Anterior loop of the mental nerve, mental foramen and incisive nerve emergency: tridimensional assessment and surgical applications

Assessment of the Anterior Loop and Pattern of Entry of Mental Nerve Into the Mental Foramen: A Radiographic Study of Panoramic Images

INTRODUCTION

The precise location of the mental foramina is an essential landmark in planning the position of dental implants in the anterior mandible. Injury to inferior alveolar nerve during anterior mandibular implant surgery causes altered sensation which greatly affects patient satisfaction.

METHODS

In this study, we assessed the prevalence of anterior loop of mental nerve and the pattern of entry of mental nerve into the mental foramen. Three hundred panoramic radiographs (600 hemimandibles) obtained from records maintained in the Department of Oral Medicine and Radiology were randomly selected for the study. The radiographs were evaluated by two independent observers for the pattern of entry of mental nerve into the mental foramen on either side of the mandible and for the presence or absence of anterior loop of mental nerve.

RESULTS

The most prevalent pattern of mental nerve observed was Straight pattern which totals to 67.5% followed by Anterior loop pattern (18.8%) and then the Perpendicular pattern (13.7%). There was no significant association between the gender and subtypes of looping pattern on the left and right side and a highly significant association between the side of the mandible and loop pattern was observed by Chi square test.

CONCLUSION

The Anterior loop pattern of mental nerve has been found in 18.8% of the population suggesting to accurate planning with three-dimensional imaging techniques to avoid injury to mental nerve during dental implant placement and other surgical procedure involving the interforaminal region of the mandible.

Prevalence, length, and patterns of Anterior Loop among the South Indian population: A comparative study between Panoramic Radiography and Cone Beam Computed Tomography

Purpose

To assess the prevalence, length, and patterns of the anterior loop of the inferior alveolar nerve by panoramic radiography and cone beam computed tomography (CBCT).

Materials and Methodology

A prospective study was conducted on 300 mental foramen regions by exposing them to panoramic radiography and CBCT scan. Two individual observers evaluated the images to assess the presence of an anterior loop, the mean length of the loop, and the most frequent pattern of the loop in our population.

Result Analysis

The prevalence of the anterior loop for male patients and female patients by panoramic radiography was 34% and 32% on the right side and 30% and 36% on left side, respectively. By CBCT, the corresponding values were 69% and 72% on the right and left side, respectively, for male patients, and 73% and 81% on the right and left side, for female patients, respectively.

Conclusion

The results from our study strongly emphasize the need for CBCT imaging before planning for procedures in the mental foramen region because the prevalence, length, and pattern of loop significantly varies with respect to age, sex, and population.

Assessment of implant-related anatomical landmarks in the mandibular interforaminal region in an Iranian population using cone-beam computed tomography

Background:

This study was aimed to assess the implant-related anatomical landmarks in the mandibular interforaminal region in an Iranian population using cone-beam computed tomography (CBCT).

Methods:

In this retrospective cross-sectional study, 378 CBCT images of the mandible were evaluated for the presence of the incisive canal, anterior loop of the inferior alveolar nerve (IAN), mandibular canal, mental foramen, and incisive canal. The effect of age and gender of patients on the abovementioned variables was also evaluated. Data were analyzed using independent t-test, analysis of variance, and Chi-square test.

Results:

The anterior loop and the incisive canal were present in 36.24% and 97.62% of the cases, respectively. The mean length of the anterior loop and the incisive canal was 2.70 ± 1.20 mm and 12 ± 3.29 mm in the right, and 2.86 ± 1.24 mm and 12.21 ± 3.38 mm in the left side, respectively. The mean diameter of the mental foramen and incisive canal was 4.25 ± 1.08 mm and 1.89 ± 0.46 mm in the right, and 4.21 ± 1.02 mm and 1.94 ± 0.45 mm in the left side, respectively. The descending path was the most common path of the incisive canal. The distance from the incisive canal to the buccal plate and inferior border of the mandible was significantly shorter in females (P < 0.001).

Conclusion:

Considering the high variability and clinical significance of the incisive canal and anterior loop of the IAN, and their high prevalence, it is recommended to assess the presence/absence of these structures in the interforaminal region of the mandible on CBCT scans before surgical procedures in this region.

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.

Anterior loop of the mental nerve in Saudi sample in Riyadh, KSA. A cone beam computerized tomography study

Background

The portion of inferior alveolar nerve (IAN) existent anterior to the mental foramen, before parting the canal, is referred to as the anterior loop (AL) of the IAN. The presence of AL is important when placing the implant interforaminal area of the mandible. These anatomical discrepancies can be assessed by cone-beam CT (CBCT), for evaluating its position and exact location. The AL is classified into Types I, II and III. In Type I, Y-shaped anatomy; in Type II, anatomy is T-shaped; and in Type III, Y-shaped anatomy is seen, and the incisive branch is thicker as compared to the main branch.

Aim

In this study, we aim to analyse the prevalence of different types of AL of the IAN in Saudi sample population.

Materials and Methods

The present study is a retrospective analysis of 149 (86 female & 63 male) CBCT images of patients records from 2018 June to 2018 September in the department of implant dentistry, KSMC, Riyadh. The age range of the patients who participated in the study was 30–60 years. The mean age of female participants is 42.5 ± 5.8, for the male participants is 48.6 ± 11.4 years respectively.

Results

The most frequent type of AL of mental nerve noticed on the right side was of type I (59.1%), followed by type II (27.5%) and type III (13.4%). The most frequent type of AL of mental nerve noticed on the left side was type I (61.7%), followed by type II (26.8%) and type III (11.4%).

Conclusion

The results of the study encourage the usage of CBCT for planning implant treatment. We also suggest that it is obligatory for professionals to categorise the presence of AL and to measure them appropriately when planning for the procedures in the interforaminal region.

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.

Available bone morphology and status of neural structures in the mandibular interforaminal region: three-dimensional analysis of anatomical structures

PURPOSE

This study aimed to clarify the size and morphology of the mandible and to determine state of neural structures for the planning of the dental implantation using cone-beam computerized tomography (CBCT).

METHODS

Of the 252 patients, CBCT images of 48 selected patients were evaluated. The bone height and width were measured and the type of the mental portion of the inferior alveolar canal, the anterior loop length (ALL), the location of the incisive canal and lingual foramen were identified with cross-sectional and multiplane reformatted CBCT images. According to buccal and lingual concavities, the shape of the mandible is classified as type A, B and C.

RESULTS

Bone widths of males were significantly higher than female (p < 0.05). The thickest part of the alveolar bone was measured in the middle triple zone (d line) and the thinnest part was measured in the area near the alveolar crest (b line). The most seen type of mandible was type B (45.8%) that mandible was concave on the buccal side. Bone heights had a tendency to increase towards to the anterior mandible, and bone height in male patients was slightly but not significantly greater than that in female patients. ALL was 4.2 ± 1.2 mm and visible incisive canal length on CBCT was 9.7 ± 3.8 mm.

CONCLUSION

CBCT assessment of morphological features of the alveolar bone and locations of nerve canals and foramina in the anterior-premolar region of mandible represent useful practical anatomical information about the interforaminal region. This information is the guide to the dentist before implant surgery.

A Prognostic Nomogram for Postoperative Bone Remodeling in Patients with ADDWoR

This study aimed to establish an effective prognostic nomogram for predicting the probability of postoperative bone remodeling of patients with anterior disc displacement without reduction (ADDWoR). The nomogram was based on a retrospective study on patients underwent surgical approaches for ADDWoR at Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University from January, 2007 to January, 2017. A multivariate logistic regression analysis was used to develop variables suitable for probability estimation model. The predictive accuracy and discriminative ability were determined by ROC (AUC-index) and calibration curve. Results were validated using bootstrap resampling with all statistical tests two-sided. 1110 patients were included in the analysis. The probability of postoperative bone remodeling in ADDWoR was 0.51. Six independent prognostic factors including age of onset, nocturnal bruxism, disc morphology, BMD, Wilkes’ classification, and postoperative splint therapy were integrated to construct the nomogram. The probability estimation model showed good discrimination in both internal and external validation with AUC-index of 0.84. The calibration curves for probability of postoperative bone remodeling showed optimal agreement with actual observation. In conclusion, a nomogram was established to provide individual prediction of postoperative bone remodeling for patients with ADDWoR treated by arthroscopy surgery.

Anatomical landmarks of mandibular interforaminal region related to dental implant placement with 3D CBCT: comparison between edentulous and dental mandibles

BACKGROUND

Anterior mandibular (interforaminal) region is important in implant applications as it serves a basis for neurovascular bedding and holds the prosthesis for patients. Treatment planning for dental implant patients is often complicated by the unknown extent of the anterior loop of the neurovascular bundle. Anatomical structures including mandibular incisive canal (MIC) and lingual foramen (LF) should also be examined as part of the detailed analysis for their neurovascular structures. This study aimed to detect the positions of LF and MIC as well as the prolongation of interforaminal region in Anatolian population to supply the reference data of the surgical safe zone in chin for the clinicians.

MATERIALS AND METHODS

Mandibles of 70 adult specimens (35 edentulous + 35 dentate) were retrieved from the Department of Anatomy, Ege University. Images of the dry mandibles were obtained using a cone beam computed tomography unit applying a standardized exposure protocol. Afterwards, mandibles were sawn into vertical sections according to the respective tomographic cross-sections. Images were evaluated for the absence/presence of the MIC, its dimensions and antero-posterior length for both edentulous and dentate groups. In addition; the presence, number, location, labial canal and LF diameter and height of the LF were determined for both groups.

RESULTS

The MIC was observed in 80 and 68.6% of the dentate and edentulous groups, consecutively (p > 0.05). The MIC continued towards the incisor region in a slightly downward direction. The LF was observed in all dentate mandibles (100%), while it was present in 94.3% of the edentulous mandibles (p > 0.05). For the dentate group, 62.9% of the specimens had two foramens and 20% had three foramens in the mandibular midline. Mean length of the MIC in dentate groups and edentulous groups was measured as 2.55 ± 0.809 and 3.08 ± 1.745 mm, respectively. Well-defined MIC mean diameter in dentate groups and edentulous groups were measured as 2.44 ± 0.702 and 2.35 ± 0.652 mm, respectively. Significant difference was found between dentate and edentulous group in most of the parameters except for the LF and the diameter of the MIC (p > 0.05). The correlation between observers' measurements ranged between 0.742 and 0.993 for all anatomical landmarks and mandible groups.

CONCLUSION

The MIC and LF are associated with neurovascular bundle variations in number, location and size. Therefore, clinicians should determine each of these anatomical structures on a case-by-case basis to recognize their presence and to take measures for the possible implications of various treatment options. These guidelines included leaving a 2 mm safety zone between an implant and the coronal aspect of the neurovascular bundle. To avoid neurovascular injury during surgery in the interforaminal area, guidelines were developed with respect to validating the presence of an anterior loop of the neurovascular bundle.