Mandibular Incisive Canal Research Articles

Assessment of the mandibular incisive and mental canal in dentate and edentulous mandibles using cone-beam computed tomography

ObjectivesThis study evaluated the prevalence, diameter and location of the mandibular incisive canal (MIC) and the transition pattern and anterior loop length (ALL) of the mental canal and compared these values between dentate and edentulous mandibles. MethodsA total of 187 cone-beam computed tomography (CBCT) images of mandibles, namely, 100 images of dentate mandibles and 87 images of edentulous mandibles, were obtained. CBCT data related to the incisive canal and mental canal were analyzed by one examiner. ResultsThe prevalence of the MIC was 75∼78 %, showing no difference based on laterality or the presence of teeth. The ALL significantly differed depending on the presence of teeth as well as sex. The presence of teeth affected the size of the MIC in the female group, and the diameter of the MIC in the edentulous group was significantly narrower than that in the dentate group. The diameter of the MIC was significantly greater in males than in females in the edentulous group. Meanwhile, the location of the MIC in the male group depended on the presence of teeth at each measuring point, and the MIC was significantly closer to the lower border of the mandible in the female group than in the male group at all measuring points except at 0 mm. ConclusionsThis study indicated that the presence of teeth significantly affects the type of transition of the mental canal, the ALL, and the diameter and location of the MIC. Additionally, sex could be a factor affecting MIC location, MIC diameter and anterior loop length.

Strategies for prevention and treatment of vascular and nerve injuries in mandibular anterior implant surgery

Important anatomical structures such as mandibular incisive canal, tongue foramen, and mouth floor vessels may be damaged during implant surgery in the mandibular anterior region, which may lead to mouth floor hematoma, asphyxia, pain, paresthesia and other symptoms. In severe cases, this can be life-threatening. The insufficient alveolar bone space and the anatomical variation of blood vessels and nerves in the mandibular anterior region increase the risk of blood vessel and nerve injury during implant surgery. In case of vascular injury, airway control and hemostasis should be performed, and in case of nerve injury, implant removal and early medical treatment should be performed. To avoid vascular and nerve injury during implant surgery in the mandibular anterior region, it is necessary to be familiar with the anatomical structure, take cone-beam computed tomography, design properly before surgery, and use digital technology during surgery to achieve accurate implant placement. This article summarizes the anatomical structure of the mandibular anterior region, discusses the prevention strategies of vascular and nerve injuries in this region, and discusses the treatment methods after the occurrence of vascular and nerve injuries, to provide clinical reference.

Evaluation of Visibility of Mandibular Incisive Canal by Using Cone-Beam Computed Tomography: An Observational Study.

Performing surgery on the anterior mandible could harm the mandibular incisive canal (MIC). To prevent it, preoperative radiographic assessment is essential. Aim of our study was to examine the visibility and presence of the MIC along with measurement of the length of MIC by utilizing cone-beam computed tomography (CBCT). Images from 50 subjects, ranging in age from 20 to 60 years, who had their mandibles examined by CBCT were taken from the archive. Reconstructed images included cross-sectional and panoramic views. The canal's visibility was obtained from the mesial to the mental foramen and finally to the incisal extension. The shortest distance between the mesial and distal portions of the canal was determined to be the length of the MIC. To analyze independent samples, t-tests were employed. In 40 cases (80%), the visibility of MIC was seen as bilateral, and in 10 cases (20%), as unilateral. The visible length among the population ranged from a minimum of 0.00 to a maximum of 25.25 mm, with an average of 15.37 ± 5.59. Future research could utilize the differences in prevalence with respect to gender and visibility as a point of reference.

Measurement of mandibular incisive canal diameter using cone beam computed tomography

Cone beam computed tomography was used for measuring the diameter of a Mandibular incisive canal. The dental practice can now visualize small bone structures with low dose and high spatial resolution due to the introduction of CBCT (Cone Beam Computed Tomography). Therefore, it is of interest to measure the diameter of the MIC (Mandibular Incisive Canal) using the CBCT. Fifty CBCT scans obtained for implant placement preoperative planning were included in the study material. Observers carefully examined the CBCT data to determine the MIC’s presence & position. The inner diameter of the MIC was measured by taking the longest distance between the inner cortical borders of the canal which was further analyzed using software CS3D software. The collected data were further subjected to statistical analysis. The average mean of the population was 1.7130±.5178. The average diameter of MIC in males was 1.735±.5406 and in females was 1.6800±.4934. Complications from implant surgery in the anterior mandible may be prevented by utilizing CBCT scans to analyze the smallest diameter of the MIC.

A Retrospective Study of Location, Dimension, and Prevalence of Mandibular Incisive Nerve Canal with the Help of Cone-Beam Computed Tomography (CBCT).

To evaluate the mandibular incisive nerve canal's prevalence, location, and size. To ascertain the frequency, relationship to surrounding critical structures, and variance in the size and position of the mandibular incisive nerve canal. Mandibular incisive canal (MIC) measurements, locations, and prevalence were noted in 80 patients' cone-beam computed tomography (CBCT), ranging in age from 18 to 80. The overall incidence of missing canals was found to be 30% on the right side, 33.75% on the left, and 23.75% on both sides. Conclusion: In summary, magnetic resonance imaging (MRI) (3 Tesla) and other higher-resolution imaging modalities should be compared with CBCT for accurate MIC measurement and location assessment.

Measurement of the mandibular canal and mandibular incisive canal using cone beam tomography in adults from South Brazil.

To identify and measure the distance from the dental apices to the mandibular (MC) and mandibular incisive (MIC) canals, the diameter of the MC and the distances of the mental foramen (MF). In this retrospective study, cone-beam computed tomography scans of 144 adult patients (males and females) from a dental school in South Brazil were evaluated. Cross-sections were selected on the MC and the MIC paths, perpendicular to the mandibular base, and measurements were taken from the dental apices to the mandibular cortices. The measurement and location of the mandibular and mental foramen on both sides were compared. Paired t-tests compared sides, while Student's t-tests compared sexes (P < 0.05). The distance from the dental apices to the upper wall of the MC was closest in the third molar and farthest in the central incisor region. In both sexes and sides, the path of the MC is in most cases lingually in the molar regions and moves to the buccal region from the second premolar. The MF emerges in the regions between the premolars or near the second premolar. The results of this study highlight the importance of evaluating specific individual characteristics of a given population.

A unique artificial intelligence-based tool for automated CBCT segmentation of mandibular incisive canal.

To develop and validate a novel artificial intelligence (AI) tool for automated segmentation of mandibular incisive canal on cone beam computed tomography (CBCT) scans. After ethical approval, a data set of 200 CBCT scans were selected and categorized into training (160), validation (20), and test (20) sets. CBCT scans were imported into Virtual Patient Creator and ground truth for training and validation were manually segmented by three oral radiologists in multiplanar reconstructions. Intra- and interobserver analysis for human segmentation variability was performed on 20% of the data set. Segmentations were imported into Mimics for standardization. Resulting files were imported to 3-Matic for analysis using surface- and voxel-based methods. Evaluation metrics involved time efficiency, analysis metrics including Dice Similarity Coefficient (DSC), Intersection over Union (IoU), Root mean square error (RMSE), precision, recall, accuracy, and consistency. These values were calculated considering AI-based segmentation and refined-AI segmentation compared to manual segmentation. Average time for AI-based segmentation, refined-AI segmentation and manual segmentation was 00:10, 08:09, and 47:18 (284-fold time reduction). AI-based segmentation showed mean values of DSC 0.873, IoU 0.775, RMSE 0.256 mm, precision 0.837 and recall 0.890 while refined-AI segmentation provided DSC 0.876, IoU 0.781, RMSE 0.267 mm, precision 0. 852 and recall 0.902 with the accuracy of 0.998 for both methods. The consistency was one for AI-based segmentation and 0.910 for manual segmentation. An innovative AI-tool for automated segmentation of mandibular incisive canal on CBCT scans was proofed to be accurate, time efficient, and highly consistent, serving pre-surgical planning.

Risk assessment of mandibular incisive canal perforation during dental implant surgery in the anterior edentulous mandible: a virtual implant placement study using cone beam computed tomography

The aim of this study was to evaluate the risk of mandibular incisive canal (MIC) perforation caused by implants placed on cone beam computed tomography (CBCT) images in the edentulous mandibular anterior region. A total of 1200 dental implants were virtually inserted on 150 eligible CBCT scans. The relationship of different implant sizes with the incidence of MIC perforation and the relationship between crest height and perforation were evaluated. A total of 1200 virtual implant applications were performed on 150 patients. In 87% of cases, MIC was identified. Perforation in 12 and 14 mm implants was significantly higher than in 8- and 10-mm implants (P < .05). Perforation was found to be statistically significantly higher in crest heights that were ≤20 mm than in crest heights >20 mm (P < .05). Our results showed high perforation rates in the 12- and 14-mm implants and crests heights that were ≤20 mm during implant surgery in the mandibular anterior edentulous region. Perforation of the MIC should be considered a complication of implant surgery in the mandibular anterior region; therefore, CBCT images should be evaluated before implant placement.

The Prevalence of Mandibular Incisive Canal among a Sample of Yemeni Adults Obtained from Cone-beam Computed Tomography

Aim of this study: It was to determine the prevalence of Mandibular Incisive Canal (MIC) among a sample of Yemeni adults obtained from Cone-beam Computed Tomography (CBCT). Materials and Methods: This is a retrospective descriptive cross-sectional study which is conducted in Yemen to evaluate CBCT images of 180 subjects, 360 sides were evaluated respectively. The samples were 74 males (41.1%) and 106 females (58.9%). Result: Of the 180 subjects and 360 sides, 167 right (92.8%) and 171 left (95%) Sides were found to have MIC. Among these subjects, 166 (96.5%) had MIC bilaterally and 6 (3.5%) were unilaterally. According to gender, females were (98.1%) and males (91.9%), while among age groups ≤ 40 years (94.3%) and &gt; 40 years (97.3%) were found to have MIC. The mean height of MIC was 1.77 ±.45mm and the mean width was 1.66 ±.44 mm. The mean length of MIC was 12.74 ±4.4 mm. The mean distance from MIC to the alveolar process was 16.77 ±4.06 mm and to the inferior border of the mandible was 8.61 ±1.9 mm. The mean distance from MIC to the labial bony surface was 3.12 ±1.09 mm and to the lingual bony surface was 4.35 ±1.5 mm. All the mean values of the linear measurements were slightly higher in males than that of females. There were statistically significant differences in D3, D5 &amp; D6 between genders and in D3, D4 &amp; D5 between ages (P &lt; 0.05). But there was no statistically difference between sides. Conclusion: The MIC is present with a significant percentage of 95.6 % of Yemeni adults, which emphasizes the need to raise the awareness of MIC position and configuration among general practitioners and maxillofacial surgeons.

Türk toplumunda mental sinir, mental lup ve insiziv kanalın retrospektif bir değerlendirmesi

Objective: 3-dimensional radiographic evaluation of the intraforaminal area are crucial to prevent complications during surgical procedures. This study aimed retrospectively to determine incidence of different shapes of the foramen, and presence of the anterior loop with aid cone beam computed tomography (CBCT).&#x0D; Materials and Methods: This retrospective study was performed on 176 patients whose CBCT images indicated were used. The shape and location of the mental foramen; distance between the mental foramen (MF) and mandibular incisive canal (MIC); length of the alveolar crest, basis, buccal, and lingual sides; and MIC length were evaluated based on the images.&#x0D; Results: The anterior loop was observed in 42.2% of patients. No significant sex dependence was found in terms of MF localization status and MF shape (P &gt; 0.05). The mean distance of the anterior loop was 4.8±1.4 mm on the right side and 4.5±1.2 mm on the left side. The MIC was observed in all images. The mean length of MIC was 6.3±3.8 mm on the right side and 6±3.4 mm on the left side.&#x0D; Conclusion: Clinicians should be aware of the importance of preoperative evaluation of the intraforaminal area. Therefore, it is beneficial to use CBCT imaging techniques for preoperative planning.

Evaluation of mandibular incisive canal and mental foramen in Turkish population by conical beam computed tomography

Surgical complications may occur in the interforaminal area when course and morphological features of anatomical structures, which includes neurovascular structures in the mandible, cannot be defined correctly. The aim of this study is to determine the course and morphological characteristics of the mental foramen (MF) and the mandibular incisive canal (MIC) in Turkish society. Cone Beam Computed Tomography (CBCT) is considered the gold standard for dental imaging; therefore, in this study 96 CBCT images were examined retrospectively. The width and the length of the MF, distance from the MF to the alveolar bone crest, lower border of the mandible, angulation of mental canal to buccal bone surface, the length of the MIC, the angle among mental foramenincisive canal and a horizontal plane parallel to the inferior border of the mandible, and the height of the angle were measured. At the endmost point of the MIC, the distance between the canal and inferior, labial, and lingual borders of the mandible was measured. The most common locations of MF were along the second premolar (23,4%). MIC was absent in 24,4% of the cases. The most common locations of the endmost point of MIC were along the first incisive (35,8%), MIC length was significantly longer in males. Although the structures show variation among individuals, the mean values in Turkish society are similar to the mean values in the literature.

PREVALENCE, DIAMETER AND FURRING OF MANDIBULAR INCISIVE CANAL IN NORTH INDIAN SUBPOPULATION: A CBCT STUDY

Objective: The Mandibular Incisive Canal (MIC) carries mandibular neurovascular bundle and it is necessary to determine the presence of MIC &amp; its relation to adjacent anatomical landmarks to avoid any potential damage to neurovascular bundle during various surgical procedures. So, this study was planned to determine the prevalence, canal diameter and its relation with adjacent anatomic structures using CBCT and to find their associations with age, gender and laterality. Methods: CBCT scans of 61 patients (33 M, 28 F) were evaluated in sagittal sections. Results: The overall prevalence of MIC on the right side was found to be 65.6% while it was 73.8% on the left side. The MIC was more prevalent in females as compared to males between the 30-50 years of age. The mean diameter on the right and left side was found to be 0.85 ± 0.25 mm &amp; 0.93 ± 0.27 mm respectively. The mean distance of MIC from buccal cortex was (3.5 ± 1.3 &amp; 3.6 ± 1.8 mm), lingual cortex (4.8 ± 1.6 &amp; 4.8± 2.0 mm) &amp; inferior border of the mandible (10.1 ± 3.7 &amp;10.4 ± 3.3 mm) on right and left side respectively. Conclusions: The preoperative assessment of CBCT is advocated especially in middle age, females and left side for MIC evaluation &amp;the findings of this study will help in identifying safe area during surgical procedures in inter-foraminal region. Periapical surgery, implants, genioplasty etc. can be planned in a better manner by avoiding potential danger areas.

Radiographic analysis of the anterior mandible and its anatomical variations using cone-beam computed tomography.

The anterior loop, the mandibular incisive canal, and the lingual symphyseal foramen are important structures in the anterior mandible. The purpose of this study was to assess the prevalence of these structures using CBCT. A total of 170 projections were analyzed in different sectional planes. The study analyzed the prevalence and extension of the anterior loop and the prevalence of both the mandibular incisive canal and the lingual symphyseal foramen by using the GALAXIS software by Sirona. In 98.2 % (n = 167) a lingual symphyseal foramen was detected. An anterior loop was present in 31.2% (n = 53) with statistically significant higher detection rate in younger patients (P = .001). The median length was 1.26 mm (range 0.53-3.70 mm). No statistically significant differences regarding patient side or sex were found in either case. In 72.4% (n = 123) a mandibular incisive canal was detected. There was a statistically significant dependence of the mandibular incisive canal on patient sex (P = .007): female patients had a mandibular incisive canal significantly more often than male patients. Among male patients a significant difference of the mandibular incisive canal regarding the mandibular side (P = .031) was found; it was significantly less frequent on the right than on the left side. Anterior loop, mandibular incisive canal, and lingual symphyseal foramen are often present. Furthermore, the anatomical, neurovascular variability in the interforaminal area of the mandible emphasizes the importance of 3D imaging like CBCT in preoperative assessment, and confirms that a general safe zone should not solely be relied upon when performing surgery in this region.

Detection Rate and Variability in Measurement of Mandibular Incisive Canal on Cone-Beam Computed Tomography: A Study of 220 Dentate Hemi-Mandibles from Italy

The mandibular incisive canal (MIC) is a small bony channel located in the interforaminal region; it represents the anterior continuation of the mandibular canal. Cone-beam computed tomography (CBCT) is the most commonly utilized radiological technique for assessing the MIC. The main purpose of this study was to evaluate the detectability and variability in measurements of the MIC on CBCT. A total of 220 dentate hemi-mandibles were retrospectively selected for this study. For each hemi-mandible, the detectability, diameter, and distance of the MIC from anatomical landmarks (cortical plates and tooth apices) were evaluated in consensus by two observers. The analysis was performed at four different levels (first premolar, canine, lateral incisor, and central incisor) and was repeated after one month. The variability of MIC measurements was expressed as the coefficient of repeatability (CR), obtained from the Bland–Altman analysis. The MIC detection rate reduced from the first premolar to the central incisor (from 82.3% to 0.5%). The CR of MIC measurements (diameter and distances from anatomical landmarks) was ≤0.74 mm. Although the MIC is difficult to detect in a non-negligible percentage of cases, the limited variability in measurements confirms that CBCT is an effective technique for the assessment of the MIC.

Assessment of the incidence and course of mandibular incisive canals in a Japanese population with cone‐beam computed tomography

AbstractAimThe mandibular incisive canal (MIC) is a continuation of the mandibular canal anterior to the mental foramen. This observational study was designed to assess the incidence and anatomical parameters of the MIC in a Japanese population using dental cone‐beam computed tomography (CBCT).MethodsCBCT images from 156 patients were acquired and processed using the Planmeca Romexis software. The frequency of the MIC; the length of the MIC; the diametter of the MIC; the distance between the mandibular border, MIC origin, and MIC termination were measured.ResultsMICs were visible in 91.0% of the scans. The mean length was 9.9 ± 6.0 mm, and the average diameter was 1.8 ± 0.7 mm. On average, the MIC was located 11.5 ± 2.6 mm from the lower cortical border and continued towards the incisor region in a slightly downward direction, with a mean distance of 9.3 ± 2.6 mm from the lower cortical border.ConclusionsThe high incidence of the MIC (91.0%) indicates that its identification on CBCT images provides useful information for surgical procedures, such as implant placement and block graft harvesting, in the mental interforaminal area of the mandible.

CBCT study on the prevalence, morphology and position of the mandibular incisive canal in a North-Brazilian population.

BackgroundThe mandibular incisive canal (MIC) is an anatomic structure to be considered in treatment planning for surgeries in the anterior region of the mandible. Awareness of the MIC increased with the use of 3D imaging for treatment planning, such as cone beam computed tomography (CBCT). This study aimed to use CBCT to assess the prevalence, morphology and position of the MIC among North-Brazilians. Material and MethodsThe sample consisted of CBCT scans of 100 hemi-mandibles (50 individuals) that were assessed for the absolute (n) and relative frequency of the MIC. The morphological component of this study was the diameter (mm) of the detected MIC in five anatomic sites between the mental foramen and the midline. Within the interformainal region, the position of the MIC was assessed by measuring (mm) the distances between the MIC and the basal, vestibular and lingual cortical bone surfaces. ResultsThe prevalence of the MIC was >76% considering the different anatomic regions screened in CBCT. The mean diameter of the MIC progressively reduced from 1.29 mm to 0.86 throughout the five anatomic regions measured. The position of the MIC showed a downward trajectory away from the lingual cortical bone surface. ConclusionsMIC was a highly prevalent anatomic structure in the studied sample. The funnel-shaped outline of the MIC and its trajectory into the interforaminal region highlighted a major risk of damage to the neurovascular bundle in surgeries (e.g. implant placement) that are close to the mental foramen and the vestibular cortical bone. Key words:Anatomy, cone beam computed tomography, imaging, mandibular incisive canal, oral radiology.

Comprehensive review of the incisive branch of the inferior alveolar nerve.

The incisive branch of the inferior alveolar nerve is a vital anatomical structure within the anterior mandible that has not been thoroughly defined and outlined in reports in the literature until recent years. Advances in radiological imaging, particularly the widespread use of cone-beam computed tomography has allowed for accurate visualization of the mandibular incisive canal (MIC) and its associated incisive branch of the inferior alveolar nerve. Surgical damage to the MIC, which could result in hemorrhage and sensory disturbance, may occur in commonly practiced oral and maxillofacial procedures, such as chin bone harvesting, implant placement, fracture repair and removal of pathologic entities of the anterior mandible. Knowledge of both the presence, dimensions and location of the incisive branch is a vital component to pre and peri-operative planning of oral and maxillofacial surgeries performed within the mandible, particularly within the interforaminal zone. In this article, the terminology, anatomy, imaging, surgical consideration, and pathology of the incisive branch will be discussed.

ASSESSMENT OF MEAN DISTANCE OF MANDIBULAR INCISIVE CANAL USING CONE BEAM COMPUTERIZED TOMOGRAPHY; A CROSS-SECTIONAL STUDY

Objective: To determine the mean distance of mandibular incisive canal from the mental foramen in patients reporting to a tertiary care centre using Cone Beam Computerized Tomography for placement of dental implants in the anterior/interforaminal region.&#x0D; Study Design: Cross-sectional study.&#x0D; Place and Duration of Study: Department of Prosthodontics, Foundation University College of Dentistry Rawalpindi, Jun to Nov 2019.&#x0D; Methodology: A total of 70 patients participated between the age of 20-45 years. Cone Beam Computerized Tomography (the investigation was carried out and measurements of the mandibular incisive canal from mental foramen were recorded with the help of measuring tools in the software and noted down on the proforma. Data were analyzed using SPSS-20.&#x0D; Results: The number of patients selected for this study was 70. Out of these 70 patients, 33 (47.1%) were males and 37 (52.9%) were females. The mean age of patients in this study was 36.31 ± 6.38 years. The mean distance/extension of the mandibular incisive canal from left mental foramen and right mental foramen in all patients was recorded to be 14.49 ± 6.31 mm and 14.97 ± 7.10 mm respectively.&#x0D; Conclusion: Within the limitations of this study, it is concluded that a maximum distance of 22mm of the incisive canal from the mental foramen was observed using cone-beam computerized tomography.

Lateral Lingual Foramina and Canals in the Mandible: CBCT Evaluation of 506 Patients in North China.

To assess the prevalence, location, diameter, course and anastomosis of the lateral lingual foramina (LLF) and canals (LLCs) in a northern Chinese population using CBCT. CBCT images of 506 patients (181 male and 325 female, mean age 21.03 ± 8.11 years) were collected. The prevalence, location, diameter, length, angle and anastomosis of the LLF and LLCs were assessed. The measurement variables were analysed by sex and age. Statistical analysis was performed using SPSS (v. 25, IBM, Armonk, NY, USA). A total of 461 LLF were detected in 307 (60.7%) subjects, 175 (57.0%) of whom had unilateral LLF and 132 (43.0%) of whom had bilateral LLF, with each lateral having one to four LLF. The majority of LLF (375/461, 81.3%) were located below the premolars, particularly the first premolar. The mean diameter of the LLF was 0.58 ± 0.20 mm. The mean vertical distance from the LLF to the inferior border and the alveolar crest was 6.68 ± 1.43 mm and 23.65 ± 2.89 mm, respectively. In total, 197 LLCs were visible in the cancellous bone and evaluated. The mean length of LLCs was 6.26 ± 1.29 mm, and the mean angle of LLCs was 140.64° ± 17.29°. The overwhelming majority (93.4%) of LLCs communicated with the mandibular incisive canal and the rest connected with the mandibular canal. The prevalence of LLCs was high in the northern Chinese population. The presence of LLCs is a significant predictor of communication with the mandibular incisive canal.

Tomographic evaluation of the mandibular nerve in the mental region and its surgical implications: a cross-sectional study

The aim of this study was to evaluate the prevalence and length of the anterior loop (AL) of the inferior alveolar nerve, nerve emergence from the mental foramen, and prevalence of sensory disorders after implant placement in the interforaminal region. Four hundred and fifty hemimandibles (225 patients) were evaluated using cone beam computed tomography and panoramic radiographs. Information on the presence of sensory disorders was obtained from the medical records. AL prevalence was 13.6% and mean AL length was 1.25 mm. The false-negative rate for the identification of the AL using panoramic radiography was 58.6%. Straight nerve emergence from the mental foramen was the most prevalent (62.7%), followed by anterior (21.8%) and posterior (15.6%) emergence. The incidence of sensory disorders was 4.4%, and 1.1% were related to the presence of the AL. When implants were placed within the planned distance of the mental foramen or further, 1.2% had sensory problems associated with the presence of the mandibular incisive canal. In cases of distances smaller than planned, 12.9% had sensory alterations. Only five (1.1%) had the AL, with a length between 0 and 4.5 mm. However, in four cases, the planned distance was respected and, even so, there was a sensory disorder. Posterior nerve emergence from the mental foramen was associated with a higher prevalence of AL.