ORIGINAL ARTICLE

Comparative analysis of traditional radiographsand cone-beam computed tomographyvolumetric images in the diagnosis and treatmentplanning of maxillary impacted canines

Eric Haney,a Stuart A. Gansky,b Janice S. Lee,c Earl Johnson,d Koutaro Maki,e Arthur J. Miller,f

and John C. Huangg

San Francisco, Calif, and Tokyo, Japan

Introduction: In this prospective study, we compared differences in the diagnosis and treatment planning ofimpacted maxillary canines between 2 imaging modalities. Methods: Twenty-five consecutive impacted max-illary canines were identified from the pool of patients seeking orthodontic treatment. The first set of radio-graphs consisted of traditional 2-dimensional (2D) images including panoramic, occlusal, and 2 periapicalradiographs. The second set comprised prints of 3-dimensional (3D) volumetric dentition images obtainedfrom a cone-beam computed tomography (CBCT) scan. Seven faculty member completed a questionnairefor every impacted canine and diagnostic radiographic modality (2D and 3D). Results: The data show thatthe judges produced different decisions regarding localization depending on the x-ray method. There were21% disagreement (or discordance) in the perceived mesiodistal cusp tip position and 16% difference inthe perceived labiopalatal position. In the perception of root resorption of adjacent teeth, there was 36%lack of congruence. Twenty-seven percent of the teeth that were planned to be left, recovered, orextracted with the 2D radiographs had different treatment plans when the judges viewed the 3D CBCTimages (McNemar test, chi-square, 4.45; P 5 0.035). The clinicians’ confidence of the accuracy ofdiagnosis and treatment plan was statistically higher for CBCT images (P\0.001). Conclusions: These resultsshowed that 2D and 3D images of impacted maxillary canines can produce different diagnoses and treatmentplans. (Am J Orthod Dentofacial Orthop 2010;137:590-7)

aPostgraduate student, Division of Orthodontics, Department of Orofacial Sci-

ences, School of Dentistry, University of California at San Francisco.bAssociate professor, Division of Oral Epidemiology and Dental Public Health,

Department of Preventive and Restorative Dental Sciences, University of Cali-

fornia at San Francisco.cAssociate professor, Department of Oral and Maxillofacial Surgery, School of

Dentistry, University of California at San Francisco.dClinical professor, Division of Orthodontics, Department of Orofacial Sci-

ences, School of Dentistry, University of California at San Francisco.eProfessor and Chair, Department of Orthodontics, Showa University, Tokyo,

Japan.fProfessor, Division of Orthodontics, Department of Orofacial Sciences, School

of Dentistry, University of California at San Francisco.gAssociate clinical professor and vice-chair, Division of Orthodontics, Depart-

ment of Orofacial Sciences, School of Dentistry, University of California at San

Francisco.

This research study was funded in part by an AAOF Orthodontic Faculty

Development Award (JH) and the University of California Orthodontic Alumni

Foundation (JH).

The authors report no commercial, proprietary, or financial interest in the

products or companies described in this article.

Reprint requests to: John Huang, Division of Orthodontics, Department of Or-

ofacial Sciences, School of Dentistry, University of California at San Francisco,

San Francisco, CA 94143-0438; e-mail, john.huang@ucsf.edu.

Submitted, February 2008; revised and accepted, June 2008.

0889-5406/$36.00

Copyright � 2010 by the American Association of Orthodontists.

doi:10.1016/j.ajodo.2008.06.035

590

Most permanent teeth erupt into occlusion un-assisted. Occasionally, some permanentteeth become impacted and fail to erupt.

This situation often requires intervention by both anorthodontist and an oral and maxillofacial surgeon.The decision for interceptive treatment takes into ac-count several factors, including how to expose, recover,extract, or not treat. Some factors include location of theimpaction, prognosis of intervention on the impactedtooth and adjacent teeth, surgical accessibility, impactof treatment on the final functional occlusion, and pos-sible surgical morbidity. This treatment decision hastraditionally been based on planar 2-dimensional (2D)radiographs.1-11 Medical technology offers 3-dimensional (3D) volumetric images, but these areexpensive and expose patients to higher doses ofradiation.12-15 New imaging techniques are nowavailable in dentistry with cone-beam computed to-mography (CBCT), which provides low radiation, rapidimage scanning with radiographic and 3D volumetricdata for each patient.16-20 This 3D technology willimprove the dental provider’s ability to diagnose andtreat patients with impacted teeth. In this study, we

Fig 1. A, Periapical radiographs of impacted canines,used to determine their labiopalatal position; B, pano-ramic radiograph of an impacted maxillary canine.

American Journal of Orthodontics and Dentofacial Orthopedics Haney et al 591Volume 137, Number 5

aimed to determine if using 2 imaging modalities, 2Dand 3D systems, would result in a different diagnosisor a different treatment plan for impacted maxillarycanines.

The maxillary canine is the second most commonlyimpacted tooth, after the third molars. The reportedincidence ranges from 0.8% to 2.8%, depending onthe population examined.21-24 It has been reported thatthe incidence of impaction is twice as likely in femalepatients.23 Even though maxillary canine tooth buds de-velop labially to adjacent tooth roots, the ratio of palatalimpactions to labial impactions is at least 3:1.25 Otherinvestigators have found impacted canines to be posi-tioned palatally 85% of the time compared with labialpositioning 15% of the time.8,10,11,26

Proper localization of an impacted tooth is requiredto make an accurate diagnosis, determine proper surgicalaccess, and plan the direction of orthodontic recoveryforces. In the past, diagnostic radiographs included peri-apical, occlusal (normal and topographic), and pano-ramic radiographs. In orthodontics, knowing the exactlocation of an impacted canine is paramount, since thedecision about whether it should be exposed, extracted,recovered, or left untreated influences the treatment plan.

For a labial impaction, the tooth can often be locatedby palpation. If the tooth is positioned in the middle ofthe alveolus or palatally, it is necessary to determine itslabiopalatal location by taking 2 or more periapical radio-graphs at different horizontal angles. Clark’s rule enablesthe practitioner to determine the location of these im-pacted teeth.27 When radiographs are taken at differenthorizontal angulations of a pair of objects, the image ofthe palatal object moves in the same direction as the x-ray beam, whereas the labial object appears to move inthe opposite direction. With this periapical film technique,the clinician can evaluate the labiopalatal position of thecanine with sufficient accuracy in 92% of patients.10,11

Additional radiographic images are often required toascertain the exact location of an impacted tooth in all 3dimensions. To aid in determining the vertical positionand horizontal angulation, a panoramic radiograph isused. Normal occlusal or topographic occlusal radio-graphs help to determine the relative positions ofadjacent teeth. In addition, they help to determine thelabiopalatal position of the impacted canine in conjunc-tion with the periapical films if the image of the im-pacted canine is not superimposed on other teeth.28

Frontal and lateral cephalograms often elucidate theproximity to other facial structures, such as the maxil-lary sinus and nasal floor.29

Orthodontists and oral surgeons have always neededto precisely locate teeth and tissues in all 3 planes ofspace. To date, only planar radiographs have been avail-

able. 3D information has been available with medicalx-ray computed tomography scanners, but limitationsinclude exposure dose, cost, and access to CT imagingservice providers. A new system, CBCT, has been devel-oped and designed for 3D imaging of the craniofacialfield.30,31 The unique feature of this system is that ituses a low-energy, fixed-anode tube, which producesa cone-shaped x-ray beam, a special image intensifier,and a solid-state sensor or an amorphous silicon platefor capturing the image. CBCT systems vary in their ra-diation, depending on the machine, the size of the radi-ated region, and the amounts of milliamps and kilovoltsof the system, but the doses are lower than medical com-puted tomography systems.32

CBCT images are inherently more accurate than tra-ditional x-rays, since beam projection is orthogonal; thismeans that the x-ray beams are approximately parallelto one another, and the object is near the sensor. This ex-plains why there is little projection effect and no magni-fication. In addition, the computer software addressesthe projection effect, resulting in undistorted 1:1 mea-surements. This contrasts with traditional imaging,which always has some projection error because the an-atomic regions of interest are at varying distances fromthe film. For example, panoramic radiographs have anunusual projection error because the main path of thex-ray beam comes from a slightly negative angulation.In this situation, the dental provider must account forthese imaging artifacts when reading the images.

Another likely advantage of the CBCT scan is thatthe data acquired include information for the entire cra-niofacial region. Additional views such as lateral ceph-alograms, panoramic radiographs, occlusograms,airway evaluations, and volumetric images are available

Fig 2. A CBCT volumetric view of impacted teeth in 1 subject with frontal, lingual, oblique, rostral,and caudal views of the dentition.

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from the original acquisition data. These images can bemanipulated with imaging software to aid the dentalprovider in diagnosis and treatment planning. The costs,efficiency, and benefits of CBCT imaging are favorable,because 1 imaging session can provide many views.30

MATERIAL AND METHODS

Eighteen consecutive patients (12 female, 6 male)with impacted maxillary canines were identified in theorthodontic clinic at the School of Dentistry, Universityof California at San Francisco. Twenty-five impactedcanines were identified they included 7 bilateral impac-tions. Six canines were unilateral on the right, and 5were unilateral on the left. The subjects ranged in agefrom 12.3 to 34.6 years (mean, 16.9 6 5.8 years). Exclu-sion criteria included presence of deciduous teeth, cra-niofacial anomalies, incomplete root formation, andexisting orthodontic appliances. For each subject, tradi-

tional 2D diagnostic radiographs and CBCT scans(Hitachi MercuRay, Hitachi Medical Technology,Tokyo, Japan) in digital imaging and communicationsin medicine (DICOM) format were obtained.

The 2D traditional radiographs included a panoramicradiograph to evaluate the vertical position, an occlusalx-ray to evaluate the proximity to adjacent teeth, and2 periapical radiographs (Fig 1) to determine the labio-palatal position. Volumetric images of the maxillarydentition were obtained from a CBCT scan. CBWorkssoftware (CyberMed, Seoul, Korea) was used for thesegmentation process. The volume operation and sculptfeatures eliminated all soft tissues and hard tissuesexcept the maxillary dentition (Fig 2). One operator(E.H.) performed segmentation of the maxillary denti-tion. Three-dimensional images included anterior, pos-terior, rostral-caudal, caudal-rostral, labial, and palatalviews. The images were illustrated on 1 sheet of glossyphoto paper (Epson, Long Beach, Calif). All identifying

Table I. Intra-rater reliability, agreement, and kappavalues

Variable 2D and 3D 2D 3D

Mesiodistal location 0.76 0.92 0.61

Labiopalatal location 0.82 0.87 0.77

Vertical location 0.63 0.73 0.53

Root resorption 0.65 0.73 0.55

Orthodontic treatment plan 0.72 0.77 0.64

Orthodontic treatment plan (recover) 0.75 0.75 0.75

Orthodontic treatment plan (extract) 0.81 0.85 0.72

Number of recovery vectors 0.54 0.53 0.54

Initial recovery vector 0.47 0.46 0.46

Second recovery vector 0.57 0.58 0.55

Expect will erupt unassisted 0.78 1.0 0.59

Expect additional root resorption 0.70 0.59 0.79

Request for additional images 0.62 0.46 0.80

Kappa key: poor, 0.0-0.2; fair, 0.2-0.4; moderate, 0.4-0.6; substantial,

0.6-0.8; perfect, 0.8-1.0.

Table II. Intra-rater reliability, Lin’s concordance

Variable 2D and 3D 2D 3D

Confidence of diagnosis 0.55 0.60 0.50

Confidence of treatment plan 0.41 0.41 0.43

American Journal of Orthodontics and Dentofacial Orthopedics Haney et al 593Volume 137, Number 5

patient information was removed, including name, sex,age, and race. The institutional review board of the Uni-versity of California at San Francisco, the Committee onHuman Research, approved this study. Informed consentto participate in this study was obtained from each sub-ject or, for minors, a guardian.

The presentation of the impacted maxillary canineswas ordered with a random number generator (www.randomizer.org). In addition, 5 impacted maxillary ca-nines were randomly selected for replicates and were in-terspersed randomly to be evaluated a second time todetermine intraoperator reliability. A total of 60 stationswere prepared; they included 30 sets of traditional 2Dradiographs and 30 CBCT 3D volumetric renderings.

Seven faculty members participated in the study:4 orthodontists (including J.H. and E.J.) and 3 oral sur-geons (including J.S.L.); 4 had less than 10 years of clin-ical experience, and 3 had more. All impacted canineswere evaluated in one session. Before starting, eachjudge reviewed the questionnaire as part of the calibra-tion process. At each station, the judge was asked tocomplete the questionnaire for that tooth. Each clinicianwas randomly assigned a starting point. The time tocomplete all 60 questionnaires ranged from 1.5 to 2.5hours.

After collection, the data were analyzed by usingStatView (version 5, SAS Institute, Cary, NC) to evalu-ate differences between traditional radiographs andCBCT volumetric renderings. Statistical analyses wereperformed, accounting for the clustering in patients,by using SAS software (version 9.1.2). Repeated mea-sures tests were used to examine the different resultsbetween using traditional 2D and CBCT 3D images.Mean confidence and 95% confidence intervals were es-timated. Paired t tests compared confidence level differ-ences. McNemar tests compared differences indichotomous (ie, yes or no) questions between the 2Dand 3D methods. Intraclass correlations with randomcase effects were estimated to determine continuousmeasure reliability of the replicates overall and sepa-rately for the 2D and 3D methods. Kappa statisticswere used to measure reliability for categorical mea-sures.

Intrarater reliability for all questions was acceptable,with a range from moderate to perfect for categoricalmeasures, and moderate for continuous ones, dependingon the question (Tables I and II). Orthodontic treatmentplans (overall, and for recovery and extraction) hadsubstantial agreement; recovery vectors had moderateagreement. It appears that raters have greateragreement with traditional 2D radiographs comparedwith CBCT images, but there was no significantdifference between the 2 modalities.

RESULTS

There were differences in the identified location ofthe impacted cusp tip depending on the radiographicmodality. For the mesiodistal tip position, there was79% agreement among the 7 judges’ responses on 25teeth (175 total responses; Fig 3) between the 2methods. In 21% of the responses, there was a differencebetween the 2 methods. The combined methods, tradi-tional 2D radiograph and 3D CBCT volumetric views,had a range of agreement from 43% to 100% for eachtooth based on the 7 judges’ responses (14 total re-sponses for each tooth; Fig 4). There was 84% agree-ment for the labiopalatal position as assessed in 175responses (Fig 5). The combined methods had a rangeof agreement from 50% to 100% for each tooth. Fiftypercent of the teeth had 100% agreement, and 76%had one or no clinician in disagreement. However, therewere no statistically significant differences between the2D and 3D methods (chi-square test, P .0.5). Therewas 50% agreement when localizing the cusp in the ver-tical dimension.

In the diagnosis of root resorption, there was 64%agreement between the 2 methods as determined bythe 7 judges (175 total responses; Fig 6). In the assess-ment of root resorption, the radiographic modality influ-enced the response (chi-square test, P \0.0001). The

Fig 3. Percentages of agreement and differences between the 2D traditional radiographs and the 3DCBCT volumetric views for the mesiodistal position (M, mesial; Dis, distal; Dir, direct) of the impactedtooth. There was high agreement (79%) or congruence between the 2 views about localization of theimpacted cusp tip among the 7 judges. There was 21% lack of congruence between the 2 modalitieswith various combinations.

Fig 4. Percentages of agreement between the 2D traditional radiographs and the 3D CBCT volumet-ric views for the mediodistal position of each tooth (M, mesial; D, distal; the number refers to eachtooth sample). There was 100% agreement in over 50% of the cases with the mode illustrated (red).

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combined methods for a tooth were never unanimous (14total responses per tooth) but, rather, ranged in agree-ment from 36% to 86%. In 8% of the cases, the modewas unsure in the diagnosis of root resorption and was

positive in the diagnosis of root resorption for only onetooth.

The resulting orthodontic treatment plans, producedby only the 4 orthodontists, were significantly influenced

Fig 5. Percentages of agreement and differences be-tween the 2D traditional radiographs and the 3D CBCTvolumetric views about the labiopalatal position (L, labial;C, centered; P, palatal) of the impacted tooth. There washigh agreement (84%) between the 2 views about thelocalization of the impacted cusp tip as defined by the7 judges. There was 16% lack of congruence betweenthe 2 modalities with various combinations.

Fig 6. Percentages of agreement between the 2D tradi-tional radiographs and the 3D CBCT volumetric viewsabout root resorption (U, unsure; Y, yes; N, no) of the im-pacted teeth. There was moderate agreement (63%) be-tween the 2 methods, with 37% lack of congruence invarious combinations.

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by the radiographic modality (P \0.0001). Twenty-seven percent of the teeth that were planned to be left, re-covered, or extracted with the traditional 2D radiographswere selected for a different treatment when the judgesviewed the 3D CBCT images (12 total responses; McNe-mar test, chi-square, 4.45; P 5 0.035; Fig 7). The overallmode for an individual tooth was unanimous in 24% ofthe teeth, with a range of agreement from 50% to100% on the other teeth. When comparing the responsesof 2D with 3D, there was complete agreement on the or-thodontic treatment plan in only 36% of the teeth, withonly 1 clinician disagreeing in another 18% of the teeth.

If the treatment plan included recovery of the tooth,then the selection of the initial recovery vector wassignificantly influenced by the radiographic modality(P\0.0001). Eleven of 12 teeth with an initial distal re-covery vector with the 2D images had a different initialrecovery vector with the 3D images. The judges’ deci-sions using the 2 methods for an individual tooth wereunanimous in only 12% of the teeth, with a range ofagreement of 20% to 100%. There was 42% lack of con-gruence for the second recovery vector. When predictingwhether the tooth would erupt unassisted, there was 19%lack of congruence. In the prediction of additional rootresorption, there was 21% lack of agreement with the 2methods.

A request for additional images to obtain a more ac-curate diagnosis was more likely with traditional radio-graphs (McNemar test, P 5 0.0016). Sixty-one percentof the teeth had no difference between 2D and 3D im-ages. For 27% of the teeth, additional images were re-quested with 2D but not 3D images. In contrast, 12%

of the teeth had requests for additional images with 3Devaluations but not 2D. The overall mode of 2D and3D images was unanimous for only 1 tooth, yet themode for every tooth was that additional images were un-necessary, with a range of agreement from 50% to 100%.

For traditional radiographs, the means for the confi-dence of the diagnosis and treatment plan were both8.6 on a scale from 1 to 10. For the CBCT images, themeans for the confidence of the diagnosis and treatmentplan were 9.4 and 9.2, respectively. The mean differencein the confidence of the diagnosis was 0.8 with a 1.3 SD.The mean difference in the confidence of the treatmentplan was 0.6 with a 1.4 SD that was not significantlydifferent.

The diagnosis of the labiopalatal position and thederived orthodontic treatment plan were influenced bytooth-to-tooth variations (Pearson chi-square test, P\0.0001). Individual tooth-to-tooth variations alsoinfluenced the self-reported confidence of the diagnosisand the treatment plan when using CBCT images(Bonferroni [Dunn] t test, P 5 0.050 and P 5 0.0003,respectively). However, for the traditional radiographs,tooth-to-tooth variations did not significantly influencethe clinicians’ confidence regardless of experience andspecialty training. Tooth complexity suggests signifi-cance in relation to 3D confidence of diagnosis (analysisof variance [ANOVA], P 5 0.052), whereas confidenceof treatment plan is significantly related (ANOVA, P 5

0.003). This implies that this confidence assessment isrelated to tooth-to-tooth variations.

DISCUSSION

This is one of the first studies to evaluate the clinicalimplications of using CBCT images for the diagnosis of

Fig 7. Percentages of agreement and differences between the 2D traditional radiographs and the 3DCBCT volumetric views about whether the orthodontic treatment plan would involve extracting, re-covering, or leaving (E, extract; L, leave; R, recover) the impacted tooth. There was high agreement(73%) or congruence by the 7 judges using the 2 imaging methods.

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impacted maxillary canines compared against using tra-ditional radiographs.20 While comparing the volumetric3D method of CBCT and traditional 2D radiographs, wefound differences between each method related to spe-cific situations. Although not all were statistically sig-nificant, differences seem to exist for critical questionssuch as the labiopalatal position of the cusp tip. An in-teresting finding was the 84% agreement among clini-cians on the labial or palatal tip position; the samelack of agreement was found when determining whichside to start surgical access, implying that these 2 ques-tions are directly related. The labiopalatal tip position isthe most critical question for the surgeon when the toothis to be removed or recovered. One could argue that,since fewer images were requested and the self reportedconfidence was significantly higher with CBCT images,this modality is superior. The surgeon is less likely to in-correctly access an impacted tooth, and the orthodontistis more likely to safely recover more impacted maxil-lary teeth.

Individual tooth variations affect the labiopalatal lo-calization of the impacted canine. As expected, most im-pacted teeth can be accurately localized with traditionalradiographs. However, this is not true for every impactedcanine; some can be incorrectly localized, poorly ac-cessed surgically, or recovered by using deleterious vec-tors. Ericson and Kurol8-10 demonstrated that 8% ofimpacted maxillary canines could not be accuratelylocalized in the labiopalatal dimension with periapicalradiographs. Bjerklin and Ericson15 showed that evalu-ating the same patients 10 to 12 months later with addi-tional information from a computed tomography scanallowed them to detect root resorption in approximately50% more incisors with retained and ectopically posi-tioned maxillary permanent canines, and the treatmentplan was changed for almost 44% of the patients.

Admittedly, in this study, we did not address the ab-solute accuracy of either radiographic modality; rather,we sought only to determine whether there were diag-nostic and clinical implications. Not having a gold stan-dard was the limiting factor in the determination ofaccuracy. Anatomic dissection would have been neces-sary to assess the accuracy of either modality; this wasnot feasible or ethical, since not all teeth were to be ac-cessed surgically or have the bone removed surroundingthe impacted anatomic crown to make an accurate as-sessment.

The maxillary dentitions were segmented by 1 in-vestigator (E.H.), and the 3D views were developedand printed. Inherent problems included the accuracyof segmentation and the selection of angles and viewsto be presented. In addition, the maximum benefit ofCBCT images was limited, since only 2D prints weredeveloped from 3D data, and the clinicians could notmanipulate the images to make diagnostic decisions.Future studies should address and compare the accuracyof the radiographic modalities to a gold standard. Clini-cians should be allowed to access and manipulate theCBCT scan data to evaluate the true capability of thistechnology.

CONCLUSIONS

These results suggest that the use of 2D and 3D im-ages of impacted maxillary canines can produce differ-ent diagnoses and treatment plans for the same patient.Individual tooth variations affect the determination ofthe labiopalatal position of an impacted maxillary ca-nine. Three-dimensional volumetric imaging might pro-vide information for improved diagnosis and treatmentplans, and ultimately result in more successful treatmentoutcomes and better care for patients.

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