Characteristic findings on panoramic radiography and cone-beam CT to predict paresthesia after extraction of impacted third molar.

The purpose of this study was to compare findings on the relationship between impacted molar roots and the mandibular canal in panoramic and three-dimensional cone-beam CT (CBCT) images to identify those that indicated risk of postoperative paresthesia. The relationship between impacted molars and the mandibular canal was first classified using panoramic images. Only patients in whom the molar roots were either in contact with or superimposed on the canal were evaluated using CBCT. Of 466 patients examined using both panoramic and CBCT images, 280 underwent surgical extraction of an impacted molar, and 15 of these (5%) reported postoperative paresthesia. The spatial relationship between the impacted third molar root and the mandibular canal was determined by examining para-sagittal sections (lingual, buccal, inter-radicular, inferior, and combinations) obtained from the canal to the molar root and establishing the proximity of the canal to the molar root (in contact with or without loss of the cortical border and separate). The results revealed that darkening of the roots with interruption of the mandibular canal on panoramic radiographs and the inter-radicular position of the canal in CBCT images were characteristic findings indicative of risk of postoperative paresthesia. These results suggest that careful surgical intervention is required in patients with the above characteristics.

Influence of horizontal condylar angle and x-ray projection angle on the appearance of the condyle on lateral temporomandibular joint panoramic radiographs.

AIMS: This study used dried human mandibles and aimed to assess the effect of different horizontal condylar angle and the effect of different beam angles from three different units in the depiction of medial, central and lateral parts of the condyle on panoramic and lateral temporomandibular joint (TMJ) panoramic images. METHODS: Standard panoramic and lateral TMJ panoramic images of four dried human mandibles with horizontal condylar angles of 5, 8,10, 15, 17 and 20 degrees were analysed. The different parts of the condyle were represented by radiopaque markers. The standard panoramic and lateral TMJ panoramic images of the four mandibles were acquired from three panoramic radiography models with different x-ray beam angle. The images were analysed for the position of these radiopaque markers. RESULTS: Standard panoramic images demonstrated almost similar images of the condyles in the three panoramic models. The lateral TMJ panoramic images demonstrated the medial pole anterior to the lateral pole when the x-ray projection angle was more than the horizontal condylar angle; superimposition of medial and lateral poles when the x-ray projection angle was equal to horizontal condylar angle; and lateral pole anterior to medial pole when the x-ray projection angle was less than beam projection angle. CONCLUSION: This study demonstrated that apart from other factors, the depiction of the mandibular condyle on lateral TMJ panoramic radiographs depends on the horizontal condylar angle, and the x-ray beam angle, which differs among different manufacturers. Therefore these limitations have to be considered when interpreting the integrity of the mandibular condyle on lateral TMJ panoramic radiographs.