Angle Orthodontist, Vol 77, No 3, 2007417DOI: 10.2319/061206-238

Original Article

Orthodontic Treatment Acceleration with Corticotomy-assisted Exposureof Palatally Impacted Canines

A Preliminary Study

T. J. Fischer

ABSTRACTObjective: To evaluate the effectiveness of a new surgical technique in the treatment of palatallyimpacted canines.Materials and Methods: Six consecutive patients presenting with bilaterally impacted canineswere compared. One canine was surgically exposed using a conventional surgical technique whilethe contralateral canine was exposed using a corticotomy-assisted technique.Results: After tooth movement was completed, statistical comparisons of the two methods re-vealed a reduction of treatment time of 2833% for the corticotomy-assisted canines. No signifi-cant differences were observed in final periodontal condition between the canines exposed bythese two methods.Conclusion: This preliminary study supports the concept that a corticotomy-assisted surgicaltechnique helps reduce orthodontic treatment time for palatally impacted canines.KEY WORDS: Impacted canines; Corticotomy

INTRODUCTIONOne of the most difficult clinical problems for the or-

thodontist to correct is the palatally impacted canine.This condition requires the close teamwork of the oralsurgeon and the orthodontistinitially to achieve ac-cess to the impacted tooth and then to use precisebiomechanics to place the tooth in its proper position.Consequently, treatment times to completion can beextended. The purpose of this paper is to evaluate theeffectiveness of a new surgical procedure in reducingtreatment time for the correction of this complex ortho-dontic problem.

The maxillary canine is second only to the mandib-ular third molars in frequency of impaction. Reportedimpaction rates have varied from 0.9%1 to 2.8%.2 Thiscondition occurs twice as frequently in women asmen.1 Maxillary palatal canine impaction is found in85% of all impaction cases, whereas labial impaction

Instructor, Graduate Orthodontics, Harvard University, Bos-ton, Mass.

Corresponding author: Dr Tom Fischer, 60 Timberlane, SouthBurlington, VT 05403 (e-mail: tfdmd@mac.com)Accepted: July 2006. Submitted: June 2006. 2007 by The EH Angle Education and Research Foundation,Inc.

Presented at the March 2006 meeting of the Angle East or-ganization in Washington, D.C.

occurs 15% of the time.3 Finally, of all the maxillarypalatal impactions 810% are bilateral.1

The etiology of palatally impacted canines is notcompletely clear. The maxillary canine has the longestpath of eruption from its point of origin, which may bea contributing factor.4 Some studies have shown ahigher incidence of palatally impacted canines in cas-es with microdontic or missing laterals.5 Furthermore,a familial trend has been advanced that concludes thatthe impacted maxillary canine is a dental anomaly be-ing a product of polygenic multifactorial inheritance.6

As palatally impacted canines seldom erupt withoutsurgical intervention,7 the conventional treatment forthese teeth usually includes surgical exposure fol-lowed by orthodontic traction. With severe palatal im-pactions, surgical intervention usually requires palatalreflection followed by removal of the bone overlyingthe canine crown. Only enough bone is removed toplace an orthodontic attachment on the tooth. The sur-gical caveat is that the cemento-enamel junction of theimpacted tooth not be exposed. Exposure of the ce-mento-enamel junction has shown to cause excessiveloss of alveolar supporting bone.8

Recently, a surgical procedure in conjunction withorthodontic therapy has been popularized, which pur-ports to reduce treatment times significantly. Althoughthis procedure, termed corticotomy-assisted orthodon-

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Figure 1. Conventional uncovering.Figure 2. Corticotomy-assisted uncovering.

Figure 3. Measured distance.

tics, was first described in 1893,9 it has only recentlygained wide usage. This surgical technique includesgingival reflection followed by partial decortication ofthe cortical plates ending with primary flap closure.Significantly reduced treatment times have been re-ported using this procedure with reductions of 75% to80% of routine treatment times.10

MATERIALS AND METHODS

For this preliminary study, a sample of six patientswith bilateral palatally impacted maxillary canines waschosen from patients presenting for orthodontic treat-ment at the authors practice. The sample was set upto use each patient as his own control, thereby in-creasing the power of a small sample. The sampleincluded four white girls and two white boys, with anage range of 11.1 to 12.9 years.

On all six patients, comprehensive orthodontic rec-ords were taken. Nonextraction treatment with prepa-ration for surgical uncovering of both canines was be-gun in a standard manner. Simultaneous surgical ex-posure of both canines was accomplished for each pa-tient by the same surgeon. By random selection, onecanine had a conventional surgical uncovering pro-cedure (Figure 1). On the other canine an additionalcorticotomy procedure was performed (Figure 2). Thisprocedure included a series of circular holes madealong the bone mesial and distal adjacent to the im-pacted tooth where possible. These holes were madewith a 1 mm round bur spaced approximately 2 mmapart and extended into the edentulous area intowhich the tooth was to be moved.

Each patient returned two weeks post surgery tohave an orthodontic attachment placed on the im-pacted teeth. The orthodontist had no knowledge asto which canine had the corticotomy procedure. Upperstudy models were taken at this time to measure thedistance from the incisal tip of each canine to its finalposition in the arch (Figure 3).

Orthodontic traction was applied to both canines ina similar manner utilizing 60 g of force in accordancewith current clinical recommendations.11 Patients wereseen at four- to six-week intervals. When a canine wasclose to its proper position, the intervals were short-ened to two weeks. All patients were treated until thetips of both canine crowns were brought into properposition in the dental arch. At that point, treatment du-ration for each canine was compared to its contralat-eral tooth. Periodontal probing of both canines wascompared once both teeth were in their final restingposition. Additionally, periapical radiographs of contra-lateral canines were taken one year after treatment tocompare the bone levels of the conventional and cor-ticotomy canines to each other. All patients were treat-ed successfully to completion (Figures 47).

RESULTSIn all six patients, the treatment time was reduced

in the corticotomy-assisted canine impactions. Ascompared to the noncorticotomy canines, the reduc-tion in treatment time ranged from 28% to 33%. Fur-thermore, the velocity, ie, distance/time, of each ca-

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Figure 4. Patient #3. Initial preparation.

Figure 5. Patient #3. Initial traction.

Figure 6. Patient #3. Thirty-four weeks later with corticotomy caninemoving faster than conventional canine.

Figure 7. Patient #3. At appliance removal.

Table 1. Distance, Time, and Velocity of Canines in Patients WithCorticotomy and Conventional Exposure

Patient#

Corticotomy ExposureDistance,

mmTime,

wkVelocity,mm/wk

Conventional ExposureDistance,

mmTime,

wkVelocity,mm/wk

123456

10.012.512.012.514.011.5

404438485254

0.250.280.320.260.270.21

11.512.511.012.015.012.0

606258687874

0.190.200.190.180.190.16

Figure 8. Velocity of canine movement (mm/wk).

Table 2a. Paired t-Test: Sample Statisticsa

Exposure Mean SD SEMCorticotomyConventional

.2650

.1867.03619.01506

.01478

.00615a SEM indicates standard error of the mean. N 6.

Table 2b. Paired t-Test: Sample Correlationsa

Exposure Correlation SignificanceConventional and corticotomy .697 .124

a N 6.

Table 2c. Paired t-Test: Sample Testa

Exposure Mean SD SEM t dfSignificance

(2-tailed)Conventional

andcorticotomy .0783 .02787 .01138 6.885 5 P .001***a SEM indicates standard error of the mean; df, degrees of free-

dom. N 6.

nine was calculated and all corticotomy-assisted ca-nines had a significantly higher tooth movement ve-locity than the contralateral conventionally exposedpalatal canine (Table 1 and Figure 8). A paired t-testwas performed and revealed a significant differencebetween the conventional and the corticotomy canineson all patients at the .001% level (Tables 2a through2c).

Periodontal probing records showed no clinical dif-ference between the corticotomy-assisted canines andtheir contralateral teeth. Comparison of bone levels onperiapical radiographs revealed no clinical differencebetween the conventional and the corticotomy canines(Figure 9).

DISCUSSIONIn evaluating the rates of canine movement, extrap-

olation of the velocities reveals that the corticotomy-assisted canines moved at a rate of 1.06 mm/monthvs 0.75 mm/month for the conventional canines.These velocities are clinically significant as well as sta-

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Figure 9a. Corticotomy (periapical). Figure 9b. Conventional (per-iapcial).

tistically significant. Given that the corticotomy proce-dure reduces the bone mass around the canine toothand reduces the bone in its way, less cellular resorp-tion would be required, perhaps allowing faster toothmovement.

In 1982 McDonald and Yap8 showed that more boneremoved during conventional uncovering yieldedgreater bone loss after treatment was completed. Al-though the corticotomy procedure removes more bonethan the conventional procedure, no clinical differencein bone support or periodontal health was seen be-tween the two groups in this study. This may be ex-plained in the manner of bone removal. The cortico-tomy procedure done was not a true ostectomy, witha block of bone removed. The procedure only perfo-rated the bone, leaving the original bony architectureintact. This allowed the resorption/deposition cellularprocess to proceed within the existing architecture.

In this study, final canine tooth position was deter-mined to be when the tip of the canine crown waspositioned ideally in the dental arch as viewed fromthe occlusal plane. All 12 of the canines evaluatedneeded root torque to finalize their position ideally.However, this study did not compare the velocities oftorquing movements between the two groups, as itproved impossible to measure initial root positions ac-curately. Given the positive associations derived usinga small sample size in this preliminary study, further

studies with larger sample sizes would be indicated toincrease the power of the statistical results.

CONCLUSIONS The results demonstrated that under the same con-

ditions the corticotomy-assisted approach producedfaster tooth movement in all six patients.

Additionally, this surgical procedure did not produceany significant difference in the periodontal health ofthe canine.

ACKNOWLEDGMENTSThanks to Dr Judy Christensen, University of Vermont, for

assistance with statistical tests. Also, thanks to Drs SheldonPeck, Samir Bishara, and David Defranco for their invaluablesuggestions.

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