articulo diagnosticotemprano de caninos impactados (1)

ORIGINAL ARTICLE

Early prediction of maxillary canine impactionfrom panoramic radiographs

Anand K. Sajnania and Nigel M. Kingb

Navi Mumbai, India, and Hong Kong SAR, China

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Introduction: Treatment of impacted maxillary canines frequently requires surgical intervention, whichcan involve substantial complications. Thus, it is desirable to identify a reliable method for the early diagnosisof canine displacement. In this study, we sought to determine whether impaction of a maxillary canine can bepredicted using measurements made on a panoramic radiograph. Methods: This retrospective study was con-ducted at a dental hospital in Hong Kong with panoramic radiographs. Geometric measurements were made on384 panoramic radiographs of patients with a unilaterally impacted maxillary canine (group I) to characterize itspresentation and compare them with the unaffected antimere (group II). Results: There was a clinically discern-ible difference of 4 mm at the age of 8 years and beyond between the mean distance of the tip of the impactedcanine (group I) and that of the antimere (group II) from the occlusal plane (P\0.05). Furthermore, there wasa statistically significant difference at the age of 9 years and beyond between the 2 groups according to theposition in different sectors and according to the mean angle made with the midline (P\0.05). Conclusions:Diagnosis of maxillary canine impaction is possible at 8 years of age by using geometric measurements onpanoramic radiographs. (Am J Orthod Dentofacial Orthop 2012;142:45-51)

The fundamental aspect in the diagnosis of andtreatment planning for an impacted maxillary per-manent canine is the ability to recognize and pre-

dict its subsequent failure of eruption. Early diagnosis ofcanine displacement, in relation to the surroundingstructures, is based primarily on a radiographic examina-tion. Ericson and Kurol,1 who studied children aged 10to 13 years, proposed that the diagnosis could bemade using a panoramic film and that the time couldbe defined as “moderately” early. They used a series ofgeometric measurements made on panoramic radio-graphs that included the angle formed by the long axisof the canine with the midline, the vertical distancefrom the tip of the canine to the occlusal plane, andthe distribution of the canine into different sectorsdepending on its location in relation to adjacent teeth.Furthermore, their final observations included the

r lecturer, pediatric dentistry, Terna Dental College and Hospital, Navibai, India.ssor, pediatric dentistry, Faculty of Dentistry, University of Hong Kong,Kong SAR, China.uthors report no commercial, proprietary, or financial interest in the prod-r companies described in this article.t requests to: Dr. Anand K. Sajnani, Bin Muftah Medical Centre, Paediatricstry, Al Markhiya Street, PO Box 201357, Doha, Qatar; e-mail, [email protected], November 2011; revised and accepted, February 2012.5406/$36.00ight � 2012 by the American Association of Orthodontists..1016/j.ajodo.2012.02.021

therapeutic effects of an interceptive approach such asextraction of a deciduous canine.1,2 Lindauer et al3

used a control group to develop a method to predict ca-nine impaction at an accuracy of 78% with a modifica-tion of the procedure originally proposed by Ericson andKurol.1 Overlapping of the lateral incisor by the canineon panoramic radiographs, when development of the in-cisor has been completed, can be considered a sign ofa possible eruptive anomaly of the canine.4 Likewise, ithas been shown that sector location is a significantlybetter predictor of impaction than tooth angulation.5

However, the relative diagnostic importance of theseradiographic factors, including angulation of the canineto the midline, height from the occlusal plane, and buc-copalatal position, has not been previously evaluated inChinese children and adolescents.

Treatment of a palatally impacted canine usuallyinvolves surgical exposure and traction to move thetooth into the correct position.6 These procedures havehigh success rates but can involve substantial time andfinancial costs. They also carry risks of gingival recession,bone loss, and detachment of the gingiva around thetreated canine.7 An interceptive treatment optionincludes extraction of the deciduous canine to preventfinal impaction of the permanent successor. However,this method must first prove a positive diagnosis ofcanine displacement that will otherwise lead to canineimpaction. Therefore, it is desirable to identify a method

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Fig 1. Diagrammatic representation of the measurementof the perpendicular distance from the tip of the impactedcanine to the occlusal plane. Fig 2. Diagrammatic representation of the distribution of

the canine in different sectors depending on the locationof the tip of the tooth.

46 Sajnani and King

that can give the clinician a reliable protocol for earlydiagnosis of displacement of a canine and predictionof subsequent impaction.

A panoramic radiograph is a primary routine investi-gation for many patients. Hence, the variable, visible onthat radiograph, could be used diagnostically to predictthe impaction of a maxillary canine. This early diagnosisof an impaction can be used to determine the advan-tages, disadvantages, success rates, and clinical benefitsof any operative technique. Thus, the objective of thisstudy was to determine whether impaction of a maxillarycanine can be predicted by using measurements madeon a panoramic radiograph.

MATERIAL AND METHODS

A total of 384 panoramic radiographs of 442 nonsyn-dromic patients known to have unilaterally impactedmaxillary canines who had attended the PaediatricDentistry and Orthodontics Clinic at Prince Philip DentalHospital in Hong Kong SAR, China, were availablefor assessment. The clinical records and the radiologicdata were used to assess and confirm the position of animpacted maxillary canine. The canine was defined asimpacted if its antimere had completely erupted in theoral cavity, but the unerupted canine showed completeroot formation radiographically (Fig 1). The radiographsmost commonly used to determine the position of the im-pacted canine are panoramic radiographs in combinationwith anterior occlusal films by using the vertical parallaxprinciple8 and periapical radiographs taken at various hor-izontal angulations with the horizontal parallax tech-nique.9 After the diagnosis had been confirmed from theclinical records and radiologic data, previous panoramicradiographs, if available, were traced to evaluate the posi-tion of the permanent canine of these patients. Thus, by

July 2012 � Vol 142 � Issue 1 American

using this mixed-longitudinal study design, the locationof a canine was determined at different chronologic agesof a patient. All radiographs were examined in a darkenedroomby using an illuminated x-ray viewing box. The pan-oramic radiographs were traced with 0.003-in matte ace-tate tracing paper and a 0.5-mm HB fine lead pencil.Geometricmeasurementsweremadeon thepanoramic ra-diographs to show the impacted canine (group I) and tocompare them with similar measurements made for theantimere tooth (group II). The measurements includedthe angulation and position (sector) of the tooth, the dis-tance from the occlusal plane, and the stage of root devel-opment (adapted from Ericson and Kurol1).

The occlusal plane was determined by drawing a hor-izontal line passing through the incisal edge ofthe central permanent incisor and the occlusal plane ofthe first permanent molar on the given side. When thecentral permanent incisor or the first permanent molarwas absent, the lateral permanent incisor or the secondpermanent molar was used to determine the occlusalplane. In the deciduous dentition stage, the central inci-sor and the second molar were used to define the occlu-sal plane. A perpendicular line was then drawn from theincisal tip of the impacted canine and the antimere to theocclusal plane. This distance was called “d1” for theimpacted canine group (group I) and “d0” for the anti-mere group (group II) (Fig 1).

Groups I and II were categorized into different sectorsdepending on the location of the tip of the tooth inrelation to the adjacent teeth (Fig 2).

The angle formed by the long axis of the impactedmaxillary canine (group I) with the midline was called“a,” and the angle formed by the long axis of the max-illary canine on the antimere side (group II) was called

Journal of Orthodontics and Dentofacial Orthopedics

Fig 3. Diagrammatic representation of the measurementof the angle made by the long axis of the impacted caninewith the midline.

Table I. Distribution by age of the 384 panoramicradiographs with unilaterally impacted canines

Age of thepatient (y)

Radiographsavailable (n)

Follow-up radiographsavailable (n)

3 1 04 4 05 7 06 7 07 18 38 17 119 32 20

10 42 2811 70 4712 91 6213 60 4314 17 415 6 216 4 017 2 018 2 119 3 121 1 0

Table II. Mean differences between the distance (inmillimeters) of the cuspal tip of the impacted canineand the unaffected antimere from the occlusal plane

Age ofpatients(y)

Mean distanceof impactedcanine fromocclusal plane

(d1)

Mean distanceof unaffectedantimere fromocclusal plane

(d0)

Meandifferencebetweengroups(d1-d0) P value

#4 19.6 19 0.6 0.35 21.9 20.4 1.4 0.01*6 21 20.3 0.7 0.04*7 20.4 18.1 2.3 0.04*8 20.2 16.5 3.7 0.001*9 19 11.2 7.8 \0.0001*

10 19.7 7 12.7 \0.0001*11 17.9 3.6 14.3 \0.0001*12 18.6 2.2 16.4 \0.0001*13 17.7 1.4 16.3 \0.0001*14 18.5 1.9 16.6 \0.0001*

$15 15.7 1.3 14.4 \0.0001*

*Statistically significant.

Sajnani and King 47

“q” (Fig 3). The midline was defined by the followinglandmarks on the radiograph: intermaxillary suture, an-terior nasal spine, nasal septum, and internasal suture.When the tip of the canine was pointing in a directionopposite to the midline, a “�ve” sign was assigned asa prefix.

The root development of the canine was divided into6 stages. The various stages and their interpretationswere stage 0, root formation not yet begun; stage 1,root formation less than a quarter complete; stage 2,root formation between a quarter and a half complete;stage 3, root formation between a half and three quar-ters complete; stage 4, root formation more than threequarters complete; and stage 5, root formation com-plete.

All data were input into an Excel worksheet (version2007; Microsoft, Redmond, Wash), and the data wereprinted out and checked for any keying-in errors. To de-termine whether there were any statistical differencesbetween the geometric measurements made on the pan-oramic radiographs, the paired t test was used with the Pvalue set at 0.05.

RESULTS

The 384 panoramic radiographs that formed thesample for this study included parts of records from111 patients with a total of 222 longitudinal follow-up radiographs. The data obtained from all 384 pano-ramic radiographs were divided into different age groups(Table I) to facilitate comparing the position of theimpacted canine (group I) with the unaffected antimere(group II). This included 54 radiographs from patients inthe age group of 3 to 8 years. No statistically significantdifference was found between the values and measure-ments obtained for patients in whom the canines were

American Journal of Orthodontics and Dentofacial Orthoped

buccally impacted and those in whom the canines werepalatally impacted. Hence, the data were combinedand the results further analyzed.

There was a statistically significant difference at theage of 5 years between the mean distance of the tip ofthe impacted canine (group I) and the unaffectedantimere (group II) (P 5 0.01). All age groups beyondthe age of 5 years also showed a highly statistically sig-nificant difference between the mean location of the im-pacted canine and the unaffected antimere (Table II).

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Fig 4. Difference between the mean distances of the cuspal tip of the impacted canine and the unaf-fected antimere from the occlusal plane according to the age of the patients.

Table III. Mean differences between sector locationsof impacted maxillary canines and their unaffectedantimeres

Age ofpatients(y)

Mean sectorlocation ofimpactedcanine (S)

Mean sectorlocation ofunaffectedantimere (N)

Meandifferencebetween thegroups (S-N) P value

#4 0 0 0 15 0 0 0 16 0 0 0 17 0.3 0.2 0.1 0.58 0.6 0.3 0.3 0.39 1.0 0.2 0.7 0.007*

10 1.2 0.1 1.1 \0.0001*11 1.3 0.0 1.3 \0.0001*12 1.7 0.0 1.7 \0.0001*13 1.6 0 1.6 \0.0001*14 2.3 0 2.3 \0.0001*

$15 2 0 2.0 \0.0001*


48 Sajnani and King

The mean distance covered by the impacted canine inthe vertical direction from 5 to 12 years of age was 3.3mm. During the same period, the mean distance coveredby the unaffected antimere was 18.2 mm (Fig 4).

There was a statistically significant difference at theage of 9 years between the mean location of the im-pacted maxillary canine (group I) and the unaffectedantimere (group II) according to the position in the sec-tor (P5 0.007) (Table III). All age groups beyond the ageof 9 years showed a highly statistically significant differ-ence between the mean location of the impacted canineand the unaffected antimere (P \0.0001). The resultsdemonstrated that, at the age of 9 years, the cusp tipof the impacted canine crosses the distal border of thelateral incisor to lie between the distal border and themidline of the lateral incisor (Fig 5).

There was a highly statistically significant differenceat the age of 9 years between the mean angle made bythe long axis of the impacted canine (group I) with themidline and the angle of the unaffected antimere (groupII) with the midline (P 5 0.0004) (Table IV). All agegroups beyond the age of 9 years also showed a highlystatistically significant difference between the locationof the impacted canine and the unaffected antimere(P \0.0001). At 9 years of age, the mean angulationformed by the long axis of the impacted canine withthe midline was 28.4�; after that, it continuouslyincreased as the age of the patient increased (Fig 6).

No statistically significant difference was obtainedbetween the mean root formation stages of the impactedcanine (group I) and the unaffected antimere (group II)in any age group (Table V; Fig 7).

DISCUSSION

Panoramic films have been used extensively for theidentification of diagnostic parameters aimed at


facilitating interceptive treatment planning. Occasion-ally, patients have distortions in the frontal dentoalveo-lar regions.1,10 However, it has been demonstrated bymathematical calculations and confirmed byexperimental tests that panoramic radiographic imagescan be reliable for geometric measurements in clinicalpractice.11,12 Linear vertical measurements, ratiocalculations, and angular measurements can be madeon a panoramic radiograph with consistent accuracy.13

Moreover, a panoramic radiograph is a reliable indicatorfor determining the buccopalatal position of uneruptedmaxillary canines.14

The need for a method to detect impaction of maxil-lary canines at an early age has been identified inthe literature.3 Hence, although the panoramicradiographs of patients with unilateral impactions


Fig 5. Difference between the mean sector location of the impacted canine and the unaffected anti-mere according to the age of the patients.

Table IV. Mean differences between angulations (indegrees) formed by the long axis of the impacted ca-nine and the unaffected antimere with the midline

Age ofpatients(y)

Mean angleformed byimpacted

canine withmidline (a)

Mean angleformed byunaffected

antimere withmidline (q)

Meandifferencebetween thetwo groups

(a-q) P value#4 0 0 0 15 0 0 0 16 5.6 0 5.6 0.27 14.3 11.3 3 0.58 24.2 20.3 3.9 0.79 28.4 11.3 17.1 0.0004*

10 26.9 6.0 20.9 \0.0001*11 37.4 3.5 33.9 \0.0001*12 36 2.3 33.7 \0.0001*13 42.7 1 41.7 \0.0001*14 44.9 1.9 43 \0.0001*

$15 41.4 0 39.9 \0.0001*


Sajnani and King 49

were derived from a mixed-longitudinal study design,they were divided into groups depending onthe patients' ages to detect changes in the position ofthe impacted canine and the unaffected antimere. Thiswould allow determination of the geometric variablesand measurements that show a significant change ata given age between the 2 groups and can thus help topredict an impaction early.

There was a significant difference between the 2groups at the age of 5 years and beyond, when thedistance from the cusp tip of the canine to the occlusalplane was used to determine the position of the tooth. Al-though this difference was small and is clinically difficultto discern, it suggests that the canine that would eventu-ally remain impacted (unerupted) loses the potential formovement in the vertical plane as early as 5 years ofage. Thus, it is possible that genetic disturbances start af-fecting the canine at an early age.15 Also, it is highly un-likely that the lateral incisor would influence themovement of the canine at this early age, as suggestedby the guidance theory.16-18 However, the antimerecanine (unaffected, erupted canine) continued to movedownward in the vertical plane and travelled almost18.2 mm from 5 to 12 years of age; this finding has alsobeen demonstrated by Coulter and Richardson.19 By 8years of age, therewas ameandifference of approximately4mmbetween the2 groups that canbedetected clinically.

There was a highly statistically significant differencebetween the 2 groups at the age of 9 years and beyond,when sector location of the cusp tip was used to deter-mine the position of the tooth. At this age, the cusptip of the impacted canine was found to lie betweenthe distal root surface and the central long axis of theadjacent lateral incisor, whereas the cusp tip of theantimere canine lay superior to the deciduous canine.At all ages beyond 9 years, the impacted canine was


found to continuously move mesially toward the facialmidline, whereas the antimere canine occupied the idealanatomic position and eventually erupted.

Also, there was a highly statistically significantdifference between the 2 groups at the age of 9 years andbeyond, when the angle made by the central long axis ofthe canine with the facial midline was used to determinethe position of the tooth. At this age, the impacted caninewas mesially tilted at an angle of approximately 30�, andthe antimere canine was almost vertical with a mean angleof approximately 11�. At all ages beyond 9 years, an im-pacted caninewas found to have a tendency to tilt mesially,thus increasing the angle that it formedwith the facial mid-line. In contrast, the antimere canine tended to lie almostvertically, and finally it erupted into the oral cavity. These


Fig 6. Difference between the mean angulations of the impacted canine and the unaffected antimerewith the midline according to the age of the patients.

Table V. Mean differences between root formationstages of the impacted canine and the unaffectedantimere

Age ofpatients(y)

Mean rootformation of

impacted canine(Sr)

Mean rootformation ofunaffected

antimere (Nr)

Differencebetween thegroups (Sr-

Nr)P

value#6 0 0 0 17 1.1 1.1 0 18 1.7 1.8 �0.1 0.39 2.8 2.7 0.1 1.0

10 3.6 3.7 �0.1 0.111 4.1 4.1 0.0 0.812 4.5 4.6 �0.1 0.613 4.7 4.7 0.0 0.814 4.9 5 �0.1 0.2

$15 5 5 0.3 0.2

50 Sajnani and King

findings, detectable on a panoramic radiograph, appear toserve as valuable features to help determine the presence ofan impacted or potentially ectopically positioned canine forclinical practitioners.

However, the various stages of root formationbetween an impacted canine and the unaffected anti-mere failed to show any difference during the entirecourse of development and eruption of the teeth. Thisgives rise to the hypothesis that intrinsic mechanismsof development (genetics) do not completely controlthe position and eventual impaction of the canine15;this in turn suggests that other environmental factors,such as guidance from the lateral incisor and crowding,influence the final outcome.16-18

Ericson and Kurol20,21 stated that a radiographicexamination before the age of 10 years does notprovide a reliable means to determine the futureunfavorable path of eruption of a maxillary canine.However, our findings suggest that early radiographicexamination aided by geometric measurements canprovide substantial information on the eruptionpattern of a maxillary canine, thus allowing earlydetection of an impaction.

Warford et al5 suggested that sector location of thecusp tip of an unerupted canine is the most importantpredictor of eventual impaction. However, in this study,we demonstrated that the vertical distance from the cusptip of the unerupted canine to the occlusal plane is themost important and an earlier predictor of eventualimpaction than all other measurements made on pano-ramic radiographs.

Althoughwe drew on a considerable body of data, thematerial had been collected for clinical purposes, and sothe radiographs were often nonsequential; this led tosome measurement restrictions. The preponderance of


available radiographs in the 11- to 13-year age groupsreflects the pattern of referrals to the clinic for treatment.The study design was determined partly by the availabil-ity of suitable radiographs, which were taken solely forclinical purposes. Consequently, longitudinal data wereavailable only for some patients. However, the studydesign also made it possible for the first time to traceand highlight the radiographic position of the maxillarycanine in children in the age group of 3 to 8 years.

A shortcoming of the radiographic technique used topredict early impaction of the maxillary canine is that itcannot be used to predict bilateral impactions. Also, thegeometric measurements obtained from the radiographsof patients with both buccal and palatal impactions werecombined, since they produced similar results. It wouldbe useful to perform a study with a similar design butwith more radiographs especially in the younger agegroup (7-10 years) and to compare the results with our


Fig 7. Difference between the mean root formation stages of the impacted canine and the unaffectedantimere according to the age of the patients.

Sajnani and King 51

study. Moreover, it would be interesting to longitudi-nally observe radiographs of all patients at differentages to better predict impaction of maxillary canines.

CONCLUSIONS

The vertical distance of the tip of the maxillary caninefrom the occlusal plane as evident on a panoramic radio-graph is a good predictor of impaction of a maxillarycanine. Diagnosis of an impacted maxillary canine canbe made after 8 years of age, especially if the angulationof the canine with the midline is also considered. Hence,screening of patients to detect an early impaction couldbe performed at this age.

REFERENCES

1. Ericson S, Kurol J. Early treatment of palatally erupting maxillarycanines by extraction of the primary canines. Eur J Orthod 1988;10:283-95.

2. Sambataro S, Baccetti T, Franchi L, Antonini F. Early predictivevariables for upper canine impaction as derived from posteroante-rior cephalograms. Angle Orthod 2005;75:28-34.

3. Lindauer SJ, Rubinstein LK, Hang WM, Andersen WC, Isaacson RJ.Canine impaction identified early with panoramic radiographs. JAm Dent Assoc 1992;123:91-7.

4. Fern�andez E, Bravo LA, Canteras M. Eruption of the permanentupper canine: a radiologic study. Am J Orthod Dentofacial Orthop1998;113:414-20.

5. Warford JH Jr, Grandhi RK, Tira DE. Prediction of maxillary canineimpaction using sectors and angular measurement. Am J OrthodDentofacial Orthop 2003;124:651-5.

6. Bishara SE, Kommer DD, McNeil MH, Montagano LN, Osterle LJ,Youngquist HW. Management of impacted canines. Am J Orthod1976;69:371-87.

7. Wisth P, Norderval K, Bøe O. Comparison of two surgical methodsin combined surgical-orthodontic correction of impactedmaxillarycanines. Acta Odontol Scand 1976;34:53-7.


8. Keur JJ. Radiographic localization techniques. Aust Dent J 1986;31:86-90.

9. Clark CA. A method of ascertaining the relative position of unerup-ted teeth by means of film radiographs. Proc R Soc Med OdontolSect 1910;3:87-90.

10. Ericson S, Kurol J. Radiographic examination of ectopically erupt-ing maxillary canines. Am J Orthod Dentofacial Orthop 1987;91:483-92.

11. Frykholm A, Malmgren O, S€amfors K, Welander U. Angular mea-surements in orthopantomography. Dentomaxillofac Radiol1977;6:77-81.

12. Tronje G, Welander U, McDavid WD, Morris CR. Image distortion inrotational panoramic radiography. III. Inclined objects. Acta RadiolDiagn (Stockh) 1981;22:585-92.

13. Stramotas S, Geenty JP, Darendeliler MA, Byloff F, Berger J,Petocz P. The reliability of crown-root ratio, linear and angularmeasurements on panoramic radiographs. Clin Orthod Res 2000;3:182-91.

14. Chaushu S, Chaushu G, Becker A. The use of panoramic radio-graphs to localize displaced maxillary canines. Oral Surg OralMed Oral Pathol Oral Radiol Endod 1999;88:511-6.

15. Peck S, Peck L, Kataja M. The palatally displaced canine as a dentalanomaly of genetic origin. Angle Orthod 1994;64:249-56.

16. Miller BH. The influence of congenitally missing teeth on theeruption of the upper canine. Dent Pract Dent Rec 1963;13:497-504.

17. Bass TB. Observations on the misplaced upper canine tooth. DentPract Dent Rec 1967;18:25-33.

18. Becker A, Smith P, Behar R. The incidence of anomalous maxillarylateral incisors in relation to palatally displaced canines. Angle Or-thod 1981;51:24-9.

19. Coulter J, Richardson A. Normal eruption of the maxillary caninequantified in three dimensions. Eur J Orthod 1997;19:171-83.

20. Ericson S, Kurol J. Longitudinal study and analysis of clinical su-pervision of maxillary canine eruption. Community Dent Oral Epi-demiol 1986;14:172-6.

21. Ericson S, Kurol J. Radiographic assessment of maxillary canineeruption in children with clinical signs of eruption disturbance.Eur J Orthod 1986;8:133-40.


articulo diagnosticotemprano de caninos impactados (1)

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