The anterior loop of the inferior alveolar nerve : prevalence and measurement using reformatted medical computed tomographic imaging

Abstract

Background: Implant placement in the anterior mandible has historically been considered a relatively safe procedure. It is now known that multiple anatomically important structures are frequently violated following implant placement in the anterior mandible. Damage to the third division of the trigeminal nerve may have dire consequences for the patient. Purpose: This paper aimed to determine the prevalence and measurement of the length of the anterior loop of the inferior alveolar nerve in a South African population and to make recommendations for the safe distance from the mental foramen for implant placement in the anterior mandible. Materials and methods: The sample population consisted of 200 patients,129 female and 71 male who were sent for CT examination for the purposes of implant planning.Using the cababilties of the software, the prevalence as well as the actual measurement of the anterior loop length was evaluated. Results: The anterior loop was present in 286 out of 400 sides (71%), with a mean length of 1.054mm and a range from 0mm to 5.29mm. Conclusions: When placing implants in close proximity to the mental foramen, caution is recommended to avoid injury to the inferior alveolar nerve, or one of its branches. The anterior loop of the inferior alveolar nerve becomes a critically important surgical reference point during treatment planning. Because of the wide range of the anterior loop lengths observed in our study, no fixed distance mesially or anteriorly from the mental foramen should be considered to be a “safe” distance without the use of 3 dimensional imaging.