Anterior Loop Length of the Inferior Alveolar Nerve to Estimate the Safe-Zone for Implant-planning in Malaysian-Chinese Population

The anterior loop length (AnLL) of the inferior alveolar nerve (IAN) is an important clinical landmark in implant dentistry as it may be injured during implant placement. Objective: To measure the prevalence of the anterior loop (AnL) of the IAN and estimate side-, gender-, and age-related variations in AnLL in the Malaysian-Chinese population. Methodology: 244 randomly chosen cone-beam computed tomography Digital Imaging and Communications in Medicine images were divided into three age groups; 18-40, 41-60, and 61-80 years. The route of the IAN was traced using a software until it exited the mental foramen. The AnLL was measured from the point where the IAN exited the mental foramen to the anterior-most margin of the AnL of the IAN by following the diagonal course of the IAN. The measurement was replicated on the opposite side. Data were analysed using one-way analysis of variance and independent and paired sample T-tests with the significance threshold set at P0.05. Results: The prevalence of AnL of the IAN was 89.1% in 488 hemimandibles. Overall, the AnLL ranged between 3.04 and 9.63mm. The mean AnLL was 5.49±1.07mm on the right side and 5.48±1.20mm on the left side. The mean AnLL in the 61-80-year group (5.62±1.00mm) was longer compared to the 41-60 (5.48±1.11mm) and 18-40 (5.46±1.19mm) year groups. There were no statistically significant differences when comparing the mean AnLL between different sides of the mandible (male: P=0.962, female: P=0.983, total: P=0.984), gender (right AnLL: P=0.048, left AnLL: P=0.086) and age (P=0.636) groups. Discussion: By using the mental foramen as a landmark, the actual AnLL and the mesiodistal spread of the AnL of the IAN may help in planning the horizontal and vertical direction of implant placement in the mandibular premolar region. Conclusions: The high prevalence of the AnL of the IAN and its varied AnLL suggests that a 3-dimensional assessment is required if implant placement is planned in the interforaminal region. Keywords: implant planning, CBCT, safe zone, surgery complications