The external gonial angle is an important angle of the craniofacial complex. It is significant for the diagnosis of craniofacial disorders. Lateral cephalogram and orthopantomograms can be used to determine this angle. In this study, we compared the external gonial angle determined from the two mentioned radiographs in Class I patients. We collected the radiographs of 70 patients with Angle's Class I (22 men and 48 women). The patients' age ranged from 15-30 years with a mean age of 18.24 years. The data gained were statistically evaluated by t-test. The following results were obtained. The mean value of the gonial angle in the lateral cephalogram was 125.00 degrees (men, 124.9 degrees and women, 125.04 degrees ) and in the orthopantomogram was 124.17 degrees (men 123.68 degrees , women 124.39 degrees ). The difference between these rates was 0.83 degrees (men 1.22 degrees , women 0.64 degrees ) and not significant (P = 0.406). Based on the obtained results, we can conclude that panoramic radiography can be used to determine the gonial angle as accurately as a lateral cephalogram. In addition, we can determine the right and left gonial angles of a patient in the orthopantomogram without interferences due to superimposed images of anatomical structures in a lateral cephalogram. For determination of the gonial angle, an orthopantomogram may be a better choice than a lateral cephalogram.

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IntroductionThe presence of an additional root canal in the maxillary central incisor is extremely rare. A number of studies of root canal anatomy have described that the maxillary central incisor has only one root and one canal in 100% of examined cases (1-4), with variations only in the number of lateral canals and the position of the apical foramen. Some clinical reports have described a maxillary central incisor with two canals or two roots (5-14). Only one report has described endodontic treatment of a very unusual maxillary central incisor that had dens invagination and four canals (15). Here we report the features and endodontic therapy of a very rare example of a maxillary central incisor with three canals in a single root. Case Report and ResultsAn 11-year-old male patient without any remarkable medical history was referred to the Department of Endodontics, Faculty of Dentistry, Mashhad, Iran. His maxillary right central incisor had suffered a traumatic complicated crown fracture 2 weeks previously. Clinical examination revealed that approximately 3 mm of the incisal edge of the tooth had been broken horizontally. There was spontaneous and severe pain due to cold, heat, and mastication, and the tooth was also tender to percussion and palpation. However, there was no mobility or crown discoloration and the pocket depth was normal. The adjacent teeth gave normal responses to cold, heat, and electrical stimulation of the pulp, percussion, palpation and mobility tests. Radiographic examination showed one root and three root canals that converged in the apical third with no periapical changes (Fig. 1). This anatomical variation of the root canal was also evident in the patient's other maxillary incisors.Journal of Oral Science, Vol. 49, No. 3, 245-247, 2007 Correspondence

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