he insertion of a miniscrew is a relatively simple and quick clinicalprocedure. However, successful insertion requires adherence to afew simple, yet important, principles. There are certainly several

methods that will yield favorable results. This article concentrates onthose insertion steps that provide the patient and the orthodontist with ahigh degree of safety. This general information must, of course, be adapt-ed to individual circumstances.

General Notes on Miniscrew InsertionThe basic prerequisite for successful treatment with miniscrews is ac-

curate preoperative diagnosis and treatment planning. This also includesa comprehensive medical and dental history, and an accurate assessmentof clinical and radiographic findings. In addition, the patient must havethe treatment goals and alternatives carefully explained as part of obtain-ing informed consent. (The IC form available from the AAO includes abasic description of the risks and limitations with TADs.1)

Proper infection-control procedures must be used during the entireminiscrew insertion process. Both the treatment station and the patientmust be prepared with this in mind. Adherence to all hygiene measuresrequired for an invasive procedure—a sterile work environment, gloves,etc—is required.

Preoperative PlanningMiniscrews depend almost exclusively on firm cortical anchorage

(primary stability), since they do not become osseointegrated like typicaldental analogue implants. In addition, it is most often preferable to insertthese anchors in the attached gingiva rather than in the buccal mucosa. Inselecting the insertion location, the orthodontist must take into accountboth clinical and paraclinical findings (radiographs, photos, and models)and plan for the orthodontic mechanics that are to be employed.

If a miniscrew is to be placed between roots, there must be at least 0.5mm of bone between the root and the miniscrew on either side. For ex-ample, for a 1.6-mm-diameter miniscrew, the roots of adjacent teethshould be at least 2.6 mm from each other. Consequently, the interradic-ular space is an important consideration when selecting the longitudinalaxis for the point of insertion. These measurements can be translatedfrom panoramic radiograph to study model. It often helps to mark thevertical axis of the teeth adjacent to the insertion site along with themucogingival junction on the model.

To ensure the accurate determination of the insertion site, radi-ographic aids (Figure 1) are useful.2 Their use may facilitate the selectionof the insertion site, but cannot replace the other diagnostic measures.The accuracy of these radiographic adjuncts (such as an x-ray pin) aredependent upon the positioning of the x-ray tube, the x-ray object, andthe x-ray film and/or sensor. Interpretations of radiographic distortions

OrthodonticProductsOnline.com October 200840

T

MiniscrewInsertionPrimer

MiniscrewInsertionPrimer A step-by-step guide to placing TADsA step-by-step guide to placing TADs

By Björn Ludwig, DMD, MSD;Bettina Glasl, DMD, MSD;Thomas Lietz, DMD;Joerg Lisson, DDS, PhD; andS. Jay Bowman, DMD, MSD

or inaccuracies in paralleling techniquemay result in false-negative or false-posi-tive results (Figures 2A–2C, page 42). Forthis reason, the placement of a miniscrewshould always be based primarily on theclinical findings. If a miniscrew is to be in-serted into an area where there is no risk ofdamage to roots, nerves, or blood vessels(such as the palatal region posterior to anartificial transpalatal intercanine line), theinsertion location of the screw may befreely chosen (Figures 3A–3C, page 43).

Safe Zones for Miniscrew InsertionSome areas of the mouth are potential-

ly “safer” for the insertion of miniscrews.This refers to the reduced risk of iatrogenicdamage, but also a lower failure rate. Poggioet al3 used a series of tomographic images todelineate locations distal to the canineswhere greater thickness of cortical bone andinterradicular space are typically found. Inthe maxilla, the largest amount of inter-radicular bone was found in the palatal alve-olus, between the first molar and secondpremolar. The least amount was found inthe tuberosity. The most substantial amountof bone in the buccolingual dimension wasbetween the first and second molars. In themandible, the largest mesiodistal dimensionwas between the first and second premolar.The thickest bone was again between first

Figure 1: An x-ray pin from Forestadent, shownin situ, in relation to the adjacent tooth axes.

OrthodonticProductsOnline.com October 200842

and second molars, with the least between the first premolar and canine.On the basis of panoramic surveys, Schnelle4 reported that adequate

bone is most often found mesial to the maxillary first molars and alsomesial or distal to the mandibular first molars. Unfortunately, the bestsites are often found halfway down the roots in the unattached buccalmucosa. As a consequence, some compromises in vertical position maybe required.

At the appointment prior to the miniscrew insertion, the proceduresfor the next visit should be discussed with the patient. Preoperative in-structions and a prescription for 0.12% chlorhexidine gluconate (forpostoperative use) can be given to the patient. At the miniscrew insertionappointment, the patient should brush, rinse thoroughly with water, andthen rinse with 15 mL of 0.12% chlorhexidine gluconate to reduce the in-traoral bacterial flora.

At this point, the exact site selection should be reviewed and can beconfirmed with radiographic evaluation of a placement guide or stint.Any last-minute changes in selection of the type, diameter, and length ofminiscrew should be made prior to initiating anesthesia.

AnestheticMost miniscrews can often be inserted using only a profound topical

anesthetic with attention to some important precautions5: TAC 20%Alternate (Professional Arts Pharmacy, Lafayette, La), EMLA (AstraZeneca,Wilmington, Del), DepBlu (Steven’s Pharmacy, Costa Mesa, Calif), or Oraqix(Dentsply Prof, York, Pa; Figure 4, page 43). In some instances, the use of alocal infiltration of about 0.5 mL of a typical dental anesthetic may be nec-essary (Figures 5A–5B, page 44). During the interradicular insertion of aminiscrew, sensitivity of the periodontal tissue of the adjacent roots shouldbe retained. The patient can then report discomfort if root encroachment oc-curs, thereby helping to prevent iatrogenic damage. It is for this exact reasonthat profound anesthetic (or “mandibular block”) is not recommended.

Soft-Tissue Depth and Miniscrew LengthIf an implant is to be placed into the unattached mucosa, then a stab

incision with a scalpel or a biopsy or tissue punch is necessary to reducethe possibility that this tissue could twist and bunch around the threadsof the screw, possibly resulting in tearing of those tissues.

If the miniscrew is placed in attached gingiva, then a dental explorer(with an rubber ring used for endodontic files) can be used to measure thethickness of the gingival tissue at the insertion site.When choosing the lengthof a miniscrew, the thickness of soft tissue is often the most important de-termining factor. The length of the miniscrew that resides in the bone shouldbe at least as long as the portion outside the bone. Since mucosa thickness inmost insertion locations is often 1 to 2 mm, the exact tissue measurement isnot often critical. Since the head of the miniscrew must be above the soft tis-sue, longer miniscrews are obviously required in regions of thick tissue (suchas the retromolar region and palate). Most importantly, miniscrew stabilitydepends more on screw diameter than screw length.6,7 However, the maxi-mum diameter is limited by the available interradicular space.

The thickness of alveolar bone and the planned insertion angulationare used to determine the appropriate length of the miniscrew:

• Alveolar width >10 mm: use miniscrews with a length of up to 10 mm;• alveolar width <10 mm and >7 mm: use miniscrews with a length

of 6 to 8 mm; and• alveolar width <6 mm: miniscrews are probably contraindicated.The following generalized guidelines can be used when selecting

miniscrew length:

2A

2B

2C

Figure 2A: Pretreatment panoramic view.

Figure 2B. After the extraction of upperpremolars, an x-ray pin was placed throughthe soft tissue between the first molar andsecond premolars to confirm the correctinsertion site for miniscrews. Note the positionof the maxillary right x-ray pin, as it wouldseem to indicate that a miniscrew could beinserted into the mesial root of the molar inthat location.

Figure 2C: Both screws were subsequentlyinserted in a manner using clinicallyobservable cues (such as noting the positionof root prominences, parallelism, andanatomy of the crowns), indicating that therewas false-positive interpretation of theradiographic guide.

• maxillary buccal region: use an 8-mm or 10-mm miniscrew;

• palatal tissue (depending on the spe-cific site): use a 6-, 8-, or 10-mmminiscrew; and

• mandibular buccal region: use a 6-mm or 8-mm miniscrew.

Transgingival PenetrationA miniscrew must obviously pene-

trate through mucosal or gingival tissue.There are two methods to accomplish this:a) excision of a corresponding diameter ofgingival tissue using a biopsy or tissuepunch; or b) direct insertion of the minis-crew through the gingival tissue. There iscurrently no definitive evidence that either

of these two variations significantly reduces postopera-tive complications, histological effects, and/or the failurerate of miniscrews.

Self-Drill or Self-TapSelf-tapping miniscrews require predrilling (also

known as pilot-drilling) of the cortical bone, appropriate tothe length and diameter of the screw as well as the density ofthe bone. A self-drilling miniscrew will find its own waythrough the bone and, in principle, requires no predrilling.

Bone is more or less “elastic” depending on the site,age, and structure. Consequently, the screw diameter, aswell as the thickness and hardness of the cortical bone atthe insertion site, determine whether or not predrilling isnecessary. Bone is strongly compressed during insertionand will suffer corresponding stresses if a screw is insert-ed without predrilling. This may result in cracking of thebone around the implant site. In addition, as it encoun-ters greater resistance, the miniscrew is also subjected tohigher torsional loads that may result in its fracture.

As a result, self-drilling miniscrews are best for re-gions with thinner and less dense cortical bone (maxilla).For regions with thicker and more dense cortical bone

(mandible), predrilling at least through the cortical bone isrequired for self-tapping and is recommended for self-drilling miniscrews. Predrilling should be done at a maxi-mum of 500 rpm, using a short pilot drill (corresponding tothe internal diameter of the miniscrew) with sterile water-cooling to reduce the risk of thermal bone damage.

Inserting the MiniscrewThe miniscrew must be removed from its sterile pack-

aging (Figures 6A–6D, page 44) or the work rack (Figures7A–7G, page 44) without contamination. Do not touch thethread of the screw. The screw should be inserted at a con-stant rotational speed (at approximately 30 rpm) and withas uniform a torque as possible.

Manual Insertion: When using a hand driver, it is im-portant to limit the torque applied to the miniscrew. This ismost often accomplished by only using your thumb and firstfinger to apply the rotation force. This also stabilizes thewrist, thereby reducing wobbling of the screw. Many manu-facturers provide various screwdrivers or hand drivers inseveral shaft lengths for the manual insertion of the screws.Long-handle drivers, especially those with large-diameterhandles, pose the risk of attaining large torque levels duringinsertion, so insertion must be carried out carefully to avoidfracturing the miniscrew. Torque ratchets are available with

October 2008 OrthodonticProductsOnline.com 43

Figure 3A. Two OrthoEasy (Forestadent)miniscrews insertedinto a “safe zone” inthe palate just distal toan intercanine artificialreference.

Figure 3B and 3C: Radiographic images confirm appropriatebone support for the miniscrews.

3A

3B 3C

Figure 4: Needle-free subgingival anesthesia (Oraqix,Dentsply Pharmaceutical, York, Pa).

Insertion Procedures OverviewA recommended sequence of procedures for insert-

ing miniscrews (modified Cope Placement Protocol™)1,2

include the following:1) have patient brush and rinse with Peridex;2) apply topical anesthesia (such as TAC 20%

Alternate);3) infiltrate anaesthetic as needed (such as 2% lido-

caine with 1:100,000 epinephrine);4) locate and mark implant site (by impressing tis-

sue with periodontal probe or using an x-rayplacement guide);

5) disinfect site with Betadine;6) measure soft-tissue thickness (bone sounding

with periodontal probe or dental explorer);7) soft-tissue punch as needed (especially in unat-

tached gingiva);8) bone surface indentation (No. 2 round bur) or

pilot hole (1.1 mm drill) through cortical plate assituation requires

8) insert implant; and 9) attach mechanical load.In many instances, the tissue punch and predrilling

may be omitted (such as when a self-drilling screw isplaced within the attached gingiva of the maxilla).

References1. Cope JB, Herman RJ. The ortho implant system. In: Cope JB, ed.

OrthoTADs: The Clinical Guide and Atlas. Dallas: Under Dog MediaLP; 2006.

2. Bowman SJ. Thinking outside the box with miniscrews. In: McNamaraJA Jr, ed. Microimplants as Temporary Orthodontic Anchorage. AnnArbor: Craniofacial Growth Series; 2008:45:327-390.

OrthodonticProductsOnline.com October 200844

some systems (tomas® by DENTAURUMand LOMAS by Mondeal) and provide acertain amount of control over the inser-tion torque.

Handpiece Insertion: Machine inser-tion requires a surgical handpiece with aspeed and torque that can be controlled(Figures 7A and 7B). The rotation rateshould not exceed 30 rpm, and torque mustbe restricted to the maximum load limit ofthe screw as specified by the manufacturer.Machine insertion permits constant torqueapplication during insertion, but, unfortu-nately, you lose the tactile feeling that al-lows you to differentiate between bone androot contact.

Attaching Linking Elements forOrthodontic Mechanics

An orthodontic load may be placed onthe miniscrew immediately after inser-tion—no healing phase is required. Luzi etal8 described the results of a prospectiveevaluation of 140 immediately loadedscrews that were inserted in 98 patients:9.3% failed and 6.4% “partially failed”(meaning that they had minimal mobilityand still might be used). The selected “link-ing element(s)” must be prepared accord-ingly and attached to the head of the screw(Figures 7C and 7D). To avoid adverse ef-fects on the teeth to be moved, the load onthe linking element should be limited to

Figures 6A–6D: Selection of driver attachments of different lengths. Insertingthe driver in the handle from the rack in preparation for use.

Figures 7A and 7B: Inserting a driver attachment from a sterilerack into an implant handpiece.

Figures 7E and 7F: Inserting two palatal miniscrews using the implantcontra-angle.

Figure 7G:Connecting asupport wiresegment fromthe miniscrewto a premolarusing light-curedadhesive.

Figures 7C and 7D: Placing the driver over the OrthoEasyminiscrew and removing from the rack, then fastening theorthodontic linking elements.

Figure 5A: Injection pen with needle andanaesthetic cartridge (Heraeus Citoject fromHeraeus Kulzer, Armonk, NY)

Figure 5B: Infiltration ofpalatal tissue using theCitoject pen.

5A

6A 6B

6C 6D

7A 7B 7C 7D

7G7F7E

5B

OrthodonticProductsOnline.com October 200846

between 0.5 and 2 N (about 50 to200 g).

Postoperative CareThe healing and continued

health of the peri-implant gingivaltissue and the status of the patient’soral hygiene must be regularly re-viewed throughout the time that theminiscrew remains in place. The pa-tient must be instructed to avoidmanipulating the screw with fingers,tongue, or lips, or with foreign ob-jects like pens or pencils. The minis-crew must be clean and free ofdebris; otherwise, the screw may beprematurely lost.

Removing the MiniscrewMiniscrews may often be re-

moved without anesthetic or usingonly topical anesthetic. First, thelinking elements of the orthodonticmechanism must be removed fromthe miniscrew. Then, the miniscrewis simply unscrewed using the inser-tion driver. The resulting smallwound requires no special care be-yond normal dental hygiene, and ittypically heals within a short time(Figures 8A–8C).z

Björn Ludwig, DMD, MSD, is in pri-vate practice in Traben-Trarbach,Germany. He can be reached at blud-wig@kieferorthopaedie-mosel.de.

Bettina Glasl, DMD, MSD, is in pri-vate practice in Traben-Trarbach,Germany. She can be reached atbglasl@kieferorthopaedie-mosel.de.

Thomas Lietz, DMD, is in privatepractice in Neulingen, Germany.

Joerg Lisson, DDS, PhD, is the head ofthe orthodontic department at theUniversity of Homburg/Saar, Germany.

S. Jay Bowman, DMD, MSD, is inprivate practice in Portage, Mich. Hecan be reached at drjwyred@aol.com.

Figure 8A: An OrthoEasyminiscrew insertedbetween upper first molarand second premolar.

Figure 8C: Completehealing noted 4 weeksafter removal.

Figure 8B:Immediately afterremoval of theminiscrew withoutanesthetic.

References for this article areavailable with the online version atOOrrtthhooddoonnttiiccPPrroodduuccttssOOnnlliinnee..ccoomm.

8A

8B

8C

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