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Risk Indicators and Interceptive TreatmentAlternatives for Palatally Displaced CaninesTiziano Baccetti

The present article reviews diagnostic, prognostic, and therapeutic as-pects related to palatal displaced canines (PDCs) and their possible evo-lution to palatally impacted canines (PICs). Through the analysis of therelevant literature, a series of dental anomalies can be identified thatpresent with a significant clinical association with PDC. Because thesetooth disturbances may appear before PDC, they represent risk indicators

for the occurrence of the eruption anomaly of the maxillary permanentcanine. The second part of this work describes comparatively the effec-tiveness of several interceptive treatment approaches to PDC to avoid theevolution from PDC to PIC. In particular, the extraction of the deciduouscanine, alone or in combination with orthodontic forces aimed to preventthe physiological mesial movement of the upper permanent molar, ap-

pears to be able to increase by 2 to 3 times the rate of eruption of PDCs(diagnosed on a panoramic radiograph) with respect to that which occursin untreated subjects with PDC (spontaneous eruption in about one third

of the cases). Rapid maxillary expansion in the early developmentalstages may represent a valid alternative for the interceptive treatment ofPDCs (diagnosed on a posteroanterior cephalogram). Although geneticfactors are known to play a fundamental role in the etiology of PDC (andsubsequent PIC), it appears that environmental local factors can be af-fected by orthodontic/orthopedic approaches during the pathogeneticevolution process leading from PDC to final PIC. (Semin Orthod 2010;16:186-192.) 2010 Elsevier Inc. All rights reserved.

Palatal impaction of maxillary permanent ca-nines (palatally impacted canines or PICs)is the final outcome of a developmental anomalythat has been defined palatal displacement ofthe canine (PDC), ie, the intraosseous malposi-tion of the upper permanent canine before theexpected time for eruption.1 Although in the

past the expected time for canine eruption wascorrelated to chronologic age2 (12 years, 3months in girls and 13 years, 1 month in boys),attention has been given recently to the skeletalmaturation of the patient. The upper perma-nent canine can erupt at any prepubertal orpubertal stage of skeletal development until cer-vical stage (CS) 5 in cervical vertebral matura-tion(Fig 1).3 Beyond this stage, which occurs onaverage 1 year after the end of the adolescentgrowth spurt, a PDC can be defined as PIC.When the developmental stages of the dentitionare used to determine the time of emergence ofthe maxillary permanent canine delayed dentalage is found in association with PDCs.4

The early diagnosis of dental abnormalitiesthat share a common genetic origin with PDC(and PIC) can lead to the identification of riskindicators for PDC. Once PDC is recognized in

Department of Orthodontics, The University of Florence, Flo-rence, Italy.Thomas M. Graber Visiting Scholar, Department of Orthodon-

tics and Pediatric Dentistry, School of Dentistry, the University of Michigan, Ann Arbor.

Address correspondence to Tiziano Baccetti, DDS, PhD, Depart-ment of Orthodontics, Universit degli Studi di Firenze, Via delPonte di Mezzo, 4648, 50127, Florence, Italy. Phone: 01139-055-354265; Fax: 01139-055-609536; E-mail:[email protected]

2010 Elsevier Inc. All rights reserved.1073-8746/10/1603-0$30.00/0doi:10.1053/j.sodo.2010.05.004

186 Seminars in Orthodontics, Vol 16, No 3 (September), 2010: pp 186-192
mailto:[email protected]:[email protected]


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the individual patient (in most instances during

the late mixed dentition phase), interceptivemeasures can be implemented to avoid the finalestablishment of a PIC. These interceptive mea-sures classically tend to facilitate eruption of thecanine by acting on local/mechanical factorsthat may affect the evolution from PDC to PIC.The aim of this work is to review the factors thatcan be used as early risk indicators for the oc-currence of the eruption disorder of maxillarycanines and to describe the effectiveness of al-ternative interceptive therapies to avoid canineimpaction in presence of PDC.

Risk Indicators for PDC and PIC

The etiology of PDC, and subsequent PIC, hasbeen associated with a multifactorial geneticcomplex that controls the expression of other,possibly concurrent, tooth anomalies.1 Peck etal1 have also indicated multiple evidential cate-gories for thegenetic origin of PDC, ie, familialoccurrence,5 bilateral occurrence (17%-45%),sex differences, differences in prevalence ratesamong different populations, and increased oc-currence of other concomitant dental anoma-

lies.6

Gender

PDC is significantly more frequent in femalesubjects, thus indicating involvement of the sex-ual chromosomes in the etiology of the disorder.In a previous investigation7 the authors analyzedthe prevalence and distribution of PDC in alarge orthodontic population of 5000 subjects.

The prevalence rate of PDC was 2.4%, with a

male-to-female ratio of 1:3.

Associated Dental Anomalies

The search for associated dental anomalies isone of the most relevant methodsto investigatethe genetic determinants of PDC.1,6 The spec-trum of possible associations among toothanomalies was studied by Hoffmeister between1975 and 1985.8 The following manifestationswere found over 3 generations of a family: mul-tiple missing teeth (aplasia of upper lateral inci-sors), peg-shaped incisors, ectopic eruption of

maxillary first permanent molars, and intraosse-ous displacement of maxillary canines. In 1992,Bjerklin et al9 investigated the associationsamong 4 tooth and eruption disturbances (ec-topic eruption of first molars and of maxillarycanines, infraocclusion of primary molars, andaplasia of premolars). The findings indicatedthe presence of significant reciprocal associa-tions. These results were interpreted supporting thehypothesis of a common, presumably hereditary, eti-ology for the studied tooth disturbances, each distur-bance having incomplete penetrance.

A very high prevalence of associated toothanomalies (70%) was calculated in 1993 in asample of 169 inherited syndromes presentingwith tooth disturbances, strongly suggesting thepossibility of genetic relationships among toothnumber, size, shape, and structure characteris-tics.10 These relationships havebeen confirmedfurther in the studiesby Baccetti6 in 1998 and byLeifert and Jonas11 in 2003. By contrast, thestudy by Baccetti6 indicated that supernumerary

Figure 1. (A) Male subject, 12 years, 3 months old. Tooth is impacted. Diagnosis of impaction is corroboratedby the presence of CS 5 in the assessment of skeletal maturation by the cervical vertebral maturation method (B).

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teeth and ectopic eruption of first molars are notsignificantly associated with PDC.

In a study by Sacerdoti and Baccetti in 20047

PDC showed reciprocal significant associationswith bilateral small-sized upper lateral incisors.

Shalish et al12

have demonstrated that the distalangulations of unerupted mandibular premolaris significantly greater in children with PDC. Theexistence of associations between different toothanomalies is not only important from an etio-logic point of view but also relevant clinicallybecause the early diagnosis of 1 anomaly mayindicate an increased risk for later appearanceof others. Table 1 illustrates the list of dentalanomalies that present with a significant associ-ation with PDC and that can be used as riskindicators for the eruption anomaly of the max-illary canine. Figures 2 and3 illustrate clinicalexamples of the associations among differentdental anomalies.

Interceptive Treatment Alternatives

As mentioned previously, although the etiologyof PDC (and subsequent PIC) has been linked toa genetic component, the evolution from PDCto PIC can be affected by local/mechanical fac-tors that have become the targets of intercep-tive treatment of PDC to prevent the final oc-currence of PIC, as well as to allow the canine to

erupt physiologically.

Extraction of the Deciduous Canine

The procedure of reducing the prevalence ofimpacted PDCs by extracting the correspondingdeciduous canine has beenreported in the den-tal literature since 1936.13 The outcomes in sev-eral individual cases during the subsequent 50years corroborated the clinical recommendation

for this interceptive measure, as reviewed by Ja-cobs.14 The prospective study by Ericson andKurol in 198815 analyzed the effects of the ex-traction of the deciduous canine on PDC in rateand time of spontaneous eruption. A total of36 of 46 PDC canines (78%) presented with animprovement in the eruption pathway after re-moval of the deciduous canines, after a timeinterval of 6 to 12 months. In a longitudinal2-year investigation in 1993, Power and Short16

described the achievement of a normal eruptiveposition of PDC in 62% of the cases after theextraction of the deciduous canines. It should be

emphasized that both the studies by Ericson andKurol and by Power and Short were conductedbefore the establishment of a genetic basis forPDC. Both studies calculated prevalence rates ofcanine eruption by use of the number of erupt-ing individual teeth, which is not recommended

Table 1. Relationship Between PDC and OtherDental Anomalies

Dental anomalies that are significantly associated with PDCSmall size of upper permanent incisors (also bilateral)Aplasia of second premolarsInfraocclusion of primary molarsDistal angulation of lower second premolars (before

their eruption)Enamel hypoplasia

Dental anomalies that are not significantly associated withPDC

Supernumerary teethEctopic eruption of first permanent molars

Figure 2. Female subject, 11 years, 6 months old. Thepanoramic radiograph reveals several dental anoma-lies associated with palatally displaced maxillary leftpermanent canine: aplasia of upper right second pre-molar, aplasia of lower left second premolar, anddistally angulated unerupted lower right second pre-molar.

Figure 3. Female subject, 11 years, 2 months old. Thepalatally displaced maxillary right permanent canineis associated with the bilateral presence of small-sizedupper lateral permanent incisors.

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because of the genetic etiology of the tooth de-velopmental disorder. In fact, cases with bilateralPDCs should not count for 2 independent statis-tical units because the same etiologic factors acton both sides of the maxillary arch. Therefore,

when analyzing data pertaining to PDCs or PICsit is indicated to use individual subjects, and notindividual teeth, as statistical units to avoid in-flated prevalence rates.

A study by Leonardi and associates17 failed tofind significant effectiveness of deciduous ca-nine extraction for treatment of PDC. However,the power of this study was limited, as stated bythe authors in a more recent study that wasrepresented by a randomized prospective ap-proach to interceptive treatment of PDC withthe incorporation of untreated controls and astatistically appropriate number of subjects en-rolled in the study.18 In this recent investigation,the removal of the deciduous canine as an iso-lated measure to intercept palatal displacementof maxillary canines showed 65.2% prevalencerate of success, which was significantly greater(almost double) than the success rate in un-treated controls (36%). The prevalence rate ofcanine eruption here was calculated on individ-ual subjects, and eruption of the tooth was de-fined when a bracket could be placed on thecrown of the canine.

Interceptive Therapies, Including the Use of Other Devices: Randomized Clinical Trials

Recently, 2 randomized clinical trials haveevaluated the role of alternative interceptiveapproaches to PDC that consisted of eitherextraction of the deciduous canine inassocia-tion using either a headgear appliance18 or arapid maxillary expander.19 The randomizedclinical trial by Baccetti et al in 200818 evalu-ated the effectiveness of deciduous canine ex-traction in combination with the use of a cer-

vical pull headgear (patients wore theheadgear only at night). The randomized pro-spective design of the investigation comprised75 subjects with PDCs (92 maxillary canines)who were randomly assigned to 3 groups, forexample, extraction of the deciduous canineonly; extraction of the deciduous canine andcervical pull headgear; and untreated controlgroup. Panoramic radiographs were evaluatedat the time of initial observation, at an average

age of 11.7 years (T1), and after an averageperiod of 18 months (T2).

At T2, an evaluation of the relative successof canine eruption was performed, with a sta-tistical comparison between the groups. A su-

perimposition study on lateral cephalogramsat T1 and T2 evaluated the changes in thesagittal position of the upper molars in the 3groups. As mentioned before, the extractionof the deciduous canine as an isolated mea-sure to intercept palatal displacement of max-illary canines showed 65.2% prevalence rate ofsuccess, which was significantly greater thanthe success rate in untreated control patients(36%). The night-time use of a headgear inaddition to the extraction of the deciduouscanine was able to induce successful eruptionin 87.5% of the cases, with a significant im-provement in the measures for intraosseouscanine position. There was no significant dif-ference between the 2 interceptive approachesas to time for canine eruption.

The cephalometric superimposition studyshowed a significant mesial movement of theupper first molars in the control group and ofthe deciduous canine only group when com-pared with the extraction of the deciduouscanine and cervical pull headgear group. Itappears therefore that the main effect of theheadgear is to prevent the mesial movement of

the posterior segments of the upper arch, thusfacilitating the maintenance of an eruptionpathway for the canine. It should be remem-bered that in a nonrandomized retrospectivestudy in 2002, Olive20 already reported thesignificantly favorable effects of a clinical pro-tocol, including the extraction of the decidu-ous canine followed by fixed appliance ther-apy to increase the maxillary arch perimeter.

A second prospective randomized clinicalstudy was aimed to assess the prevalence rate oferuption of PDCs when diagnosed at an early

developmental stage by posteroanterior headfilms and consequently treated by rapid maxil-lary expansion (RME). A sample of 60 subjectsin the early mixed dentition with PDC diagnosedon posteroanterior cephalogram radiographsac-cording to the method by Sambataro et al21 wasenrolled in the trial. The age range of the sub-jects at first observation (T1) was 7.6 to 9.6 years,with a prepubertal stage of skeletal maturity (CS1 or 2). The diagnosis of PDC was performed on



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posteroanterior cephalograms because the as-sessment of PDC on panoramic films is not reli-able at these early ages. The 60 subjects wererandomly allocated to the treatment group (35cases) or the no-treatment group (25 cases). The

treatment group was treated with a banded rapidmaxillary expander; at the end of expansion allpatients were retained with the expander in placefor 6 month; thereafter, the expander was re-moved, and patients wore a retention plate atnight for 1 year. The no-treatment group did notreceive any treatment. At T2 (early permanentdentition, postpubertal, CS 5) all cases were reeval-uated. No statistically significant differences werefound for any variable at T1. It should be notedthat subjects with PDCs in the early mixed denti-tion did not exhibit transverse deficiency of the

maxillary arch. Therefore, the transverse featuresof the upper maxilla were not related to the etiol-ogy of the eruption disorder of the canine, asindicated previously by Langberg and Peck.22 Infact, the indication for RME in the cases enrolledin the clinical study was the presence of mild-to-moderate tooth-size/arch-size discrepancy and/orClass II or Class III tendency, and not transversemaxillary deficiency.

The use of the orthopedic device RME assistedin preventing final impaction of PDC, during thedevelopmental stages from PDC to PIC. Once

again, although a genetic etiology has been postu-lated for initial palatal displacement of upper ca-nines, the pathogenesis of the displacement and offinal impaction is related especially to the anatom-ical complexity of the eruption pathway of thistooth,23 that can be affected by environmentalalterations. The prevalence rate of successful erup-tion of the maxillary canines was 65.7% in thegroup treated with RME, whereas it was only13.6% in the untreated control group. The com-parison was obviously statistically significant andled to the conclusion that the use of a rapid max-

illary expander as an early interceptive approach isan effective procedure to increase the rate of erup-tion of palatally displaced canines. The low preva-lence rate for spontaneous eruption of canines inthe control patients is caused by methodologicalaspects of the study that included subjects not onlywith a diagnosis of PDC but also with a prognosisof PIC, as derived by the analysis of posteroante-rior cephalogram films according to the methodby Sambataro et al.21

The comparison of the prevalence rate forsuccessful outcomes of RME as an interceptiveprocedure in PDC subjects with those reportedby previous studies on alternative treatment ap-proaches to potentially impacted canines reveals

that RME treatment shows a rate of effectiveness(65.7%) similar to the one described for extrac-tion of the deciduous canines alone (78% ac-cording to Ericson and Kurol, including im-provement of eruption path;15 62% according toPowerand Short;16 65.2% according to Baccettiet al18), or in combination with fixed appliances(75% according to Olive20), and smaller thanthe prevalence rate for eruption of the caninesfollowing the use of a cervical-pull headgear(87.5% according Baccetti et al;18 Table 2).

Several factors need to be considered whenevaluating the outcomes of the alternative inter-ceptive treatment approaches to PDC. Althoughthe extraction of the deciduous canine alone is lesseffective than when carried out in combinationwith a headgear appliance, does allow a signifi-cantly smaller burden of treatment for the pa-tient. Obviously, patients who require the use oforthodontic forces to distalize upper molars (ClassII or end-to-end patients, or patients with a ten-dency to crowding of the upper arch) will benefitfrom the combined treatment of extraction of thedeciduous canine and headgear, both in correc-tion of their malocclusions and of improvement in

the probability of canine eruption. In addition, theRME approach (which is independent from theextraction of the deciduous canine) has been eval-uated at an early developmental age (7-9 years),when diagnosis of PDC on panoramic films is un-reliable and a posteroanterior cephalogram is re-quired. Moreover, the diagnosis of PDC on pos-teroantrerior cephalograms can be effectivelyperformed only in cases with severe displacementof the canine towards the midfacial structures. Afurther study is currently evaluating the role ofmaxillary expansion therapy (in combination with

the extraction of the deciduous canine) in moremature patients in the late mixed dentition, withdiagnosis of PDC performed classically on a pan-oramic film.

Conclusions

In conclusion, PDC is the developmental an-tecedent of PIC. If not intercepted with earlytreatment modalities, PDCs become PICs in 2

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of 3 cases. Skeletal maturation(by the cervicalvertebral maturation method)3 can assist inthe determination of the evolution from PDCto PIC: the canine is impacted when it is still inan intraosseous position at CS 5 or beyond (2or more years after the adolescent growth

spurt). Several dental anomalies that are sig-nificantly associated with the occurrence ofPDC and that become clinically manifest be-fore PDC can represent risk indicators for theeruption anomaly of the maxillary permanentcanine. Finally, different interceptive ap-proaches to PDC are able to promote eruptionof the displaced canine with a success rate thatranges from 2 to 3 times the rate shown byuntreated controls, as assessed in several evi-dence-based literature reports. Interceptivetreatment of PDC to avoid PIC would seem tobe clinically recommended.

References

1. Peck S, Peck L, Kataja M: The palatally displaced canineas a dental anomaly of genetic origin. Angle Orthod64:249-256, 1994

2. Hurme V: Range of normalcy in the eruption of perma-nent teeth. J Dent Child 16:11-15, 1949

3. Baccetti T, Franchi L, De Lisa S, et al: Eruption of themaxillary canines in relation to skeletal maturity. Am JOrthod Dentofac Orthop 133:748-751, 2008

4. Becker A, Chaushu S: Dental age in maxillary canine ectopia.

Am J Orthod Dentofac Orthop 117:657-662, 2000

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Table 2. Comparative Tabulation of the Outcomes of Studies on Interceptive Treatment of PDCs

Study Interceptive Treatment Age at Time of Interceptive

Treatment

Prevalence Rate of SuccessfulCanine Eruption in Treated

Subjects

Prevalence Rate of Successful Canine

Eruption in UntreatedControl Subjects

Ericson and Kurol,198815 Extraction of deciduouscanine alone 10-13 yrs 78% (includes eruption andimprovement in eruptionpathway; percentagecalculated on number ofteeth)

No controls

Power and Short,199316

Extraction of deciduouscanine

11.2 yrs 1.43 yrs 62% (Eruption; percentagecalculated on number ofteeth)

No controls

Olive, 200220 Extraction of deciduouscanine and fixedappliances to gainarch perimeter

11.4-16.1vyrs 75% (Eruption; percentagecalculated on number ofteeth)

No controls

Baccetti et al,200818

Extraction of deciduouscanine alone

11.7 yrs 0.8 yrs 65.2% (Eruption;percentage calculated onnumber of subjects)

36%


Extraction of deciduouscanine and headgearon maxillary molars(at night)

11.9 yrs 0.9 yrs 87.5% (Eruption;percentage calculated onnumber of subjects)

36%


Rapid maxillaryexpansion

7-9 yrs 65.7% (Eruption;percentage calculated onnumber of subjects)

13.6% (severe PDCswith prediction ofimpaction)



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15. Ericson S, Kurol J: Early treatment of palatally erupting

maxillary canines by extraction of the primary canines.

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16. Power SM, Short MB: An investigation into the re-

sponse of palatally displaced canines to the removal of

primary canines and an assessment of factors contrib-

uting to favourable eruption. Br J Orthod 20:215-223,1993

17. Leonardi M, Armi P, Franchi L, et al: Two interceptive

approaches to palatally displaced canines: A prospec-

tive longitudinal study. Angle Orthod 75:581-586,

2004

18. Baccetti T, Leonardi M, Armi P: A randomized clinical

study of two interceptive approaches to palatally dis-

placed canines. Eur J Orthod 30:381-385, 2008

19. Baccetti T, Mucedero M, Leonardi M, et al: Interceptive

treatment of palatal impaction of maxillary canines with

rapid maxillary expansion: A randomized clinical trial.

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20. Olive RJ: Orthodontic treatment of palatally impacted

maxillary canines. Aust Orthod J 18:64-70, 2002

21. Sambataro S, Baccetti T, Franchi L, et al: Early predictivevariables for upper canine impaction as derived from pos-

teroanterior cephalograms. Angle Orthod 75:28-34, 2005

22. Langberg BJ, Peck S: Adequacy of maxillary dental arch

width in patients with palatally displaced canines. Am J

Orthod Dentofac Orthop 118:220-223, 2000

23. Peck S, Peck L, Kataja M: Site-specificity of tooth maxil-

lary agenesis in subjects with canine malpositions. Angle

Orthod 66:473-476, 1996

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