A comparison is made between conventional X-rays and computerized tomography (CT) based on eight patients with thirteen impacted upper permanent canines. The use of CT yields information which is much more detailed than that observed on conventional X-rays, such as: pathological resorption on adjacent teeth caused by aberrant canines; the localization of the injury and the position of the canine in relation to one or both incisors. The amount of radiation per exposure is still rather high for the CT (Köster and Ewen, 1986). Further research is necessary in order to reduce this exposure and to determine the appropriate and most effective use of CT in the dental field.
Ten orthodontists were asked to diagnose the number of impacted upper canines and the number of resorbed lateral and/or central incisor roots in 30 panoramic radiographs (P1) from 30 patients. In order to objectify these diagnoses, transversal CT images of all 30 patients were examined in addition. Addition of the recordings in the 30 patients revealed that the 10 orthodontists had diagnosed 350 impacted/displaced canines. On comparison of the P1 and CT results, the latter revealed that, in fact, 390 canines were impacted or displaced, not just 350. Addition of the recordings further showed that, based on P1, the investigators had diagnosed 73 resorptions in the 1,200 incisors examined. However, the CT showed 160 resorptions; this corresponds to a sensitivity value of 45.6%. The CT showed 1,040 incisors with no resorptions, whereas the investigators diagnosed only 925 teeth as not resorbed in the P1. The specificity was thus 88.9%. These results show that, due to their low reliability, panoramic radiographs are not an appropriate means of diagnosing resorptions in front teeth in connection with impacted canines.
Panoramic radiographs (OPGs) and computer tomograms (CTs) of 30 patients, the latter taken on average 2.5 months later, were evaluated for the purpose of comparing the relation of their roots to the bottom of the maxillary sinus. The CT and OPG images yielded significant differences in the topographic relations between the roots and the maxillary sinus. In the OPG 64 out of 129 roots seemed to penetrate the maxillary sinus. In the CT transversal slices, on the other hand, penetration could be observed for only 37 roots. This phenomenon became more apparent when the relations between the mesial, distal, buccal, and oral root surfaces and their relations to the sinus were assessed. Applying a three stage scoring scheme, it was found that in the large majority of cases only the apices were in contact with the mucosa of the sinus. Thus, the possible loss of anchorage in these cases is below five percent.
25 patients with 35 retained upper canines were examined by high resolution CT; only 5 patients did not show evidence of damage to the remaining teeth. 8 patients showed resorption related to medial and lateral incisors. 19 teeth were in contact with the crowns of the displaced canines and were therefore liable to damage. The average extent of the resorption was 4.5 mm. Contact between teeth was demonstrable by means of two consecutive CT cuts.
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