas, 6 mandibles). In two of the models (1

mandible, 1 maxilla), designated the master models, 8 implant osteotomies were placed in

the regions of missing teeth (3 posterior left, 3 posterior right, 2 anterior), in the depth of

10 mm with a diameter of 4 mm.

Accuracy estimation

10. Finally, all boreholes were assessed with the experimental surgical navigation system’s

MicronTracker and the inaccuracy of the boreholes was calculated comparing the master

typodonts to the slave typodonts. In order to estimate the accuracy and precision of the

system "accuracy jigs" were constructed. These provided a single coordinate system, to

precisely overlay and compare measurements from both the master and slave phantom

models. Accuracy was then determined by comparing the measurements from the master

to each of the slave jaws.

38

Figure 21. Accuracy estimation jigs to secure master and slave typodonts

(a) accuracy estimation devices with fiducial markers for maxilla and mandible(b) accuracy

estimation devices with fiducial markers for maxilla and mandible with master tyopodonts in

position

11. The jig consisted of a hand piece with a drill bit affixed (Figure 21). The drill bit was

inserted in each drilled hole of the master and the system recorded the position and

orientation at the entry point and at the apex of the tip. The same process was repeated

for each of the slaves. The following errors were evaluated by the accuracy evaluation

software:

a. Error at the entry point of the implant, measured in mm

b. Error at the apex of the implant, measured in mm

c. Error in the orientation/direction of the drill axis compared to planned implant

axis (or the angular error), express in degrees

d. Error in depth, measured in mm

12. Errors a and b are estimated by a 2D (x, y) Euclidean distance of the position vectors of the

drill and the planned implant. Error c or the angular error was estimated by taking the

angle between the directional vectors of the drill vs. the implant. Error d is the difference

in the z-component of the position vectors (Figure 21, 22).

39

Figure 22. Accuracy estimation software for evaluation of osteotomy positions

User interface with panels for different guidance methods and positions of osteotomies for

master typodont and slave typodont

13. Figure 23 illustrates the different inaccuracy calculations that we performed (entry error,

apex error, vertical error, angular error and total error).

Figure 23. Measurements adopted from Brief et al.[24]

Blue – ideal position, green – position to compare to ideal position

40

14. After assessment, the boreholes were re-cemented with specific cement (A-J OP UK K for

mandible and A-J OP OK K for maxilla, Frasaco GmbH, Tettnang, Germany) with the same

radiopacity as the Frasaco typodont jaw and reused for evaluation of the next modality.

The used material re-created a radiographically homogeneous mass without porosities,

and perceptible anisotropic sponginess upon drilling.

41

Statistics

Drilling was performed on each tooth for each mold using each technique five times (three

were performed by a single operator (ESG), and the remaining two by different operators). This

resulted in 400 sets of matched measurements across techniques. Power to detect statistical

differences was based on the simple case of a paired t-test (e.g., comparing one technique to

another).

Box plots were created with the QI Macros software (KnowWare International Inc.,

Denver, CO), using the minimum, 25th percentile, median, 75th percentile and maximum values

of any given dataset.

Deviation in total error, vertical error, horizontal error of the apex and entry position,

as well as angular error, were measured and collected for each hole drilled across each: jaw

type (e.g. mandible vs maxilla), model, surgical method, and attempt by operator (e.g. 3

operators). Mean and standard deviations are reported aggregating the measurement

deviations separately by surgical method, jaw type, model and tooth. A marginal linear model

using a generalized estimating equations (GEE) method was used to compare surgical methods,

jaw types, models and individual teeth while accounting for the lack of independence in the

outcome measurements (i.e., teeth are nested within attempts, and models, which are nested

within operators. This lack of independence in outcome measurements violates a critical tenet

of standard frequentist statistical approaches (e.g., linear regression and analysis of variance).

Marginal models overcome this restriction by adjusting the standard errors, and thus p-values

and confidence intervals, to account for the lack of independence. Omnibus Chi-square tests

were used to determine if statistically significant differences across key factors (e.g., surgical

method) could be identified. Where differences were found, pairwise comparisons were

conducted with an F-test of difference in least-square means of each level of the factor. Given

the nature of the data it is equivalent to a paired samples t-test in that it accounts for the

clustered correlation between and within measurements. Corrections for multiple comparisons

were not performed. A p-value of 0.05 or less was used as the criterion for statistical

significance. All analyses were conducted using SAS v9.2 (Cary, NC).

42

Results

Power calculations

Power to detect statistical differences was based on the simple case of a paired t-test.

Assuming a type I error rate of 5%, a within cluster correlation of 0.5, 400 matched pairs of

data provides 80% power to detect a small effect size (Cohen’s d = mean difference / SD) of

0.15. An effect size of 0.15 translates to a difference in measurements of approximately 0.3

mm for total deviation, 0.18 mm for lateral deviation of entry and apex, as well as vertical

deviation and 0.6 degrees for angle discrepancy. Figure 23 shows the statistical power for

detecting effect sizes ranging from 0.01 to 0.3 assuming various scenarios of intra-cluster

correlation.

Figure 24. Statistical power of effect sizes

43

The following tables are a summary of the means of the different measurements presented as

mean ± SD (min-max). Each cell in each table represents 400 osteotomies, compiled by 3

different operators. The results are pooled from the maxilla and the mandible, as well as from

all three operators. One operator performed 3 repetitions (240 osteotomies), while the other

two executed one each (80 osteotomies). The tables show the condensation of all data for

total - and in detail - lateral, vertical and angular deviation.

Descriptive statistics – Summary of means and standard deviations

Table 8. Lateral deviation of entry and apex (Figure 22 A and B)

Laboratory guide

Straumann Guided Surgery

Simplant SurgiGuide

NobelGuide Experimental Navigation

System

Entry 1.19 ± 0.68 (0.02-4.95)

0.9 ± 0.48 (0.05-4.66)

0.76 ± 0.54 (0.02-2.92)

0.81 ± 0.55 (0.05-4.31)

1.14 ± 0.55 (0.04-3.64)

Apex 1.82 ± 1.07 (0.04-5.95)

1.19 ± 0.62 (0.09-4.78)

0.99 ± 0.64 (0.07-3.36)

1.24 ± 0.8 (0.02-5.99)

1.18 ± 0.56 (0.05-3.19)

Lateral deviation of the pilot borehole position in the slave models compared to the master model

(all data: mean ± SD (min-max) (mm)).

Table 9. Vertical deviation of apex (Figure 22 C)

Laboratory guide

Straumann Guided Surgery

Simplant SurgiGuide

NobelGuide Experimental Navigation

System

Apex 0.31 ± 0.71 (0.00-3.40)

1.05 ± 0.86 (0.00-4.81)

1.1 ± 0.79 (0.00-2.98)

1.27 ± 0.86 (0.00-4.06)

1.04 ± 0.71 (0.00-3.34)

Longitudinal deviation of the apex of the pilot borehole in the slave models compared to the

master model (all data: mean ± SD (min-max) (mm)).

Table 10. Total deviation of apex (Figure 22 D)

Laboratory guide

Straumann Guided Surgery

Simplant SurgiGuide

NobelGuide Experimental Navigation

System

Apex 2.02 ± 1.18 (0.14-9.96)

1.71 ± 0.86 (0.23-5.05)

1.46 ± 0.76 (0.10-4.99)

1.91 ± 0.94 (0.06-6.23)

1.71 ± 0.61 (0.22-3.92)

Total deviation of the apex of the pilot borehole in the slave models compared to the master model

(all data: mean ± SD (min-max) (mm)).

44

Table 11. Angular deviation of apex (Figure 22 E)

Laboratory guide

Straumann Guided Surgery

Simplant SurgiGuide

NobelGuide Experimental Navigation

System

Axis deviation 9.18 ± 4.65 (0.33-20.79)

3.31 ± 1.86 (0.20-12.52)

3.09 ± 1.9 (0.16-14.58)

4.24 ± 2.66 (0.09-17.05)

2.99 ± 1.68 (0.14-11.94)

Angular deviation of the axis of the pilot borehole in the slave models compared to the axis of the pilot

bore hole in the master model (all data: mean ± SD (min-max) (deg)).

Descriptive statistics – Box plots of different outcomes in the mandible

The following box plots were created to show a descriptive summary of the results respective

to each outcome, in the mandible (Tables 12-16), maxilla (Tables 17-21) and in both jaws

combined (Tables 22-26). Each surgical method is represented by a separate box plot,

depicting the five individual series performed. Series 1, 2 and 3 were carried out by one

investigator, while 4 and 5 were executed by two different operators. The sixth diagram on

each page is a summary of all five series respective of all implant surgical transfer modalities.

45

Table 12. Box plots of total deviation of apex in the mandible (Figure 22 E)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental navigation system

0

1

2

3

4

5

6

7

8

9

10

mm

46

Table 13. Box plots of vertical deviation of apex in the mandible (Figure 22 C)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided Surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental Navigation System

0

1

2

3

4

5

6

mm

47

Table 14. Box plots of lateral deviation of apex in the mandible (Figure 22 B)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided Surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental Navigation System

0

1

2

3

4

5

6

mm

48

Table 15. Box plots of lateral deviation of entry in the mandible (Figure 22 A)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided Surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental Navigation System

0

1

2

3

4

5

6

mm

49

Table 16. Box plots of angular deviation of apex in the mandible (Figure 22 D)

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

Laboratory guide

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

Simplant SurgiGuide

02468

1012141618202224

#1 #2 #3 #4 #5

de

gre

es

Straumann Guided Surgery

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

NobelGuide

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

Experimental Navigation System

0

5

10

15

20

25

de

gre

es

50

Descriptive statistics – Box plots of different outcomes in the maxilla

Table 17. Box plots of total deviation of apex in the maxilla (Figure 22 E)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided Surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental Navigation System

0

1

2

3

4

5

6

mm

51

Table 18. Box plots of vertical deviation of the apex in the maxilla (Figure 22 C)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided Surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental Navigation System

0

1

2

3

4

5

6

mm

52

Table 19. Box plots of lateral deviation of apex in the maxilla (Figure 22 B)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided Surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental Navigation System

0

1

2

3

4

5

6

mm

53

Table 20. Box plots of lateral deviation of entry in the maxilla (Figure 22 A)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided Surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental Navigation System

0

1

2

3

4

5

6

mm

54

Table 21. Box plots of angular deviation of apex in the maxilla (Figure 22 D)

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

Laboratory guide

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

Simplant SurgiGuide

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

Straumann Guided Surgery

0

5

10

15

20

25

#1 #2 #3 #4 #5

mm

NobelGuide

0

5

10

15

20

25

#1 #2 #3 #4 #5

mm

Experimental Navigation System

0

5

10

15

20

25

de

gre

es

55

Descriptive statistics – Box plots of different outcomes in both jaws combined

Table 22. Box plots of total deviation of apex in both jaws combined (Figure 22 E)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided Surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental Navigation System

0

1

2

3

4

5

6

mm

56

Table 23. Vertical deviation of apex in both jaws combined (Figure 22 C)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided Surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental Navigation System

0

1

2

3

4

5

6

mm

57

Table 24. Lateral deviation of apex in both jaws combined (Figure 22 B)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided Surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental Navigation System 0

1

2

3

4

5

6

mm

58

Table 25. Lateral deviation of entry in both jaws combined (Figure 22 A)

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Laboratory guide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Simplant SurgiGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Straumann Guided Surgery

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

NobelGuide

0

1

2

3

4

5

6

#1 #2 #3 #4 #5

mm

Experimental Navigation System

0

1

2

3

4

5

6

mm

59

Table 26. Angular deviation of apex in both jaws combined (Figure 22 D)

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

Laboratory guide

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

Simplant SurgiGuide

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

Straumann Guided Surgery

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

NobelGuide

0

5

10

15

20

25

#1 #2 #3 #4 #5

de

gre

es

Experimental Navigation System 0

5

10

15

20

25

de

gre

es

60

Overall statistical comparison of surgical methods

The comparison of each outcome measurement across the five surgical methods is presented

in Table 27. All outcome measure differed significantly across the surgical methods (p0.001

for all outcomes). Estimations of differences along with statistical probabilities were assessed

for the overall measurements (tables 28-32), as well as differences between the jaw type

(table 33), the typodont jaws (tables 34-39) and the intra-jaw sites in the mandible (tables 40-

45 ) as well as the maxilla (tables 46-51. )

Table 27. Overall comparison of surgical methods

Laboratory

guide

(mm)

Simplant

SurgiGuide

(mm)

Straumann

Guided

Surgery

(mm)

NobelGuide

(mm)

Experimental

Navigation

System

(mm)

Overall difference

Mean SD Mean SD Mean SD Mean SD Mean SD X2 P

Total deviation

of apex 2.32 2.69 1.68 1.77 1.67 0.82 1.86 0.92 1.64 0.61 17.71 0.001

Lateral deviation

of apex 1.74 1.05 1.07 1.67 1.22 0.61 1.21 0.76 1.18 0.56 26.50 <0.001

Vertical

deviation of

apex

0.52 0.73 1.12 0.87 0.96 0.82 1.24 0.84 0.94 0.69 23.68 <0.001

Lateral deviation

of entry 1.14 0.74 0.86 1.72 0.91 0.47 0.82 0.55 1.11 0.55 21.63 <0.001

Angular

deviation of

apex

8.95 5.00 3.31 2.09 3.33 1.84 4.22 2.55 3.26 1.93 30.85 <0.001

Pairwise comparison of methods for different outcomes

Overall measurements

An overall difference in total apex deviation was found by surgical method (2 = 17.71, p =

0.001). Pairwise comparisons across surgical methods are presented in Table 28. With an

61

average deviation of 2.32, osteotomies drilled with a laboratory guide had significantly higher

deviations compared to all other methods. The NobelGuide had the second highest average

total deviation of apex, which was significantly higher than for the Simplant SurgiGuide,

Straumann Guided Surgery or the Experimental Navigation System. There were no significant

differences in the total deviation of apex between these three latter methods.

Table 28. Pairwise comparison of methods for total deviation of apex (difference in mm)

Laboratory guide Simplant

SurgiGuide

Straumann Guided

Surgery NobelGuide

Laboratory guide

Simplant SurgiGuide 0.64***

Straumann Guided Surgery 0.65** 0.01

NobelGuide 0.46** 0.18* 0.19**

Experimental Navigation

System 0.68*** 0.04 0.03 0.22*

An overall difference in lateral apex deviation was found by surgical method (2 = 26.50, p <

0.001). Pairwise comparisons across surgical methods are presented in Table 29. With an

average deviation of 1.74, osteotomies drilled with a laboratory guide had significantly higher

deviations compared to all other methods. There were no significant differences in the total

deviation of apex between the other methods.

Table 29. Pairwise comparison of methods for lateral deviation of apex (difference in mm)

Laboratory guide Simplant

SurgiGuide

Straumann Guided

Surgery NobelGuide

Laboratory guide

Simplant SurgiGuide 0.67***

Straumann Guided Surgery 0.52*** 0.15

NobelGuide 0.53*** 0.14 0.01

Experimental Navigation

System 0.56*** 0.11 0.04 0.03

62

An overall difference in vertical apex deviation was found by surgical method (2 = 23.68, p <

0.001). Pairwise comparisons across surgical methods are presented in Table 30. With an

average deviation of 0.73, osteotomies drilled with a laboratory guide had significantly lower

deviations compared to all other methods. The NobelGuide had the highest average total

deviation of apex, which was significantly higher than for the Straumann Guided Surgery or the

Experimental Navigation System. There were no significant differences in the total deviation of

apex between the Simplant SurgiGuide, Straumann Guided Surgery and the Experimental

Navigation System.

Table 30. Pairwise comparison of methods for vertical deviation of apex (difference in mm)

Laboratory guide Simplant

SurgiGuide

Straumann Guided

Surgery NobelGuide

Laboratory guide

Simplant SurgiGuide 0.6***

Straumann Guided Surgery 0.44*** 0.16

NobelGuide 0.72*** 0.12 0.28**

Experimental Navigation

System 0.42*** 0.18* 0.02 <0.3***

An overall difference in lateral deviation of entry was found by surgical method (2 = 21.63, p <

0.001). Pairwise comparisons across surgical methods are presented in Table 31. With an

average deviation of 1.14, osteotomies drilled with a laboratory guide had significantly higher

deviations compared to Simplant SurgiGuide, Straumann Guided Surgery and NobelGuide. The

Experimental Navigation System had the second highest average lateral deviation of entry,

which was significantly higher than for Straumann Guided Surgery or NobelGuide. There were

no significant differences in the total deviation of apex between the other methods.

63

Table 31. Pairwise comparison of methods for lateral deviation of entry (difference in mm)

Laboratory guide Simplant

SurgiGuide

Straumann Guided

Surgery NobelGuide

Laboratory guide

Simplant SurgiGuide 0.28**

Straumann Guided Surgery 0.23*** 0.05

NobelGuide 0.32*** 0.04 0.09

Experimental Navigation

System 0.03 0.25 0.2*** 0.29***

An overall difference in angular deviation was found by surgical method (2 = 30.85, p < 0.001).

Pairwise comparisons across surgical methods are presented in Table 32. With an average

deviation of 8.95, osteotomies drilled with a laboratory guide had significantly higher

deviations compared to all other methods. The NobelGuide had the second highest average

angular deviation of apex, which was significantly higher than for the Simplant SurgiGuide,

Straumann Guided Surgery or the Experimental Navigation System. There were no significant

differences in the angular deviation of apex between these three latter methods.

Table 32. Pairwise comparison of methods for angular deviation of apex (difference in degrees)

Laboratory guide Simplant

SurgiGuide

Straumann Guided

Surgery NobelGuide

Laboratory guide

Simplant SurgiGuide 5.64***

Straumann Guided Surgery 5.62*** 0.02

NobelGuide 4.73*** 0.91*** 0.89***

Experimental Navigation

System 5.69*** 0.05 0.07 0.96**

64

Jaw type

The comparison of each outcome measurement between the maxilla and mandible is

presented in Table 33. Lateral deviation of entry (p = 0.005) and angular deviation of apex (p =

0.003) differed significantly between the two jaws.

Table 33. Comparison of outcomes between jaw types (mm and degree)

Mandible Maxilla Difference

Mean SD Mean SD X2 P

Total deviation of apex 1.83 1.80 1.84 1.34 0.04 0.845

Lateral deviation of apex 1.23 0.87 1.34 1.19 3.00 0.083

Vertical deviation of apex 1.02 0.79 0.90 0.86 4.31 0.038

Lateral deviation of entry 0.90 0.56 1.04 1.20 7.90 0.005

Angular deviation of apex 4.30 3.48 4.93 3.81 8.58 0.003

Typodont jaw models

The comparison of each outcome measurement across the five slave typodont models is

presented in Table 34. All outcome measure differed significantly across the five models,

except lateral deviation of entry (p 0.005 for all outcomes).

Table 34. Overall comparison of five slave typodont models (mm and degree)

1 2 3 4 5 Overall difference

Mean SD Mean SD Mean SD Mean SD Mean SD X2 P Total

deviation of apex

1.95 1.14 1.56 0.78 1.48 0.66 2.52 2.97 1.66 0.83 20.78 <0.001

Lateral deviation of

apex 1.31 0.91 1.16 0.76 1.07 0.61 1.67 1.73 1.22 0.67 15.82 0.003

Vertical deviation of

apex 0.77 0.88 0.84 0.64 0.84 0.64 1.41 0.97 0.93 0.81 17.53 0.002

Lateral deviation of

entry 0.93 0.57 0.88 0.54 0.91 0.54 1.18 1.76 0.95 0.61 6.98 0.137

Angular deviation of

apex 4.97 4.80 4.09 3.22 3.81 2.89 5.59 3.80 4.62 2.99 18.17 0.001

65

P-values for pairwise comparisons of models for different outcomes

An overall difference in total apex deviation was found by individual number of slave typodont

(2 = 20.78, p < 0.001). Pairwise comparisons across typodonts are presented in Table 35. With

an average deviation of 2.52, osteotomies drilled in typodont #4 had significantly higher

deviations compared to all typodonts. Typodont #1 had the second highest average total

deviation of apex, which was significantly higher than for #2, 3 and 5. There were no

significant differences in the total deviation of apex between these three latter typodonts.

Table 35. P-values for pairwise comparisons of models for total deviation of apex (difference in mm)

1 2 3 4

1

2 0.39**

3 0.47** 0.08

4 0.57** 0.96*** 1.04 ***

5 0.29** 0.1 0.18 0.86**

An overall difference in lateral apex deviation was found by individual number of slave

typodont (2 = 15.82, p = 0.003). Pairwise comparisons across typodonts are presented in Table

36. With an average deviation of 1.67, osteotomies drilled in typodont #4 had significantly

higher deviations compared to all typodonts. Typodont #1 had the second highest average

lateral deviation of apex, which was significantly higher than for # 3 and 4. There were no

significant differences in the lateral deviation of apex between the other typodonts.

Table 36. P-values for pairwise comparisons of models for lateral deviation of apex (difference in mm)

1 2 3 4

1

2 0.15

3 0.24** 0.09

4 0.36** 0.51*** 0.6***

5 0.09 0.06 0.15 0.45**

66

An overall difference in vertical apex deviation was found by individual number of slave

typodont (2 = 17.53, p = 0.002). Pairwise comparisons across typodonts are presented in Table

37. With an average deviation of 1.41, osteotomies drilled in typodont #4 had significantly

higher deviations compared to all typodonts. Typodont #1 had the lowest average vertical

deviation of apex, which was significantly lower than all other typodonts. There were no

significant differences in the lateral deviation of apex between the other typodonts.

Table 37. P-values for pairwise comparisons of models for vertical deviation of apex (difference in mm)

1 2 3 4

1

2 0.07*

3 0.07* 0

4 0.64*** 0.57*** 0.57***

5 0.16*** 0.09* 0.09* 0.48***

An overall difference in lateral deviation of entry was not found by individual number of slave

typodont (2 = 6.98, p = 0.137). Pairwise comparisons across typodonts are presented in Table

38. With an average deviation of 1.41, osteotomies drilled in typodont #4 had significantly

higher deviations compared to #2 and 3. There were no significant differences in the lateral

deviation of entry between the other typodonts.

Table 38. P-values for pairwise comparisons of models for lateral deviation of entry (difference in mm)

1 2 3 4

1

2 0.05

3 0.02 0.03

4 0.25* 0.3** 0.27**

5 0.02 0.07 0.04 0.23*

67

An overall difference in angular deviation was found by individual number of slave typodont

(2 = 18.17, p = 0.001). Pairwise comparisons across typodonts are presented in Table 39. With

an average deviation of 5.59, osteotomies drilled in typodont #4 had significantly higher

deviations compared to #2, 3 and 5 typodonts. Typodont #3 had lowest average angular

deviation, which was significantly lower than for all the other typodonts. There were no

significant differences between the other typodonts.

Table 39. P-values for pairwise comparisons of models for angular deviation of apex (difference in degrees)

1 2 3 4

1

2 0.88**

3 1.16 ** 0.28**

4 0.62 1.5*** 1.78***

5 0.35 0.53 0.81** 0.97**

68

Overall comparison of osteotomy positions for different outcomes

The comparison of each outcome measurement across the eight osteotomy locations (by tooth number) in the mandible is presented in

Table 40. Total (p = 0.018), lateral (p = 0.007) and vertical deviation (p = 0.007) of the apex measures, as well as angular deviation of the

apex (p = 0.024) differed significantly across the eight models.

Table 40. Overall comparison of osteotomy positions in the mandible for different outcomes (mm and degree)

36 35 34 32 42 44 45 46 Overall

difference

Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD X2 P Total deviation of

apex 2.60 4.32 1.80 1.02 1.65 0.84 1.97 1.10 1.45 1.09 1.55 0.72 1.62 0.79 2.00 1.09 16.90 0.018

Lateral deviation

of apex 1.57 0.96 1.15 0.77 1.16 0.79 1.47 1.09 0.92 0.63 0.94 0.59 1.20 0.79 1.45 0.99 19.33 0.007

Vertical deviation

of apex 1.27 0.80 1.10 0.72 0.98 0.77 0.98 0.75 0.88 0.76 1.01 0.82 0.86 0.75 1.09 0.88 19.59 0.007

Lateral deviation

of entry 1.21 0.83 0.78 0.47 0.83 0.50 0.94 0.54 0.92 0.55 0.82 0.45 0.78 0.49 0.92 0.42 12.49 0.086

Angular

deviation of apex 4.31 3.19 4.72 3.93 4.57 3.50 4.87 3.84 3.51 2.01 2.97 2.14 4.49 3.37 4.97 4.62 16.13 0.024

69

P-values for pairwise comparisons of teeth for different outcomes in the mandible

An overall difference in total deviation of the apex was found by individual number of

osteotomy locations (2 = 16.90, p = 0.018). Pairwise comparisons across osteotomy locations

are presented in Table 41. With an average deviation of 1.45, the osteotomies drilled in the

#32 positions had significantly lower deviations compared to #36, 35, 44 and 45 positions.

Osteotomy location #42 had the second lowest average total apex deviation, which was

significantly lower than for #36 and #35 locations. There were no significant differences

between the other locations.

Table 41 P-values for pairwise comparisons of teeth for total deviation of apex in the mandible (differences in mm)

36 35 34 32 42 44 45

36

35 0.8*

34 0.95* 0.15

32 0.63* 0.17* 0.32

42 1.15 * 0.35* 0.2 0.52

44 1.05* 0.25 0.1 0.42 0.1

45 0.98 0.18 0.03 0.35* 0.17* 0.07

46 0.6 0.2 0.35* 0.03* 0.55* 0.45 0.38

An overall difference in lateral deviation of the apex was found by individual number of

osteotomy locations (2 = 19.33, p = 0.007). Pairwise comparisons across osteotomy locations

are presented in Table 42. With an average deviation of 1.57, the osteotomies drilled in the

#36 positions had significantly higher deviations compared to #35, 34, 32, 42 and 44 positions.

Osteotomy location #32 and 42 had the lowest and second lowest average lateral apex

deviation, which was significantly lower than for #44, 45 and 46 locations, respectively. There

were no significant differences between the other locations.

70

Table 42. P-values for pairwise comparisons of teeth for lateral deviation of apex in the mandible (differences in mm)

36 35 34 32 42 44 45

36

35 0.42**

34 0.41** 0.01

32 0.1** 0.32 0.31*

42 0.65** 0.23 0.24* 0.55

44 0.63* 0.21 0.22 0.53* 0.02*

45 0.37 0.05 0.04* 0.27** 0.28* 0.26

46 0.12 0.3 0.29* 0.02** 0.53** 0.51 0.25

An overall difference in vertical deviation of the apex was found by individual number of

osteotomy locations (2 = 19.59, p = 0.007). Pairwise comparisons across osteotomy locations

are presented in Table 43. With an average deviation of 1.27, the osteotomies drilled in the

#36 positions had significantly higher deviations compared to all the other positions.

Osteotomy locations #44 and 32 had the lowest and second lowest average vertical apex

deviation, which was significantly lower than for #35 and 46 locations. There were no

significant differences between the other locations.

Table 43. P-values for pairwise comparisons of teeth for vertical deviation of apex in the mandible (differences in mm)

36 35 34 32 42 44 45

36

35 0.17*

34 0.29** 0.12

32 0.29** 0.12** 0

42 0.39** 0.22 0.1 0.1*

44 0.26** 0.09* 0.03 0.03 0.13

45 0.41** 0.24 0.12 0.12 0.02 0.15

46 0.18* 0.01 0.11 0.11** 0.21 0.08* 0.23

An overall difference in lateral deviation of the entry was not found by individual number of

osteotomy locations (2 = 12.49, p = 0.086). Pairwise comparisons across osteotomy locations

are presented in Table 44. With an average deviation of 1.21, the osteotomies drilled in the

71

#36 positions had significantly higher deviations compared to all other positions. There were

no significant differences between the other locations.

Table 44. P-values for pairwise comparisons of teeth for lateral deviation of entry in the mandible (differences in mm)

36 35 34 32 42 44 45

36

35 0.43**

34 0.38** 0.05

32 0.27* 0.16 0.11

42 0.29** 0.14 0.09 0.02

44 0.39** 0.04 0.01 0.12 0.1

45 0.43* 0 0.05 0.16 0.14 0.04

46 0.29* 0.14 0.09 0.02 0 0.1 0.14

An overall difference in angular deviation was not found by individual number of osteotomy

locations (2 = 16.13, p = 0.024). Pairwise comparisons across osteotomy locations are

presented in Table 45. With an average deviation of 2.97, the osteotomies drilled in the #42

positions had significantly lower deviations compared to all other, but the #32 positions.

Osteotomy location #32 had the second lowest average angular deviation, which was

significantly lower than for #35, 34, 45 and 46 locations. There were no significant differences

between the other locations.

Table 45. P-values for pairwise comparisons of teeth for angular deviation of apex in the mandible (differences in degrees)

36 35 34 32 42 44 45

36

35 0.41

34 0.26 0.15

32 0.56 0.15** 0.3**

42 0.8* 1.21** 1.06** 1.36

44 1.34 1.75 1.6 1.9 0.54**

45 0.18 0.23 0.08 0.38** 0.98** 1.52

46 0.66 0.25 0.4 0.1* 1.46** 2 0.48

72

The comparison of each outcome measurement across the eight osteotomy locations in the maxilla is presented in Table 46. Total (p =

0.004) and vertical deviation (p < 0.001) of the apex measures differed significantly across the eight models.

Table 46. Overall comparison of osteotomy positions by tooth number in the maxilla for different outcomes (mm and degree)

16 15 14 12 22 24 25 26 Overall

difference

Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD X2 P Total deviation of

apex 2.59 2.87 1.93 0.78 2.20 0.96 1.59 0.62 1.55 0.69 1.44 0.77 1.79 1.04 1.63 1.01 20.99 0.004

Lateral deviation

of apex 1.76 2.88 1.38 0.67 1.41 0.61 1.20 0.60 1.30 0.61 1.14 0.54 1.32 0.65 1.22 0.71 10.67 0.154

Vertical deviation

of apex 1.32 1.08 0.99 0.85 1.38 1.14 0.88 0.62 0.61 0.67 0.58 0.62 0.73 0.68 0.68 0.68 26.61 <0.001

Lateral deviation

of entry 1.63 3.02 0.99 0.46 0.92 0.48 0.80 0.37 1.00 0.57 0.90 0.49 1.01 0.64 1.05 0.71 9.01 0.252

Angular

deviation of apex 5.25 3.77 5.29 3.77 5.40 3.39 4.66 3.20 4.84 3.90 4.10 3.44 4.76 4.48 5.12 4.31 7.15 0.414

73

P-values for pairwise comparisons of teeth for different outcomes in the maxilla

An overall difference in total deviation of the apex was found by individual number of

osteotomy locations (2 = 20.99, p = 0.004). Pairwise comparisons across osteotomy locations

are presented in Table 47. With an average deviation of 2.59, the osteotomies drilled in the

#16, and of 2.20, the osteotomies drilled in the #14 positions had significantly higher

deviations compared to #12, 22, 24 and 26 positions. Osteotomy location #15 had the third

highest average total apex deviation, which was significantly higher than for #22 and #24

locations. There were no significant differences between the other locations.

Table 47. P-values for pairwise comparisons of teeth for total deviation of apex in the maxilla (differences in mm)

16 15 14 12 22 24 25

16

15 0.66

14 0.39 0.27

12 1.0* 0.34 0.61**

22 1.04* 0.38* 0.65** 0.04

24 1.15** 0.49** 0.76** 0.15 0.11

25 0.8 0.14 0.41* 0.2 0.24 0.35*

26 0.96* 0.3 0.57** 0.04 0.08 0.19 0.16

An overall difference in lateral deviation of the apex was not found by individual number of

osteotomy locations (2 = 10.67, p = 0.154). Pairwise comparisons across osteotomy locations

are presented in Table 48. There were no significant differences between the locations.

Table 48. P-values for pairwise comparisons of teeth for lateral deviation of apex in the maxilla (differences in mm)

16 15 14 12 22 24 25

16

15 0.38

14 0.35 0.03

12 0.56 0.18 0.21

22 0.46 0.08 0.11 0.1

24 0.62 0.24 0.27 0.06 0.16

25 0.44 0.06 0.09 0.12 0.02 0.18

26 0.54 0.16 0.19 0.02 0.08 0.08 0.1

An overall difference in vertical deviation of the apex was found by individual number of

osteotomy locations (2 = 26.61, p < 0.001). Pairwise comparisons across osteotomy locations

74

are presented in Table 49. With the highest average deviation of 1.38, the osteotomies drilled

in the #14 positions had significantly higher deviations compared to all but the #16 positions.

With an average deviation of 1.38, the osteotomies drilled in the #16 positions had significantly

higher deviations compared to all but the #15 and 14 positions. Osteotomy location #15 had

the third highest average vertical apex deviation, which was significantly higher than for #14,

22, 24, 25 and 26 locations. There were no significant differences between the other locations.

Table 49. P-values for pairwise comparisons of teeth for vertical deviation of apex in the maxilla (differences in mm)

16 15 14 12 22 24 25

16

15 0.33

14 0.06 0.39**

12 0.44* 0.11 0.5**

22 0.71** 0.38** 0.77** 0.27*

24 0.74** 0.41** 0.8** 0.3* 0.03

25 0.59** 0.26** 0.65** 0.15 -0.12 -0.15

26 0.64** 0.31** 0.7** 0.2* -0.07 -0.1 0.05

An overall difference in lateral deviation of the entry was not found by individual number of

osteotomy locations (2 = 9.01, p = 0.252). Pairwise comparisons across osteotomy locations

are presented in Table 50. There were no significant differences between the locations.

Table 50. P-values for pairwise comparisons of teeth for lateral deviation of entry in the maxilla (differences in mm)

16 15 14 12 22 24 25

16

15 0.64

14 0.71 0.07

12 0.83 0.19 0.12

22 0.63 0.01 0.08 0.2

24 0.73 0.09 0.02 0.1 0.1

25 0.62 0.02 0.09 0.21 0.01 0.11

26 0.58 0.06 0.13 0.25 0.05 0.15 0.04

75

An overall difference in angular deviation was not found by individual number of osteotomy

locations (2 = 7.15, p = 0.414). Pairwise comparisons across osteotomy locations are

presented in Table 51. There were no significant differences between the locations.

Table 51. P-values for pairwise comparisons of teeth for angular deviation of apex in the maxilla (differences in degrees)

16 15 14 12 22 24 25

16

15 0.04

14 0.15 0.11

12 0.59 0.63 0.74

22 0.41 0.45 0.56 0.18

24 1.15 1.19 1.3 0.56 0.74

25 0.49 0.53 0.64 0.1 0.08 0.66

26 0.13 0.17 0.28 0.46 0.28 1.02 0.36

Intra- and inter-rater agreement

Agreement in deviation scores across the three operators was moderate to go. The lowest

agreement occurring in the vertical deviation measurements (intraclass correlation coefficient

(ICC) = 0.55; 95% CI: 0.50 to 0.60). Agreement was highest for angular deviation where the

operators all had similar deviation scores for each tooth (ICC = 0.72; 95% CI: 0.69 to 0.75).

Table 52. Intra- and inter-rater agreement

INTRA-rater agreement (among

3 trials done by one operator)

INTER-rater agreement (between

3 different operators)

ICC (95% CI) ICC (95% CI)

Total deviation of apex 0.16 (0.11, 0.21) 0.61 (0.56, 0.65)

Lateral deviation of apex 0.21 (0.16, 0.26) 0.60 (0.56, 0.64)

Vertical deviation of apex 0.60 (0.56, 0.65) 0.55 (0.50, 0.60)

Lateral deviation of entry 0.14 (0.09, 0.20) 0.60 (0.56, 0.64)

Angular deviation of apex 0.66 (0.62, 0.69) 0.72 (0.69, 0.75)

76

Discussion

In this preclinical pilot study we have set out to investigate the accuracy of an

experimental dental implant surgical navigation system and validate applicability on a patient

population. We also compared the accuracy of our implant transfer and placement results to

freehand and static transfer methodologies. There are several possible sources of error in

accuracy in guided surgery, which might add up or compensate for each other [87]. These

deviations can result from errors in image processing, virtual planning, technical fabrication of

a surgical stent phase or during the surgery phase.

Image processing

During image acquisition, the brand of cbCT machine, its settings, the resulting voxel

size and the field of view will all influence the accuracy [11]. A recent study compared cbCT

images of human mandibles with the actual measurements and found that the cbCT

measurements tend to underestimate the distances by approximately 1 mm on a full arch’s

length [88] and very much depend on the unit used and the exposure settings [89]. Also, added

inaccuracy could follow incorrect positioning of the radiographic guide during image

acquisition, especially with a decreasing number of remaining dentition. We have used surgical

typodonts with only three teeth remaining in either jaw, which is close to edentulism, to

simulate a compromising situation, resembling real life cases. Since patient movement [90] did

not influence our image gathering, positioning of our radiographic stents was as accurate as

possible for all tested modalities. The resulting DICOM files were processed with the individual

softwares without any modifications. In the literature the mean error reported from image

processing and segmentation was <0.5 mm, which also might need to be taken into account

when analyzing results [87].

77

Virtual planning

Throughout the virtual planning phase the greatest care was taken to follow the

outlines of the osteotomies in the master cast. However, because of the low contrast

resolution, precise outlining of the borehole was not possible; therefore the closest spacing

was chosen symmetrically.

Technical fabrication of a surgical stent

For dynamic systems there is no need for a surgical guide in the traditional sense. The scanning

template is used as a reference for the fiducial markers, which in our case was molded

specifically in the mannequin, decreasing the chance of error. However, for static systems

fabrication of radiographic and surgical guides is necessary. Ideally, the guide should be made

out of a rigid material to avoid deformation and proper fitting for reproducibility of positioning.

During fabrication of surgical guides an error range of 0.1-0.2 mm was reported, which might

be due to human error or material properties, e.g shrinkage [87]. When it comes to

stereolithographically produced static guides, the reported error range of fit varied between

0.56-2.17 mm based on four systems, one of them being the NobelGuide (mean - 0.56 mm)

and another one the Simplant SurgiGuide (mean – 1.12 mm), which is ascribed to planning and

manufacturing errors, such as faulty ISO value setting in the planning software and different

production protocols [91].

Also, different systems require different preparatory steps. For the Simplant SurgiGuide

the cast was requested for manufacturing and the resulting guides were retentive and very

well fitting, just like the Straumann Guided Surgery templates, fabricated by a local laboratory.

The NobelGuide radiographic template was constructed in the same laboratory and scanned

with the double scanning procedure, required by the manufacturer. However, when the

surgical guide was received directly from the manufacturing facility, it did not fit the typodont

precisely and had to be slightly modified to achieve correct seating.

78

Surgery

The possible sources of error in the last part of the process, surgical application, are numerous.

Correct seating of the templates is of utmost importance in any system, since a minor error can

be amplified during drilling of the osteotomy at the apex level. With all the investigated

methods the error at entry level was always less than at the apex level with the same system,

which is supported by other studies (Tables 6 and 7) . According to Behneke et al. the

discrepancy depends on the amount of remaining teeth as well, the range of error in reduced

residual dentition was shown to be 2-3 times as much as in a single tooth gap osteotomy [54].

Since our typodonts represented a severely reduced dentition, our error ranges are in the

higher end of the spectrum in the reported data. According to a recent systematic review on

accuracy the mean deviation of entry was found to be 1.07 mm with static guides on cadavers

and models, which correspond to our relevant data with the static systems (0.76-0.9 mm) [92].

Also, the mean error at the apex was defined as 1.00-1.42 mm, which agreed to our data of

0.99-1.24 mm and the angular error as 4.70 mm, which can be related to our finding of 3.09-

4.24 mm.

Another possible source of error is the number of drills used; therefore we tried to

emulate surgical circumstances and followed the Straumann Guided Surgery Protocol in all

modalities with four drills, with the following diameters: 2.2, 2.8, 3.5 and 4.2 mm.

Furthermore, mechanical errors can also be caused by the incorrect angulation of the drills,

since the acrylic guides have some minimal flexibility (possibly cracks or lost sleeves), especially

if there is a Kennedy Class I or II situation [87]. Our data show significantly higher deviations in

the maxilla at the free end positions, but mostly in the vertical direction, less so laterally.

Restricted mouth opening can also interfere with instrument positioning, which is less of an

influence during freehand drilling and navigation surgery and in the anterior region of the

arches. Our data substantiate this finding, since we have found that both in the maxilla and

mandible the anterior osteotomies are more accurate than the posterior ones. Another

explanation for this phenomenon could also be that it is possible to use direct vision in the

anterior of both the mandible and maxilla, as opposed to the posterior, where visibility would

79

be more compromised. Furthermore, maxillary osteotomies showed higher deviations in

lateral error at the crest and angulation than the mandible in general, which might be due to

indirect vision.

During osteotomies, human mistakes can be considerable with all methods, such as not

utilizing the full length of the drill or not having the guide fully seated. Therefore it is

interesting to note that based on our data the most accurate vertical boreholes were achieved

with freehand drilling under visual guidance (0.31 mm) vs. all other methods (1.04-1.27 mm).

Another human variable is the surgeon’s dexterity – hand tremor and perception inaccuracies

were reported to cause deviations of up to 0.25 mm and 0.5 degrees in angulation [23]. All the

operators in our study were right handed, which eliminated a bias based on left or right side

inaccuracies in the osteotomies. In our dataset lateral deviation at entry was significantly

higher with freehand implant placement and the experimental navigation system, since they

were both placed without mechanical guidance. This was also true for the angular error, where

the manual placement showed significantly higher deviation than any other modality (9.18 vs

2.99-4.24˚). These latter data is higher than that reported in the literature previously [24], but

in contrast to that study the surgeons had no knowledge of the ‘ideal’, virtually planned

implant position. Therefore there are personal differences as to where an ‘ideal’ position

would be, which might result in diverse angulations. Also, a higher angular deviation observed

with NobelGuide could be explained by the difference in template fabrication, since it was

made out of the thinnest acrylic and allowed for some flexibility of the guide. This material

property might also explain the significantly higher horizontal error values of the osteotomies

in the free-end position of the maxilla.

A decisive factor is also the surgeon’s computer literacy, since there is a learning curve

in all systems, especially with navigation surgery. There is a significant paradigm shift, where

the operator has to accept and get used to following the surgery on the monitor instead of

intraorally, as well as the eye-hand coordination has to be mastered to translate lateral and

angle deviation information from the monitor to the patient. Another difference in thinking is

the prompt for corrections during drilling with the navigation systems. Since there is a live

80

feedback about position and angulation of the drill, one tends to correct for eventual mistakes

in position or angulation, which might lead to a funnel shaped osteotomy, possibly resulting in

reduced primary stability.

Often the use of guides is accompanied by flapless surgery to allow for better seating of

the surgical template and less morbidity than with a full mucoperiosteal flap reflection [93]. In

its simplest form this method involves a tissue punch device to gain access to the alveolar ridge

in a minimally invasive fashion. The technique has numerous advantages, such as preservation

of circulation, soft tissue architecture and hard tissue volume at the site; decreased surgical

time, improved patient comfort and accelerated healing, allowing the patient to revert to

normal hygiene routines earlier. The reported shortcomings include restricted visibility of

landmarks and vital structures, the potential for thermal damage secondary to reduced access

for irrigation during the drilling sequence of the osteotomy, the increased risk of malposed

angle or implant depth in case the surgical guide is misaligned, a decreased ability to contour

osseous topography and the surgeon’s inability to manipulate soft tissues to ensure sufficient

keratinized tissues around the implant structures [94].

Based on a recent systematic review [95], there were 115 technical and biologic

complications reported following flapless surgical placement of 4900 implants in 1086 patients

with at least a year of follow up. The greater part of these problems (69%) was in connection

with surgical procedures, while the rest with immediate loading. The most common

complication was surgical stent fracture, and misfit of the prosthesis. Hundred sixty-eight late

complications were noted, with 107 implant failures (3% of placed) and prosthesis fracture.

However, implant and prosthesis survival rates did not differ between guided and conventional

implant treatment. According to a different review summarizing 428 patient treatments [92],

the majority of early surgical complications (39 patients) consisted of limited access to surgical

site (25.6%) and the necessity of primary bone augmentation (20.5%). The top three causes of

the 13 recorded prosthetic complications were misfit of abutment to bridge (38.5%), extensive

adjustments of the occlusion (23.1%) and incomplete seating of prosthesis due to bony

interference (15.4%)

81

With dynamic guidance, some of these difficulties can be compensated for, some cannot. The

available dynamic systems introduce real time visualization of drill movements during

osteotomies on the patient’s previously acquired cbCT dataset with optic tracking of fiducial

markers. Therefore both static and dynamic methods require a cbCT scan of the patient, and a

well-fitting template for surgery. For spatial registration of the cbCT images, reference points

are used with both technologies. After importing the DICOM files into the specific softwares

and virtually planning implant positions, the static guides need to be manufactured in a

decentralized facility or dental laboratory, where either separate surgical templates are

fabricated or the scanning templates are transformed into surgical guides and titanium sleeves

are inserted. Sometimes there is a difficulty fitting the titanium sleeves, especially if the

mesiodistal space is limited and narrow implants need to be used. The dynamic reference

templates or fiducial markers can be used in the same form and shape as they were scanned

and after insertion into the patient’s mouth the incorporated fiducial markers are recognized

with an attached camera. The accuracy of the latter system can be verified with touching

anatomical reference points, while the static guides cannot be easily controlled because of the

extent of the flanges and limited transparency of the devices. Also, because of the extent of

the static templates and the intimate fit of the inserted titanium sleeves for drill guidance,

cooling of the bits is difficult and might cause overheating of the bone; whereas with dynamic

systems the reference templates can be relieved around the surgical site to provide better

access. For the same reason dynamic systems provide an easier approach to posterior regions

or in case of limited mouth opening [46].

Moreover, it is impossible to change surgical plans once the static guides were

fabricated, while it can be carried out relatively easily with the dynamic systems. In contrast,

the intraoperative handling of static guides is less complicated in comparison to navigation

systems as there is no necessity to handle extra equipment. With navigation, usually there is a

learning curve of different software and hardware components and the system setup before

surgery might be intricate and time consuming. Also, one needs to be careful not to impinge

on the line of sight between the camera and the trackers, as the system would cease to

82

provide navigation feedback. The cost-benefit ratio might be similar in the long run; however

both methods require purchasing either a costly software package or an even costlier

navigation device in the beginning. The static guides will continue to pose an extra expense

with every purchased one, but the navigation systems usually do not incur an extra fee after

the initial investment.

To come around some of the current inadequacies of the existing navigation systems, within

the scope of this study a visible light experimental navigation system was developed and

tested. In performing its main functions, the device had a straightforward user interface; even

dentists with very minimal training in the system's operation could be able to obtain

satisfactory results with minimal guidance. The calibration of the drill axis and tip was very fast

and straightforward, adjustment simple whenever necessary. The system would allow for

navigated implant placement if the implant apex was calibrated instead of the drill tip. Three

operators have tested the system and found that there was a minimal difference between

initial and later results, as opposed to the learning curve of the other methods (Tables 12-26).

The overall accuracy of the system was comparable to that of the static guides and (Tables 8-

11) and previously reported data on different navigation systems [46]. The system did not

introduce major interferences in the preclinical implantation work environment. Specifically,

the operator’s time investment for each case was not substantially higher than that required

for static surgical drill guides, as well as navigation system setup and tear-down was quick and

simple. The surgical navigation system’s intra-oral device did not take up a considerable

amount of space and did not interfere with irrigation of the drilling sites. Finally, the drill and

surgical navigation system setup and line of sight requirements did not considerably

inconvenience the dentist and their assistance.

Clinical relevance

Our investigation was conducted as a pilot study to establish the applicability and accuracy of a

novel surgical navigation system in a preclinical setting; to validate and further investigate later

in humans. In this arrangement, we used mannequins in our clinics to simulate a real surgical

83

environment as close as possible. The typodonts employed are specifically designed for

implant surgery, with an electron density and clinical bone density that closely resembles that

of a human maxilla or a mandible, with a silicone lining that emulates gingiva. The results

acquired should reasonably be comparable to that of other studies in similar settings, but

probably show less accuracy than a controlled bench top, laboratory setting.

The results show a reasonable accuracy when one considers the means of the different

methods. The lateral accuracy ranges from 0.76 to 1.19 mm at the entry and 0.99 to 1.82 mm

at the apex. These values are clinically acceptable, well within the 2 mm safety range that is

suggested in most implant manufacturers’ protocols. However, if one considers the maximum

errors measured, the range is lot higher, 2.92 to 4.95 mm at the entry and 3.19 to 5.99 mm at

the apex, not necessarily the manual surgery showing the worst outliers. When one scrutinizes

the results regarding vertical inaccuracies, they show a similar tendency. The means range

from 0.31 (for manual implant placement) to 1.27 mm, which again is well within the 2 mm

safety range. In comparison, the maximum deviations vary from 3.34 to 4.81 mm, which paints

a scarier picture – the safety reported with static guides is acceptable on average, but it might

show dangerous deviations in selected cases, meaning possible nerve damage, bleeding, injury

to the maxillary sinus, nasal cavity or adjacent teeth.

The axis deviation data are less important for damage to vital structures, but absolutely

necessary for future prosthetic rehabilitation. Our reported mean values range from 2.99 to

9.18 degrees (manual placement), but the outliers are surprisingly high across all systems

examined from 11.94 to 20.79 degrees. Today, when there is a considerable effort to restore

patients’ dentitions in the shortest possible time with the least amount of post-surgical

morbidity, flapless surgeries with immediate implant and prosthesis placement have become

widely practiced. However, the latest reports show that the inaccuracies can cause various

complications following such procedures, which might be due to inaccurate implant

placement, as shown by the high variation of data or imprecise prosthesis fabrication [96-102].

Taken all together, there are countless sources of error when applying guided surgery, some

dependent on the operator, some not. Therefore one needs to use ample precaution and

84

continuous self-assessment during all steps of the planning, transfer and surgical procedure to

avoid possible iatrogenic results for the patient.

85

Summary

We have implemented a new experimental surgical navigation system and determined that it

was reasonably accurate for implant transfer and placement in typodonts in a near clinical

setting. Furthermore, we have also established implant transfer and placement accuracy in

typodonts in a near clinical setting in four commercially available static planning and transfer

systems. We compared the above results obtained with the experimental surgical navigation

system with those four commercially available static planning and transfer systems and

established that the static and dynamic guiding systems provide superior accuracy related to

manual implant placement, except vertically.

We ascertained that there were discrepancies in accuracy between the upper and

lower jaw, the upper jaw being less accurate in lateral deviations. There was also a significant

difference in the accuracy of implants placed in free-end positions as opposed to anterior sites.

We demonstrated that all operators exhibited an initial learning curve with the different

planning and transfer systems.

86

Conclusions

Based on our results, the null hypothesis, that the accuracy of an experimental surgical

navigation system is not better than commonly used freehand methods for the positioning the

placement of dental implants, could be rejected. However, the alternative hypothesis that the

experimental surgical navigation system facilitates accurate placements of dental implants

could not be rejected, since the performance of the system was comparable to that of static

guides.

87

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