Evaluation of the accessory mental foramen in a pediatric population using cone-beam computed tomography

Identification of anterior loop in different populations to avoid nerve injury during surgical procedures-a systematic review and meta-analysis

Exact recognition of the anterior loop is very important to avert any injury to the neurovascular bundle during surgical procedures. The purpose of this review was to evaluate the prevalence and length of the anterior loop in different populations. A comprehensive search of Medline/Pubmed and Cochrane database was done. The focused question was the presence of anterior loop (including loop length) of the inferior alveolar nerve in mental foramen region in CBCT images of the various subjects. Articles related to the presence of anterior loop (including loop length) were only included. Initial literature search resulted in 3024 papers, after removing duplicate articles, 2821 articles were left. Two thousand seven hundred eighty-four articles were further excluded by the reviewers after screening the abstracts which resulted in 37 studies. Hand searching resulted in 2 additional papers. Seven full-text articles were excluded for not fulfilling the inclusion criteria. Finally, 32 articles were included in the review. Two thousand five hundred three subjects with anterior loop were found, which approximates 38% with 48.4% bilateral, 27.8% right side, and 23.8% left side. The loop distribution in males and females was also found to be different. There was highly significant (P < 0.001; I² = 98.81%) heterogeneity found in the included studies. Variations were found in the prevalence, length, gender, and side distribution of anterior loop in various populations. This systematic review highly recommends not relying on any average values and the clinician should compulsorily make use of imaging modalities available in each and every case, wherever surgical procedure is to be performed near mental foramen region.

Cone beam CT-based measurement of the accessory mental foramina in the Chinese Han population

Anatomical data of accessory mental foramina (AMFs) were investigated in a Chinese Han population using cone beam CT (CBCT). A retrospective analysis was performed on 527 selected sets of CBCT images. The average frequency and diameter of AMFs, the diameter of the ipsilateral mental foramen (MF), and the center distance and relative position between the AMFs and MF were measured and calculated by three professional dentists. Among the 527 patients, AMFs were identified in 36 cases (frequency 6.83%), of which 68.75% of AMFs were larger than 1 mm. The mean diameters of the AMFs and the ipsilateral MF were 1.32±0.61 mm and 3.26±0.90 mm, respectively. The average distance from the AMFs to the alveolar ridge crest (ARC) was 15.05±3.50 mm, and the average distance to the mandibular plane was 15.87±3.64 mm. The positions of the AMFs relative to the MF varied widely. The AMFs were mostly positioned distal-inferior to the ipsilateral MF and under the mandibular second premolars. Nutrient foramina around the MFs were distinguished from AMFs. The reference plane for measuring AMFs was suggested to be the mandibular plane to increase the repeatability and accuracy of the experiment. Standard planes were proposed to determine the relative position between AMFs and the MFs. Based on our results, we propose that for implant surgeries, the safety region of 2 mm above the MFs should be reevaluated. CBCT examination is recommended before the operation to identify important anatomical structures around the MF region and their variations and set the safety distance on an individual basis.

Detection and characterization of the accessory mental foramen using cone-beam computed tomography

OBJECTIVE

This study aimed to investigate the frequency and characteristics of accessory mental foramina (AMFs) and their bony canals in a selected Chinese population using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

Reconstructed CBCT images of the mandible in 784 Chinese patients (305 males and 479 females) were retrospectively analysed to identify the AMF. The presence, dimension and location of the AMF as well as the origin and course of the associated bony canal were evaluated and classified. Variations in these characteristics were analysed according to gender, side and age.

RESULTS

A total of 66 AMFs were found in 57 (7.3%) of the 784 patients. The frequency of AMFs was significantly influenced by gender and side of the mandible (p < .05). Most AMFs were located apically between apices of the first and second premolars. The high-position AMFs (above the mental foramen) accounted for 54.5% of the total. The mean horizontal and vertical diameters of the AMF were 1.38 ± 0.47 and 1.23 ± 0.37 mm, respectively. Two typical types of the bony canal leading to the AMF were identified according to their bifurcation site from the mandibular canal. Most bony canals originated from the anterior loop of the mental canal (56.1%) and coursed posterosuperiorly (36.3%). The mean length of the bony canals was 5.78 ± 2.31 mm.

CONCLUSIONS

This study presents a considerable frequency of AMFs in a Chinese population. The high-position AMF and the associated bony canal coursing in the oblique upward direction appear frequently. Thus, clinicians should be alert to the presence of the AMF to avoid neurovascular complications especially when dental procedures require periosteum detachment and implant insertion in the mental region.

[Cone beam computed tomography evaluation of bifid mandibular canals in the adult population in Sichuan Province]

OBJECTIVE

To investigate the incidence of bifid mandibular canals (BMC), and analyze the types, courses, and anatomic features of the variant canals in the adult population in Sichuan Province.

METHODS

Five hundred patients (1 000 hemimandibles) underwent cone beam computed tomography (CBCT) were included in this study. The incidence, bifurcate types and courses of the BMC were evaluated.

RESULTS

The incidence of BMC was 13.8% (69/500) in the study, 9.2% in terms of total hemimandibles. The most frequently type was retromolar canals, followed by the dental and buccolingual type, meanwhile the lowest was the forward type. The mean diameter of the accessory canals was 0.90 mm and the mean length was 9.39 mm.

CONCLUSIONS

CBCT used in this study has shown that the incidence of BMC assessed by CBCT was significantly higher than panoramic radiography. Furthermore, CBCT can depict the position, course, size and the branches of the mandibular canals.
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