Effect of surgical exposure technique, age, and grade of impaction … · Effect of surgical...

ORIGINAL ARTICLE

Effect of surgical exposure technique, age, andgrade of impaction on ankylosis of an impactedcanine, and the effect of rapid palatal expansionon eruption: A prospective clinical study

Stylianos I. Koutzogloua and Anastasia Kostakib

Rethymno and Athens, Greece

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Introduction: This study had 2 aims: (1) to assess whether the surgical exposure technique, the patient's age,and the grade of impaction are associated with ankylosis of the impacted canine; and (2) to investigate the effectof rapid palatal expansion on an impacted canine's automatic eruption. Methods: The sample for this prospec-tive longitudinal study consisted of 118 orthodontic patients (72 female, 46male) whowere treated surgically andorthodontically by the first author (S.I.K.) over 18 years. The patients' ages at the beginning of therapy rangedfrom 11.2 to 46.1 years. They had 157 impacted canines (150 maxillary, 7 mandibular), grouped in 7 categories(grades I-VII) according to their radiographic position in the orthopantomogram at the onset of treatment. Univar-iate andmultivariate generalized estimating equation logistic regression analyses were used to assess the effectof the predictors of interest on ankylosis. (In this research, a broad definition of “ankylosis” was used, to includeimpacted canines immobilized a priori or during traction, due to all the possible causes that could contribute toimmobilization, such as all types of external tooth resorption and other known or unknown factors.) Results:Thirty-eight canines erupted spontaneously after space gaining, and the other 119 were treated surgicallywith an open (57 cases) or a closed (62 cases) exposure technique. Eleven canines of the 119 that were treatedsurgically had ankylosis, either a priori or during orthodontic traction. The percentages of ankylosis were 3.5% inthe open technique and 14.5% in the closed technique. Evidence of statistical association was found betweenage and ankylosis, grade of impaction and ankylosis, and rapid palatal expansion and automatic eruption of theimpacted canine. Conclusions: Evidence of an association between exposure technique and ankylosis wasfound. Additionally, there was evidence that the grade of impaction and the patient's age are significant predic-tors of ankylosis, as is the use of rapid palatal expansion a predictor of automatic eruption. (Am J OrthodDentofacial Orthop 2013;143:342-52)

There are numerous surgical procedures to exposean impacted canine and to bring it to its properposition in the dental arch.1-11 The open

exposure technique allows natural eruption of theimpacted canine; the closed exposure techniqueinvolves placement of an auxiliary attachment, whichis then used for orthodontic traction. When theneighboring teeth are intruded and the canine remains

te practice, Rethymno, Greece.ciate professor of statistics, Athens University of Economics and Business,s, Greece.uthors report no commercial, proprietary, or financial interest in the prod-r companies described in this article.t requests to: Stylianos I. Koutzoglou, L. Kountouriotou 129-131,100, Rethymno, Crete, Greece; e-mail, [email protected], April 2012; revised and accepted, October 2012.5406/$36.00ight � 2013 by the American Association of Orthodontists./dx.doi.org/10.1016/j.ajodo.2012.10.017

immobile despite the application of orthodontic force,this is commonly recognized by clinicians as anindication of “ankylosis.”12

The term ankylosis is generally associated withresorption (replacement root resorption).13 Inankylosis-related resorption, immobilization is ob-served clinically, since the root surface (cement ordentin) of the tooth is fused with the alveolar bone.In this study, we broadened the definition to includeimpacted canines immobilized a priori or duringtraction, due to the many possible causes that couldcontribute to immobilization, such as all thetypes of external tooth resorption13,14 and otherknown12,15,16 or unknown factors.

In the literature, the failure in the therapy of the im-pacted canine has been studied,12,15,16 but there areaspects of this failure that have yet to be considered.Indicatively, an unusual a priori ankylosis in the form

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http://dx.doi.org/10.1016/j.ajodo.2012.10.017

Fig 1. A andB,Cone-beam computed tomography images of an impacted and transmigrated mandib-ular left permanent canine in a 32-year-old woman, who was not included in the study because hertreatment began in 2011. The arrows show the area of the a priori ankylosis. C and D, The surgical ex-posure of the canine and its extraction in 2 pieces. E and F, Coronal part of the tooth directly after ex-traction, showing the resorption cavity produced by the pathologic process of ankylosis, with theaffected area after treatment marked with India ink before fixing in 10% formalin.G,Demineralized sec-tion of the treated area of the tooth; the replacement of dentin by bone is obvious.P, Pulp;D, dentin;BT,bone tissue; C, resorptive cavity.

Koutzoglou and Kostaki 343

of an ankylosis-related resorption of the crown (not theroot) of the impacted canine is shown in Figure 1. Thisprocess could lead to the failure of the therapy of the im-pacted canine.

Additionally, whether there is an association be-tween surgical exposure technique, age of the patient,or severity of impaction and ankylosis has not yet beenfully determined. Hence, the main objective of thisstudy was to assess whether there is an associationbetween ankylosis of the impacted canine and eitherthe surgical exposure technique, the grade of its impac-tion, or the patient's age. A secondary objective was toassess the effect of rapid palatal expansion on the au-tomatic eruption of the impacted canine without surgi-cal intervention.

MATERIAL AND METHODS

All participants in this clinical study came fromthe private practice of the first author, who treatedall the impacted canines surgically and orthodonti-cally over a period of 18 years (1994-2012). No spe-cific inclusion or exclusion criteria were applied, sinceall patients who agreed to undergo therapy were in-cluded.

American Journal of Orthodontics and Dentofacial Orthoped

The canines were considered impacted when theirroots were fully developed but the teeth were still cov-ered with bone or mucosa.

We implemented a new grading method to catego-rize the severity of canine impaction. The impacted ca-nines were grouped into 7 categories, according totheir radiographic position in the orthopantomogramat the onset of treatment. The position of the cusptip and its relationship to concrete anatomic structuresof the neighboring lateral and central incisors deter-mined the grade of impaction (I-VII) as follows (Figs2 and 3).

Grade I: The tip of the cusp has no contact with thedistal aspect of the lateral incisor, regardless of the dis-tance between the cusp tip and the plane of occlusion.

Grade II: The tip of the cusp touches, or can reach asfar as, the distal aspect of the root canal of the lateral in-cisor.

Grade III: The tip of the cusp appears radiographicallythrough the root canal of the lateral incisor and canreach as far as its mesial aspect.

Grades IV and V: The tip of the cusp can reach as faras the mesial aspect of the root canal of the central in-cisor; in grade V impaction, the tip of the cusp appears

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Fig 3. A, Orthopantomogram of a boy (age, 13½ years) with 2 palatally impacted canines; B, sche-matic presentation of the impacted maxillary canines. The left canine is grade IV, and the right canineis grade V of impaction.

Fig 2. A, Orthopantomogram of a 15-year-old female patient; B, schematic presentation of the posi-tions of all 4 impacted canines. The mandibular left canine is grade I, the maxillary right canine is gradeII, the maxillary left canine is grade III, and the mandibular right canine is grade VI of impaction.

344 Koutzoglou and Kostaki

radiographically through the root canal of the central in-cisor and can reach as far as its mesial aspect or even themidline of the respective jaw.

For grades II to V, the tip of the cusp appearsvertically on or below the border between the apicaland coronal halves of the root of the lateral or centralincisor in the maxilla, and on or above this border inthe mandible.

Grade VI: The tip of the cusp is located above the bor-der between the apical and coronal halves of the lateralor central incisors' roots in the maxilla and below thisborder in the mandible.

Grade VII includes canines that are in transposi-tion17,18 or transmigration19,20 in the maxilla or themandible (Fig 1).

The accurate location of the crown of the impactedcanine was evaluated by examining the orthopantomo-gram and by clinical examination before the surgicalexposure. This included intraoral palpation and meticu-lous observation of the characteristics of the anatomic

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structures (crown and root) of the adjacent teeth (pre-molars, deciduous canine, and incisors) and especiallythe lateral incisors.

Digital volume tomography21 (specifically, cone-beam computed tomography images) was used for diag-nosis of the accurate position and verification of theankylosis of the impacted tooth only in complicatedcases (Fig 1).

The following open surgical technique, with mini-mal modifications, was used. For palatally dislocatedcanines after local anesthesia, an incision was madeas far as the cortical bone, following the palatal con-tour of the teeth in most patients from the mesial as-pect of the central incisor up to the distal aspect of thefirst premolar. Then, a full-thickness mucoperiostealflap was raised so that the exposed cortical plate al-lowed the surgeon, using a low-speed bur with carefulcooling, to remove the bone that covered the canine'scrown approximately 1 to 2 mm above the cementoe-namel junction as well as the follicular tissue from its

Journal of Orthodontics and Dentofacial Orthopedics

Fig 4. CONSORT flowchart of the study.


socket. The cementoenamel junction area and otheranatomic structures, such as the roots of the adjacentincisors, were respected. Consequently, the full-thickness flap was repositioned apically and suturedwith 3-0 silk sutures. Finally, the tooth and the opera-tive area were covered with a eugenol-free periodontaldressing (Coe-Pak; GC America, Alsip, Ill) for woundprotection and short-term patient comfort. The dress-ing was positioned carefully, and we tried to placethe dressing cover as apically as possible over the ex-posed crown, so that between the mucosa and thetooth crown there would be a layer of dressing. Underthese circumstances, the proliferation of the gingivaltissue was controlled, a quick covering of the toothwas prevented, and the tooth could erupt more freelywithout being impeded by the gingival tissue. The


sutures were removed a week after the operation. Aftereruption, an auxiliary attachment was bonded onto thecrown, and orthodontic traction was initiated.

The following closed surgical technique was per-formed. For palatally dislocated canines, the same surgi-cal procedure as in the open surgical exposure techniquewas used under local anesthesia. For enamel surfacepreparation, 35% phosphoric acid in gel form was ap-plied for 10 seconds, and an eyelet with a small metallicchain was bonded onto the tooth. This attachment(eruption appliance; GAC, Central Islip, NY) was thesame for the whole period of the study. Finally, thefull-thickness mucoperiosteal flap was placed in its orig-inal position and sutured with 3-0 silk sutures. One weekafter surgery, the sutures were removed, and the ortho-dontic traction began.


Table I. Pretreatment demographic and clinical characteristics of the participants and the impacted canines arrangedby study group

Total (nc 5 157) OP0 (nc 5 38) OP1 (nc 5 57) OP2 (nc 5 62)

nc Mean (SD) or % nc Mean (SD) or % nc Mean (SD) or % nc Mean (SD) or %Demographic characteristicsAge (y)11-17 112 14 (1.4) 32 13.5 (1.2) 38 14 (1.8) 42 14.3 (1.5)18-46 45 28.4 (8) 6 21.9 (4) 19 26.1 (7.1) 20 32.5 (7.6)

SexFemale 96 61.1 21 55.3 31 54.4 44 71Male 61 38.9 17 44.7 26 45.6 18 29

Clinical characteristicsGrade of impaction

I 13 8.9 9 23.7 1 1.8 3 4.8II 37 23.6 20 52.6 10 17.5 7 11.3III 31 19.7 8 21.1 13 22.8 10 16.1IV 33 21 1 2.6 14 24.6 18 29V 26 16.6 - - 12 21.1 14 22.6VI 14 8.9 - - 6 10.5 8 12.9VII 3 1.9 - - 1 1.8 2 3.2

Location of impactionLabial-maxilla 36 22.9 24 63.2 4 7 8 12.9Palatal-maxilla 114 72.6 12 31.6 52 91.2 50 80.6Labial-mandible 6 3.8 2 5.3 1 1.8 3 4.8Lingual-mandible 1 0.6 - - - - 1 1.6

Persistence of deciduous canineYes 112 71.3 18 47.4 47 82.5 47 75.8No 45 28.7 20 52.6 10 17.5 15 24.2

nc, Number of impacted canines; OP0, spontaneous eruption; OP1, open surgical procedure; OP2, closed surgical procedure.


The rapid palatal expansion technique (bandedrapid maxillary expander) was used extensivelyin our treatment to reduce premolar extractiontherapy.

Statistical analysis

Demographic and clinical characteristics were inves-tigated with descriptive statistics. Univariate andmultivariate generalized estimating equation logistic re-gression with robust standard errors modeling was ap-plied to assess whether surgical exposure technique,age (as a continuous variable), grade of impaction, sex,and location of the maxillary impaction (labial or palatal)were associated with ankylosis. For assessment of the ef-fect of grade of impaction on the ankylosis, the grade VIIcategory, which includes the most severe impaction inour categorization and the rarest cases, was excludedfrom the analysis, and the variable was dichotomizedto the “nonsevere” group (grades I-V) or the “severe”group (grade VI). Additionally, the effect of rapid palatalexpansion on the automatic eruption of the impactedcanines was assessed. All analyses were implementedin the SPSS statistical package (version 15.0; SPSS,Chicago, Ill) and Stata (version 12.1; StataCorp, CollegeStation, Tex).


RESULTS

From 1994 to 2010, the number of patients whocame to the surgery and remained for therapy after thediagnosis of a dental or skeletal problem of their maxil-lofacial system was 2899 (number of canines, 11,596). In118 (4.1%) of these patients, the impaction of at least 1canine was diagnosed.

This clinical study was based on 118 orthodontic pa-tients, 72 female and 46 male, with 157 impacted ca-nines. The CONSORT flowchart (Fig 4) shows patientflow, and Table I gives the baseline characteristics ofthe study participants.

From June 1994 to October 1996, the open surgicalprocedure was performed on all patients who came tothe surgery. From November 1996 to May 2006, theclosed surgical procedure was strictly used; for the latterperiod of the study (June 2006 to March 2010), the opensurgical exposure was performed on all other patientswho came to the surgery, except in 3 cases: 2 in the max-illa and 1 in the mandible.

The study sample included 150 impacted canines inthe maxilla and 7 in the mandible. Thirty-eight canineserupted spontaneously after space gaining, and theother 119 were treated surgically by using open (57cases) and closed (62 cases) exposure techniques.


Table II. Occurrence of ankylosis by surgical exposuretechnique, age, grade of impaction, sex, and locationof impaction in the maxilla in the surgically treatedcases (nc 5 119)

Ankylosis nc (%) No ankylosis nc (%)

nc total 5 11 (9.2) nc total 5 108 (90.8)Surgical exposure techniqueOP1 (nc 5 57) 2 (3.5) 55 (96.5)OP2 (nc 5 62) 9 (14.5) 53 (85.5)

Age\18 (nc 5 80) 4 (5) 76 (95)$ 18 (nc 5 39) 7 (17.9) 32 (82.1)

Grade of impactionNonsevere(I-V, nc 5 102)

6 (5.9) 96 (94.1)

Severe (VI, nc 5 14) 5 (35.7) 9 (64.3)SexMale (nc 5 44) 2 (4.5) 42 (95.5)Female (nc 5 75) 9 (12) 66 (88)

Location of impaction in the maxilla*Labial (nc 5 12) 1 (8.3) 11 (91.7)Palatal (nc 5 102) 9 (8.8) 93 (91.2)

nc, Number of impacted canines; OP1, open surgical procedure;OP2, closed surgical procedure.*One case of ankylosis was diagnosed in the mandible.


The patients' ages at the beginning of therapy rangedfrom 11.2 to 46.1 years (mean, 18.11 years; SD, 7.88).Eleven of the 119 surgically treated canines had thecomplication of ankylosis a priori or during their ortho-dontic traction.

The risk of ankylosis in the open exposure techniquewas 3.5% (2 of 57 canines); for the closed exposure tech-nique, the risk was 14.5% (9 of 62 canines). In the youn-ger age group (\18 years), 5.0% (4 of 77) showedankylosis, whereas in the older group (.18 years),17.9% (7 of 39) had ankylosis. In the “nonsevere” group(grades I-V), 6 cases (5.9%) showed ankylosis; in the “se-vere” group (grade VI), there were 5 cases (35.7%). Therisks of ankylosis were 4.5% (2 of 44) and 12% (9 of75) in male and female patients, respectively. Finally,the risk of ankylosis was 8.3% (1 of 12) in labially and8.8% (9 of 102) in palatally impacted canines in themaxilla (Table II).

Rapid palatal expansion was performed in 51 of the150 maxillary cases. Twenty-three of those resulted inautomatic eruption (45.1%), whereas, of the other 99cases in the maxilla that did not receive rapid palatal ex-panison, only 13 (13.1%) resulted in automatic eruption(odds ratio [OR], 5.43; 95% confidence interval [CI],2.43-12.14; P\0.001).

The results of the univariate and multivariate gener-alized estimating equation logistic regression with anky-losis as the dependent variable and surgical exposuretechnique (open or closed), age (continuous), severityof impaction (“nonsevere” group, grades I-V; “severe”group, grade VI), sex (male or female); and location ofimpaction in the maxilla (labial or palatal) as ankylosispredictors are shown in Table III. The automatic eruptioncases (n 5 38), the cases of grade VII (n 5 3), and theimpaction cases in the mandible (n 5 7) were excludedfrom this analysis. The univariate analysis showedweak evidence of an association between ankylosis andsurgical exposure technique and evidence of associa-tions between age, grade of impaction, and ankylosis.No evidence of association between ankylosis and eithersex or location of the impaction in the maxilla was de-tected. The multivariate analysis showed similar findingsand reaffirmed that sex and location of impaction in themaxilla make no significant contribution to the predic-tion of ankylosis, whereas surgical exposure technique,age, and severity of impaction appear to be significantankylosis predictors.

The ankylosis analysis of our 11 cases showed 4 casesof a priori ankylosis (Figs 1 and 5); 3 cases of ankylosis-related resorption in the roots of the impacted canines; 3cases of fibrous connective tissue fusion, in which thetissue fuses to the bonded attachment and the chain(Fig 6), or even to the crown of the tooth (Fig 7); and


1 case in which the impacted canine was pulled in aninappropriate direction (Table IV).

In 4 cases of 157 (2.5%; 2 spontaneous eruption, 1open surgical procedure, and 1 closed surgical proce-dure), the proximal lateral incisor was extracted duringtherapy because of severe root resorption.

Premolar extraction therapy was performed in only11 of 157 (7%) impacted canine cases.

DISCUSSION

Our clinical study focused first on the complication ofankylosis regarding the surgical exposure technique(open or closed), the patient's age, and the grade of im-paction, and then on the effect of rapid palatal expan-sion on the automatic eruption of the impactedcanines in the maxilla.

All participants for this clinical study came from theprivate practice of the first author, who treated all im-pacted canines orthodontically and surgically. In thisway, every patient, at each stage of the orthodonticor surgical therapy, was examined by the same clini-cian, who thus had full and direct control of, and infor-mation about, the outcome of every treatment method.

Evidence of an association between the closed surgi-cal exposure technique and ankylosis was found. Therewas also evidence that older patients have a higher riskof developing ankylosis, either a priori or during therapy.


Table III. Crude and adjusted odds ratios (OR) and 95% confidence intervals (CIs) from logistic regression for the ef-fect of surgical exposure technique, age, grade of impaction, sex, and location of impaction in the maxilla on canineankylosis

Category

Univariable model Multivariable model

OR 95% CI for OR P value OR 95% CI for OR P valueSurgical exposure techniqueOP1 Referent ReferentOP2 4.59 0.93-22.46 0.06 6.66 1.20-37.05 0.03

AgeReferent Referent

Per unit 1.01 1.04-1.02 0.001 1.11 1.03-1.19 \0.01Grade of impactionNonsevere (I-V) Referent ReferentSevere (VI) 9.13 2.28-36.52 0.002 13.53 1.85-98.75 0.01

SexMale Referent ReferentFemale 2.89 0.60-14.10 0.30 2.10 0.53-7.99 0.30

Location of impaction in the maxillaLabial Referent ReferentPalatal 1.40 0.27-7.24 0.69 2.46 0.38-15.88 0.35

OP1, Open surgical procedure; OP2, closed surgical procedure.

Fig 5. A, Orthopantomogram of a 41-year-old woman with a palatally impacted maxillary right canine(grade VI); B and C, open surgical exposure procedure; D, appropriate force vector during canine trac-tion; E, orthopantomogram of the same patient 1½ years after the initiation of treatment. A first reexpo-sure procedure had already been performed, but there had been no response to the orthodontictraction. An a priori ankylosis was present. F and G, With the cone-beam computed tomography im-ages, external and internal resorption of the impacted canine's crown was diagnosed. “Tunnels”through the enamel and dentin connected the 2 entities. H, Second open reexposure procedure;fine instruments were used to remove the inflammatory tissue on the labial surface of the impacted ca-nine's crown. I, The force vector did not change; J, the arrow indicates the area affected by ankylosis onthe labial surface of the tooth; K, the resorptive area on the labial surface of the pulp chamber and thegutta percha filling of the root canal are shown; L, final result.


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Fig 6. A, A bonded attachment with fused tissue was re-moved after reexposure of an impacted maxillary caninethat had been ankylosed for months after a closed surgi-cal exposure; B, the histologic examination of the fusedtissue showed edematous fibrous connective tissuewith mild chronic inflammatory infiltration of the substrateand irregular calcified deposits (diffuse calcification). CD,Calcified deposits; F, fibroblasts; L, lymphocytes.


Additionally, evidence of an association between theseverity of impaction, based on the categorization devel-oped during this study, and the appearance of ankylosiswas found. Finally, rapid palatal expansion appears to beassociated with automatic eruption of the impactedcanines.

The choice of the surgical exposure technique (openor closed) was independent of age and the grade of im-paction. The relatively large sample size of our study andcases in which rapid palatal expansion was performedalso allowed us to consider this space-gaining techniquein relation to canine impaction. Our study was in accor-dance with previous studies that have also indicated thatthe higher the mean age of the examined population, thesmaller the percentage of impaction of maxillarycanines.22,23 This means that, as age increases, thepercentage of automatic eruption also increases. Rapidpalatal expansion, usually performed in youngpatients, was used in our study as the main techniqueto gain space in all cases that met the criteria. Rapidpalatal expansion affects the whole maxilla in contrastto other space-gaining techniques such as premolar


extraction therapy and local space gaining with an open-ing spring. In this case, the use of a control group wouldbe of great importance, but it would be unethical to waitto see whether the impacted canine spontaneouslyerupts.

Using rapid palatal expansion in a group of patientsyounger (7.6-9.6 years) than our group (11.5-23.6 years)with palatally dislocated canines, Baccetti et al24 drewsimilar conclusions regarding automatic canine erup-tion.

The effect of age on the success rate and duration oftreatment of palatally impacted canines has also beenstudied by Becker and Chaushu.25

In the cases of ankylosis-related resorption, fibrousconnective tissue, and inappropriate direction of trac-tion presented in Table IV, there was movement ofthe impacted tooth between the start of traction andthe diagnosis of ankylosis. This was not so in the a pri-ori cases. Nevertheless, even in these cases, if, aftera proper diagnosis with cone-beam computed tomog-raphy, the surgeon can remove the ankylosed tissuefrom the crown of the canine without damaging theanatomic parts of adjacent teeth, then the orthodontistcan move the tooth into its proper position (Fig 5). Mo-bilization of the tooth with forceps in this form of an-kylosis was not necessary.

In our opinion, 3 main causes could result in traumato the periodontal ligament or the cementum of thecervical root of the impacted tooth and lead toankylosis-related resorption: (1) the low-speed bur dur-ing exposure, (2) chemical trauma26 to the periodontalligament from the 35% phosphoric acid, and (3) traumato the periodontal ligament in the cervical region be-cause of the direction or magnitude of the orthodonticforce. In these cases, during reexposure, the ankylosedteeth were mobilized with forceps, and orthodontic trac-tion began immediately. In 2 of 3 cases, we noticed thesame side effect of ankylosis after some weeks.

With regard to the a priori (Figs 1 and 5) and fibrousconnective tissue (Fig 6) cases as well as the case shownin Figure 7, the role of the dental follicle must be studiedfurther. In the dental follicle, stem cells are available;they are pluripotent and capable of differentiating intoother cell types.27,28 These cells could create ankylosedcavities in the crowns of the impacted teeth.

The orthodontist should obtain all available informa-tion from both traditional diagnostic means (orthopan-tomogram and lateral cephalogram, for which almost allof our patients are referred) and meticulous clinical ex-aminations, and not thoughtlessly refer the patient fora cone-beam computed tomogram that, although pro-viding additional diagnostic and therapeutic benefits,exposes the patient to higher levels of radiation.29-31


Fig 7. A, Orthopantomogram of an 18-year-old female patient with a palatally impacted maxillary rightpermanent canine of grade VI and delayed shedding of the maxillary right deciduous canine; B, closedexposure; C, the orthodontic movement of the impacted canine stopped 8½ months after its exposureand its orthodontic traction. An open reexposure procedure was performed. The rest of the impactedcanine's coronal part of the dental follicle and other fibrous connective and inflammatory tissue aroundthe bonded attachment are shown. The impacted canine was ankylosed. D, A large cavity became ap-parent in the distopalatal aspect of the tooth after removal of the fibrous connective tissue (arrow); E,final result.

Table IV. Ankylosis analysis of our 11 cases presented chronologically

Tooth and form ofimpaction

Surgicalexposure Reexposure Final outcome

Main causeof ankylosis

Affected area

Crown Root Other23, palatally OP2 Closed Extraction ARR O23, palatally OP2 Closed Extraction AP O13, palatally OP2 Closed Extraction ARR O23, palatally OP2 Closed Extraction AP O13, palatally OP2 Open Success FCT O23, palatally OP2 Open Success ARR O13, labially OP2 Open Success AP O23, palatally OP1 Open Success IDT O43, lingually OP2 Open Success FCT O13, labially OP2 Open Success FCT O13, palatally OP1 Open Success AP O

23, Maxillary left canine; 13, maxillary right canine; 43, mandibular right canine; OP1, open surgical procedure; OP2, closed surgical procedure;ARR, ankylosis-related resorption; AP, a priori ankylosis; FCT, fibrous connective tissue; IDT, inappropriate direction of traction.


The categorization of our impacted canines on pan-oramic radiographs (grades I-VII) was based on anatomicstructures and not on the angulations and linear mea-surements that many authors have included in theirstudies.32-40 Our method can be used in both themaxilla and the mandible, and its main advantage isthat it is virtually unaffected if the patient's head isincorrectly positioned in the cephalostat during


exposure. The improper positioning of the patient'shead, especially in the horizontal or median-sagittalplane during orthopantomogram exposure, might affectthe angular and linear measurements41 as well as thecategorization of the impaction based on those mea-surements.42

The estimation of the anatomic position of the im-pacted canines was accurately determined in most cases



from the orthopantomogram, lateral cephalogram, andclinical examination. However, some patients withsevere impactions (grades VI and VII) were referred fora cone-beam computed tomography image; this wasalso done when an a priori ankylosis was suspected(Fig 5).

Study limitations might be associated with the lack ofrandomization and the small number of ankylosisevents. However, the choice of surgical procedure was,in every case, predetermined for the whole period ofthe study, regardless of age, severity of impaction(grades I-VII), sex, or location of the impaction. Thus,the open procedure was performed on all patients whocame at the beginning of the study, the closed procedureon those in the middle, and the open procedure again onthose in the last period, except for 3 cases in which theclosed procedure was used. Selection bias because ofthe nonrandomized design is unlikely to have severelyinfluenced the results, since the baseline characteristicsbetween treatment groups were similar; although the in-terventions changed, the changes did not depend on thecases. The small number of events related to ankylosis isreflected in the low precision of the estimates, and thisshould be considered when interpreting the results.Performance, observer, and attrition bias are unlikelyto have affected the results of this trial, since the out-come was not subjective, and there were no losses to fol-low up.

The methods of this study in which the investigatorperformed both surgical and orthodontic proceduresmight not be a common practice. On the other hand,the inclusion of patients with characteristics commonlytreated by orthodontists worldwide, as well as the main-stream treatment approach, could allow us to considerour findings applicable to other settings.

CONCLUSIONS

There is some evidence of an association betweensurgical exposure technique, age, severity of impaction,and ankylosis. However, these findings should be inter-preted with caution because the number of events wassmall.

Rapid palatal expansion appears to be associatedwith automatic eruption of impacted canines.

This study is dedicated to Professor Emeritus JoachimTr€ankmann of University of Hannover, Hannover, Ger-many, for his lifetime dedication to orthodontic teach-ing. We also thank Ioulia Chatzistamou, lecturer in theDepartment of Basic Sciences, Section of Basic Sciencesand Oral Biology, University of Athens, for examiningthe 2 histologic preparations.


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