A Rare Anatomical Finding: Bilateral Accessory Mental Foramen

Aim. Accessory mental foramen (AMF) is a not common anatomical variation. During the surgical procedures involving the mandible such as implant surgery, periapical surgery, jaw surgeries, and periapical surgery and enucleation of pathologies at the mental region, obvious attention should be given to prevent postoperative sequelae. Case Report. Orthopantomograph (OPG) is routinely taken to visualize the maxillofacial region at a dental clinic. OPG shows exactly upper and lower jaw and teeth but superficially reveals some pathology or anatomic variation. It misses sometimes an anatomic landmark such as AMF. As the surgery is planned to a maxillofacial region, a detailed knowledge should be known before going into surgery to not interfere with anatomic landmarks. A 52-year-old male patient was referred to Kütahya Health Science University Dental Hospital, Turkey, to rehabilitate his bilateral partial edentulous lower jaw region. Implant surgery was planned in our patient. OPG was taken to evaluate the maxillofacial region but was unremarkable. Before the implant surgery, CBCT was obtained from our patient. CBCT and a three-dimensional reconstructed model of the male patient showed bilateral accessory mental foramen (AMF). Conclusion. Accessory mental foramen (AMF) carries additional innervation to the chin, mandibular anterior gingiva, and mental region. Reflection and protection of the AMF during the surgery can prevent hemorrhage and neurosensory disturbance at the mental region and can improve quality of life for the patient. CBCT has higher precision but also a higher price and radiation dose. Although anatomical variations are uncommon, they can be found on digital panoramic radiographs but in limited percentage.

Prevalence and Anatomic Characteristics of Accessory Mental Foramen Using Cone-Beam Computed Tomography Views in an Iranian Population

Background: Determining the incidence and anatomic features of accessory mental foramen (AMF) in the Iranian population is of vital importance. This study investigated the prevalence and anatomic characteristics of AMF using cone-beam computed tomography (CBCT) in a selected Iranian population. Methods: A total of 853 CBCT images from 440 women and 413 men were examined in this cross-sectional retrospective study. The images were evaluated by two independent observers using reconstructed 3-dimensional, cross-sectional, and panoramic views. Several parameters were assessed, including the location of AMF relative to mental foramen (MF), size and the point of canal bifurcations, and the distance between the main and accessory canals. Finally, statistical differences in the AMF prevalence in terms of gender and direction and its location were evaluated by the Mann-Whitney U test (P<0.05). Results: The prevalence of AMF was 10.55%, which was more frequently located in the posterior inferior area relative to the main MF, and its nerve was more frequently originated from the anterior loop (P=0.001). There were no statistically significant differences in gender (P=0.26) and direction (P=0.4). The mean distance of AMF was 7.62 mm. The mean height of MF and the AMF vertical height were 13.65 mm and 52.12 mm in those with AMF on one side, respectively, and this difference was statistically significant (P=0.001). The sizes of the MF and AMF were 3.2 mm (large diameter), 2.3 mm (small diameter), and 1.4 mm (large diameter), and 1.1 mm (small diameter), respectively. Conclusions: Based on the findings of the present study, the prevalence of AMF according to hemi-mandibular was 5.80% in the selected Iranian population. Thus, AMF might branch from any section of the inferior alveolar nerve and the mandibular canal.

An Alternative Classification Scheme for Accessory Mental Foramen.

Background: The mental foramen (MF) is an important anatomical landmark on the mandible. MFs may occur singly or with extra foramina (accessory mental foramen (AMF)). Objective: The aim of the present study was to discuss the importance of recognition and classification of AMFs. Methods: This study assessed CBCT images of 593 patients (208 male, 385 female) and proposed an AMF classification scheme based on three different characteristics: (1) location of the AMF with respect to the MF; (2) relationship of AMFs with tooth apices; and (3) origin of the AMF. The chi-squared test was used to compare the qualitative data as well as descriptive statistical methods when the study data were evaluated. Significance was assessed at the p < 0.05 level. Results: A total of 80 AMFs were found in 71 patients. Six cases involved bilateral AMFs, whereas three cases showed double AMFs. The most common AMF location was the region posterior of the MF. Notably, all the AMFs detected in line with the mesial half of the first molar were present in female patients. Based on AMF origins, 44.5%, 48.6%, and 6.7% of the AMFs were categorized as type I, type II, and a new category identified in this study, type III. Conclusion: This study revealed some foramina locations were not considered in the previous classification. Recognition and identification of these foramina might be critical to prevent possible complications. The proposed classification scheme may facilitate this objective and can be a new focus for future studies.

Frequency of accessory mental foramen and anatomical variability of mental nerve anterior loop in a Peruvian population: A retrospective cone-beam computed tomography study.

Objective: To evaluate the frequency of accessory mental foramen (AMF) and anatomical variants of the mental nerve anterior loop using cone-beam computed tomography (CBCT) in a Peruvian population. Material and methods: This retrospective cross-sectional study evaluated 80 hemi-mandibles from 40 subjects using CBCT. The sample included 38 females and 42 males, with an average age of 25±4.45 years. A 3D multi-planar reconstruction was performed to identify the location and presence of accessory mental foramina, their morphological characteristics (oval or circular), their position with respect to the mental foramen (MF), anterior loop (AL) path and other anatomical landmarks including lengths and angles. Statistical analyses included chi square and t-tests. The significance level was p<0.05. Results: The frequency of AMF was 17% and the average distance AL-MF was 4.76±1.97mm. The measurements of the anterior border of AL and MF to the inferior mandibular border showed significant differences according to the sex (p<0.001 and p=0.009, respectively). Conclusion: The AMF prevalence was approximately 17%. There is no association between the AMF position and its morphology, sex or side evaluated. The distances from the anterior border of the AL and from the inferior border of the MF to the inferior mandibular border were greater in males. These findings should be considered when planning implant or mini-implant placement in this region.