Buccal Bone Changes With Self Ligating Brackets Versus Conventional Brackets. A

Comparative Study

Thesis

Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the

Graduate School of The Ohio State University

By

Sahira Ibrahim Kortam, B.D.S., M.Sc.

Graduate Program in Dentistry

The Ohio State University

2010

Master‟s Examination Committee:

Dr. Do-Gyoon Kim, Advisor

Dr. Henry Fields

Dr. Martin Palomo

Dr. William Johnston

Copyright by

Sahira Ibrahim Kortam

2010

ii

ABSTRACT

Introduction: Self ligating brackets (SLB) manufacturers claim that expansion of arches and

alveolar bone building is facilitated by their bracket design. The objective of this study was to

determine whether SLB brackets have a different effect on buccal bone changes compared with

conventional brackets (NSLB) during orthodontic treatment. Methods: Cone beam computed

tomography (CBCT) images were obtained before and after treatment of 45 patients (26 treated with

conventional brackets (NSLB) and 19 with SLB). The CBCT images were compared between

groups for buccal bone height and thickness at the maxillary first molars, maxillary second and first

premolars using imaging software. The intermolar distance and buccolingual angulation were

assessed for the maxillary first molars as potentially confounding factors. Differences for each

variable measured before and after treatment were compared between the two groups. Results:

Initial and final thickness and height of buccal bone were significantly different between the teeth (p

<0.001). The buccal bone height (p <0.001) and thickness (p= 0.018) significantly decreased after

treatment for both groups. The mean changes of buccal bone height and thickness measured were not

significantly different between SLB and NSLB groups (p>0.05). The intermolar distance and molar

angulation changes were not significantly different between the 2 groups (p >0.05). The change in

bone height depended on the initial bone thickness where the greater the initial bone thickness, the

less the decrease in bone height (p <0.01). The change in bone thickness was affected by the change

iii

in intermolar distance where the bone thickness decreased when the intermolar distance increased (p

<0.01). Conclusions: The buccal bone changes during orthodontic treatment regardless of which

bracket type is used. Based on these data and those from RME studies, the implication is that, in the

absence of other data, there is a trend that increased arch dimensions may lead to adverse bony

changes depending on the patient‟s initial bony status. Arch expansion and molar angulation can be

similarly controlled by either type of appliance.

iv

Dedicated to my family

v

ACKNOWLEDGMENTS

I would like to thank my Thesis committee, Dr. Do-Gyoon Kim, Dr. Henry Fields, Dr.

Martin Palomo and Dr. William Johnson for their time and tremendous effort.

I would like to thank faculty, residents and staff of Case Western Reserve University for their

tireless support in gathering data and making this project successful.

I would like to thank the faculty, residents and staff of The Ohio State University Section of

Orthodontics.

I would like to thank Paul Geuy for his diligent work in helping with the measurements.

I would like to recognize the financial support for this research provided by the Dental

Master‟s Thesis Award Program sponsored by Delta Dental Foundation which is the philanthropic

affiliate of Delta Dental of Michigan, Ohio, and Indiana.

Lastly, I would like to thank my family for their love and support over the years.

vi

VITA

Feb. 8, 1974…………………………Born- Cairo, Egypt

1998………………………………....B.D.S. Cairo University, Egypt

2005…………………………………M.Sc. Cairo University, Egypt

2007-present………………………Graduate Resident in Orthodontics

The Ohio State University

Columbus, Ohio

FIELDS OF STUDY

Major Field: Dentistry

Specialty: Orthodontics

vii

TABLE OF CONTENTS

Page

Abstract………………………………………………………………...ii

Dedication……………………………………………………………...iv

Acknowledgments……………………………………………………..v

Vita…………………………………………………………………….vi

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

List of Figures…………………………………………………………..ix

Chapters:

1. Introduction………………………………………………………..1

2. Materials and Methods…………………………………………….25

3. Manuscript……..…………………………………………………..30

4. Discussion and Conclusions………………………………………..53

Bibliography……………………………………………………………57

viii

LIST OF TABLES

Table Page

3.1 Demographic distribution of patients studied……………………………48

3.2 Means and standard deviations for the initial, final and change in bone

height… ………………………………………………………………….48

3.3 Means and standard deviations for the initial, final and change in bone

thickness …………………………………………………………………48

3.4 Means and standard deviations for the initial, final and change in intermolar

distance .………………………………………………………………….49

3.5 Means and standard deviations for the initial, final and change for molar

angulation…………………………………………..….…………………49

ix

LIST OF FIGURES

Figure Page

3.1 The orientation was set to be parallel to the occlusal plane of the first molar;

the cut was done at the level of the cementoenamel junction. The trough was

drawn to bisect the maxillary first molar..…………………………..………44

3.2 Buccal bone height and thickness measurements…………………………...45

3.3 Landmark identification for buccolingual angulation and intermolar distance

measurements……………………………………………………………….46

3.4 Buccolingual angulation and intermolar distance measurements…………...47

1

CHAPTER 1

INTRODUCTION

Self ligating brackets (SLB) have received much popularity in the past few years. Many

manufacturers offer SLB indicating the increased demand of this product. They are not new in

orthodontics. They were introduced in the early 20th century with the „Russell Lock‟ edgewise

attachment being described in 1935.1 Some early SL brackets were the Ormco Edgelok (1972),

Forestadent Mobil-Lock (1980), Orec SPEED (1980), and “A” Company Activa (1986).2 Other

designs have appeared including the Time bracket in 1994, the Damon SL bracket in 1996, the

TwinLock bracket in 1998, and the Damon 2 and In-Ovation brackets in 2000.1 Currently, the

popular SLB are Damon, Time, Speed, SmartClip, and In-Ovation R.3

SLB have an inbuilt labial face, which can be opened and closed.

4 They are promoted on the

premise that elimination of ligatures reduces friction and allows for better sliding mechanics.

SLB can be dichotomized into those with a spring clip that can press against the archwire

(active) and those with a passive system of ligation, in which the clip, ideally, does not press against

the wire. However, the term “passive” is somewhat of a misnomer because it is passive only when

teeth are ideally aligned in 3 dimensions (torque, angulation, and inout), and an undersized wire

would not touch the walls of the bracket slot. Examples of active brackets are In-Ovation “R” (GAC

International, Bohemia, NY), SPEED (Strite Industries, Cambridge, Ontario, Canada), and Time

2

(American Orthodontics, Sheboygan, Wis). Examples in the passive group are the Damon bracket

(Ormco.Glendora, Calif) and the SmartClip bracket (3M Unitek, Monrovia, Calif).3

Despite the presentation of much empirical and anecdotal evidence, no documented evidence

exists on the manufacturer's claims on the efficiency of self-ligating brackets in both, space closure

and torque control. This is particularly intriguing because of the contradictory demands involved in

the mechanotherapeutic setup for these cases, as space closure with sliding mechanics requires low

friction, whereas torque control necessitates the development of frictional forces between the wire

and the bracket slot walls.5

Various claims are made by SLB manufacturers. For example, some of these claims are

increased patient comfort, better oral hygiene, increased patient cooperation, less chair time, shorter

treatment time, greater patient acceptance, and expansion. Sound scientific evidence is needed

before we accept manufacturers‟ claims about SLB. Unfortunately, the evidence for most claims is

lacking.3

The Damon system claims that using biologically sensible forces which work with the body‟s

natural adaptive processes will create space naturally so most cases can be treated without extraction

and without the need for headgear or palatal expanders.

They also claim that posttreatment CT image shows transverse arch development and normal

alveolar bone on lingual and buccal surfaces. Low friction and low force are purported to be good

for physiologically rebuilding the alveolar bone.6

On the other hand, excessive expansion can force the teeth through the cortical plate.7 This

can ultimately cause bone dehiscence, and gingival recession.8

3

The three-dimensional capability of cone-beam computed tomography (CBCT) technology

makes it possible to assess alveolar bone loss for posterior teeth 9 where buccal bone defects can be

detected and quantified. 10

REVIEW OF THE LITERATURE

Self ligating brackets (SLB) versus conventional brackets (NSLB)

Various researchers have conducted studies to investigate the differences between SLB and NSLB.

Frictional resistance:

Several investigators11,

12,13,

14,

15,

16,

17,

18,

19, 20,

21

found that SLB had lower frictional

resistance than conventional brackets.

Kusy and Whitley22

divided resistance to sliding into 3 components: (1) friction, static or

kinetic due to contact of the wire with bracket surfaces; (2) binding, created when the tooth tips or

the wire flexes so that there is contact between the wire and the corners of the bracket (3) notching,

when permanent deformation of the wire occurs at the wire-bracket corner interface. This often

occurs under clinical conditions. Tooth movement stops when a notched wire catches on the bracket

corner and resumes only when the notch is released.

Burrow23

in 2009 pointed out that the clinical advantage of reduced resistance to sliding

should be a reduction in the amount of time to align the teeth and close the spaces. Several clinical

studies found no evidence to support the claim of reduced treatment time with self-ligating

4

brackets.24,

25,

26,

1 He concluded that a binding and releasing phenomenon, not frictional resistance,

is the major determinant of how well bracketed teeth move along an archwire and that is about the

same with conventional and self-ligating brackets.

Treatment duration:

Several investigators assessed the treatment efficiency of SLB. Damon27

in 1998 stated that

the self-ligating bracket design allowed for rapid leveling because teeth drifted along the path of

least resistance with little or no friction between the bracket and slot of the wire. Thus, this system

was capable of increasing the appointment intervals, and possibly reducing the overall treatment

time.

Harradine2 in 2001 found that SLB cases required an average of four fewer months and four

fewer visits to be treated to an equivalent level of occlusal regularity as measured by the PAR scores.

Eberting et al28

in 2001 found an average reduction in treatment time of 6 months (from 31 to 25)

and 7 visits (from 28 to 21) for SLB patients compared with conventional ligation patients.

On the other hand, several clinical studies found no evidence to support the claim of reduced

treatment time with self-ligating brackets. Miles26

in 2005 concluded that SLB were no more

effective in reducing irregularity than NSLB. Miles et al25

in 2006 found that SLB were no better

during initial alignment than a conventional bracket. Also in 2007, Miles1 compared the rate of en-

masse space closure and found that there was no significant difference in the rate of en-masse space

closure between SLB and NSLB. Scott et al29

in 2008 concluded that SLB were no more efficient

than NSLB during tooth alignment. Hamilton et al30

in 2008 conducted a study to determine if self-

5

ligating brackets are more efficient. They concluded that SLB appear to offer no measurable

advantages in orthodontic treatment time, number of treatment visits and time spent in initial

alignment over NSLB. Fleming et al31

in 2009 concluded that efficiency of alignment in the

mandibular arch in nonextraction patients is independent of bracket type.

Torque control:

Pandis et al5 in 2006 found that self-ligating brackets were equally efficient in delivering

torque to maxillary incisors relative to conventional brackets in extraction and non-extraction cases.

Badawi et al32

examined the torque expression of 2 active self-ligating brackets (In-Ovation,

GAC, Bohemia, NY; Speed, Strite Industries, Cambridge, Ontario, Canada) and 2 passive self-

ligating brackets (Damon2, Ormco, Orange, Calif; Smart Clip, 3M Unitek, Monrovia, Calif) using a

bracket/wire assembly torsion device. They concluded that active self-ligating brackets were more

effective in torque expression than passive self-ligating brackets.

Morina et al33

in 2008 examined the torque expression of active and passive self-ligating

brackets compared with metallic, ceramic, and polycarbonate edgewise brackets. Six types of

orthodontic brackets were included in the study: the self-ligating Speed and Damon2, the stainless

steel (SS), Ultratrimm and Discovery, the ceramic bracket, Fascination 2, and the polycarbonate

bracket, Brillant. All brackets had a 0.022-inch slot size and were torqued with 0.019 x 0.025-inch

SS archwires. The ceramic bracket (Fascination 2) presented the highest torquing moment and,

together with a SS bracket, the lowest torque loss (4.6 degrees). Self-ligating, polycarbonate, and

6

selective metallic brackets demonstrated almost a 7-fold decreased moment developed during

insertion and a 100 per cent increase in loss.

Transverse dimensions:

Tecco et al34

in 2009 evaluated the transverse dimensions of the maxillary arch induced by

fixed self-ligating and traditional straight-wire appliances during orthodontic therapy. Forty

consecutive patients (age range 14 to 30 years) with normal or low mandibular plane angle, normal

overbite, and mild crowding were included. The traditional appliance was composed of Victory

Series MBT brackets (3M Unitek), and the self-ligating appliance of Damon-3MX brackets

(Ormco). Intercanine, first and second interpremolar, and intermolar widths in the maxilla were

recorded before treatment (T0) and 12 months later (T1). They found in both groups, a significant

increase was recorded for all transverse measurements from T0 to T1, but no significant difference

was observed between groups. They concluded that within 12 months of treatment, both appliances

increased maxillary dentoalveolar widths.

Other researchers investigated the mandibular dental arch changes. Mandibular arch

alignment resulted in transverse expansion and incisor proclination irrespective of the appliance

system used. However a statistically greater increase in intermolar width in the group treated with

the self-ligating appliance, the difference was only 0.91 mm by Fleming et al35

; 1.3 mm by Pandis et

al36

and 0.77 mm by Jiang and Fu37

. On the other hand, Scott et al29

found no significant difference

for either bracket system where their patients had premolar extractions.

7

Periodontal condition:

Pandis et al38

in 2008 investigated the periodontal condition of the mandibular anterior

dentition in patients with conventional and self-ligating brackets to explore whether the use of self-

ligating brackets is associated with better values for periodontal indices because of the lack of

elastomeric modules and concomitantly, reduced availability of retentive sites for microbial

colonization and plaque accumulation. They concluded that the self-ligating brackets do not have an

advantage over conventional brackets with respect to the periodontal status of the mandibular

anterior teeth.

Pellegrini et al39

in 2009 examined plaque retention by self-ligating vs elastomeric

orthodontic brackets. They concluded that self ligating appliances promote reduced retention of oral

bacteria.

Pandis et al40

in 2010 investigated the salivary Streptococcus mutans levels in patients with

conventional and self-ligating brackets. No difference was found in the oral hygiene indices between

the two groups. The levels of S. mutans in whole saliva of orthodontically treated patients were not

significantly different between conventional and self-ligating brackets.

Systematic reviews:

Fleming and Johal41

in 2010 conducted a systematic review to evaluate the clinical

differences (alleviation of irregularity using Little‟s irregularity index, rate of orthodontic space

closure, dimensional changes during orthodontic alignment, plaque retention, extent of root

resorption developing during treatment, and attachment debond rate) in relation to the use of self-

8

ligating brackets in orthodontics. They concluded that at this stage there is insufficient high-quality

evidence to support the use of self-ligating fixed orthodontic appliances over conventional appliance

systems or vice versa.

Ehsani et al42

in 2009 conducted a systematic review on frictional resistance in self-ligating

orthodontic brackets and conventionally ligated brackets in vitro. They concluded that compared

with conventional brackets, self-ligating brackets produce lower friction when coupled with small

round archwires in the absence of tipping and/or torque in an ideally aligned arch. Sufficient

evidence was not found to claim that with large rectangular wires, in the presence of tipping and/or

torque and in arches with considerable malocclusion, self-ligating brackets produce lower friction

compared with conventional brackets.

Rapid maxillary expansion studies and buccal bone

The effect of rapid maxillary expansion on buccal bone has been investigated utilizing

computed tomography.

Ballanti et al43

in 2009 investigated by low-dose computed tomography (CT) protocol the

dental and periodontal effects of rapid maxillary expansion (RME). Their sample comprised 17

subjects (7 males and 10 females), with a mean age of 11.2 years. Each patient underwent expansion

of 7 mm. Multislice CT scans were taken before rapid palatal expansion (T0), at the end of the active

expansion phase (T1), and after a retention period of 6 months (T2). All interdental transverse

measurements were significantly increased at both T1 and T2 with respect to T0. In the evaluation of

T0-T1 changes, a significant reduction in buccal alveolar bone thickness of maxillary molars with

9

the greatest amount of bone resorption being 0.4mm. In the evaluation of changes between the end

of active expansion (T1) and the end of retention (T2), and of overall T0-T2 changes, periodontal

measurements were significant on the lingual aspects, but not on the buccal side.

Rungcharassaeng et al44

in 2007 used cone-beam computed tomography (CBCT) images to

determine the factors that might affect buccal bone changes of maxillary posterior teeth after rapid

maxillary expansion. They found that buccal crown tipping and reduction of buccal bone thickness

and buccal marginal bone level of the maxillary posterior teeth are immediate effects of RME.

Factors that showed significant correlation to buccal bone changes and dental tipping were age,

appliance expansion, initial buccal bone thickness, and differential expansion, but rate of expansion

and retention time had no significant association.

Garib et al45

in 2006 examined the periodontal effects of rapid maxillary expansion with

tooth-tissue-borne and tooth-borne expanders by computed tomography. Their sample comprised 8

girls, 11 to 14 years old. The appliances were activated 7-mm. Spiral CT scans were taken before

expansion and after the 3-month retention period when the expander was removed. They found that

RME reduced the buccal bone plate thickness of supporting teeth 0.6 to 0.9 mm and increased the

lingual bone plate thickness 0.8 to 1.3 mm. RME induced bone dehiscences on the anchorage teeth‟s

buccal aspect where there was a significant reduction of alveolar crest level of 7.1 ± 4.6mm at the

first premolars and 3.8 ± 4.4 mm at the mesiobuccal area of the first molars. They found a negative

statistically significant correlation between the thickness of the buccal alveolar crest at treatment

onset and the alveolar crest level changes after expansion.

10

CBCT validity

Several studies have been conducted to examine the validity and reliability of linear and

angular measurements made on CBCT images. Others examined the ability of CBCT to detect

periodontal bone defects.

Kau et al46

in 2010 analyzed CBCT scans of 30 subjects using InVivoDental (Anatomage,

San Jose, Calif) software. They concluded that CBCT digital models are as accurate as OrthoCAD

digital models in making linear measurements for overjet, overbite, and crowding measurements.

Moreira et al47

in 2009 researched the precision and accuracy of maxillofacial linear and

angular measurements obtained by cone-beam computed tomography (CBCT) images. They utilized

15 dry human skulls that were submitted to CBCT. Linear and angular measurements based on

conventional craniometric anatomical landmarks, and were identified in CBCT images by 2

radiologists on two occasions, independently. Subsequently, physical measurements were made by a

third examiner using a digital caliper and a digital goniometer. Regarding accuracy tests, no

statistically significant differences were found from the comparison between the physical and

CBCT-based linear and angular measurements for both examiners. The mean difference between the

physical and 3D-based linear measurements varied from 0.04 to −0.27 mm. The highest difference

between the physical and 3D-based angular measurements was 2.76° and the lowest value was

−0.03%. They concluded that CBCT images can be used to obtain dimensionally accurate linear and

angular measurements from bony maxillofacial structures and landmarks.

Baumgaertel et al48

in 2009 investigated the reliability and accuracy of dental measurements

made on cone-beam computed tomography (CBCT) reconstructions. Thirty human skulls were

scanned with dental CBCT, and 3-dimensional reconstructions of the dentitions were generated. Ten

11

measurements (overbite, overjet, maxillary and mandibular intermolar and intercanine widths, arch

length available, and arch length required) were made directly on the dentitions of the skulls with a

high-precision digital caliper and on the digital reconstructions with commercially available

software. They concluded that dental measurements from CBCT volumes can be used for

quantitative analysis. They found a small systematic error, which became statistically significant

only when combining several measurements.

Stratemann et al49

in 2008 conducted a study to determine the accuracy of measuring linear

distances between landmarks commonly used in orthodontic analysis on a human skull using two

cone beam CT (CBCT) systems; the NewTom® QR DVT 9000 (Aperio

Inc, Sarasota, FL) and the

Hitachi MercuRay (Hitachi Medico Technology, Tokyo, Japan). For the CB MercuRay, the mean

absolute error to the gold standard caliper measurements for the human skull was 0.00±0.22 mm,

with a median of 0.01 mm and a range of –0.39 mm to 0.24 mm. The

error was slightly smaller in the

CB MercuRay than in the NewTom. They concluded that the volumetric data rendered with both

CBCT systems provided highly accurate data compared with the gold standard

of physical measures

directly from the skulls, with less than 1% relative error.

Mol and Balasundaram,9 in 2008 assessed the accuracy of NewTom 9000 cone beam

CT

images for the detection and quantification of periodontal bone defects in three dimensions. A

sample of 146 sites in 5 dry skulls provided the ground truth. Half of the sample had bone loss of at

least 3 mm. Measurements on the CBCT images were compared to measurements on a full mouth

X-ray series. They concluded that the NewTom 9000 cone beam CT scanner provides better

diagnostic and quantitative information on periodontal bone levels in three dimensions than

conventional radiography. The accuracy in the anterior aspect of the jaws is limited.

12

Misch et al10

in 2006 evaluated the accuracy of cone beam computed tomography for

periodontal defect measurements. Artificial osseous defects were created on mandibles of dry skulls.

CBCT scanning, periapical radiography (PA), and direct measurements using a periodontal probe

were compared to an electronic caliper that was used as a standard reference. All bony defects were

identifiable and measurable directly or with CBCT. In comparison, buccal and lingual defects could

not be measured with radiographs. They concluded that all three modalities are useful for identifying

interproximal periodontal defects and that compared to radiographs, the three-dimensional capability

of CBCT offers a significant advantage because all defects including buccal and lingual defects can

be detected and quantified.

Orthodontic treatment and periodontal condition

Huynh-Ba et al50

in 2010 analyzed the socket bone wall dimensions in the upper maxilla in

relation to immediate implant placement. At the time of extraction of the tooth and after the tooth

had been removed, intra-operative measurements of the socket, including the width of the buccal and

palatal walls of the sockets were recorded. The width was measured 1mm apical to the alveolar crest

level. Premolars buccal bone thickness mean was 1.1mm (range: 0.5–3mm, SD 0.5mm).

The relationship between orthodontic treatment and the periodontal condition has been

investigated in various studies.

A systematic review by Bollen et al51

in 2008 found that subjects in the orthodontically

treated group had, on average, a pocket depth 0.3 millimeter deeper

than that of subjects in the

untreated groups. The mean alveolar bone loss was 0.13 mm greater among the groups that had been

13

orthodontically treated than among the groups that had not. The orthodontically

treated

group had

gingival recession 0.03 mm greater than did the untreated group.

Allais and Melsen52

in 2003 evaluated the association between the extent of labial movement

of the lower incisors and the prevalence and severity of gingival recession in orthodontically treated

adult patients. They analyzed study casts and intra oral slides of 300 adult patients. One hundred and

fifty pairs matched by age and sex were selected using simple random sampling. Although the

difference in prevalence of individuals with gingival recession among cases and controls was

statistically significant, no significant difference in the mean recession value could be found between

cases and controls. The mean value of the extent of recession of the four lower incisors amounted to

0.36 mm for treated subjects and 0.22 mm for the controls. This mean difference of 0.14 mm was not

clinically relevant. They recommended that labial movement of lower incisors is a valuable

alternative to extraction leading to no clinically relevant deterioration of the periodontium.

Janson et al53

in 2003 compared the heights of the alveolar bone crests among orthodontic

patients treated with either the standard edgewise technique, the edgewise straight-wire system, or

bioefficient therapy. These 3 groups were compared with an untreated control group. The first

premolars were extracted in every treated patient, and measurements were performed on bitewing

radiographs taken after a mean posttreatment period of 2.17 years. The distances from the AC to the

cementoenamel junction (CEJ) on the mesial and distal surfaces of the first molars and second

premolars and on the distal surface of the canines were measured. All treated groups had larger,

statistically significant CEJ-AC distances than the untreated group, primarily at the extraction areas.

14

Thomson54

in 2002 examined the long term outcomes of orthodontic treatment. According to

his findings, there were no significant differences in caries experience, periodontal disease

occurrence, or tooth loss between those who had and had not been treated by the age of 26.

Bondemark55

in 1998 investigated the periodontal condition for two groups of 20

adolescents, one treated orthodontically and one untreated, and followed them longitudinally for 5

years. The interdental alveolar bone level was estimated as the distance between the cementoenamel

junction and the alveolar bone crest on bite-wing radiographs of the upper and lower premolars and

molars on three occasions, the first at the start of treatment, the second after 2.8 years, and the third

at the end of the 5-year study period. At the start of this study, no significant difference in alveolar

bone level between treated and untreated groups was found. It was demonstrated that there was a

small but significant decrease in interdental alveolar bone support ranging between 0.1 and 0.5 mm

during the 5-year observation period both in the treated and untreated group. Neither group had any

sites with clinically significant bone loss, i.e., a distance > 2 mm between the cementoenamel

junction and the alveolar bone crest.

Jager et al56

in 1990 examined the long term influence of orthodontic mandibular arch

expansion therapy on the periodontal condition of the posterior teeth. 11 years after the end of

treatment, 31 former patients were compared with a control group of matched age and sex

distribution. They found some additional loss of periodontal attachment for the treated group,

however the differences were not considered to be of clinical significance.

Zachrisson and Alnaes57, 58

in 1973 and 1974 examined 51 patients with Cl II Div. 1

malocclusion treated with all first premolars extracted. The treatment duration was 19.1 months; the

15

mean age of the patients was 16.2 years. They selected 54 individuals to match the treated group.

The patients were examined 2 years after finishing orthodontic treatment. They clinically found the

orthodontic patients to demonstrate slightly but significantly more loss of attachment than the

control group. Radiographically the orthodontic patients showed more alveolar bone loss than did

the control group.

Statement of the Problem

Based on this review of the literature, several aspects of differences between SLB and NSLB

have been studied however there are no reports that investigated the difference in the buccal bone

changes between the SLB and NSLB. Several studies have investigated the buccal bone changes

with rapid maxillary expansion and indicated that bone loss occurs with expansion. Several clinical

studies indicate that orthodontic treatment can have a mild detrimental effect on the periodontium

but there is limited quantitative data. There are limited reports that compared the arch dimension

changes but none compared the angulation changes for the posterior teeth. This study will examine

the buccal bone changes and will investigate the difference in posterior arch dimensions and molar

angulation for the different types of brackets.

Specific Aim and Hypothesis to be tested

The specific aim is to compare the changes in buccal bone and buccal angulation of posterior

teeth after orthodontic treatment with SLB or conventional brackets and to determine if the change

in tooth position affects the buccal bone changes.

The first null hypothesis is that there is no difference between patients treated with SLB or

conventional brackets for buccal bone changes (buccal bone height and buccal bone thickness).

16

The second null hypothesis is that there is no difference between patients treated with SLB or

conventional brackets for buccal angulation of posterior teeth and intermolar distance.

The third null hypothesis is that the change in buccal angulation of posterior teeth and intermolar

distance does not affect the buccal bone changes (buccal bone height and buccal bone thickness).

References

1. Miles PG. Self-ligating vs conventional twin brackets during en-masse space closure with sliding

mechanics. Am J Orthod Dentofacial Orthop. 2007 Aug;132(2):223-5.

2. Harradine NW. Self-ligating brackets and treatment efficiency. Clin Orthod Res. 2001

Nov;4(4):220-7.

3. Rinchuse DJ, Miles PG. Self-ligating brackets: present and future. Am J Orthod Dentofacial

Orthop. 2007 Aug;132(2):216-22.

4. Harradine NW. Self-ligating brackets: where are we now? J Orthod. 2003 Sep;30(3):262-73.

5. Pandis N, Strigou S, Eliades T. Maxillary incisor torque with conventional and self-ligating

brackets: a prospective clinical trial. Orthod Craniofac Res. 2006 Nov;9(4):193-8.

6. Yu YL, Qian YF. The clinical implication of self-ligating brackets. Shanghai Kou Qiang Yi Xue.

2007 Aug;16(4):431-5.

7. GEiger AM. Mucogingival problems and the movement of mandibular incisors: a clinical review.

Am J Orthod. 1980 Nov;78(5):511-27.

17

8. Engelking G, Zachrisson BU. Effects of incisor repositioning on monkey periodontium after

expansion through the cortical plate. Am J Orthod. 1982 Jul;82(1):23-32.

9. Mol A, Balasundaram A. In vitro cone beam computed tomography imaging of periodontal bone.

Dentomaxillofac Radiol. 2008 Sep;37(6):319-24.

10. Misch KA, Yi ES, Sarment DP. Accuracy of cone beam computed tomography for periodontal

defect measurements. J Periodontol. 2006 Jul;77(7):1261-6.

11. Berger JL. The influence of the SPEED bracket's self-ligating design on force levels in tooth

movement: a comparative in vitro study. Am J Orthod Dentofacial Orthop. 1990 Mar;97(3):219-28.

12. Sims AP, Waters NE, Birnie DJ, Pethybridge RJ. A comparison of the forces required to produce

tooth movement in vitro using two self-ligating brackets and a pre-adjusted bracket employing two

types of ligation. Eur J Orthod. 1993 Oct;15(5):377-85.

13. Shivapuja PK, Berger J. A comparative study of conventional ligation and self-ligation bracket

systems. Am J Orthod Dentofacial Orthop. 1994 Nov;106(5):472-80.

14. Read-Ward GE, Jones SP, Davies EH. A comparison of self-ligating and conventional

orthodontic bracket systems. Br J Orthod. 1997 Nov;24(4):309-17.

15. Pizzoni L, Ravnholt G, Melsen B. Frictional forces related to self-ligating brackets. Eur J

Orthod. 1998 Jun;20(3):283-91.

18

16. Thomas S, Sherriff M, Birnie D. A comparative in vitro study of the frictional characteristics of

two types of self-ligating brackets and two types of pre-adjusted edgewise brackets tied with

elastomeric ligatures. Eur J Orthod. 1998 Oct;20(5):589-96.

17. Loftus BP, Artun J, Nicholls JI, Alonzo TA, Stoner JA. Evaluation of friction during sliding

tooth movement in various bracket-arch wire combinations. Am J Orthod Dentofacial Orthop. 1999

Sep;116(3):336-45.

18. Thorstenson GA, Kusy RP. Resistance to sliding of self-ligating brackets versus conventional

stainless steel twin brackets with second-order angulation in the dry and wet (saliva) states. Am J

Orthod Dentofacial Orthop. 2001 Oct;120(4):361-70.

19. Cacciafesta V, Sfondrini MF, Ricciardi A, Scribante A, Klersy C, Auricchio F. Evaluation of

friction of stainless steel and esthetic self-ligating brackets in various bracket-archwire

combinations. Am J Orthod Dentofacial Orthop. 2003 Oct;124(4):395-402.

20. Matarese G, Nucera R, Militi A, Mazza M, Portelli M, Festa F, et al. Evaluation of frictional

forces during dental alignment: an experimental model with 3 nonleveled brackets. Am J Orthod

Dentofacial Orthop. 2008 May;133(5):708-15.

21. Cordasco G, Farronato G, Festa F, Nucera R, Parazzoli E, Grossi GB. In vitro evaluation of the

frictional forces between brackets and archwire with three passive self-ligating brackets. Eur J

Orthod. 2009 Dec;31(6):643-6.

19

22. Kusy RP, Whitley JQ. Influence of archwire and bracket dimensions on sliding mechanics:

derivations and determinations of the critical contact angles for binding. Eur J Orthod. 1999

Apr;21(2):199-208.

23. Burrow SJ. Friction and resistance to sliding in orthodontics: a critical review. Am J Orthod

Dentofacial Orthop. 2009 Apr;135(4):442-7.

24. Pandis N, Polychronopoulou A, Eliades T. Self-ligating vs conventional brackets in the treatment

of mandibular crowding: a prospective clinical trial of treatment duration and dental effects. Am J

Orthod Dentofacial Orthop. 2007 Aug;132(2):208-15.

25. Miles PG, Weyant RJ, Rustveld L. A clinical trial of Damon 2 vs conventional twin brackets

during initial alignment. Angle Orthod. 2006 May;76(3):480-5.

26. Miles PG. SmartClip versus conventional twin brackets for initial alignment: is there a

difference? Aust Orthod J. 2005 Nov;21(2):123-7.

27. Damon DH. The rationale, evolution and clinical application of the self-ligating bracket. Clin

Orthod Res. 1998 Aug;1(1):52-61.

28. Eberting JJ, Straja SR, Tuncay OC. Treatment time, outcome, and patient satisfaction

comparisons of Damon and conventional brackets. Clin Orthod Res. 2001 Nov;4(4):228-34.

29. Scott P, DiBiase AT, Sherriff M, Cobourne MT. Alignment efficiency of Damon3 self-ligating

and conventional orthodontic bracket systems: a randomized clinical trial. Am J Orthod Dentofacial

Orthop. 2008 Oct;134(4):470.e1,470.e8.

20

30. Hamilton R, Goonewardene MS, Murray K. Comparison of active self-ligating brackets and

conventional pre-adjusted brackets. Aust Orthod J. 2008 Nov;24(2):102-9.

31. Fleming PS, DiBiase AT, Sarri G, Lee RT. Efficiency of mandibular arch alignment with 2

preadjusted edgewise appliances. Am J Orthod Dentofacial Orthop. 2009 May;135(5):597-602.

32. Badawi HM, Toogood RW, Carey JP, Heo G, Major PW. Torque expression of self-ligating

brackets. Am J Orthod Dentofacial Orthop. 2008 May;133(5):721-8.

33. Morina E, Eliades T, Pandis N, Jager A, Bourauel C. Torque expression of self-ligating brackets

compared with conventional metallic, ceramic, and plastic brackets. Eur J Orthod. 2008

Jun;30(3):233-8.

34. Tecco S, Tete S, Perillo L, Chimenti C, Festa F. Maxillary arch width changes during

orthodontic treatment with fixed self-ligating and traditional straight-wire appliances. World J

Orthod. 2009 Winter;10(4):290-4.

35. Fleming PS, DiBiase AT, Sarri G, Lee RT. Comparison of mandibular arch changes during

alignment and leveling with 2 preadjusted edgewise appliances. Am J Orthod Dentofacial Orthop.

2009 Sep;136(3):340-7.

36. Pandis N, Polychronopoulou A, Makou M, Eliades T. Mandibular dental arch changes associated

with treatment of crowding using self-ligating and conventional brackets. Eur J Orthod. 2009 Dec 3.

37. Jiang RP, Fu MK. Non-extraction treatment with self-ligating and conventional brackets.

Zhonghua Kou Qiang Yi Xue Za Zhi. 2008 Aug;43(8):459-63.

21

38. Pandis N, Vlachopoulos K, Polychronopoulou A, Madianos P, Eliades T. Periodontal condition

of the mandibular anterior dentition in patients with conventional and self-ligating brackets. Orthod

Craniofac Res. 2008 Nov;11(4):211-5.

39. Pellegrini P, Sauerwein R, Finlayson T, McLeod J, Covell DA,Jr, Maier T, et al. Plaque retention

by self-ligating vs elastomeric orthodontic brackets: quantitative comparison of oral bacteria and

detection with adenosine triphosphate-driven bioluminescence. Am J Orthod Dentofacial Orthop.

2009 Apr;135(4):426.e1,9; discussion 426-7.

40. Pandis N, Papaioannou W, Kontou E, Nakou M, Makou M, Eliades T. Salivary Streptococcus

mutans levels in patients with conventional and self-ligating brackets. Eur J Orthod. 2010

Feb;32(1):94-9.

41. Fleming PS, Johal A. Self-ligating brackets in orthodontics. Angle Orthod. 2010 May;80(3):575-

84.

42. Ehsani S, Mandich MA, El-Bialy TH, Flores-Mir C. Frictional resistance in self-ligating

orthodontic brackets and conventionally ligated brackets. A systematic review. Angle Orthod. 2009

May;79(3):592-601.

43. Ballanti F, Lione R, Fanucci E, Franchi L, Baccetti T, Cozza P. Immediate and post-retention

effects of rapid maxillary expansion investigated by computed tomography in growing patients.

Angle Orthod. 2009 Jan;79(1):24-9.

22

44. Rungcharassaeng K, Caruso JM, Kan JY, Kim J, Taylor G. Factors affecting buccal bone

changes of maxillary posterior teeth after rapid maxillary expansion. Am J Orthod Dentofacial

Orthop. 2007 Oct;132(4):428.e1,428.e8.

45. Garib DG, Henriques JF, Janson G, de Freitas MR, Fernandes AY. Periodontal effects of rapid

maxillary expansion with tooth-tissue-borne and tooth-borne expanders: a computed tomography

evaluation. Am J Orthod Dentofacial Orthop. 2006 Jun;129(6):749-58.

46. Kau CH, Littlefield J, Rainy N, Nguyen JT, Creed B. Evaluation of CBCT Digital Models and

Traditional Models Using the Little's Index. Angle Orthod. 2010 May;80(3):435-9.

47. Moreira CR, Sales MA, Lopes PM, Cavalcanti MG. Assessment of linear and angular

measurements on three-dimensional cone-beam computed tomographic images. Oral Surg Oral Med

Oral Pathol Oral Radiol Endod. 2009 Apr 20.

48. Baumgaertel S, Palomo JM, Palomo L, Hans MG. Reliability and accuracy of cone-beam

computed tomography dental measurements. Am J Orthod Dentofacial Orthop. 2009

Jul;136(1):19,25; discussion 25-8.

49. Stratemann SA, Huang JC, Maki K, Miller AJ, Hatcher DC. Comparison of cone beam

computed tomography imaging with physical measures. Dentomaxillofac Radiol. 2008

Feb;37(2):80-93.

23

50. Huynh-Ba G, Pjetursson BE, Sanz M, Cecchinato D, Ferrus J, Lindhe J, et al. Analysis of the

socket bone wall dimensions in the upper maxilla in relation to immediate implant placement. Clin

Oral Implants Res. 2010 Jan;21(1):37-42.

51. Bollen AM, Cunha-Cruz J, Bakko DW, Huang GJ, Hujoel PP. The effects of orthodontic therapy

on periodontal health: a systematic review of controlled evidence. J Am Dent Assoc. 2008

Apr;139(4):413-22.

52. Allais D, Melsen B. Does labial movement of lower incisors influence the level of the gingival

margin? A case-control study of adult orthodontic patients. Eur J Orthod. 2003 Aug;25(4):343-52.

53. Janson G, Bombonatti R, Brandao AG, Henriques JF, de Freitas MR. Comparative radiographic

evaluation of the alveolar bone crest after orthodontic treatment. Am J Orthod Dentofacial Orthop.

2003 Aug;124(2):157-64.

54. Thomson WM. Orthodontic treatment outcomes in the long term: findings from a longitudinal

study of New Zealanders. Angle Orthod. 2002 Oct;72(5):449-55.

55. Bondemark L. Interdental bone changes after orthodontic treatment: a 5-year longitudinal study.

Am J Orthod Dentofacial Orthop. 1998 Jul;114(1):25-31.

56. Jager A, Polley J, Mausberg R. Effects of orthodontic expansion of the mandibular arch on the

periodontal condition of the posterior teeth. Dtsch Zahnarztl Z. 1990 Feb;45(2):113-5.

57. Zachrisson BU, Alnaes L. Periodontal condition in orthodontically treated and untreated

individuals. II. Alveolar bone loss: radiographic findings. Angle Orthod. 1974 Jan;44(1):48-55.

24

58. Zachrisson BU, Alnaes L. Periodontal condition in orthodontically treated and untreated

individuals. I. Loss of attachment, gingival pocket depth and clinical crown height. Angle Orthod.

1973 Oct;43(4):402-11.

25

CHAPTER 2

MATERIALS AND METHODS

Human Subjects Approval

This study was approved by the Institutional Review Board of the Ohio State University,

Columbus, OH (OSU protocol number: 2008H0210). In addition; the research was approved for the

inclusion of children, waiver of the consent process, and waiver of HIPAA Research Authorization

throughout the entire research study.

Patient Selection

The CBCT images before and after treatment of fifty patients were obtained from a university

graduate clinic. The patients were treated with full fixed appliances-- either SLB or NSLB. A

sensitivity power analysis was compled using G power software.9,

10

A sample size of 45 patients

had 85% power and could detect a difference in intermolar distance of 1.5mm, molar angulation of

3.3⁰, bone height of 0.2mm and bone thickness of 0.2mm.

The exclusion criteria were patients who received RPE or headgear; patients with craniofacial

anomalies; patients with facial asymmetry or patients who had orthognathic surgery.

Forty five images (26 with NSLB and 19 with SLB) were analyzed because five images were

removed due to errors in the data set. The SLB used were Damon 3 (Ormco, Orange, California),

Smart clip (3M Unitek, Monrovia, California) and GAC Innovation R (GAC, Bohemia, NY). The

26

conventional brackets used were preadjusted edgewise twin bracket (3M Unitek; TP Orthodontics,

La Porte, IN).

The CBCT images were analyzed using Dolphin Imaging software (version 10.5 Dolphin

Imaging and Management Solutions, Chatsworth, CA).

1) Buccal bone height and bone thickness measurements (Fig. 2)

The pretreatment images were designated T1 and the post treatment images were designated

T2. The orientation tool was used where the image was first oriented from the front so that a

horizontal line connected hard tissue Orbitale to Orbitale. A vertical orientation line was constructed

perpendicular to the horizontal line at hard tissue Nasion.

For the measurements of the first molar, the orientation was set to be parallel to the occlusal

plane of the first molar with the cut at the level of the cementoenamel junction. The trough was

drawn to bisect the maxillary first molar mesiodistally and buccolingually (Fig. 1). Ten cross

sections with a thickness of 1mm and uniform spacing were made through the maxillary first molar

(M1), the second premolar (P2) and the first premolar (P1).The slice with the maximum bone

thickness was utilized for comparison.

To measure buccal bone height (BBH), the long axis of the buccal root (LA) was drawn from

the buccal cusp tip to the buccal root tip. At the most occlusal point where the bone was in contact

with the tooth, the first perpendicular line (PL1) was drawn to LA. The distance on the LA from the

PL1 to the cusp tip was the BBH. A second perpendicular line (PL2) was drawn where the buccal

bone curvature stabilized and reached a consistent maximum thickness. The distance from the root

surface to the bone surface on the second perpendicular line was the buccal bone thickness (BBT).

The distance on the LA from PL2 to the cusp tip represented the buccal bone thickness level (BTL)

27

and where the BBT of the post treatment (T2) image would be measured. The procedure was

repeated for the T2 measurements and BTL at T1 determined the position of PL2 on the T2 image

(Fig. 2). The same procedure was repeated for the measurements of the first and second maxillary

premolar.

The BBT change resulted by subtracting the T1 value from the T2 value; whereas the BBH

change was derived by subtracting the T2 value from the T1 value. Negative values of those changes

accounted for bone loss. This method of measurement was adopted from a previous study by

Rungcharassaeng et al.1

2) Intermolar distance (ID) measurement (Fig. 3)

From the axial section of the T1 images, at the crown level of the maxillary first molar, a cut

was made buccolingually at the center of the crown (determined both mesiodistally and

buccolingually) so that it passed through the greatest depth of the central fossae bilaterally. On the

coronal image derived from the cut, a line connecting the central fossae was drawn and the

measurement represented the intermolar distance (ID). The procedure was repeated for the T2

measurements, and their difference was the amount of dental expansion (positive) or constriction

(negative).

3) Molar angulation (MA) measurement (Fig. 3)

On the coronal image derived from the previous cut, lines were drawn from the central fossa to

the furcation area. The angle formed by the intersection of this line and a line tangent to the greatest

height of the palate represented the buccolingual inclination of the tooth. The procedure was

repeated for the T2 measurements, and their difference represented the amount of molar tipping. A

28

positive value represented buccal crown tipping and a negative value represented lingual crown

tipping.

The difference between SLB and NSLB were compared in terms of: initial, final and change in

buccal bone height and buccal bone thickness for the maxillary first molar, maxillary first and

second premolars; initial, final and change in intermolar distance and buccolingual angulation of the

maxillary first molars.

Statistical analysis

Ten CBCT images were randomly selected and remeasured at least 2 weeks apart to assess

intraexaminer reliability for bone height, bone thickness, intermolar distance and molar angulation

measurements.

The data were analyzed with SAS 9.2 software (SAS Institute Inc., Cary, NC). Means and

standard deviations were calculated for each parameter. The data was analyzed by the t-test,

ANOVA and ANCOVA.

ANOVA was used to detect the effect of the bracket type (SLB and NSLB), time, tooth (M1,

P2, P1) and side (right and left) on the measured parameters (buccal bone height and thickness,

intermolar distance and molar angulation).

T-tests was used to compare the difference between SLB and NSLB for initial, final and

change in buccal bone height and buccal bone thickness of the maxillary first molar, maxillary first

and second premolars, and for initial, final and change in intermolar distance and buccolingual

angulation of the maxillary first molars.

29

ANCOVA was used to determine if the change in buccal bone height, thickness, molar

angulation and intermolar distance depended on their respective initial values. ANCOVA was also

used to determine if the change in molar angulation and intermolar distance affected the change in

buccal bone thickness and height and whether the change in buccal bone height depended on the

initial buccal bone thickness. The significance level of 0.05 was used for all statistical analyses.

References

1. Rungcharassaeng K, Caruso JM, Kan JY, Kim J, Taylor G. Factors affecting buccal bone changes

of maxillary posterior teeth after rapid maxillary expansion. Am J Orthod Dentofacial Orthop. 2007

Oct;132(4):428.e1,428.e8.

30

CHAPTER 3

MANUSCRIPT

BUCCAL BONE CHANGES WITH SELF LIGATING BRACKETS VERSUS

CONVENTIONAL BRACKETS. A COMPARATIVE STUDY

AUTHORS:

Sahira Kortam, D.D.S., M.Sc.

Paul Geuy

William Johnston, PhD

Henry W. Fields, D.D.S., M.S., M.S.D.

Martin Palomo, D.D.S., M.S.D.

Do-Gyoon Kim, PhD

Dr. Kortam is a resident, The Ohio State University, College of Dentistry.

Paul Geuy is a student at The Ohio State University.

Dr. Johnston is a Professor, Division of Restorative and Prosthetic Dentistry, The Ohio State

University, College of Dentistry.

Dr. Fields is Professor and Chair, Division of Orthodontics, The Ohio State University, College of

Dentistry.

31

Dr. Palomo is an Associate Professor, Program Director, Department of Orthodontics, Craniofacial

Imaging Center Director, Case Western Reserve University, School of Dental Medicine.

Dr. Kim is an Assistant Professor, Research Program Director, Division of Orthodontics, The Ohio

State University, College of Dentistry.

ABSTRACT

Introduction: Self ligating brackets (SLB) manufacturers claim that expansion of arches and

alveolar bone building is facilitated by their bracket design. The objective of this study was to

determine whether SLB brackets have a different effect on buccal bone changes compared with

conventional brackets (NSLB) during orthodontic treatment. Methods: Cone beam computed

tomography (CBCT) images were obtained before and after treatment of 45 patients (26 treated with

conventional brackets (NSLB) and 19 with SLB). The CBCT images were compared between

groups for buccal bone height and thickness at the maxillary first molars, maxillary second and first

premolars using imaging software. The intermolar distance and buccolingual angulation were

assessed for the maxillary first molars as potentially confounding factors. Differences for each

variable measured before and after treatment were compared between the two groups. Results:

Initial and final thickness and height of buccal bone were significantly different between the teeth (p

<0.001). The buccal bone height (p <0.001) and thickness (p= 0.018) significantly decreased after

treatment for both groups. The mean changes of buccal bone height and thickness measured were not

significantly different between SLB and NSLB groups (p>0.05). The intermolar distance and molar

angulation changes were not significantly different between the 2 groups (p >0.05). The change in

32

bone height depended on the initial bone thickness where the greater the initial bone thickness, the

less the decrease in bone height (p <0.01). The change in bone thickness was affected by the change

in intermolar distance where the bone thickness decreased when the intermolar distance increased (p

<0.01). Conclusions: The buccal bone changes during orthodontic treatment regardless of which

bracket type is used. Based on these data and those from RME studies, the implication is that, in the

absence of other data, there is a trend that increased arch dimensions may lead to adverse bony

changes depending on the patient‟s initial bony status. Arch expansion and molar angulation can be

similarly controlled by either type of appliance.

KEY WORDS: CBCT, self ligating, buccal bone, intermolar

INTRODUCTION

Self ligating brackets (SLB) have received much attention in the past few years and many

manufacturers now offer SLB, but they are not new in orthodontics. They were introduced in the

early 20th century with the „Russell Lock‟ edgewise attachment described in 1935.1 Some early SLB

were the Ormco Edgelok (1972), Forestadent Mobil-Lock (1980), Orec SPEED (1980), and “A”

Company Activa (1986).2 Other designs have appeared, but currently the popular SLB are Damon,

Time, Speed, SmartClip, and In-Ovation R.3

Various claims are made by SLB manufacturers. One of these possibilities is increased arch

dimension changes. Sound scientific evidence is required in order to accept manufacturers‟ claims

about SLB.

33

The Damon self ligating system claims that using biologically sensible forces which work with

the body‟s adaptive processes will naturally create space allowing most cases to be treated without

extraction and without the need for headgear or palatal expanders. They also claim that

posttreatment computed tomography (CT) images show transverse arch development and normal

alveolar bone on lingual and buccal surfaces. Low friction and low force are purported to be good

for physiologically rebuilding the alveolar bone.4

On the other hand, excessive expansion can force the teeth through the cortical plate.5 This can

ultimately cause bone dehiscence and gingival recession.6

The three dimensional capability of cone beam computed tomography (CBCT) technology

makes it possible to non-invasively assess alveolar bone changes for posterior teeth7 where buccal

bone defects can be detected and quantified.8

The objective of this study was to compare the difference between patients treated with SLB

and conventional brackets (NSLB) in regards to the changes in buccal bone height and thickness,

while monitoring buccolingual root angulation and intermolar distance.

MATERIALS AND METHODS

This study was approved by the Institutional Review Board. The CBCT images before and

after treatment of fifty patients were obtained from a university graduate clinic. The patients were

treated with full fixed appliances either SLB or NSLB. A sensitivity power analysis was done using

G power software.9,

10

A sample size of 45 patients was used for 85% power that could detect a

34

difference in intermolar distance of 1.5mm, molar angulation of 3.3⁰, bone height of 0.2mm and

bone thickness of 0.2mm.

The exclusion criteria were patients who received RPE or headgear; patients with craniofacial

anomalies; patients with facial asymmetry or patients who had orthognathic surgery.

Forty five images (26 with NSLB and 19 with SLB) were analyzed because five images were

removed because of errors in the data set. The SLB used were Damon 3 (Ormco, Orange,

California), Smart clip (3M Unitek, Monrovia, California) and GAC Innovation R (GAC, Bohemia,

NY). The conventional brackets used were preadjusted edgewise twin bracket (3M Unitek; TP

Orthodontics, La Porte, IN).

The CBCT images were analyzed using Dolphin Imaging software (version 10.5 Dolphin

Imaging and Management Solutions, Chatsworth, CA).

1) Buccal bone height and bone thickness measurements (Fig. 2)

The pretreatment images were designated T1 and the post treatment images were designated

T2. The orientation tool was used where the image was first oriented from the front so that a

horizontal line connected hard tissue Orbitale to Orbitale. A vertical orientation line was constructed

perpendicular to the horizontal line at hard tissue Nasion.

For the measurements of the first molar, the orientation was set to be parallel to the occlusal

plane of the first molar with the cut at the level of the cementoenamel

junction. The trough was drawn to bisect the maxillary first molar mesiodistally and buccolingually

(Fig. 1). Ten cross sections with a thickness of 1mm and uniform spacing were made through the

maxillary first molar (M1), the second premolar (P2) and the first premolar (P1).The slice with the

maximum bone thickness was utilized for comparison.

35

To measure buccal bone height (BBH), the long axis of the buccal root (LA) was drawn from

the buccal cusp tip to the buccal root tip. At the most occlusal point where the bone was in contact

with the tooth, the first perpendicular line (PL1) was drawn to LA. The distance on the LA from the

PL1 to the cusp tip was the BBH. A second perpendicular line (PL2) was drawn where the buccal

bone curvature stabilized and reached a consistent maximum thickness. The distance from the root

surface to the bone surface on the second perpendicular line was the buccal bone thickness (BBT).

The distance on the LA from PL2 to the cusp tip represented the buccal bone thickness level (BTL)

and where the BBT of the post treatment (T2) image would be measured. The procedure was

repeated for the T2 measurements and BTL at T1 determined the position of PL2 on the T2 image

(Fig. 2). The same procedure was repeated for the measurements of the first and second maxillary

premolar.

The BBT change resulted by subtracting the T1 value from the T2 value; whereas the BBH

change was derived by subtracting the T2 value from the T1 value. Negative values of those changes

accounted for bone loss. This method of measurement was adopted from a previous study by

Rungcharassaeng et al.11

2) Intermolar distance (ID) measurement (Fig. 3)

From the axial section of the T1 images, at the crown level of the maxillary first molar, a cut

was made buccolingually at the center of the crown (determined both mesiodistally and

buccolingually) so that it passed through the greatest depth of the central fossae bilaterally. On the

coronal image derived from the cut, a line connecting the central fossae was drawn and the

measurement represented the intermolar distance (ID). The procedure was repeated for the T2

36

measurements, and their difference was the amount of dental expansion (positive) or constriction

(negative).

3) Molar angulation (MA) measurement (Fig. 3)

On the coronal image derived from the previous cut, lines were drawn from the central fossa to

the furcation area. The angle formed by the intersection of this line and a line tangent to the greatest

height of the palate represented the buccolingual inclination of the tooth. The procedure was

repeated for the T2 measurements, and their difference represented the amount of molar tipping. A

positive value represented buccal crown tipping and a negative value represented lingual crown

tipping.

The difference between SLB and NSLB were compared in terms of: initial, final and change in

buccal bone height and buccal bone thickness for the maxillary first molar, maxillary first and

second premolars; initial, final and change in intermolar distance and buccolingual angulation of the

maxillary first molars.

Statistical analysis

Ten CBCT images were randomly selected and remeasured at least 2 weeks apart to assess

intraexaminer reliability for bone height, bone thickness, intermolar distance and molar angulation

measurements.

The data were analyzed with SAS 9.2 software (SAS Institute Inc., Cary, NC). Means and

standard deviations were calculated for each parameter. The data was analyzed by the t-test,

ANOVA and ANCOVA.

37

ANOVA was used to detect the effect of the bracket type (SLB and NSLB), time, tooth (M1,

P2, P1) and side (right and left) on the measured parameters (buccal bone height and thickness,

intermolar distance and molar angulation).

T-tests was used to compare the difference between SLB and NSLB for initial, final and

change in buccal bone height and buccal bone thickness of the maxillary first molar, maxillary first

and second premolars, and for initial, final and change in intermolar distance and buccolingual

angulation of the maxillary first molars.

ANCOVA was used to determine if the change in buccal bone height, thickness, molar

angulation and intermolar distance depended on their respective initial values. ANCOVA was also

used to determine if the change in molar angulation and intermolar distance affected the change in

buccal bone thickness and height and whether the change in buccal bone height depended on the

initial buccal bone thickness. The significance level of 0.05 was used for all statistical analyses.

RESULTS

The study included 45 patients; 18 males and 27 females with a mean age of 14.1 ± 1.3 years

and a range of 12-17 years. Twenty-six patients had NSLB and 19 had SLB. The demographic

distribution for the patients is presented in Table I.

The intraclass correlation coefficients for the bone thickness and bone height measurements

were 0.73 and 0.78, respectively. The intraclass correlation coefficients for the intermolar distance

and molar angulation measurements were 0.88 and 0.81, respectively. The measurement error for the

bone thickness and bone height measurements were 0.32mm and 0.4mm, respectively. The

38

measurement error for the intermolar distance and molar angulation measurements were 0.8mm and

2.71,⁰ respectively.

The means and standard deviations for the buccal bone height, bone thickness, intermolar

distance and molar angulation at pretreatment (T1), post treatment (T2) and the change (T1-T2) are

shown in Table II through V.

The bone height significantly decreased after treatment for both bracket types (p <0.001). The

initial (p=0.183), final (p=0.184) and change (p=0.973) in bone height were not statistically

significantly different between the two bracket types. The change in bone height was not affected by

the initial bone height (p=0.187). Bone height (initial and final) was significantly different between

the maxillary first molar, second premolar and first premolar (p <0.001) regardless of bracket type.

There was no significant difference between right and left side for bone height (p=0.097).

The bone thickness significantly decreased after treatment for both bracket types (p= 0.017).

The initial bone thickness (p=0.021) and the final bone thickness (p=0.006) were significantly

different between the two bracket types (the initial and final bone thickness was less for the self

ligating bracket group) but the change (p=0.270) was not significantly different between the two

bracket types. The change in bone thickness was not affected by the initial bone thickness (p=0.652).

Bone thickness (initial and final) were significantly different between the maxillary first molar,

second premolar and first premolar (p <0.001) regardless of bracket type. There was a significant

difference between the right and left side for bone thickness (p= 0.022); the right side was greater.

The intermolar distance increased after treatment for both bracket types. The initial (p=0.130),

final (p=0.159) and change (p=0.719) in intermolar distance were not significantly different between

the 2 bracket types. The change in intermolar distance was affected by the initial intermolar distance

39

where the greater the initial intermolar distance, the lesser the change in intermolar distance

(p=0.007).

The molar angulation decreased after treatment for both bracket types. The initial (p=0.312),

final (p=0.489) and change (p=0.767) in molar angulation were not significantly different between

the two bracket types. There was no significant difference between right and left side for molar

angulation (p=0.220). The change in molar angulation was affected by the initial molar angulation

where the greater the initial molar angulation, the lesser the change in molar angulation (p=0.037).

The change in bone height did not depend upon the change in molar angulation (p=0.919) and

intermolar distance (p=0.402). The change in bone height depended on the initial bone thickness

(p=0.006) where the greater the initial bone thickness, the less the decrease in bone height.

The change in bone thickness was not affected by the change in molar angulation (p=0.748)

however it was affected by the change in intermolar distance (p=0.007) where the bone thickness

decreased when the intermolar distance increased.

DISCUSSION

Information from available CBCT images can provide noninvasive insight into the dynamics of

tooth movement. Various studies12,

13

have indicated that CBCT images can be used to obtain

accurate linear and angular measurements. Others14

found a small systematic error, which became

statistically significant only when combining several measurements.

The accuracy of CBCT images for the detection and quantification of periodontal bone defects

in three dimensions has been evaluated. Misch et al8 concluded that the three dimensional capability

40

of CBCT offered a significant advantage because all defects including buccal and lingual defects

could be detected and quantified. Mol and Balasundaram7 concluded that CBCT images provide

better diagnostic and quantitative information on periodontal bone

levels in three dimensions than

conventional radiography but the accuracy in the anterior aspect of the jaws was limited.

Our data represents baseline information for buccal bone height and thickness in cases of

comprehensive orthodontic treatment that can be compared to rapid maxillary expansion (RME)

studies.11,

15,

16

The initial bone height and thickness dimensions were comparable for the current

study and previous studies.11,

15,

16

This appears to verify the usual pretreatment status of posterior

buccal bone.

In a systematic review by Bollen et al

17, they suggested that orthodontic therapy was associated

with small amounts of alveolar bone loss, gingival recession and increased pocket

depth. Our

findings also showed small, but statistically significant buccal bone loss after orthodontic treatment,

most probably changes that would be considered clinically insignificant.

With rapid maxillary expansion, a significant amount of bone loss was reported by Garib et al15

who found that RME reduced the buccal bone plate thickness of supporting teeth 0.6 to 0.9 mm and

induced bone dehiscences on the buccal aspect where there was a significant reduction of alveolar

crest level of 7.1 ± 4.6 mm at the first premolars and 3.8 ± 4.4 mm at the mesiobuccal area of the

first molars. Rungcharassaeng et al11

found that buccal crown tipping and reduction of buccal bone

thickness and height of the maxillary posterior teeth were immediate effects of RME. Ballanti et al16

found a significant reduction in buccal alveolar bone thickness of maxillary molars with the greatest

amount of bone resorption being 0.4mm.

41

So, in cases where substantial and purposeful RME expansion was accomplished, a significant

amount of bone loss was reported. We found that increasing the intermolar distance minimally

would negatively affect the bone thickness. This appears to suggest there is a trend and relationship

between bone loss and increased transverse dimension. Without precise data for intervening

magnitudes of expansion, there is a need for care when decisively increasing posterior arch width,

regardless of the appliance used in order to avoid potential bone loss.

We found that the change in bone height depends on the initial bone thickness where the

greater the initial bone thickness, the less the decrease in bone height. This is in agreement with the

findings of Rungcharassaeng et al11

whose results suggest that buccal bone level was better

preserved with greater buccal bone thickness. Garib et al15

also found a negative correlation between

the thickness of the buccal alveolar crest at treatment onset and the alveolar crest level changes after

expansion.

The clinical significance of buccal bone loss is the accompanying gingival recession with

exposure of cementum that has been reported to occur at an early age on single or multiple teeth, and

can be associated with orthodontic treatment.6 Localized recession during orthodontic treatment has

been associated with excessive forces that have not permitted the repair and remodeling of the

alveolar bone.5 Gingival recession is always accompanied by bone dehiscence which can happen as

a result of uncontrolled expansion of teeth through the cortical plate.6 Pretreatment buccal bone

thickness appears to be a determining factor related to bone loss. In the absence of a practical means

to assess buccal bone thickness on a routine basis and given the potential for buccal bone loss as

noted above, again, it appears judicious to avoid aggressive transverse arch expansion.

42

Claims have been made that SLB can result in broader archforms than conventional brackets.18

We found that the maxillary intermolar width increased insignificantly for both the SLB group and

the NSLB group and there was no significant difference between the two brackets groups. Consistent

with this finding, Tecco et al19

found that both self ligating and traditional straight wire appliances

increased maxillary dentoalveolar widths but there was no significant difference between the groups

in patients with mild crowding.

We found no difference in controlling buccolingual angulation of the maxillary first molar

between the two bracket types. Other studies evaluated torque control for maxillary incisors where

Pandis et al20

found that SLB were equally efficient in delivering torque to maxillary incisors. On the

other hand, Morina et al21

found that the torque expression of SLB was less than conventional

brackets.

It does not appear that one appliance offers an advantage over the other in terms of changes in

buccal bone and control of molar angulation and intermolar distance when modest changes in arch

form are the goal and result. Based on these data and those from RME studies, the implication is

that, in the absence of other data, there is a trend that increased arch dimensions may lead to adverse

bony changes depending on the patient‟s initial bony status.

CONCLUSIONS

1. There is no difference between patients treated with SLB or conventional brackets for buccal

bone changes (buccal bone height and buccal bone thickness).

2. Buccal bone height and buccal bone thickness decrease significantly after treatment.

43

3. There is no difference between patients treated with SLB or conventional brackets for buccal

angulation of maxillary first molar and intermolar distance.

4. The change in bone height depends on the initial bone thickness where the greater the initial

bone thickness, the less the decrease in bone height.

5. The change in bone thickness is affected by the change in intermolar distance where the bone

thickness decreases when the intermolar distance increases.

44

LEGEND

Fig 1. The orientation was set to be parallel to the occlusal plane of the first molar; the cut was done

at the level of the cementoenamel junction. The trough was drawn to bisect the maxillary first molar.

45

Fig. 2 Buccal bone height and thickness measurements

46

Fig. 3 Landmark identification for buccolingual angulation and intermolar distance measurements

47

Fig. 4 Buccolingual angulation and intermolar distance measurements

48

Table I: Demographic distribution of patients studied

Type of bracket Number of patients

Gender

Male Female

Age

Mean ± SD

Treatment duration

Mean ± SD

NS 26 12 14 14.3 ± 1.3y 20.5 ± 3.6 m

S 19 6 13 13.7 ± 1.3y 19.5 ± 4.1 m

Overall 45 18 27 14.1 ± 1.3y 20.1 ± 3.8 m

NSLB: Conventional brackets, SLB: Self ligating brackets

Table II: Means and standard deviations for the initial, final and change in bone height (mm)

Type Tooth* T1 (Mean ± SD) T2 (Mean ± SD) Change (T1-T2)**

SLB M1

P2

P1

7.66 ± 0.57 7.78 ± 0.44 * -0.12 ± 0.28

7.90 ± 0.54 8.04 ± 0.54 -0.14 ± 0.20

8.78 ± 0.61 8.96 ± 0.62 -0.19 ± 0.16

NSLB M1

P2

P1

7.92 ± 0.65 8.04 ± 0.60 -0.11 ± 0.26

7.96 ± 0.59 8.08 ± 0.59 -0.12 ± 0.30

9.00 ± 0.71 9.23 ± 0.80 -0.23 ± 0.29

T1: Before treatment, T2: After treatment

SLB: Self ligating brackets, NSLB: Conventional brackets

M1: Maxillary first molar, P2: Maxillary second premolar, P1: Maxillary first premolar

* Significant difference between teeth

**Significant difference for the change

Table III: Means and standard deviations for the initial, final and change in bone thickness (mm)

Type Tooth * T1 (Mean ± SD)** T2 (Mean ± SD) † Change (T2-T1)

††

SLB M1

P2

P1

1.87 ± 0.43 1.79 ± 0.40* -0.08 ± 0.26

1.91 ± 0.42 1.75 ± 0.56 ** -0.16 ± 0.37

1.07 ± 0.40 0.96 ± 0.42 -0.11 ± 0.14

NSLB M1

P2

P1

2.21 ± 0.38 2.20 ± 0.46 -0.01 ± 0.21

2.22 ± 0.54 2.11 ± 0.49 -0.12 ± 0.34

1.16 ± 0.54 1.11 ± 0.47 -0.05 ± 0.30

T1: Before treatment, T2: After treatment

SLB: Self ligating brackets, NSLB: Conventional brackets

M1: Maxillary first molar, P2: Maxillary second premolar, P1: Maxillary first premolar

*Significant difference between teeth

** Significant difference for the initial values between SLB and NSLB † Significant difference for the initial values between SLB and NSLB

†† Significant difference for the change

49

Table IV: Means and standard deviations for the initial, final and change in intermolar distance

(mm)

Type T1 (Mean ± SD) T2 (Mean ± SD) Change (Mean ± SD)

S 45.41 ± 2.47 45.56 ± 2.27 0.15 ± 1.39

NS 44.15 ± 2.86 44.48 ± 2.64 0.33 ± 1.83

T1: Before treatment, T2: After treatment

NSLB: Conventional brackets, SLB: Self ligating brackets

Table V: Means and standard deviations for the initial, final and change for molar angulation (⁰)

Type T1 (Mean ± SD) T2 (Mean ± SD) Change (Mean ± SD)

S 95.15 ± 2.59 94.77 ± 3.23 -0.38 ± 3.30

NS 93.96 ± 5.11 93.87 ± 5.39 -0.09 ± 3.22

T1: Before treatment, T2: After treatment

NSLB: Conventional brackets, SLB: Self ligating bracket

Acknowledgements

We would like to recognize the financial support for this research provided by the Dental

Master‟s Thesis Award Program sponsored by Delta Dental Foundation which is the philanthropic

affiliate of Delta Dental of Michigan, Ohio, and Indiana.

We would like to thank the Orthodontic Department at Case Western Reserve University for

providing us with the CBCT images needed for this study.

References

1. Miles PG. Self-ligating vs conventional twin brackets during en-masse space closure with sliding

mechanics. Am J Orthod Dentofacial Orthop. 2007 Aug;132(2):223-5.

50

2. Harradine NW. Self-ligating brackets and treatment efficiency. Clin Orthod Res. 2001

Nov;4(4):220-7.

3. Rinchuse DJ, Miles PG. Self-ligating brackets: present and future. Am J Orthod Dentofacial

Orthop. 2007 Aug;132(2):216-22.

4. Yu YL, Qian YF. The clinical implication of self-ligating brackets. Shanghai Kou Qiang Yi Xue.

2007 Aug;16(4):431-5.

5. GEiger AM. Mucogingival problems and the movement of mandibular incisors: a clinical review.

Am J Orthod. 1980 Nov;78(5):511-27.

6. Engelking G, Zachrisson BU. Effects of incisor repositioning on monkey periodontium after

expansion through the cortical plate. Am J Orthod. 1982 Jul;82(1):23-32.

7. Mol A, Balasundaram A. In vitro cone beam computed tomography imaging of periodontal bone.

Dentomaxillofac Radiol. 2008 Sep;37(6):319-24.

8. Misch KA, Yi ES, Sarment DP. Accuracy of cone beam computed tomography for periodontal

defect measurements. J Periodontol. 2006 Jul;77(7):1261-6.

9. Faul F, Erdfelder E, Buchner A, Lang AG. Statistical power analyses using G*Power 3.1: tests for

correlation and regression analyses. Behav Res Methods. 2009 Nov;41(4):1149-60.

51

10. Faul F, Erdfelder E, Lang AG, Buchner A. G*Power 3: a flexible statistical power analysis

program for the social, behavioral, and biomedical sciences. Behav Res Methods. 2007

May;39(2):175-91.

11. Rungcharassaeng K, Caruso JM, Kan JY, Kim J, Taylor G. Factors affecting buccal bone

changes of maxillary posterior teeth after rapid maxillary expansion. Am J Orthod Dentofacial

Orthop. 2007 Oct;132(4):428.e1,428.e8.

12. Moreira CR, Sales MA, Lopes PM, Cavalcanti MG. Assessment of linear and angular

measurements on three-dimensional cone-beam computed tomographic images. Oral Surg Oral Med

Oral Pathol Oral Radiol Endod. 2009 Apr 20.

13. Stratemann SA, Huang JC, Maki K, Miller AJ, Hatcher DC. Comparison of cone beam

computed tomography imaging with physical measures. Dentomaxillofac Radiol. 2008

Feb;37(2):80-93.

14. Baumgaertel S, Palomo JM, Palomo L, Hans MG. Reliability and accuracy of cone-beam

computed tomography dental measurements. Am J Orthod Dentofacial Orthop. 2009

Jul;136(1):19,25; discussion 25-8.

15. Garib DG, Henriques JF, Janson G, de Freitas MR, Fernandes AY. Periodontal effects of rapid

maxillary expansion with tooth-tissue-borne and tooth-borne expanders: a computed tomography

evaluation. Am J Orthod Dentofacial Orthop. 2006 Jun;129(6):749-58.

52

16. Ballanti F, Lione R, Fanucci E, Franchi L, Baccetti T, Cozza P. Immediate and post-retention

effects of rapid maxillary expansion investigated by computed tomography in growing patients.

Angle Orthod. 2009 Jan;79(1):24-9.

17. Bollen AM, Cunha-Cruz J, Bakko DW, Huang GJ, Hujoel PP. The effects of orthodontic therapy

on periodontal health: a systematic review of controlled evidence. J Am Dent Assoc. 2008

Apr;139(4):413-22.

18. Miles PG. Self-ligating brackets in orthodontics: Do they deliver what they claim? Aust Dent J.

2009 Mar;54(1):9-11.

19. Tecco S, Tete S, Perillo L, Chimenti C, Festa F. Maxillary arch width changes during

orthodontic treatment with fixed self-ligating and traditional straight-wire appliances. World J

Orthod. 2009 Winter;10(4):290-4.

20. Pandis N, Strigou S, Eliades T. Maxillary incisor torque with conventional and self-ligating

brackets: a prospective clinical trial. Orthod Craniofac Res. 2006 Nov;9(4):193-8.

21. Morina E, Eliades T, Pandis N, Jager A, Bourauel C. Torque expression of self-ligating brackets

compared with conventional metallic, ceramic, and plastic brackets. Eur J Orthod. 2008

Jun;30(3):233-8.

53

CHAPTER 4

DISCUSSION AND CONCLUSIONS

Information from available CBCT images can provide noninvasive insight into the dynamics of

tooth movement. Various studies1,

2 have indicated that CBCT images can be used to obtain accurate

linear and angular measurements. Others3 found a small systematic error, which became statistically

significant only when combining several measurements.

The accuracy of CBCT images for the detection and quantification of periodontal bone defects

in three dimensions has been evaluated. Misch et al4 concluded that the three dimensional capability

of CBCT offered a significant advantage because all defects including buccal and lingual defects

could be detected and quantified. Mol and Balasundaram5 concluded that CBCT images provide

better diagnostic and quantitative information on periodontal bone

levels in three dimensions than

conventional radiography but the accuracy in the anterior aspect of the jaws was limited.

Our data represents baseline information for buccal bone height and thickness in cases of

comprehensive orthodontic treatment that can be compared to rapid maxillary expansion (RME)

studies.6,

7,

8 The initial bone height and thickness dimensions were comparable for the current study

and previous studies.6,

7,

8 This appears to verify the usual pretreatment status of posterior buccal

bone.

54

In a systematic review by Bollen et al

9, they suggested that orthodontic therapy was associated

with small amounts of alveolar bone loss, gingival recession and increased pocket

depth. Our

findings also showed small, but statistically significant buccal bone loss after orthodontic treatment,

most probably changes that would be considered clinically insignificant.

With rapid maxillary expansion, a significant amount of bone loss was reported by Garib et al7

who found that RME reduced the buccal bone plate thickness of supporting teeth 0.6 to 0.9 mm and

induced bone dehiscences on the buccal aspect where there was a significant reduction of alveolar

crest level of 7.1 ± 4.6 mm at the first premolars and 3.8 ± 4.4 mm at the mesiobuccal area of the

first molars. Rungcharassaeng et al6 found that buccal crown tipping and reduction of buccal bone

thickness and height of the maxillary posterior teeth were immediate effects of RME. Ballanti et al8

found a significant reduction in buccal alveolar bone thickness of maxillary molars with the greatest

amount of bone resorption being 0.4mm.

So, in cases where substantial and purposeful RME expansion was accomplished, a significant

amount of bone loss was reported. We found that increasing the intermolar distance minimally

would negatively affect the bone thickness. This appears to suggest there is a trend and relationship

between bone loss and increased transverse dimension. Without precise data for intervening

magnitudes of expansion, there is a need for care when decisively increasing posterior arch width,

regardless of the appliance used in order to avoid potential bone loss.

We found that the change in bone height depends on the initial bone thickness where the

greater the initial bone thickness, the less the decrease in bone height. This is in agreement with the

findings of Rungcharassaeng et al6 whose results suggest that buccal bone level was better preserved

with greater buccal bone thickness. Garib et al7 also found a negative correlation between the

55

thickness of the buccal alveolar crest at treatment onset and the alveolar crest level changes after

expansion.

The clinical significance of buccal bone loss is the accompanying gingival recession with

exposure of cementum that has been reported to occur at an early age on single or multiple teeth, and

can be associated with orthodontic treatment.10

Localized recession during orthodontic treatment

has been associated with excessive forces that have not permitted the repair and remodeling of the

alveolar bone.11

Gingival recession is always accompanied by bone dehiscence which can happen as

a result of uncontrolled expansion of teeth through the cortical plate.10

Pretreatment buccal bone

thickness appears to be a determining factor related to bone loss. In the absence of a practical means

to assess buccal bone thickness on a routine basis and given the potential for buccal bone loss as

noted above, again, it appears judicious to avoid aggressive transverse arch expansion.

Claims have been made that SLB can result in broader archforms than conventional brackets.12

We found that the maxillary intermolar width increased insignificantly for both the SLB group and

the NSLB group and there was no significant difference between the two brackets groups. Consistent

with this finding, Tecco et al13

found that both self ligating and traditional straight wire appliances

increased maxillary dentoalveolar widths but there was no significant difference between the groups

in patients with mild crowding.

We found no difference in controlling buccolingual angulation of the maxillary first molar

between the two bracket types. Other studies evaluated torque control for maxillary incisors where

Pandis et al14

found that SLB were equally efficient in delivering torque to maxillary incisors. On the

other hand, Morina et al15

found that the torque expression of SLB was less than conventional

brackets.

56

It does not appear that one appliance offers an advantage over the other in terms of changes in

buccal bone and control of molar angulation and intermolar distance when modest changes in arch

form are the goal and result. Based on these data and those from RME studies, the implication is

that, in the absence of other data, there is a trend that increased arch dimensions may lead to adverse

bony changes depending on the patient‟s initial bony status.

CONCLUSIONS

1. There is no difference between patients treated with SLB or conventional brackets for buccal

bone changes (buccal bone height and buccal bone thickness).

2. Buccal bone height and buccal bone thickness decrease significantly after treatment.

3. There is no difference between patients treated with SLB or conventional brackets for buccal

angulation of maxillary first molar and intermolar distance.

4. The change in bone height depends on the initial bone thickness where the greater the initial

bone thickness, the less the decrease in bone height.

5. The change in bone thickness is affected by the change in intermolar distance where the bone

thickness decreases when the intermolar distance increases.

57

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American Board of Orthodontics, 133(5), 721-728.

Ballanti, F., Lione, R., Fanucci, E., Franchi, L., Baccetti, T., & Cozza, P. (2009). Immediate and

post-retention effects of rapid maxillary expansion investigated by computed tomography in

growing patients. The Angle Orthodontist, 79(1), 24-29.

Baumgaertel, S., Palomo, J. M., Palomo, L., & Hans, M. G. (2009a). Reliability and accuracy of

cone-beam computed tomography dental measurements. American Journal of Orthodontics and

Dentofacial Orthopedics : Official Publication of the American Association of Orthodontists, its

Constituent Societies, and the American Board of Orthodontics, 136(1), 19-25; discussion 25-8.

Baumgaertel, S., Palomo, J. M., Palomo, L., & Hans, M. G. (2009b). Reliability and accuracy of

cone-beam computed tomography dental measurements. American Journal of Orthodontics and

58

Dentofacial Orthopedics : Official Publication of the American Association of Orthodontists, its

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Bollen, A. M., Cunha-Cruz, J., Bakko, D. W., Huang, G. J., & Hujoel, P. P. (2008a). The effects of

orthodontic therapy on periodontal health: A systematic review of controlled evidence. Journal

of the American Dental Association (1939), 139(4), 413-422.

Bollen, A. M., Cunha-Cruz, J., Bakko, D. W., Huang, G. J., & Hujoel, P. P. (2008b). The effects of

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Cacciafesta, V., Sfondrini, M. F., Ricciardi, A., Scribante, A., Klersy, C., & Auricchio, F. (2003).

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60

Faul, F., Erdfelder, E., Buchner, A., & Lang, A. G. (2009). Statistical power analyses using

G*Power 3.1: Tests for correlation and regression analyses. Behavior Research Methods, 41(4),

1149-1160.

Faul, F., Erdfelder, E., Lang, A. G., & Buchner, A. (2007). G*Power 3: A flexible statistical power

analysis program for the social, behavioral, and biomedical sciences. Behavior Research

Methods, 39(2), 175-191.

Fleming, P. S., DiBiase, A. T., Sarri, G., & Lee, R. T. (2009a). Comparison of mandibular arch

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Association of Orthodontists, its Constituent Societies, and the American Board of

Orthodontics, 136(3), 340-347.

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Constituent Societies, and the American Board of Orthodontics, 135(5), 597-602.

Fleming, P. S., & Johal, A. (2010). Self-ligating brackets in orthodontics. The Angle Orthodontist,

80(3), 575-584.

Garib, D. G., Henriques, J. F., Janson, G., de Freitas, M. R., & Fernandes, A. Y. (2006). Periodontal

effects of rapid maxillary expansion with tooth-tissue-borne and tooth-borne expanders: A

computed tomography evaluation. American Journal of Orthodontics and Dentofacial

61

Orthopedics : Official Publication of the American Association of Orthodontists, its Constituent

Societies, and the American Board of Orthodontics, 129(6), 749-758.

GEiger, A. M. (1980). Mucogingival problems and the movement of mandibular incisors: A clinical

review. American Journal of Orthodontics, 78(5), 511-527.

Hamilton, R., Goonewardene, M. S., & Murray, K. (2008). Comparison of active self-ligating

brackets and conventional pre-adjusted brackets. Australian Orthodontic Journal, 24(2), 102-

109.

Harradine, N. W. (2001). Self-ligating brackets and treatment efficiency. Clinical Orthodontics and

Research, 4(4), 220-227.

Harradine, N. W. (2003). Self-ligating brackets: Where are we now? Journal of Orthodontics, 30(3),

262-273.

Huynh-Ba, G., Pjetursson, B. E., Sanz, M., Cecchinato, D., Ferrus, J., Lindhe, J., et al. (2010).

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implant placement. Clinical Oral Implants Research, 21(1), 37-42.

Jager, A., Polley, J., & Mausberg, R. (1990). Effects of orthodontic expansion of the mandibular

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