Anterior loop of the mental nerve: a morphological and radiographic study

Treatment planning for dental implant patients is often complicated by the unknown extent of the anterior loop of the mental neurovascular bundle. The aim of this study was to determine the correlation between the visual interpretation of the panoramic radiographs and the anatomical dissection findings in a cadaveric sample. Panoramic radiographs of the 22 randomly selected coronally sectioned human head specimens were taken using the Scanora (Soridex, Orinon Corporation Ltd, Helsinki, Finland) radiographic unit jaw panorama (Programme 001, magnification 1.3) and dental panorama (Programme 003, magnification 1.7) and interpreted by two calibrated observers. Bilateral anatomical dissection was then performed on all specimens. The anterior loop of the mental canal was only identified in six panoramic radiographs (27%) (range 0.5-3 mm). There was a significant positive correlation between both observers of the radiographs and between the two radiographic programmes used. Anatomical measurements of the anterior loop of the mental neurovascular bundle revealed its presence in eight dissected specimens (range 0.11-3.31 mm; mean 1.20, +/-0.90). Fifty percent of the radiographically observed anterior loops of the mental canal were misinterpreted by observers with both radiographic programmes and 62% of the anatomically identified loops were not observed radiographically. Clinicians should not rely on panoramic radiographs for identifying the anterior loop of the mental nerve during implant treatment planning. However, a safe guideline of 4 mm, from the most anterior point of the mental foramen, is recommended for implant treatment planning, on the basis of our anatomical findings.