Clinical significance of the anterior loop of the mental nerve: anatomical dissection of a cadaver population

Introduction Dental implant placement in the region of the mental foramen has been known to cause neurosensory deficit due to nerve injury.1-4 The identification and preservation of the anterior loop (AL) of the mental nerve is an important means of avoiding such neurosensory deficit.5-7 There is a general consensus that plain film radiographs are inadequate for the accurate identification of the AL. Bavitz et al8 compared periapical radiographs to anatomical dissection on 24 cadaveric mandibles. They could not find a reliable relationship between the anatomical dissection and the periapical radiographs in determining the AL length. The radiographic examination revealed AL lengths of 0mm to 7mm while the anatomical dissection revealed AL lengths of 0mm to 1mm. A safety zone of 1mm was proposed to avoid injury to the mental nerve. Mardinger et al, in a similar study on 46 cadaveric hemi-mandibles showed that periapical radiography show false positive presence of an AL in 40% of the sample and failed to identify the AL in 70% of the sample.9 AL length ranged from 0,5mm to 2,95mm on periapical films and 0,4mm to 2,19mm on anatomical dissection. They proposed a safety zone of 3mm anterior to the mental foramen. Alternative imaging modalities such as Spiral Computed Tomography (SCT), as well as Cone Beam Computed Tomography (CBCT), have been used for the identification of the AL. The proposed advantage of these techniques is their ability to create an accurate three-dimensional representation of the structure under investigation, thus eliminating the error of image distortion inherent in plain film radiography.10 Kaya et al11 evaluated 73 preoperative patients using panoramic radiographs as well as SCT C L I N I C A L