CBCT analysis of the extension of the anterior loop of the mental nerve and its relation to age, gender, and dentate status
Hussein, Omer Hani M A
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INTRODUCTION: The mental foramen region is important in dental implant placement as it serves as essential neurovascular bed. Despite the belief that the interforaminal area is a safe area for implant placement, a detailed anatomical examination should be done before surgery to prevent injury to the nerve. The inferior alveolar nerve runs outward, upward and backward to the mental foramen and forms the anterior loop of the mental nerve. The anterior loop is the most mesial point of the mental foramen. Methods to determine the extension of the anterior loop include surgical cadaver dissections, panoramic films of markers in dried skulls and cadaver mandibles, panoramic films of patients, periapical radiographs and CT scans of patients. These different methods and dissimilar diagnostic techniques have led to diverse results. The aim of this study was to measure the extension of the anterior loop of the mental foramen by using cone-beam computed tomography (CBCT). METHODS: Randomly selected sagittal, axial, and coronal CBCT images of the maxillofacial region of 100 patients (50 males, and 50 females) aged between 18-80 were retrospectively screened to determine the extension of the anterior loop. Categorized into (1) younger males, (2) younger females aged (18-44), (3) older males, and (4) older females aged (45-80). Four groups based on dental status were added (1) fully edentulous males, (2) fully edentulous females, (3) dentated males, and (4) dentated females. Measurement tools provided by the software were used to determine the extension of the mental loop. Data was collected for statistical analysis to determine the association between CBCT findings and the patient's gender, age, and dentate status. RESULTS: In this study, 50 male, and 50 female patients were included for anterior loop measurements. The median age of the sample population was 45 [range 33 to 59]. The mean anterior loop measurements for right and left side were 1.36 mm (0.80 SD) and 1.37 mm (0.79 SD) respectively. Eighty percent of our study participants were dentate and 20% were fully edentulous. Discussion Prior to implant placement proper planning is necessary to avoid misplacement of dental fixtures and injury to the mental nerve. The anterior loop is one of the crucial anatomical structures that clinicians have to consider during the planning. CBCT proved to be the most reliable method of examining the maxillofacial region. No correlation was found between age, gender, and dentate status with changes in the anterior loop measurements. Even though there was no statistical difference among the groups, but there were variations in the anterior loop measurements. In some of the individual cases the anterior loop was 0 mm in one side and 2.5 mm on the other side. This is a big measurement variation of a clinical significance when it comes to implant placement. Looking to the results among groups statistically doesn’t give us the real measurement of the anterior loop. Instead every case should be examined individually to identify the extension of the anterior loop in both sides, even if it was not detected in one of the sides. CONCLUSION: An implant placed in proximity to mental foramen requires planning to avoid complications or nerve injury. Because of possible variations in the anterior loop measurements should be done for each individual case. CBCT is the imaging method of choice to assess the anterior loop.