Analysis of the mental foramen using cone beam computerized tomography

Presurgical Assessment of Anatomical Landmark Position Using Two Views of Cone Beam Computed Tomography: A Comparative Radiological Study

BACKGROUND

Cone beam computerized computed tomography (CBCT) has been widely indicated in dental implant procedure. The first step that the doctors should perform in local hospitals is to use orthopantomography for surgical planning to avoid and limit the risk of complications. As a result, determining the magnification amount of orthopantomography to achieve a precise diagnosis is clinically important. This study investigated the difference in measurement of the mental foramen (MF) position before dental surgery using 2 views of CBCT.

MATERIALS AND METHODS

Cone beam computed tomography scan was performed for 100 patients who required implant placement. In the panoramic and three-dimensional views of CBCT, the vertical distance between the margin of the mandible and the lower border of MF, and the horizontal distance between the mandibular symphysis and the mesial anterior border of MF were calculated. The differences between the 2 views were compared using Wilcoxon-rank U test with P value ≤ 0.05 considered statistically significant.

RESULTS

The findings of this study showed a substantial statistical difference in the horizontal distance for the dentate patients in panoramic and three-dimensional views (22.7 ± 3.04 versus 21.1 ± 1.6), (22.5 ± 2.4 versus 20.9 ± 1.5) and left side (22.4 ± 2.8 versus 21.2 ± 1.6), (22.4 ± 2.8 versus 20.6 ± 1.4) of both genders. Concerning the vertical distance, a significant difference was also observed in the dentate (12.1 ± 2.1 versus 11.1 ± 1.4), (10.6 ± 1.4 versus 9.6 ± 1.3) and left side of the jaw (11.6 ± 1.95 versus 10.9 ± 1.2), (10.5 ± 1.2 versus 9.96 ± 1.4) for both genders in both views. In the edentulous and right side of the jaw, however no statistical difference was observed between male and female patients in terms of horizontal and vertical measurements.

Assessment of the anterior and caudal extent of inferior alveolar nerve canal, location of inferior alveolar canal and mental foramen, and the depth of submandibular fossa using computed tomography

Background:

A well-versed knowledge of the precise location of various anatomical landmarks is necessary to avoid complications during surgery. The study was conducted for the assessment of the anterior and caudal extent of the inferior alveolar nerve canal, location of inferior alveolar canal and mental foramen, and the depth of the submandibular fossa using computed tomography (CT).

Materials and Methods:

One hundred CT scans were randomly selected for this study accounting for 200 hemimandibles. Both axial and coronal images were obtained and evaluated concurrently. Results were subjected to statistical analysis for correct inferences.

Results:

A total of 200 hemimandibles (n = 200) from 100 patients with a mean age was 23.89 ± 1.75 years ranging from 21 to 33 years were evaluated. The mean length of the anterior loop was 0.95 mm for all of the observation combined and measurement range from 0 to 5.1 mm. The total frequency of type I, type II, and type III of mental nerve was found as 71%, 4.5%, and 24.5%, respectively. At the level of the first molar, the mean distance from the center of the inferior alveolar canal to the external surface of the buccal cortex (Q) was 5.44 ± 1.38 mm ranging from 2.4 to 10.4 mm. Furthermore, there was no statistically significant difference in MF-IMB (mental foramen to the inferior border of mandible) between the right and left sides of the mandible. (P = 0.87).

Conclusion:

Our study demonstrates that analyzing CT scans using the methods described in this study can be a useful tool in avoiding the iatrogenic injuries to inferior alveolar nerve and arteries during various maxillofacial surgical procedures.

Mental Foramen and Anterior Loop Anatomic Characteristics: A Systematic Review and Meta-analysis of Cross-sectional Imaging Studies

INTRODUCTION

The present study aimed to review the epidemiologic, topographic, and morphometric aspects of the mental foramen (MF) and anterior loop (AL) on cone-beam computed tomographic imaging studies.

METHODS

An International Prospective Register of Systematic Reviews (PROSPERO)-registered systematic review (CRD42018112991) was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Two reviewers independently performed data extraction from observational studies that evaluated MF and AL on 7 electronic databases. MedCalc (MedCalc Software bv, Ostend, Belgium) software was used to perform a meta-analysis with a 95% confidence level.

RESULTS

Of 1545 articles, 66 met the inclusion criteria, totaling 14,233 patients from 5 continents, with a total of 6655 females and 5884 males (some studies did not report sex), with an age range between 8 and 89 years. The most prevalent shapes of MF were oval (48.72%) and circular (44.36%), and the most frequent horizontal positions were between premolars (43.66%) and in line with the long axis of the second premolar (43.12%).

CONCLUSIONS

Based on the articles that assessed AL, the mean prevalence was 43.18%, with most studies reporting bilateral localization as the most prevalent.

Association between the Anatomy of the Mandibular Canal and Facial Types: A Cone-Beam Computed Tomography Analysis

We evaluated the anatomical variations of the mandibular canal associated with various facial types, age, sex, and side of the face studied. We analyzed 348 hemimandibles in subjects without a history of trauma, lesions in the lower arch, or orthognathic or repair surgery in the posterior mandible. Facial type was determined using the VERT index. The canal path was classified as Type 1 (a large, single structure passing very close to the root tips); Type 2 (a canal passing closest to the mandibular base); and Type 3 (a canal present in the posterior mandibular region, with a lower canal running through the mandibular branch, reaching the anterior region). Bifid canals (type 3) were classified into four categories according to the course and number of mandibular canals. The brachyfacial and mesofacial types presented a Type 1 canal in 95.5% (n=166) of subjects, in dolichofacial types, 68.2% (n=45) presented a Type 2 canal, while in the mesofacial type, a lower prevalence of the bifid mandibular canal was observed (13.0%, n=23) than in the other facial types. The bifid canal showed significant association with facial type only (p < 0.05), but no significant association was observed with the anterior loop type (p > 0.05). Facial type is significantly associated with the path and morphological variations of the mandibular canal, independently of the side of the face studied, age, and sex.

Morphometric Analysis of the Mental Foramen Using Cone-Beam Computed Tomography

This study evaluated the effects of age and sex on the location and size of the mental foramen (MF). A total of 104 cone-beam computed tomography (CBCT) scans from patients' aged 18–80 years were selected. Images were evaluated using the following parameters: position and size of the MF, and Distances A (distance from the upper limit of the MF to the apex of the first lower premolar), B (distance from the upper cortical border of the MF to the alveolar crest), and C (distance from the border of the MF to the base of the mandible). Results revealed that the location of the MF was predominantly apical (44.4%), between the long axes of the premolars, at an average distance of 4.92 mm from the root of the first lower premolar. The height of the MF was significantly different between both sexes (3.41 and 2.99 mm, resp.; mean height: 3.11 mm; P=0.003). The MF was located on average at 11.21 mm from the alveolar crest and 12.31 mm from the base of the mandible; the former measurement was significantly different between both sexes (13.13 and 11.98 mm, resp.; P ≤ 0.001). In conclusion, the location of the MF was predominantly apical between the long axes of the premolars, and the mean size and distance of the MF were greater in men.

Prevalence evaluation and classification of bifid mandibular canals in CBCT exams in different facial types

Abstract Objetive The aim of this study is to establish the prevalence and classification of mandibular canal alterations using cone beam computed tomography (CBCT) in different facial types. This research was submitted and approved by the research ethics committee, registration number 2.065.839. Material and method The sample consisted of 90 CBCTs from the São Leopoldo Mandic Dental School database (Campinas-SP), divided into three groups according to brachycephalic, dolichocephalic and mesocephalic facial types. Result Of the 90 patients, 23 presented bifid mandible canals (25.6%), of which 60.9% were in males and 39.1% in females. In 39.1%, the canal bifurcation occurred towards the retromolar region (class D), 21.7% had a trajectory to an alveolar or upper direction (class C) and 13.1% were classified as C-E. For the remaining classifications (A, E, F and A-E), the frequencies were in the range of 8.7% to 4.3%. None of the 23 cases of mandibular canal bifurcation was classified as B (mesial direction). Conclusion According to the results obtained from this study, the prevalence of bifid mandibular canals was found to be 25.6%, with class D being the most prevalent for the retromolar region and the highest occurrence was unilaterally on the left side. When evaluating the occurrence of bifid mandibular canals in relation to facial types, brachycephalic patients were the most affected.