Three-dimensional anatomic analysis of the lingula and mandibular foramen: a cone beam computed tomography study

Positioning of the Inferior Alveolar Nerve and Surgical Implications: A Study on Thai Mandibles

BACKGROUND

The inferior alveolar nerve (IAN), a crucial branch of the trigeminal nerve, innervates the mandible. Precise knowledge of IAN positioning ensures surgical safety.

METHODS

This cross-sectional study analyzed head and neck computed tomography scans from Maharaj Nakorn Chiang Mai Hospital. Inclusion criteria comprised dentate adults. Exclusion criteria included mandibular trauma/pathology or prior surgery. The study aimed to determine IAN positioning relative to key surgical landmarks: the first molar, lingula, and mental foramen.

RESULTS

A total of 450 Thai mandibles (900 hemimandibles) with a mean age of 36 years (58.2% male) were included. No significant differences were observed in IAN positioning relative to the first molar between the left and right sides in superior and inferior landmarks. However, the buccal distance was significantly closer on the left. The lingula distance was higher on the left, whereas that to the mental foramen was lower.

CONCLUSION

Surgical implications suggest maintaining a 15-mm distance from the lower mandibular border during osteotomy and upper plate placement, restricting horizontal cuts within this 15-mm range from the lingula, and ensuring screws do not extend more than 7 mm from the buccal surface. This study provides valuable guidance for minimizing the risk of iatrogenic injury to the IAN.

Comparison of methods for detecting mandibular lingula and can antilingula be used in lingula mandibula detection?

OBJECTIVE

The aim of this study is to evaluate the relationship between anatomical reference points used during orthognathic surgery and to minimize the risks of iatrogenic neurovascular damage.

MATERIALS AND METHODS

This retrospective study included cone-beam computed tomography (CBCT) images involving the mandible from patients who visited Recep Tayyip Erdoğan University Faculty of Dentistry between January 2018 and September 2023. The age range of the included individuals was set between 18 and 80 years. Horizontal and vertical distances between mandibular anatomical structures, such as the lingula mandibula (LM), mandibular foramen (MF), antilingula (AL), and surrounding structures were measured using CBCT software. Individuals with intraosseous pathology, insufficient image quality, or a history of surgical/orthodontic treatment were excluded from the study.

RESULTS

A total of 240 hemimandibles from 120 patients were analyzed (55.83% female, 44.17% male; mean age: 46.78 ± 15.30 years). Significant differences were identified in LM positions according to different AL types. The LM was found to be more inferior and posterior relative to hill and ridge type ALs, while it was more anterior relative to plateau type ALs. In 26.25% of mandibular rami, AL was not detected.

CONCLUSION

The position of the AL can serve as a guide in determining the osteotomy line during inferior vertical ramus osteotomy (IVRO). However, relying solely on AL as a reference point may increase the risk of inferior alveolar nerve (IAN) injury. Preoperative tomographic evaluations to determine the relationships among LM, MF, and AL can provide a safer approach in surgical planning, reduce complications, and help protect neurovascular structures.

Gender Estimation from Morphometric Measurements of Mandibular Lingula by Using Machine Learning Algorithms and Artificial Neural Networks

BACKGROUND

Sex determination from the bones is of great importance for forensic medicine and anthropology. The mandible is highly valued because it is the strongest, largest and most dimorphic bone in the skull.

AIM

Our aim in this study is gender estimation with morphometric measurements taken from mandibular lingula, an important structure on the mandible, by using machine learning algorithms and artificial neural networks.

METHODS

Cone beam computed tomography images of the mandibular lingula were obtained by retrospective scanning from the Picture Archiving Communication Systems of the Department of Oral, Dental and Maxillofacial Radiology, Faculty of Dentistry, İnönü University. Images scanned in Digital Imaging and Communications in Medicine (DICOM) format were transferred to RadiAnt DICOM Viewer (Version: 2020.2). The images were converted to 3-D format by using the 3D Volume Rendering console of the program. Eight anthropometric parameters were measured bilaterally from these 3-D images based on the mandibular lingula.

RESULTS

The results of the machine learning algorithms analyzed showed that the highest accuracy was 0.88 with Random Forest and Gaussian Naive Bayes algorithm. Accuracy rates of other parameters ranged between 0.78 and 0.88.

CONCLUSIONS

As a result of the study, it is thought that mandibular lingula-centered morphometric measurements can be used for gender determination as well as bones such as the pelvis and skull as they were found to be highly accurate. This study also provides information on the anatomical position of the lingula according to gender in Turkish society. The results can be important for oral-dental surgeons, anthropologists, and forensic experts.

Three-dimensional evaluation of mandibular lingula: Comparisons of skeletal angle classifications and growth patterns

OBJECTIVES

This study aimed to evaluate the position of the mandibular lingula (ML) in adult patients (aged between 18 and 35 years old) with different skeletal and growth patterns using cone-beam computed tomography (CBCT).

DESIGN

Cross-sectional.

SETTING

Dentistry department of University.

SUBJECTS

Subjects comprised CBCT images of 150 adult patients, including 300 rami.

METHODS AND MATERIALS

In total, 150 CBCT aged between 18 and 35 were selected and divided into three main groups of 50 samples based on their skeletal relationships (classes I, II and III). Patients were subdivided based on their growth pattern (vertical vs. horizontal), resulting in 25 samples per subgroup. Distances between the mandibular lingula and occlusal plane (ML-OP), sigmoid notch (ML-SN), external oblique ridge (ML-EOR), internal oblique ridge (ML-IOR), posterior border of the ramus (ML-PBR), inferior border of the ramus (ML-IBR), and horizontal and vertical distances to the mandibular foramen (ML-hMF and ML-vMF). One-way ANOVA variance analysis was employed to compare different angle classifications, and Bonferroni analysis was used for multiple comparisons. The Student's t-test was also used to compare growth patterns within each main group and genders within the subgroup.

RESULTS

The study revealed statistically significant differences in the position of the mandibular lingula between different angle classifications, growth patterns, and genders. Class II samples showed a more anterior position of the ML, whereas Class III samples displayed a more posterior position of the ML. Patients with horizontal growth patterns and Angle Class III had a more posteriorly positioned ML. Gender differences were observed, particularly in Class I and Class III classifications, suggesting that gender may influence the variability of ML position in these specific classifications.

CONCLUSION

The position of the mandibular lingula showed high variability among individuals with different angle classifications, growth patterns and genders.

Automated localization of mandibular landmarks in the construction of mandibular median sagittal plane

OBJECTIVE

To use deep learning to segment the mandible and identify three-dimensional (3D) anatomical landmarks from cone-beam computed tomography (CBCT) images, the planes constructed from the mandibular midline landmarks were compared and analyzed to find the best mandibular midsagittal plane (MMSP).

METHODS

A total of 400 participants were randomly divided into a training group (n = 360) and a validation group (n = 40). Normal individuals were used as the test group (n = 50). The PointRend deep learning mechanism segmented the mandible from CBCT images and accurately identified 27 anatomic landmarks via PoseNet. 3D coordinates of 5 central landmarks and 2 pairs of side landmarks were obtained for the test group. Every 35 combinations of 3 midline landmarks were screened using the template mapping technique. The asymmetry index (AI) was calculated for each of the 35 mirror planes. The template mapping technique plane was used as the reference plane; the top four planes with the smallest AIs were compared through distance, volume difference, and similarity index to find the plane with the fewest errors.

RESULTS

The mandible was segmented automatically in 10 ± 1.5 s with a 0.98 Dice similarity coefficient. The mean landmark localization error for the 27 landmarks was 1.04 ± 0.28 mm. MMSP should use the plane made by B (supramentale), Gn (gnathion), and F (mandibular foramen). The average AI grade was 1.6 (min-max: 0.59-3.61). There was no significant difference in distance or volume (P > 0.05); however, the similarity index was significantly different (P < 0.01).

CONCLUSION

Deep learning can automatically segment the mandible, identify anatomic landmarks, and address medicinal demands in people without mandibular deformities. The most accurate MMSP was the B-Gn-F plane.

A detailed radiomorphometric analysis of the mandibular foramen, lingula and anti-lingula with a special emphasis on mandibular prognathism

INTRODUCTION

The aim of this study was to evaluate radiomorphometric differences of mandibular foramen (MF), lingula (Li), and anti-lingula (AL) between prognathic and non-prognathic patients, using cone-beam computed tomography (CBCT).

METHODS

A total of 228 3D CBCT images of 57 prognathic and 57 non-prognathic patients were retrospectively evaluated. The distances between MF or Li to occlusal plane (OP), anterior border of ramus (AR), posterior border of ramus (PR), sigmoid notch (SN), gonion (Go) and distances Li to MF were measured. The presence of AL, and the distances to Li were also assessed in both groups.

RESULTS

In prognathic patients the mean distances of MF-AR and Li-PR were lesser, and Li-OP was greater (p < 0.05). However, distances from MF or Li to the other ramal landmarks were similar in both groups (p > 0.05). Presence of AL was found at 53 sides in prognathic and 20 sides in non-prognathic groups (p < 0.05). The horizontal distance of Li-MF was greater in prognathic patients (p < 0.05). On the other hand, there was no difference between groups regarding the horizontal distance of Li-Al, and the vertical distances of Li-MF and Li-AL (p > 0.05).

CONCLUSION

The present study provided valuable data regarding morphological differences of MF-AR, Li-MF and Li-OP, which should be considered in the preoperative assessment of patients with mandibular prognathism. Presence of AL was more common in prognathic patients and mainly located above Li. 3D CBCT applications facilitated assessment of AL and its relationship with Li.

Locating the Mandibular Lingula Using Cone-Beam Computed Tomography: A Literature Review

This study aimed to review the literature on adult mandibular lingula (ML) locations and related distances determined using cone-beam computed tomography (CBCT). A search was conducted for studies on CBCT using the following databases: PubMed, Web of Science, and Embase. The search results were limited to studies published between 1970 and 2021. The inclusion criteria were the investigation of ML location, CBCT, and participants aged ≥18 years. Eligible studies were examined for the distances from the lingual tip to the anterior ramus border, posterior ramus border, sigmoid notch, inferior ramus border, and occlusal plane. Eight studies on CBCT qualified for inclusion in the study. The mean distances from the ML to the anterior ramus border were 15.57 to 20 mm. In most of these, the ML was located above the occlusal plane. No significant differences were observed in the location and related distances for the ML among patients of different sexes, ethnicities, or skeletal patterns.

A three-dimensional statistical shape model of the growing mandible

Mandibular growth and morphology are important topics in the field of oral and maxillofacial surgery. For diagnostic and planning purposes, a normative database or statistical shape model of the growing mandible can be of great benefit. A collection of 874 cadaveric children's mandibles with dental age between 1 and 12 years old were digitized using computed tomography scanning and reconstructed to three-dimensional models. Point correspondence was achieved using iterative closest point and coherent point drift algorithms. Principal component analysis (PCA) was applied to find the main modes of variation in the data set. The average mandible was presented, along with the first ten PCA modes. The first mode explained 78% of the total variance; combining the first ten modes accumulated to 95% of the total variance. The first mode was strongly correlated with age and hence, with natural growth. This is the largest study on three-dimensional mandibular shape and development conducted thus far. The main limitation is that the samples lack information such as gender and cause of death. Clinical application of the model first requires validation with contemporary samples.

Position of the Mandibular Foramen in Different Facial Shapes Assessed by Cone-Beam Computed Tomography - A Cross-Sectional Retrospective Study

Purpose:

The mandibular foramen, located on the internal surface of the mandibular ramus, is an important anatomical landmark for the success during the inferior alveolar nerve block. This cross-sectional retrospective study aimed to evaluate the location of the mandibular foramen through Cone-Beam Computed Tomography (CBCT) in different facial shapes.

Materials and Methods:

The determination of the location of the mandibular foramen was performed using CBCT of mesocephalic, dolichocephalic and brachycephalic patients (n=40 each). The ramus width (W), the distance from the mandibular foramen to the deepest point of the anterior border of the mandibular ramus (D), the distance from the mandibular foramen to the lowest point of the mandibular notch (V) and the distance from the inferior border of the mandible to the lowest point in of the mandibular border (R), as well as the ratios W/D and V/R, were measured. ANCOVA, two-way ANOVA and Chi-square tests were used to analyze the variation among the facial shapes.

Results:

The ramus width (W) was greater (p<0.0001) in the brachycephalic (28.4±0.5 mm) than in both mesocephalic (26.8±0.36 mm) and dolichocephalic (25.5±0.39 mm) patients. D (p=0.0433) and R (p=0.0072) were also greater in the brachycephalic (17.7±0.36 mm; 43.4±0.75 mm, respectively) than dolichocephalic (16.5±0.3 mm; 40.3±0.63 mm, respectively), but both did not differ from mesocephalic (17.3±0.36 mm; 41.8±0.66 mm, respectively) patients. The other measurements (V, W/D and R/V) did not significantly differ among facial shapes.

Conclusion:

The localization of the mandibular foramen was, in the horizontal direction, more posterior in the brachycephalic patients and, in the vertical direction, higher in the dolichocephalic patients, when compared to the other groups analyzed. Thus, the anatomic data found in this study may help dentists to increase the success of the inferior alveolar nerve block and prevent surgical complications.

The mandibular plane: a stable reference to localize the mandibular foramen, even during growth

Objectives

The location of the mandibular foramen is essential for the quality of the inferior alveolar nerve block anaesthesia and has often been studied with contradictory results over the years. The aim of this study was to locate the mandibular foramen, according to the dental age of the subject, through 3D analysis.

Methods

Three-dimensional images were reconstructed from mandibular computed tomography of 260 children, adolescents and adults. The occlusal plane was determined as the average plane passing through the buccal cusps of mandibular molars, premolars, and canines, and through the incisor edge. The mandibular foramen was located three dimensionally in relation to the anterior edge of the ramus (or coronoid notch), the sagittal plane and the occlusal plane.

Results

All along mandibular growth, the three distances defining the relative position of the mandibular foramen showed negligible changes. The mandibular foramen is located from − 0.4 to 2.9 mm above the occlusal plane. The distance between the mandibular foramen and the leading edge of the mandibular ramus ranged from 17 to 19.5 mm. The angle between the ramus and the sagittal plane ranged from 3° to 5.4°.

Conclusion

In our sample, and using the occlusal plane and the anterior edge of the ramus as anatomical references, the location of the mandibular foramen was considered to be similar in all patients regardless of age.

The variable position of the inferior alveolar nerve (IAN) in the mandibular ramus: a computed tomography (CT) study

INTRODUCTION

This study was designed to quantify the important anatomical landmarks and the path of the inferior alveolar nerve (IAN) within the human mandibular body and ramus, in particular with reference to the bilateral sagittal split osteotomy (BSSO).

MATERIALS AND METHODS

Four hundred and eleven CT scans were studied, 299 of these were involved in determining the position of lingula; and 230 were involved in determining the course of IAN in the mandibular molar region, namely from the mesial of the mandibular first molar to the distal of the mandibular second molar; 118 were involved with both measurements.

RESULTS

On average, the lingula was located 17.0 ± 2.2 mm from the external oblique ridge; 11.6 ± 2.0 mm from the internal oblique ridge; 17.2 ± 2.7 mm from the sigmoid notch; and 15.6 ± 1.9 mm from the posterior border of the mandible. The course of the IAN in the mandibular molar region was found to descend vertically from the distal of the mandibular second molar (7) to reach its lowest point between the first and second molars (6 and 7), and then ascend towards the mesial of the first molar (6). Horizontally, the IAN was found to traverse medially between the distal of the 7 and the middle of the 7, and then changes its path laterally towards the mesial of the 6.

CONCLUSION

Precise knowledge of the individual's position of the IAN will help surgical planning.

Novel three-dimensional position analysis of the mandibular foramen in patients with skeletal class III mandibular prognathism

PURPOSE

To analyze the relative position of the mandibular foramina (MnFs) in patients diagnosed with skeletal class III malocclusion.

MATERIALS AND METHODS

Computed tomography (CT) images were collected from 85 patients. The vertical lengths of each anatomic point from the five horizontal planes passing through the MnF were measured at the coronoid process, sigmoid notch, condyle, and the gonion. The distance from the anterior ramus point to the posterior ramus point on the five horizontal planes was designated the anteroposterior horizontal distance of the ramus for each plane. The perpendicular distance from each anterior ramus point to each vertical plane through the MnF was designated the horizontal distance from the anterior ramus to the MnF. The horizontal and vertical positions were examined by regression analysis.

RESULTS

Regression analysis showed the heights of the coronoid process, sigmoid notch, and condyle for the five horizontal planes were significantly related to the height of the MnF, with the highest significance associated with the MnF-mandibular plane (coefficients of determination (R(2)): 0.424, 0.597, and 0.604, respectively). The horizontal anteroposterior length of the ramus and the distance from the anterior ramus point to the MnF were significant by regression analysis.

CONCLUSION

The relative position of the MnF was significantly related to the vertical heights of the sigmoid notch, coronoid process, and condyle as well as to the horizontal anteroposterior length of the ascending ramus. These findings should be clinically useful for patients with skeletal class III mandibular prognathism.