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.

Introduction: The mental nerve, a branch of the trigeminal nerve’s mandibular division provides sensory innervation to the lower lip, dentition, gingiva, and mucosa. Knowing the exact location of the mental foramen along with its accompanying structures including possible accessory foramina, and the anterior loop is crucial for avoiding surgical complications. Advancements in Cone Beam Computed Tomography (CBCT) have provided unparalleled insights into these anatomical structures. This study uses the CBCT modality to investigate the anatomical variations of the mental foramen and anterior loop within a United States dental school patient population, aiming to improve surgical outcomes and patient safety. Materials and Methods: A retrospective cross-sectional analysis was conducted on 1,006 CBCT scans from patients at Temple University's Dental School between January 2020 and July 2022. Inclusion criteria encompassed patients aged 18 years and above who underwent pre-operative CBCT scans, with exclusions for maxillary-only scans and images lacking crucial mandibular structures. A total of 558 scans met these criteria and were analyzed. Data collected included patient demographics noting the location of the mental foramen, presence of accessory foramina, presence of the anterior loop and the length of the anterior loop for both the right and left side of the mandible. Results: The total number of scans included in the study was 558. The mean age of the patients from whom the data was collected was 54.95. Of the total subjects 185 were older than 50, and 373 were younger than 50 years of age. 311 of the subjects were female and 247 were male. The race distribution is as follows: 263 Caucasians, 170 African Americans, 72 Hispanics, and 53 Asians. As for the dentition status: 454 individuals had partial dentition, 79 had complete dentition, and 25 were edentulous. The study revealed a 0.05% occurrence of accessory mental foramina and a predominant location of the mental foramen apical to the second premolar, consistent across racial groups but not significantly influenced by age or gender. The anterior loop was present in 56.5% of scans, with an average length of 3.3 mm. Notably, the distance between the anterior loop and the mental foramen correlated significantly, suggesting potential surgical implications. Discussion: The findings highlight significant anatomical variability, challenging the reliability of traditional anatomical landmarks in surgical planning. The presence of the anterior loop and its variable length underscores the importance of individualized CBCT analysis before dental implant placement. Search for comparison within existing literature indicates a lower prevalence of accessory mental foramina in our study, suggesting population-specific anatomical variations. Conclusion: This study underscores the critical role of CBCT in identifying the anatomical nuances of the mental foramen and anterior loop, advocating for its routine use in pre-surgical planning for dental implants. The variability observed in these structures, even within the same patient, emphasizes the need for personalized surgical approaches to mitigate risks and enhance patient care. Future research should aim to expand the sample size and diversity to validate these findings further and explore their clinical implications. / Oral Biology