Finding the mental foramen

Morphological Characteristics of the Double Mental Foramen and Its Relevance in Clinical Practice: An Observational Study

The mental foramen (MF) is an opening found bilaterally on the anterolateral aspect of the mandible; it can be round or oval and have different diameters. One of the anatomical variants of the jaw is the presence of an accessory mental foramen (AMF). These are usually smaller than the MF and can be located above, below, or to the sides of the main MF. The objective of this study was to recognize the presence of AMF in dry jaws of the Chilean population and collect information about its clinical relevance reported in the literature. In this descriptive observational study, we have collected dried jaws obtained from three higher education institutions in Santiago de Chile, from the Department of Morphology of the Andrés Bello University, the Normal Human Anatomy Unit of the University of Santiago, and the Human Anatomy pavilion from the Faculty of Medicine of the Finis Terrae University. The samples for this research were obtained by convenience, and the observation of the jaws was carried out in the human anatomy laboratories of each institution by three evaluators independently, and a fourth evaluator was included to validate that each evaluation was correct. The sample for this research came from 260 dry jaws, showing the following findings from the total jaws studied, and to classify as an accessory MF, it will be examined and measured so that it complies with what is declared in the literature as the presence of AMF, which is between 0.74 mm. and 0.89 mm. There were 17 studies included with a sample that fluctuated between 1 and 4000, with a cumulative total of 7946 and an average number of jaws analyzed from the studies of 467.4, showing statistically significant differences between the means with the sample analyzed in this study; p = 0.095. For the cumulative prevalence of the presence of AMF, this was 3.07 in this study, and in the compared studies, the average of AMF was 8.01%, which did not present a statistically significant difference; p = 0.158. Regarding the presence of variants of unilateral AMF, this occurred in five jaws, which is equivalent to 1.84% in the sample of this study, while in previous studies, it was 7.5%, being higher on the left side than on the right. The presence of AMF is a variant with high prevalence if we compare it with other variants of the jaw. Knowledge of the anatomy and position of the AMF is crucial to analyze different scenarios in the face of surgical procedures or conservative treatments of the lower anterior dental region.

Multiple Mental Foramina: A Rare Anatomical Variation Detected by Cone-Beam Computed Tomography (CBCT)

The mental foramen is a single anatomical structure that can be seen bilaterally in the body of the mandible and generally in the lower area of the premolars. Sometimes, the mental foramen can have accessory foramina that should be considered. Clinical evaluation of the accessory mental foramina is critical because of its neurovascular fibers. Identifying the secondary mental foramen reduces the possibility of paraesthesia and pain after surgery.

Mental Foramen Position, Shape, Continuity, and Symmetry Among Malocclusion Patients: A Radiographic Study

INTRODUCTION

Many dental treatments need exact knowledge of the anatomical location of the mental foramen (MF). This retrospective research uses orthopantomograph (OPG) to assess the MF of orthodontic patients in Saudi Arabia and their position, symmetry, shape, and connectivity.

MATERIALS AND METHOD

One hundred and eighty panoramic radiographs of patients having orthodontic treatment were analyzed for the location, form, symmetry, as well as bilateral preservation of the MF. The patients were of varied ages, genders, and degrees of malocclusion and were divided into three classes: Class I (60), Class II (60), and Class III (60). Chi-squared tests and other descriptive statistics were employed to examine the data for statistical significance.

RESULT

When looking at the right side of the mouth, the most frequent location for MF was position 3 (between the apexes of the first and second premolars; 50.6%), whereas on the left side, it was location 4 (near the apical of the second premolar; 47.2%). The most typical form of MF has an irregular shape. MF location on the left side and continuity types differed significantly across malocclusion groups (p<0.05).

CONCLUSION

 OPGs of Saudi orthodontic patients demonstrated a significant variability of position and continuity of the MF across different classes of malocclusion. The third most frequent position was between the first and second premolars, while the shape of MF showed variation across the age of the patients. Hence, this precise comprehension of the anatomical and morphological diversity of the MF is of utmost significance for dental professionals.

Evaluation of the validity of mental foramen USG measurements by comparison with CBCT and determination of blood flow

OBJECTIVES

To examine mental foramen (MF) morphology and morphometry in comparison with ultrasonography (USG) and cone-beam computed tomography (CBCT), and to determine the relationship between mental artery blood flow parameters and age, gender, dental status, alveolar crest height, mandibular cortical index (MCI) with USG.

METHODS

A total of 120 MF and mental arteries of 60 patients (21 males and 39 females), including 20 patients in each group, aged 18-39, 40-59, and 60 years and above, were evaluated. The horizontal and vertical diameter of the MF and the distance between it and the alveolar crest were evaluated with USG and CBCT. In addition, mental artery blood flow parameters were examined by USG.

RESULTS

When the horizontal diameter values of MF were compared in USG and CBCT measurements; the diameter was significantly lower in the measurements obtained by USG (p < 0.05). It was observed that there were no mental arteries whose blood flow could not be recorded, 31 (25.8%) had strong blood flow and 89 (74.2%) had weak blood flow. No significant correlation was observed between gender and blood flow parameters (p > 0.05).

CONCLUSIONS

Considering that CBCT images are used as gold standard in our study, it may be said that USG is not as reliable as CBCT in evaluating the MF dimensions in the maxillofacial region. Nevertheless, USG is a suitable technique for determining the visualizing and blood flow of the MF.

Intraoperative Mapping of the Sensory Root of the Trigeminal Nerve in Patients with Pontocerebellar Angle Pathology

OBJECTIVE

The aim of the present study was to determine the position of the 3 sensory branches of the trigeminal nerve in the preganglionic tract using intraoperative neurophysiological mapping.

METHODS

We included consecutive adult patients who underwent neurosurgical treatment of cerebellopontine angle lesions. The trigeminal nerve was antidromically stimulated at 3 sites along its circumference with different stimulus intensities at a distance of ≤1 cm from the brainstem. The sensory nerve action potentials (SNAPs) were recorded from each main trigeminal branch (V1 [ophthalmic branch], V2 [maxillary branch], and V3 [mandibular branch]).

RESULTS

We analyzed 13 patients. The stimulation points at which we obtained the greatest number of congruous and exclusive SNAPs (SNAPs only on the stimulated branch) was the stimulation point for V3 (20.7%). The stimulation intensity at which we obtained the highest number of congruent and exclusive SNAPs with the stimulated branch was 0.5 mA.

CONCLUSIONS

Using our recording conditions, trigeminal stimulation is a reliable technique for mapping the V3 and V1 branches using an intensity not exceeding 0.5. However, reliable identification of the fibers of V2 is more difficult. Stimulation of the trigeminal nerve can be a reliable technique to identify the V3 and V1 branches if rhizotomy of these branches is necessary.

Trifurcated Mental Foramina: A Cone-Beam Computed Tomography Incidental Finding During the Implant Treatment Planning

The mental foramen is a known skull anatomical structure located bilaterally on the mandible along the buccal cortical plate. It is located approximately between the roots of premolars in the anteroposterior dimension, and its supero-inferior level on the alveolar height varies in every individual. The position of the mental foramen is very crucial when surgical interventions are planned in the area. An accessory mental foramina can be very well detected in the three-dimensional (3D) imaging modality, especially in 3D volume rendering images. It can still be appreciated in two-dimensional (2D) imaging modalities such as a panoramic; however, at times it can be confused with periapical pathology, especially in cases where caries are present in the teeth. Three-dimensional imaging modality plays a critical role in identifying such anatomical variation, and hence, it is important to evaluate any surgical site in three dimensions prior to surgical intervention.

Automatic detection of the mental foramen for estimating mandibular cortical width in dental panoramic radiographs: the seventh survey of the Tromsø Study (Tromsø7) in 2015–2016

Objective

To apply deep learning to a data set of dental panoramic radiographs to detect the mental foramen for automatic assessment of the mandibular cortical width.

Methods

Data from the seventh survey of the Tromsø Study (Tromsø7) were used. The data set contained 5197 randomly chosen dental panoramic radiographs. Four pretrained object detectors were tested. We randomly chose 80% of the data for training and 20% for testing. Models were trained using GeForce RTX 2080 Ti with 11 GB GPU memory (NVIDIA Corporation, Santa Clara, CA, USA). Python programming language version 3.7 was used for analysis.

Results

The EfficientDet-D0 model showed the highest average precision of 0.30. When the threshold to regard a prediction as correct (intersection over union) was set to 0.5, the average precision was 0.79. The RetinaNet model achieved the lowest average precision of 0.23, and the precision was 0.64 when the intersection over union was set to 0.5. The procedure to estimate mandibular cortical width showed acceptable results. Of 100 random images, the algorithm produced an output 93 times, 20 of which were not visually satisfactory.

Conclusions

EfficientDet-D0 effectively detected the mental foramen. Methods for estimating bone quality are important in radiology and require further development.

Structural Features of the Mental Foramen in a Saudi Subpopulation: A Retrospective CBCT Study

Introduction

Accurate and precise knowledge about the position, size, and shape of the mental foramen (MF) are critical in avoiding procedural complications. The MF's anatomical features vary among different ethnic groups, and various radiographic techniques have been used to determine these variations.

Aims

To evaluate the MF's shape, vertical and horizontal positions, and distance from the border of the mandible. To evaluate the differences among genders as they pertain to the right and left sides of the mandible and research the bilateral symmetry regarding the same variables.

Materials and Methods

Cone beam computer tomography (CBCT) scans of 155 Saudi patients (69 males and 86 females) who visited the college of dentistry's clinics were obtained from the college database for this retrospective study. All the scans were analyzed by 3 calibrated examiners. The data collected was analyzed statistically, and results were obtained.

Results

The MF was located under the mandibular second premolar in 56.9% of cases, whereas in 26.9% of cases, it was located between the first and second mandibular premolar. The most prevalent position was below the level of the apices of the mandibular premolar teeth (87.2%). The round shape was most frequent (44.9%) compared to the H-oval (34.7%) and V-oval (20.4%). The V-oval shape was more frequent in males, while the H-oval shape was more frequent in females. The average distance from the center of the MF to the mandibular border was 14.03 ± 1.58 mm, with males exhibiting a greater distance than females. Overall, there were no significant differences between the bilateral symmetry and the right and left sides for all parameters.

Conclusion

The most common position of the MF was under the root apex of the mandibular second premolar, with an average distance of about 14 mm from the border of the mandible. The position and shape of the MF were the same bilaterally in the majority of individuals.

Neural Network Detection and Segmentation of Mental Foramen in Panoramic Imaging

Objective: To apply the technique of deep learning on a small dataset of panoramic images for the detection and segmentation of the mental foramen (MF). Study design: In this study we used in-house dataset created within the School of Dental Medicine, Tel Aviv University. The dataset contained randomly chosen and anonymized 112 digital panoramic X-ray images and corresponding segmentations of MF. In order to solve the task of segmentation of the MF we used a single fully convolution neural network, that was based on U-net as well as a cascade architecture. 70% of the data were randomly chosen for training, 15% for validation and accuracy was tested on 15%. The model was trained using NVIDIA GeForce GTX 1080 GPU. The SPSS software, version 17.0 (Chicago, IL, USA) was used for the statistical analysis. The study was approved by the ethical committee of Tel Aviv University. Results: The best results of the dice similarity coefficient ( DSC), precision, recall, MF-wise true positive rate (MF_TPR) and MF-wise false positive rate (MF_FPR) in single networks were 49.51%, 71.13%, 68.24%, 87.81% and 14.08%, respectively. The cascade of networks has shown better results than simple networks in recall and MF_TPR, which were 88.83%, 93.75%, respectively, while DSC and precision achieved the lowest values, 31.77% and 23.92%, respectively. Conclusions: Currently, the U-net, one of the most used neural network architectures for biomedical application, was effectively used in this study. Methods based on deep learning are extremely important for automatic detection and segmentation in radiology and require further development.

Clinical and anatomical study of foramen locations in jaw bones and adjacent structures

This study aims to find and locate foramens exactly in maxilla and mandible in case of complications during surgeries.Computer topographic angiography (CTA) images of 120 cases were reviewed. The measurements were performed on coronal, sagittal and axial planes after the 3 dimension volume reconstruction. The distances among foramens, bony landmarks, teeth, and facial artery were all measured with the angles as adjustments.The incisive foramen (IF) was measured 20.55 ± 2.81 mm to margo inferior of incisor, and 45.27 ± 5.27 degree from the axial midline. The greater palatine foramen located 43.17 ± 2.55 mm from the IF, while 21.08 ± 3.75 degree from the midline in axial plane. The lesser palatine foramina located 44.56 ± 5.74 mm from the IF and 20.05 ± 3.59 degree to the midline. The Mandibular foramen (MBF) was 91.15 ± 1.86 mm horizontally to the margo inferior of incisor. The angle that the MBF-margo inferior of incisor line made with the axial midline was 31.25 ± 2.89 degree. The shortest horizontal distance from the mental foramen (MF) to the facial artery in sagittal plane was 21.90 ± 1.86 mm, while it became 13.00 ± 2.05 mm in coronary section. The horizontal distance from the MF to the margo inferior of incisor in sagittal plane was 22.04 ± 3.22 mm. It turned out to be 25.78 ± 5.23 mm between MF and mid-sagittal line in coronary section. The vertical distance was 25.20 ± 3.06 mm from the upper margin of the second premolar to the MF.The foramens were clearly seen through CTA. Moreover, linear and angular measurements were presented, which makes it safer and wiser for surgeons to consider the biometric data before operations.

Surgically-oriented anatomical study of mandibular premolars: A CBCT study

Background

The knowledge of root canal anatomy and of the anatomical relationship should be considered mandatory when planning surgical endodontics. The aim of the study was to investigate the anatomical features of mandibular premolars, evaluating their relationship with mental nerve.

Material and Methods

CBCT scans were evaluated recording the number of roots, root canal configuration and the relationship with mental nerve of 100 mandibular premolars. After simulating a resection of 3 mm of the root, the shape and the number of canals, and the distance to the buccal and lingual bone plate and to the mental foramen was evaluated.

Results

The one root - one canal configuration was the most common configuration. The mental foramen was located at the level of MSPs in 40% cases, and it was between MSP and MFP in 46% of cases. The distance between the apex and the vestibular plate was lower than the distance to the lingual one.

Conclusions

We found a significant heterogeneity in the anatomy of mandibular premolars. CBCT could be considered important when planning surgical endodontics in this region. Key words:Cone-Beam Computed Tomography, bicuspid, root canal, root canal therapy, apicoectomy, mandibular nerve.

A rare anatomic variation: Triple mental foramina

Multiple mental foramina (MF) are rarely found in the human mandible. We report on the case, as documented using cone beam computed tomography (CBCT), of the triple MF that were identified on the right hemimandible of a 28-year-old female patient. The distal foramen was located on the mandible between the apices of the second premolar root and the first molar mesiovestibular root, being reached by a thin canal that left the mandibular canal. A pair of mesial foramina were identified between the apices of the premolar teeth. Thus, the three foramina corresponded to a surface area of 23.49mm² of the mandible. On the opposite side, a single mental foramen had a surface area of just 13.25mm². On each side, retromolar canals that opened into the retromolar fossae were also found. The anatomic possibility of multiple MF increases the surface area at risk during surgical procedures, increases the risk of neurovascular damage and obscures the common tooth-related location of the mental foramen. Practitioners should, therefore, consider a personalised and imaging-documented approach so as to avoid treatment failure.

Locating the mental foramen at the bedside with point of care ultrasound imaging

Introduction

Ultrasound guided neuro-anaesthesia is a developing field of interest to clinicians from various disciplines. The objective of this proof of concept study was to explore the ability, ease and rapidity of ultrasonography in locating the mental foramen.

Methods

A convenience sample of 100 patients aged 18 years or older, with no known pathology to the mandibular region, that presented to a single urban ED were enrolled. All patients underwent an ultrasound examination on both sides of the face to locate the mental foramina.

Results

A total of 100 patients' mental foramina were studied. Mean age was 35.7 years (SD 9.1 years), 50% were black and 25% each were asian and white. The mental foramina were ultrasonographically identified in all (100%) of the subjects in the study group. Although requiring a larger quantity of ultrasound gel, the mental foramina were also visualized in all twelve subjects with facial hair. Three out of the 100 subjects were noted to have accessory mental foramina. The overall mean time taken to locate the first mental foramen in each patient was 16.1 seconds (SD 12.9 seconds). For the first 25 subjects studied, the mean time taken was 34.7 seconds (SD 13.4 seconds), whereas for the next 75 subjects studied, the mean time taken was 9.9 seconds (SD 3.0 seconds).

Conclusion

Bedside ultrasound imaging is a potentially reliable method to identify and locate the mental foramen. With practice and experience, the mental foramen can be more easily identified.

Ultrasonographically locating the mental foramen and its soft tissue relations

OBJECTIVES

This ultrasound-based cross-sectional study aimed to visualize, locate and compare the position of the mental foramen with regard to its relationship to various soft tissue landmarks.

METHODS

100 Black and Caucasian subjects were included. An ultrasound transducer was used to locate the mental foramina. Distances to various landmarks were measured and compared.

RESULTS

All mental foramina were visualized. The mean soft tissue distance of the entire group from the mental foramen on the right and left sides, respectively, were as follows: (a) 3.4 mm [standard deviation (SD) 1.7 mm] and 3.4 mm (SD 1.5 mm) lateral to a vertical line passing through the chelion; (b) 20.1 mm (SD 2.6 mm) and 20.1 mm (SD 2.6 mm) distal to a horizontal line bisecting the chelions; (c) 15.1 mm (SD 2.4 mm) and 15.0 mm (SD 2.4 mm) proximal to the inferior border of the mandible. We found no statistically significant differences between race groups, between gender group and between age categories with regard to the horizontal soft tissue distance from a vertical line passing through the chelion to the mental foramen on the right or left sides. There were statistically significant (but not clinically significant) differences between race groups and between gender groups but not between age groups with regard to the vertical soft tissue distance from a horizontal line bisecting the chelions to the mental foramen as well as from the inferior border of the mandible to the mental foramen on both the right and left sides.

CONCLUSIONS

This study suggests that ultrasound is a feasible imaging modality that can be utilized to locate the mental foramen. Differences in the position of the mental foramen with regard to various soft tissue landmarks are minor and clinically insignificant.

The Ultrasonographic Determination of the Position of the Mental Foramen and its Relation to the Mandibular Premolar Teeth

INTRODUCTION

The position of the mental foramen has been well researched in cadaver specimens, radiographically as well as intraoperatively. To our knowledge, this landmark study is the first to make use of ultrasonography in a study population to determine the position of the mental foramen in relation to the mandibular premolar teeth. Ultrasonography has great potential to further revolutionize the practice of medicine and dento-maxillofacial surgery.

AIM

To make use of ultrasound to determine the position of the mental foramen and its relation to the mandibular premolar teeth.

MATERIALS AND METHODS

One hundred Black and Caucasian subjects were enrolled. A high frequency (8MHz) transducer (PLF.805ST) of a diagnostic ultrasound system (model SSA-510A) was applied above the inferior border of the mandible, just lateral to the mentum. With the marker of the transducer pointing cranially, the position of the mental foramen in relation to the closest mandibular premolar tooth was determined. The position was compared across race, sex and age groups.

RESULTS

All mental foramina (100%) were visualised. Overall the most frequent position of the mental foramen was in line with the long axis of the second premolar on the right (44%) and between the first and second premolars on the left (44%). There were no statistical differences (p >0.05) between race groups, sex and age groups with regard to the position of the mental foramen in relation to the mandibular premolars. However, in Blacks, the most frequent position of the mental foramen was in line with the long axis of the second premolar and in Caucasians the most common position was between the first and second premolars. The most frequent position of the mental foramen in females was in line with the long axis of the second premolar on the right and between the first and second premolars on the left. In males, the most frequent position of the mental foramen was in line with the long axis of the second premolar bilaterally. The most common position of the mental foramen in the age group category 18-30 years was between the first and second premolars. In patients aged 31-60 years the most frequent position was in line with the long axis of the second premolar.

CONCLUSION

Ultrasound is a sensitive modality to locate the mental foramen. There are differences in the most common position of the mental foramen with regard to the long axis of the premolar teeth. Ultrasonography has the potential to revolutionize the practice of dento-maxillofacial surgery.