Injury Risk Estimation in Mandible-Related Surgical Procedures: A CBCT Study Based on Vital Interforaminal Anatomical Structures.

The mandibular interforaminal region has been considered safe for surgical procedures; nevertheless, the risk of injury to neurovascular structures, such as the mental foramen (MF) and its related structures (anterior loop [AL] and lingual foramina [LF]) should not be overlooked. The study aimed to evaluate the relative risk of injury to these structures during surgical procedures in the anterior region of the mandible based on cone-beam computed tomography (CBCT) scans. A retrospective cross-sectional and observational study was performed on 250 CBCTs from adults (18-69 years) with dentate jaws. Linear measurements of the MF, AL, and LF were evaluated to estimate the risk of injury to these structures during chin-related surgical procedures. The most frequent distance between the base of the mandible (BM) and MF was 8 mm (30.2%). In addition, 20.4% of the CTs had 6 mm from the vestibular cortical bone to the LF. The commonly found measurement from LF to the apex of the nearest tooth was 7 mm (24.0%); 64.2% of the CTs showed a 2-mm distance between the most distal point of the dental implant site to the most anterior point of the AL. Safety distances for genioplasty techniques (MF to mandible base > 6 mm, 96.6% [CI 95%, 95.0%-98.2%]) were observed. Considering the 5-mm cut-off point between the lower limit of a hypothetical bone graft and the chin, 65.4% (CI 95%, 58.9%-71.9%) of CTs were within this distance. Regarding the safety margin of 8 mm, 85.6% (CI 95%, 80.8%-90.4%) were up to this value. This study found safety margins for genioplasty and chin bone grafting surgical techniques that adopt a 5-mm cut-off point. Further similar studies assessing other surgical methods and employing larger samples from different geographical origins may contribute to this field of investigation.

Morphometric studies of supraorbital foramen, infraorbital foramen and mental foramen in a thai population related with nerve blocks / Estudios morfométricos del foramen supraorbitario, foramen infraorbitario y foramen mental en una población tailandesa relacionados con bloqueos nerviosos

SUMMARY: The aim of this study was to study the anatomical landmarks and variations of supraorbital, infraorbital, and mental foramina. One hundred and sixty Thai dry skulls were randomly selected from the Forensic Osteology Research Center. The distances of the parameters were measured by using Vernier caliper. The supraorbital foramen could be found in a notch form 13.8 %, single supraorbital foramen accounted for 82.5 %, and supraorbital foramen with an accessory foramen represented 3.8 %. Single infraorbital foramen was found 90.0 %, and infraorbital foramen with an accessory foramen represented 10.0 %. Single mental foramen was observed 96.6 %, and the frequency of mental foramen with an accessory foramen was determined 3.4%. The majority of infraorbital foramina (48.0 %) was detected above the second premolar area. 19.0 % of the infraorbital foramina was seen in the region between the first premolar and the second premolar, and 22.8 % of the infraorbital foramina was located between the second premolar and the first molar. The infraorbital foramen is anatomically positioned above the first molar (10.2 %). The majority of mental foramina (53.5 %) can be identified below second premolar area. The region between the first premolar and the second premolar is the site for the mental foramen 26.0 % of the total variations. The region between the second premolar and the first molar is the site for the mental foramen 16.9 % of the total variations. The mental foramen is approximately situated below the first molar (3.6 %). The present study of anatomical variations of various foramina demonstrates a useful application in cosmetic and ophthalmic plastic surgery. The findings could improve the efficacy of the surgeons and accuracy for the indicated localization of these foramina during maxillofacial operations and local anesthetic procedures.

RESUMEN: El objetivo de este estudio fue estudiar los puntos de referencia anatómicos y las variaciones de los forámenes supraorbitario, infraorbitario y mental. Ciento sesenta cráneos secos tailandeses fueron seleccionados al azar del Centro de Investigación de Osteología Forense. Las distancias de los parámetros se midieron utilizando un calibre Vernier. El foramen supraorbitario se pudo encontrar en forma de muesca el 13,8 %, el foramen supraorbitario único representó el 82,5 % y el foramen supraorbitario con un foramen accesorio representó el 3,8 %. El foramen infraorbitario único se encontró en un 90,0 % y el foramen infraorbitario con un foramen accesorio representó el 10,0 %. Se observó foramen mental único 96,6 % y se determinó la frecuencia de foramen mental con foramen accesorio 3,4 %. La mayoría de los forámenes infraorbitarios (48,0 %) se detectaron por encima del área del segundo premolar. El 19,0 % de los forámenes infraorbitarios se observó en la región entre el primer premolar y el segundo premolar, y el 22,8 % de los forámenes infraorbitarios se ubicó entre el segundo premolar y el primer molar. El foramen infraorbitario se ubica anatómicamente por encima del primer molar (10,2 %). La mayoría de los forámenes mentales (53,5 %) se pudieron identificar inferior al área del segundo premolar. La región entre el primer premolar y el segundo premolar es el sitio del foramen mental 26,0 % de las variaciones totales. La región entre el segundo premolar y el primer molar es el sitio del foramen mental 16,9 % del total de variaciones. El foramen mental se sitúa aproximadamente por debajo del primer molar (3,6 %). El presente estudio de variaciones anatómicas de estos forámenes demuestra una aplicación útil en la cirugía plástica y oftálmica. Los hallazgos podrían mejorar la eficacia de los cirujanos y la precisión para la localización de estos forámenes durante las operaciones maxilofaciales y los procedimientos anestésicos locales.

Prevalence and morphometric analysis of double mental foramen and double mandibular foramen from digital panoramic radiographs / Prevalencia y análisis morfométrico de foramen mental y foramen mandibular dobles a través de radiografías panorámicas digitales

The morphological variations of the mental foramen (MF) and mandibular foramen (MBF) have been studied for several years, and the prevalence and morphometric characteristics of double and triple foramina have been reported. The objective of this study was to establish the prevalence of variations in the MF and MBF, and to carry out a morphometric analysis of a Chilean population using digital panoramic radiographs. The study included 927 radiographs; the observed prevalence of double MF was 2.58 %, while the prevalence of double MBF was 1.51 %. No cases of triple foramina were found. In men, double MF was found more frequently in the left hemiarch (64.28 % of cases), while in women it was more frequent in the right hemiarch (80 %). Double MBF was found more frequently in the right hemiarch in women (80 % of cases), while the distribution between left and right in men was even. The mean area, width and height of the double MF were 5.46 mm2, 2.77 mm and 2.57 mm respectively. The means of the same morphometric measurements in double MBF were 6.37 mm2, 2.27 mm and 3.19 mm respectively. In both foramina, statistically significant differences were only found between the height of the foramen and the age of the subjects, with the observation that the greater the subject's age, the smaller the height. Dental surgeons must take these anatomical variants into consideration in clinical and surgical actions; timely diagnosis by radiograph is important to avoid possible complications.

Las variaciones morfológicas del foramen mental (FM) y mandibular (FMB) han sido estudiadas durante varios años, reportándose su prevalencia y las características morfométricas de forámenes dobles y triples. El objetivo de este estudio fue establecer la prevalencia de variaciones de los FM y FMB y realizar un análisis morfométrico a través de radiografías panorámicas digitales de una muestra de población chilena. En el estudio se incluyeron 927 radiografías y se observó una prevalencia de FM doble de 2,58 %, mientras que la prevalencia de FMB doble fue de 1,51 %. No se encontraron casos de forámenes triples. En hombres, el FM doble se encontró mayoritariamente en la hemiarcada izquierda (64,28 % de los casos), mientras que en mujeres fue en la hemiarcada derecha (80% de los casos). Para el caso de los FMB dobles, en mujeres se presentó mayoritariamente en la hemiarcada derecha (80 % de los casos), mientras que en hombres fue equitativo en ambos lados. El promedio del área, ancho y alto de los FM dobles fue de 5,46 mm2, 2,77 mm y 2,57 mm, respectivamente. Asimismo, los promedios de estas medidas morfométricas para el FMB doble fueron 6,37 mm2, 2,27 mm y 3,19 mm, respectivamente. Para ambos forámenes sólo se encontraron diferencias estadísticamente significativas entre el alto y la edad de los sujetos, observando que, a mayor edad menor era el alto del foramen. Los cirujanos dentistas deben tener en consideración estas variantes anatómicas para la realización de distintas acciones clínicas y quirúrgicas, su diagnóstico radiográfico oportuno es importante para prevenir posibles complicaciones.

Variation in accessory mental foramen frequency and number in extant hominoids.

Nerves providing sensation to the lower face and jaw exit the mandibular canal via the mental foramen. In humans, there are many documented occurrences of additional foramina (accessory mental foramina, AMFs) on the lateral mandibular surface that may also contain nervous structures. There are large discrepancies in the literature regarding how often AMFs occur in humans, and investigations of non-human hominoid AMFs are rare. Consequently, the causes of interspecific diversity in this variable have not been explored. This project seeks to compare the frequency and number of AMFs between males and females, and among human regional groups and hominoid subspecies and species, and to investigate possible causal factors for any differences identified. No significant differences were found between males and females in any group. Gorillas and orangutans had the highest percentages of individuals with AMFs and the highest mean number of foramina, while modern humans and siamangs had the lowest figures for these variables. Significant differences (p < .05) were found for the mean number of foramina between most pairs of species. The results also showed that species with mandibles that are larger overall, have a larger area anterior to mental foramen, and a longer mandibular canal typically present more AMFs. The strongest correlation was found between the mean number of mental foramina and mandibular canal length. We suggest that these results provide preliminary support for the hypothesis that increasing mandibular canal length increases the likelihood that that nerves will ramify, leading to greater frequencies of accessory mental foramina.

Double mandibular canal and triple mental foramina: detection of multiple anatomical variations in a single patient.

Having complete information about a patient's mandibular canal and mental foramen is fundamental to performing safer procedures and avoiding intraoperative and postoperative complications. Cone beam computed tomography (CBCT) produces accurate images for the analysis of maxillomandibular bone structures and is widely used in dentistry. The aim of this study is to report a case of mandibular bifid canal associated with triple mental foramina that was revealed with CBCT images. A 45-year-old woman was referred for a CBCT scan of remaining bone quantity to assist in preoperative implant planning. The patient had reported problems related to anesthesia during extraction of the mandibular right second and third molars. Examination showed bilateral bifurcation of the mandibular canal, from the mandibular foramen to the gonial angle. In addition, exteriorization of the mandibular canal was noticed in 3 regions; that is, there were 3 distinct mental foramina. Clinicians must be aware of these anatomical variations in the mandibular region during dental procedures to avoid complications such as difficulty in obtaining anesthesia or postoperative sensory dysfunction.

Prevalence and anatomical characteristics of the accessory mental foramen: a study using cone beam computed tomography.

The purpose of this study was to evaluate the prevalence of accessory mental foramina (AMFs) through the use of cone beam computed tomography (CBCT). The secondary purpose was to analyze the location of AMFs, mean distance from the nearest tooth, mean distance from the alveolar bone crest, exit angle dimensions, and whether sex, side of the mandible, or racial disparities exist. Two hundred CBCT scans were analyzed for the presence and characteristics of bifurcations of the inferior alveolar nerve. AMFs were observed in 11.5% of patients and 6.5% of all hemimandibles examined. The majority of patients with 1 or more AMFs were female (60.9%). Bilateral AMFs were found in 1.52% of patients. The location of the AMF relative to the mental foramen (MF) was evaluated, and 30.0% of AMFs were located anterosuperiorly and 23.3% posterosuperiorly to the MF. Associations between patient sex and the greatest and smallest diameters of AMFs, circumference and area of AMFs, and ratio of AMF-MF area were evaluated via statistical analysis. Additional analyses evaluated the prevalence on each side of the mandible as well as the association between race/ethnicity and occurrence of AMFs. Statistical analyses showed no association between the occurrence of AMFs and sex, side of the mandible, or race/ethnicity of the study population. This demonstrates the importance of preoperative CBCT prior to all mandibular surgery to reduce the risk of injury to the neurovascular bundles that pass through AMFs.

Anthropometrics Analysis of Mental Foramen and Accessory Mental Foramen in Zambian Adult Human Mandibles.

The mental foramen (MF) and accessory mental foramen (AMF) are the strategically important landmarks during surgical interventions and anaesthetic nerve blocks procedures involving the mental nerve. The study aimed at evaluating anthropometrics of MF and AMF in Zambian adult human mandibles and it was cleared for ethics from TDRC Ethics Review Committee (Reg. No.: 00002911; FWA: 00003729). A total of 33 Zambian adult human mandibles were evaluated for shape, position, and direction of opening of foramen. All measurements were performed using a Digital Vernier Calliper and statistically analysed for per cent frequency and mean and standard deviations, and we performed the one sample t-test for comparative analysis. Data were considered significant at p<0.05. All mandibles that were examined had bilateral MF while unilateral AMF was found in two mandibles (6%). The foramens were mostly oval in shape and their most common position was between the second premolar and first molar and the most common orientation was posterior-superior. The comparative analysis of mandibular anthropometrics showed significant variations (p<0.05) with different ethnic groups. The findings emphasize the ethnic variations and edify that the foramen position is not always as stated in reference textbooks. The clinical creditability of the study is cautioning the surgeons on possible variations of the MF and AMF anthropometrics compared to existing literature in order to avoid any unforeseen injury related to anaesthesia or dental surgeries. Further studies with large sample sizes representing whole country are recommended to establish the standard MF and AMF anthropometrics of Zambian population.

Prevalence of Accessory Mental Foramina: A Study of 4,000 CBCT Scans.

The presence of accessory mental foramina (AMF) is an important consideration prior to any dental implant and surgical treatment to avoid injury to the neurovascular bundle and subsequent postoperative complications. The aim of this retrospective study was to determine the prevalence of AMF from a substantially large sample of the Australian population. The cone beam computed tomography (CBCT) scans of 4,000 patients showing the mandible were examined. All mental foramen (MF) were visualized and no cases were excluded. The number of MF/AMF, sex, and age were recorded. The prevalence of AMF was found to be 6.4% (254 patients) in this study. Twelve patients exhibited bilateral AMF, and 11 had three mental foramina on one side. One case had a total of five mental foramina with three on the right and two on the left side. No significant sex preference was discovered. This is the largest study ever to be conducted to evaluate the prevalence of AMF. With nearly one in 15 individuals found to have AMF, clinicians must be acutely aware of this anatomical variation and treatment plan for each case accordingly. Clin. Anat. 32:1048-1052, 2019. © 2019 Wiley Periodicals, Inc.

Review of Risk Assessment of Major Anatomical Variations in Clinical Dentistry: Accessory Foramina of the Mandible.

Most of the studies of the mandible's anatomical variations have presented the authors' speculations, and only a limited number has provided evidence that demonstrated the actual complications injury to the variant structures caused. To our knowledge, no study has evaluated the risks associated with these variant anatomical structures' injury. We reviewed articles that described clinical cases of the injury to, and anatomical studies of, three anatomical variants of the mandible-the accessory mental, lingual, and retromolar foramina-with which dentists are relatively familiar and that are mentioned often in the context of implant and third molar surgeries, to describe risk assessment methods with which to evaluate potential complications preoperatively. Only a limited number of the clinical reports of injury to the mandible's accessory foramina were available. The potential severe complication of injury of the accessory mental foramen (AMF) is sensory disturbance of the lower lip. Risk of neurosensory disturbance of lower lip can be assessed by AMF/MF ratio and positional relations to the MF. Potential severe complication of injury of the lingual foramen is bleeding and hemorrhage in the oral cavity's floor. Risk of bleeding can be assessed by diameter and positional relation between the mental spine/mylohyoid line. A risk assessment of the retromolar foramen could not be made because of inadequate data. We hope the risk assessments suggested will encourage dentists to predict intraoperative/postoperative complications caused by damaging the mandible's accessory foramina. Clin. Anat. 32:672-677, 2019. © 2019 Wiley Periodicals, Inc.