Descriptive study of the bifid mandibular canals and retromolar foramina: cone beam CT vs panoramic radiography

Mandibular Canal Branching Assessed With Cone-Beam Computed Tomography

This study aimed to evaluate the prevalence and type of mandibular canal branching in a sample of the Iranian population through cone-beam computed tomography (CBCT) images. This cross-sectional study was performed on CBCT records of 300 patients (112 males and 188 females; mean age 30.14 ± 10.96 y). The presence of mandibular canal branch (MCB) was evaluated by reconstructing multiple panoramic views and buccolingual cross-sections, according to Naitoh's classification. The prevalence of MCB, the type of MCB, and the demographic information of all patients were recorded. The maximum number of branching and the maximum type of branching were also registered for each patient. Mandibular canal branching was observed in 131(43.7%) of 300 CBCT images without side or sex differences ( P > 0.05). The most frequent type was dental, followed by the retromolar, forward, and buccolingual types, respectively. There was a statistically higher frequency of retromolar canal in females than in males (odds ratio: 1.14 ± 4.25; P = 0.013). About 46% of patients with MCB had more than one accessory canal and 29% displayed more than one type of MCB. The coincidence of dental and retromolar canals in a patient was the most prevalent combination. Considering the relatively high prevalence of MCB (43.7%), it is recommended to keep in mind the possibility of anatomical variations of the inferior alveolar nerve during dental procedures to avoid postsurgical complications. The high possibility of observing multiple numbers and types of branching in the patients should also be considered during preoperative assessments.

An evaluation of mandibular canal variations: a systematic review and meta-analysis

The inferior alveolar nerve and vessels are carried via the mandibular canal, which extends bilaterally from the inferior alveolar foramen to the mental foramen. Bifid and trifid mandibular canals result from abnormal fusions of nerve canals. The purpose of this study was to provide an up-to-date and comprehensive analysis of the prevalence of mandibular canal variations among healthy adults, and to identify any potential ethnic, sex, or laterality predilections. The prevalence of the bifid mandibular canal was 18.87% and that of the trifid canal 1.3%. Unilateral variants were three times commoner than bilateral. Each mandibular half had four canals emanating from separate openings on the lingual surface of the mandibular ramus. Retromolar and forward canals were the predominant subtypes, followed by dental; buccolingual were the least frequent. The mean length and diameter of the bifid mandibular canal were 13.62 mm and 1.63 mm, respectively. The possibility of a bifid mandibular canal is a crucial consideration in dental medicine. Because anatomical variations of the mandibular canal are fairly common, awareness of them is essential for anatomy teachers and for surgeons who operate in the oromaxillofacial region.

Bifid Mandibular Canal: A Proportional Meta-Analysis of Computed Tomography Studies

Introduction

Growing body of evidences showed different grades in prevalence of bifid mandibular canals. Because the previous reviews focused solely on patient-level occurrence, hemi-mandible-level prevalence, bilateral symmetry, length, and diameter of bifid mandibular canals were required to be estimated collectively. The research question of this meta-analysis was "What is the prevalence of bifid mandibular canal among patients seeking computed tomography examinations"?

Materials and Methods

In vivo, computed tomography, and cross-sectional studies were eligible. Studies, with less than 100 subjects or anatomic site restriction or controlled class of bifid mandibular canal, were excluded. Joanna Briggs Institute (JBI) critical appraisal tool for prevalence studies was used to assess methodological quality of all included studies. Random effect meta-analyses for proportion of bifid mandibular canal were done.

Results

40 studies met the inclusion criteria. All studies were selected for both systematic review and meta-analyses. Totally, 17714 patients and 31973 hemi-mandibles were included. All eligible studies showed moderate risk of bias on average. Resulting from the random effect model, more than 20% of patients seeking computed tomographic examinations had bifid mandibular canals (BMCs) which penetrated into slightly more than 14% of hemi-mandibles. Of the patients having bifid mandibular canals (BMCs), nearly 23% exhibited such anatomy on both sides of their mandibles. Estimated mean length and diameter of the accessory canals of bifid mandibular canals were 12.17 mm and 1.54 mm, respectively.

Conclusion

The geographical locations, classifications, reliability test, and voxel size of computed tomography were all implicated in the prevalence of bifid mandibular canals along with gender and laterality, although considerable heterogeneity and bias were detected.

Prevalence of Bifid Mandibular Canal: A Systematic Review and Meta-analysis

Objectives

The aim of this study was to evaluate the prevalence of bifid mandibular canal (BMC) using cone-beam computed tomography (CBCT) and panoramic images through meta-analysis.

Methods

Databases of Scopus, PubMed, and Web of Science were searched to find the relevant studies. Studies the met the inclusion criteria were selected. Variables of prevalence, side, length and diameter of BMC and sex were assessed. Data was analyzed using STATA software version 17.

Results

Of the 1164 articles initially selected, 36 were enrolled. A total of 38077 patients were considered. The overall prevalence of BMC was 18.0%. Studies that evaluated CBCT images reported higher prevalence of BMC compared to panoramic images (25.0% vs 3.0%). The prevalence of BMC was higher in men than women and slightly higher in right side than the left side of the jaw, but none of those differences were significant.

Conclusion

The results have shown a total prevalence of 18.0% for BMC. Detection power of CBCT images were higher than panoramics. There was no significant relation between prevalence of BMC with sex or side of the jaw.

Variation of Mandibular Canal Branching Related to Anatomical Regions in Mandible: A Radiographic Study Without Contrast

PURPOSE

Screening mandibular canal branches and awareness of these possible canal branches is vital for patient safety and surgical success. The aim of this study was to evaluate the prevalence and localization of mandibular canal branching (MCB).

METHODS

This is an institutional and retrospective cohort study of patients who presented for evaluation of cone beam computed tomography (CBCT) between 2019 and 2020. The prevalence of MCB and the related foramina was estimated according to anatomical regions. Predictor variables were gender, age, anatomical region, and side of branches. Outcome variable of the study was MCB. Thus, multiple correspondence analysis was performed to determine the relationships between the categories of the variables, as well as between variables.

RESULTS

CBCT images were obtained from 180 patients (n = 360 hemimandible; 90 males, 90 females). MCB was observed in 130 (72.2%) of 180 patients (mean age = 38.2 ± 11.8 years). MCB was observed in 63 (48.5%) males and 67 (51.5%) females, and the prevalence of MCB did not differ significantly according to gender (P = .618). MCB was mostly observed in the molar region (69 branches, 34.3%). Foramina were detected in 60 of 248 branches (24.19%) and were mostly observed in the retromolar region (28 foramina, 46.7%). "Quadrafid" branching was detected in 2 females (1.11%). Female patients aged 19-38 years were more prone to have MCB in molar and retromolar regions. MCB was more likely to occur bilaterally. There was also a high positive correlation among the MCB, side, and anatomical regions.

CONCLUSIONS

MCB is not a rare anatomical variation, and even quadrafid branching can be observed in the hemimandible. CBCT images should be examined carefully for possible MCB to minimize postoperative complications during dental surgery.

Systematic review and meta-analysis of mandibular canal variations on cone beam computed tomography

OBJECTIVE

The purpose of this systematic review was to evaluate the mandibular canal (MC) variations and their anatomical incidences using cone-beam computed tomography (CBCT).

DESIGNS

Related articles on the anatomical variations of the MC using CBCT were searched through PubMed, Cochrane, and China National Knowledge Infrastructure (CNKI) to identify all relevant articles eligible for inclusion. Data extracted included incidences of the anatomical variations of the MC including the accessory mental foramen (AMF), retromolar foramen (RMF), mandibular lingual foramina (MLF), and the bifid mandibular canal (BMC).

RESULTS

In total, 16 descriptive cross-sectional studies (one low quality and fifteen high quality) were included in the meta-analysis analyzing 8862 MC. The meta-analysis performed with a random-effects model showed that the incidence of AMF was 9.54% (95% CI 6.39-12.69%), the incidence of RMF was 23.64% (95% CI 14.44-32.84%). MLF was found in almost all adults studied, and the incidence of BMC was about 38.0%.

CONCLUSIONS

The foramina and canals branched from the MC presented significant anatomical variations among individuals. CBCT-based study on the anatomical variations of the MC could provide guidance for clinical practice.

Prevalence and Characterization of bifid mandibular Canal Using Cone Beam Computed Tomography: A Retrospective Cross-Sectional Study in Saudi Arabia

Aim

The purpose of this study is to determine the prevalence and morphological characteristics of the bifid mandibular canal in a Saudi Arabian subpopulation, to aid in preventing surgical complications near the mandibular canal.

Patients and Methods

Using CBCT images obtained from the Radiology unit database in a University Hospital Clinics. A total of 488 CBCT images were investigated (244 Female – 178 Male). In the present study, the Naitoh classification was used to categorize the bifid mandibular canal into the following types: 1) Retromolar canal; 2) Dental canal; 3) Forward canal (with or without confluence); and 4) Buccolingual canal. Additional variation (Trifid canal) was included. All CBCTs were assessed in coronal, sagittal, axial, as well as panoramic views using specialized software.

Results

The prevalence of BMC was 28.7% (95% CI, 24.5 to 33.2), Gender (p = 0.404) and age (p = 0.654) had no statistical significances, laterality of BMC, patients with unilateral BMC were significantly older than those with bilateral BMC (mean ± SD ages of 40.5 ± 13.5 and 32.9 ± 13.8, respectively, p = 0.009). About two-thirds (67.5%) of the investigated BMC cases were found unilateral. The most common reported type of BMC was retromolar canal.

Conclusion

The incidence of bifid mandibular canal using CBCT is considered relatively high in Saudi Arabian subpopulation, with the most common type was the retro-molar canal.

Prevalence and Characteristics of Accessory Mandibular Canals: A Cone-Beam Computed Tomography Study in a European Adult Population

The purpose of this observational study is to evaluate the prevalence and main characteristics of bifid canals within a European adult population, analyzing cone-beam-computed tomography (CBCT). The population study examined 300 subjects. The CBCTs were performed between 2012 and 2019, using PaX-Zenith3D with a standard protocol of acquisition. The parameters analyzed were the presence and lengths of the bifid mandibular canals. The sample included 49% male and 51% female participants. The mean age of the patients was 47.07 ± 17.7 years. Anatomical variants of the mandibular canal were identified in 28.8% of the sides and 50.3% of the patients. In 7.3% of the subjects, the anatomical variants were present bilaterally. The most frequently encountered bifid canal was Type 3 (40.5%), followed by the Type 1 canal (39.3%), the Type 2 canal (14.5%), and the Type 4 canal (5.9%), 40% on the right side and 60% on the left side. The average length of the bifid canals located on the right side of the mandible was 11.96 ± 5.57 mm, compared to 11.38 ± 4.89 mm for those measured on the left side. The bifid mandibular canal is a common anatomical variation of the mandibular canal. It is fundamental to performing an accurate preoperative evaluation using CBCT analysis to avoid and/or reduce intraoperative and postoperative complications.

What are the retromolar and bifid/trifid mandibular canals as seen on cone-beam computed tomography? Revisiting classic gross anatomy of the inferior alveolar nerve and correcting terminology

PURPOSE

Since cone-beam computed tomography was developed, a number of radiological studies on the bifid mandibular canals (BMCs) and trifid mandibular canals (TMCs) have been reported. However, many of the suggested subtypes of the BMC described in the literature seem to be normal branches of the inferior alveolar nerve. This might be due to a lack of revisiting classic anatomical studies in the field of radiology. Therefore, such studies are revisited here.

METHODS

A database search using PubMed and Google Scholar was conducted on BMC and TMC. Eighty-nine articles underwent full-text assessment. The reported three classifications of BMC and the six modified classifications were reviewed and compared to the intramandibular inferior alveolar nerve branches.

RESULTS

Some subtypes of BMC and TMC simply represent normal inferior alveolar nerve branches, i.e., retromolar branch, molar branch (alveolar branch/dental branch), large mental branch, or communicating branch. Others such as Naitoh's type III BMC and forward canal might be a true BMC.

CONCLUSION

We found that the bifid mandibular canal is an additional intramandibular canal running parallel to the mandibular canal with/without confluence with the main canal through comparison of classifications of BMC/TMC between the radiology and anatomy fields.

Do anatomical variations of the mandibular canal pose an increased risk of inferior alveolar nerve injury after third molar removal?

OBJECTIVES

The present study aimed to assess whether anatomical variations of the mandibular canal are associated with neurosensory disturbances of the inferior alveolar nerve (IAN) following mandibular third molar removal.

METHODS

Two observers compared the detection of third molar root-nerve relations and bifurcations of the mandibular canal on panoramic radiographs and CBCT images of 201 patients undergoing removal of 357 mandibular third molars. Potential neurosensory disturbances of the IAN were surveyed ten days after surgery. Fisher's Exact was performed to correlate presence of canal variations to postoperative neurosensory disturbances. Positive and negative predictive values (PPV, NPV) and likelihood ratios (LR + , LR-) were calculated.

RESULTS

Thirteen patients reported postoperative altered sensation of the lower lip, with 2 of them having mandibular canal bifurcations on the ipsilateral side of the injury. Fisher's Exact showed that the studied mandibular canal variations were not related to postoperative neurosensory disturbances. CBCT was superior in visualization of anatomical variations of the mandibular canal. Prevalence of bifurcations was 14% on CBCT and 7% on panoramic radiographs. In both imaging modalities and for all parameters, PPVs were low (0.04 - 0.06) and NPVs were high (0.92 - 0.98), with LR ranging around 1.

CONCLUSION

In the present study, the assessed mandibular canal variations had limited predictive value for IAN neurosensory disturbances following third molar removal.

CLINICAL RELEVANCE

While a close relation between the third molar and the mandibular canal remains a high risk factor, mandibular canal variations did not pose an increased risk of postoperative IAN injury after third molar removal.

Prevalence of bifid and trifid mandibular canals with unusual patterns of nerve branching using cone beam computed tomography

Lack of knowledge concerning the inferior alveolar canal anatomical variations had proven to increase the incidence of surgical complications, so the study aimed to assess the configuration and prevalence of bifid and trifid mandibular canals using cone beam CT in Egyptian subpopulation. Cone beam CT scans of 278 patients (530 hemi-mandibles) were included in the study, in which bifid and trifid mandibular canals or any other branching patterns were recorded and evaluated. Bifid canals were categorized following Naitoh classification, and the diameter of the main mandibular and accessory canals was measured. Bifid canals were detected in 181 canals (34%) while trifid canals in 46 canals (8.7%). Upon classifying the bifid canals, 78 canals showed forward type, 40 retromolar type, 33 dental type, and 7 canals showed buccolingual type. Two special bifid canals subtypes were reported in 23 canals and nine distinct patterns of trifid canals were reported in our study. In addition, unusual patterns of canal branching were reported in 5 cases. The mean diameter of the accessory canals was 1.18 ± .54 mm and the main canal was 3.98 ± 1.31 mm. This study reported a high prevalence (54%) of canal branching, which reinforces the importance of cone beam CT in pre-surgical planning.

Anatomical variations of the mandibular canal and their clinical implications in dental practice: a literature review

INTRODUCTION

The anatomical variations of the mandibular canal have been described according to the number of additional branches it presents, bifid and trifid. Within the bifids we can also find subtypes of variations such as the retromolar mandibular canal. These anatomical variations can have important clinical implications for the work of dental professionals.

METHODS

A systematic search of the literature was carried out in different databases that met the following criteria: articles published between 2000 and 2020, and articles that established a clinical correlation with variations in the mandibular canal.

RESULTS

After applying inclusion and exclusion criteria, 32 articles were obtained, in which the variations of the mandibular canal were identified, their prevalence and incidence, which was very varied between the different articles, it was also found that the CBCT was the main technique to identify the anatomical variations of the mandibular canal. Lastly, the anatomical variations of the mandibular canal have a direct clinical correlation with pre-surgical, intra-surgical and postsurgical complications in pathologies that require surgical intervention.

CONCLUSIONS

The anatomical variations of the mandibular canal have a high incidence, so knowing them is of vital importance both for clinicians and anatomy professors who provide morphological training. We believe that research should focus on describing and diagnosing the causes of these anatomical variations. That said, there is also a continuous challenge for all health professionals to learn about the different anatomical variations that the human body presents and how these can affect clinical practice.

[Importance of cone beam computed tomography in the recognition of the trajectory and anatomical variants of the mandibular canal. A review of the literature]

The objective of this study was to provide an updated review of the literature on the importance of the use of cone beam computed tomography (CBCT) in the recognition of the trajectory and variants of the mandibular canal (MCV).CBCT allows obtaining high quality images and visualization with an accuracy of approximately 94%, compared to 53% with periapical intraoral radiography (RIP) and 17% with panoramic extraoral radiography (REP), making CBCT an important diagnostic tool.The incidences of MCV in CBCT studies were between 1.3% and 69%, with differences between patients of different ethnic origins and within the same ethnic population, and in the types and configurations of MCV within each ethnic group. The studies available in the literature provide a histological description of the content of MCV. The presence of nerve and artery bundles of different calibers suggests that patients present clinical symptoms only if the neurovascular bundle reaches a certain size and number of fascicles. This review provides a description of the different classifications available and updated with CBCT.

Assessment of the configuration of the mandibular canal using cone beam computed tomography

BACKGROUND

During dental implants placement and bone augmentation procedures, it is important to determine the presence and location of mandibular canal anatomical variation in order to avoid injuries to inferior alveolar bundle. This study aimed to describe the prevalence and configuration of mandibular canal branching in the posterior region of the mandible using cone beam computed tomography (CBCT).

METHODS

The interpretation of the images was conducted according to the presence, classification and location of the mandibular canal. Horizontal and vertical distances from mandibular canal in the ramus region to the molar region was recorded. CBCT images of 751 patients, 486 women (64.7%) and 265 men (35.3%), with a mean age of 54.57 (±13.23; 14-93) years, were interpreted by one calibrated examiner.

RESULTS

Out of 1502 hemi-mandibles images, mandibular canal variations were observed in 130 (8.6%). Sixty-four (49.2%) mandibular canal variations were identified on the right side and 66 (50.8%) on the left side. The mean distances between superior cortical of the mandibular canal and the base of mandible, buccal cortical of mandibular canal and buccal cortical bone, and superior cortical of mandibular canal and alveolar ridge were 12.16 mm (±2.68), 4.17 mm (±1.30), and 12.97mm (±4.01), respectively. Type I mandibular canal variation was the most frequent (68; 52.2%), followed by type III (34; 26.1%).

CONCLUSIONS

Prevalence of mandibular canal variations was 8.6%, type I was the most common and its direction showed proximity with lingual surface in the second molar region.

Incidence and Anatomical Properties of Retromolar Canal in an Iranian Population: A Cone-Beam Computed Tomography Study

Objectives

Retromolar canal (RC) is an anatomic structure, and due to increasing demand for surgical procedure in the retromolar area of the mandible, the identification of the retromolar canal has become an issue of clinical concern. It can innervate the third molar and some of the muscles around the posterior segment of the mandible, complicating surgical procedures in the retromolar area and root canal treatment of third molars. The aim of this study was to evaluate the incidence and anatomical properties of RC in a western Iranian population using cone-beam computed tomography (CBCT) images. Materials and Methods. Two hundred bilateral CBCT images were collected and screened in the three spatial planes for the presence of an RC. Anatomical properties and location of the RCs were assessed according to their course and distance from the surrounding structures. The relationship between the presence of RC and age, sex, side, and presence of second and third molars was also evaluated. Independent samples t-test, ANOVA, Tukey's post hoc test, paired t-test, ANOVA, Tukey's post hoc test, paired

Results

At least one RC was observed in 22% of the mandibles. Its bilateral incidence was 5.5%. Two major types of canals were detected, namely, type I, following a straight or curved course from the mandibular canal (MC) to the retromolar area (47.3%), and type II, coursing from the retromolar area to the radicular part of the third molar (52.7%). Regarding linear measurements, the mean RC diameter and the mean distance to the MC, second, and third molars were 0.68 ± 0.31, 13.7 ± 2.8, 15.3 ± 3.0, and 7.3 ± 2.3 mm, respectively.

Conclusion

Based on the results of this study, RC was found in 22% of the cases; thus, it should be considered as a normal anatomical variation in the Iranian population rather than a rare finding.

The clinical significance of the retromolar canal and foramen in dentistry

The mandibular canal is nowadays acknowledged as a major trunk with multiple smaller branches running roughly parallel to it. Most of these accessory canals contain branches of the inferior alveolar neurovascular bundle that supplies the dentition, jawbone, and soft tissue around the gingiva and lower lip. This article reviews the prevalence, classification and morphometric measurements of the retromolar canal and its aperture. A retromolar canal is a bifid variation of the mandibular canal that divides from above this main canal, and travels anterosuperiorly within the bone to exit via a single foramen or multiple foramina into the retromolar fossa. This foramen, termed the retromolar foramen, allows accessory branches of the inferior alveolar neurovascular bundles to supply tissues at the retromolar trigone. Clinically, it is of the utmost importance to determine the exact location of the mandibular canal and to identify its retromolar accessory branches when surgery in the posterior mandible is to be performed.

Double Retromolar Canal: a Case Report

AbstractThe retromolar canal is an anatomical variation of the mandibular canal. Its neurovascular bundle may extend to areas of the temporalis tendon, and areas of buccinator muscle insertion in the alveolar process at lower third molar region, beside the retromolar fossa. The observation of the retromolar canal in conventional radiographs is limited by the presence of increased bone condensation in the region due to overlapping anatomical structures. The use of three-dimensional imaging techniques, such as cone beam computed tomography can contribute significantly for the treatment planning.Some complications may occur in surgical procedures involving the retromolar area when the retromolar canals are present, such as hemorrhage, failure in anesthesia and injuries to nerve branches. This study reported an unusual case of a double retromolar canal on the left side of the mandible, that led  to the change of the treatment planning in a 54-year-old male patient. Furthermore, the clinical and surgical consequences of these findings in oral rehabilitation were discussed. The cone beam computed tomography was  an important diagnostic tool in the observation of the presence and the exact location of retromolar canal. Retromolar canals may be detected on a panoramic radiograph. However, more precise information about the anatomical variation can be shown on cross sectional cone beam computed tomography images. Keywords: Anatomic Variation. Mandible. Cone-Beam Computed Tomography. ResumoO canal retromolar é uma variação anatômica do canal da mandíbula. Seu feixe vásculo-nervoso pode se estender para áreas do tendão do músculo temporal, áreas de inserção do músculo bucinador e no processo alveolar na região do terceiro molar inferior, além da fossa retromolar. A observação do canal retromolar em radiografias convencionais é limitada pela presença de condensação óssea com sobreposição de estruturas anatômicas. Devido a esse fato o uso de técnicas de imagem tridimensionais, como a tomografia computadorizada de feixe cônico, contribuem significativamente para o planejamento do tratamento. Algumas complicações podem ocorrer em procedimentos cirúrgicos envolvendo a região retromolar quando o canal retromolar está presente, como hemorragia, falha na anestesia e lesões aos ramos nervosos. Este estudo relatou um caso incomum de canal retromolar duplo, do lado esquerdo da mandíbula, causando alterações no planejamento clínico do tratamento de um paciente do sexo masculino de 54 anos de idade. Além disso, as consequências clínicas e cirúrgicas desses achados na reabilitação bucal foram discutidas. Atomografia computadorizada de feixe cônico apresentou-se como importante ferramenta diagnóstica na observação da presença e localização exata do canal retromolar. Canais retromolares podem ser detectados em uma radiografia panorâmica. No entanto, informações mais precisas sobre esta variação anatômica podem ser mostradas em imagens de tomografia computadorizada de feixe cônico. Palavras-chave: Variação Anatômica. Mandíbula. Tomografia Computadorizada de Feixe Cônico.AbstractThe retromolar canal is an anatomical variation of the mandibular canal. Its neurovascular bundle may extend to areas of the temporalis tendon, and areas of buccinator muscle insertion in the alveolar process at lower third molar region, beside the retromolar fossa. The observation of the retromolar canal in conventional radiographs is limited by the presence of increased bone condensation in the region due to overlapping anatomical structures. The use of three-dimensional imaging techniques, such as cone beam computed tomography can contribute significantly for the treatment planning.Some complications may occur in surgical procedures involving the retromolar area when the retromolar canals are present, such as hemorrhage, failure in anesthesia and injuries to nerve branches. This study reported an unusual case of a double retromolar canal on the left side of the mandible, that led  to the change of the treatment planning in a 54-year-old male patient. Furthermore, the clinical and surgical consequences of these findings in oral rehabilitation were discussed. The cone beam computed tomography was  an important diagnostic tool in the observation of the presence and the exact location of retromolar canal. Retromolar canals may be detected on a panoramic radiograph. However, more precise information about the anatomical variation can be shown on cross sectional cone beam computed tomography images. Keywords: Anatomic Variation. Mandible. Cone-Beam Computed Tomography. ResumoO canal retromolar é uma variação anatômica do canal da mandíbula. Seu feixe vásculo-nervoso pode se estender para áreas do tendão do músculo temporal, áreas de inserção do músculo bucinador e no processo alveolar na região do terceiro molar inferior, além da fossa retromolar. A observação do canal retromolar em radiografias convencionais é limitada pela presença de condensação óssea com sobreposição de estruturas anatômicas. Devido a esse fato o uso de técnicas de imagem tridimensionais, como a tomografia computadorizada de feixe cônico, contribuem significativamente para o planejamento do tratamento. Algumas complicações podem ocorrer em procedimentos cirúrgicos envolvendo a região retromolar quando o canal retromolar está presente, como hemorragia, falha na anestesia e lesões aos ramos nervosos. Este estudo relatou um caso incomum de canal retromolar duplo, do lado esquerdo da mandíbula, causando alterações no planejamento clínico do tratamento de um paciente do sexo masculino de 54 anos de idade. Além disso, as consequências clínicas e cirúrgicas desses achados na reabilitação bucal foram discutidas. Atomografia computadorizada de feixe cônico apresentou-se como importante ferramenta diagnóstica na observação da presença e localização exata do canal retromolar. Canais retromolares podem ser detectados em uma radiografia panorâmica. No entanto, informações mais precisas sobre esta variação anatômica podem ser mostradas em imagens de tomografia computadorizada de feixe cônico. Palavras-chave: Variação Anatômica. Mandíbula. Tomografia Computadorizada de Feixe Cônico.

Prevalence of bifid mandibular canal according to gender, type and side

Background/purpose

An awareness of mandibular canal variations may help prevent complications due to nerve damage that can occur during surgery. The aim of this study is to evaluate the variations of mandibular canal distribution and frequency via cone beam computed tomography (CBCT), retrospectively, in a Turkish population.

Materials and methods

The study population comprises 500 (250 female, 250 male) randomly selected participants between the ages of 14 and 79 years. The study was conducted in Marmara University, Faculty of Dentistry, in the Department of Dentomaxillofacial Radiology. The distribution and frequency of mandibular canal variations were evaluated using the Naitoh classification, which includes retromolar canal, forward canal, dental canal, and buccolingual canal. The trifid canal was also included in this study. The data were analysed using IBM SPSS statistics 20.0. The data were then compared based on age group and gender.

Results

Bifid mandibular canals (BMCs) were found in 200 (40%) of the 500 subjects, and in 248 of the 1000 sides (24.8%). Mandibular canal variations were observed in 71.5% of patients on the right side, 52.5% on left side and 24% bilaterally. The forward canal was the most common type (48.8%), followed by the retromolar canal (26.2%), the dental canal (12.9%), the buccolingual canal (9.7%), and the trifid canal (2.4%).

Conclusion

BMCs were detected at a high rate in the Turkish subpopulation. Moreover, CBCT appears to be an appropriate method to assess the entity and shape of BMCs.

Imaging the bifid mandibular canal using high resolution MRI

OBJECTIVE:

This study aimed to investigate the incidence of bifid mandibular canals (BMCs) using high-resolution MRI with a three-dimensional volumetric interpolated breath-hold examination sequence (3D-VIBE) through the neurovascular bundle (NVB).

METHODS:

In this retrospective study, we extracted 154 datasets from our archive of patients who underwent MRI examination with a 3D-VIBE sequence for mandible lesions from January 2015 to April 2016. The right and the left mandibles were treated independently with 59 cases excluded due to NVB morphology or artifacts, yielding 249 hemi-mandible cases classified among three subtypes: Type 0 with no BMC, Type one with one NVB and two NVBs on route to it, and Type two with two NVBs. We also investigated the incidence of nutrient canals (NCs) using MRI. Finally, we determined whether each BMC case could also be identified via panoramic radiography (PR) or CT.

RESULTS:

Of the 249 cases examined, 6.4% were found to have BMC (Types 1 and 2). Subtypes were classified as follows: 233 as Type 0 (93.6%), 11 as Type 1 (4.4%), and 5 as Type 2 (2.0%). The NC was identified on MRI in a majority of cases. No BMCs were identified using PR or CT except for one, which was identified by CT.

CONCLUSION:

The incidence rate of BMC per MRI was 6.4% in this study. NCs, including the retromolar canal, had an incidence rate of 58.4-97.6%. Further, BMCs were not verified by PR or CT, indicating that MRI should be used to assess BMCs.

Topographical distribution of neurovascular canals and foramens in the mandible: avoiding complications resulting from their injury during oral surgical procedures

Purpose

Certain oral surgical procedures can injure neurovascular canals and foramens in the mandible. Hence, before performing surgical procedures, it is important to assess the distribution of the bifid mandibular canal (BMC), accessory mental foramen (AMF), medial lingual canal (MLC), lateral lingual canal (LLC), buccal foramen (BF), and lingual alveolar canal (LAC). This study aimed to assess the distribution of different types of canals and foramens. Furthermore, we investigated the limitations associated with finding these structures in panoramic images.

Methods

Fifty-eight patients who had undergone panoramic radiography and computed tomography (CT) scans at our hospital were randomly selected for this study. Imaging data obtained from these patients were retrospectively reviewed.

Results

We found that the occurrence of BMC was 60.3%, AMF was 6.9%, MLC was 98.2%, LLC was 75.9%, BF was 43.1%, and LAC was 98.3%. Edge-contrasted inverted panoramic images revealed BMCs in 21.7% and AMFs in 25%; however, most of these canals could not be detected. In the panoramic images, the average diameter of the BMC was significantly different between the detected group and not detected group. The number of canals and foramens in the anterior region to the molar region decreased on the buccal and lingual sides, and most BMCs were in the retromolar to the ramus region.

Conclusion

Our results indicated different distributions and occurrence rates of each type of neurovascular canal and foramens.

Bifurcation of the inferior dental nerve canal: an anatomical study

The aims of this study were to find the incidence of bifurcation of the inferior dental nerve (IDN) canal, to describe the characteristics of this variant, and to examine the sensitivity and specificity of dental panoramic tomography to identify it. We classified bifurcations by size and position relative to the main canal and the lower third molar using cone-beam computed tomography (CT) and dental panoramic tomography. In our study of 281 patients, 106 (38%) had bifurcations, and in one quarter, these were classified as large accessory canals. Bifurcations were most commonly found posterior to the lower third molar (n=64, 57%) or within 2mm of the roots of the third molar (n=40, 38%). The sensitivity and specificity of dental panoramic tomography to identify all bifurcations was 11% (95% CI: 5.67 to 17.97) and 91% (95% CI: 85.58 to 94.68), respectively; this was 33% (95% CI: 15.63 to 55.32) and 94% (95% CI: 90.34 to 96.50), respectively, for large bifurcations. Our use of cone-beam CT suggested an incidence of bifid canals of 38%, with a variation in size and distribution in relation to the lower third molar. It also showed that the sensitivity of panoramic radiography to identify them was poor.

Clinical Anatomy and Significance of the Retromolar Foramina and Their Canals: A Literature Review

The retromolar foramina (RMF) and the retromolar canal (RMC) are anatomic variants in the mandible located distally to the last molar. The retromolar nerve, which runs through the RMC, is a type 1 bifidity of the mandibular canal. The investigations of the RMF and RMC have been performed by dry mandible studies, the panoramic radiograph (PAN), computed tomography (CT), and the cone beam computed tomography (CBCT) studies. The CBCT has been shown to be the superior method for visualizing the RMF and RMC. There is wide variation in the frequency, location, diameter, and distance of the canal in different individuals. Overall, there is no significant difference in the frequency of the canal in the mandible between sexes or sides of the mandible. The peak incidence of the RMF may occur in adolescence. The RMC is significant due to the neurovascular bundle which runs through it. Injury to this neurovascular bundle during surgical procedures, such as third molar extraction, implant placement, or split sagittal osteotomy, may lead to paresthesia, excessive bleeding, or traumatic neuroma. The presence of RMC may also lead to insufficient anesthesia in the mandible which may be overcome with alternative anesthetic techniques.

The prevalence of mandibular retromolar canals on cone beam computed tomography and its clinical repercussions

Abstract Introduction Knowledge on the normal morphology of the human mandible and its possible anatomical variations are of fundamental importance in dental practice, especially in the areas of surgery and implantodontics. The retromolar region is delimited by the anterior margin of the ramus of the mandible, the temporal crest and the distal surface of the last lower molar. In this area, a retromolar canal may be observed emerging through the retromolar foramen. Objective This study aims to evaluate the prevalence of retromolar canals in cone beam computed tomography (CBCT) images and to correlate it with their possible clinical repercussions. Material and method 300 CBCT images were selected from the Department of Radiology of the São Leopoldo Mandic Dental School. This was an observational descriptive study and all the images were processed and analyzed on XoranCat®. Result Of the 300 CFCT scans analyzed, a single mandibular canal was observed in 210 (70.0%). In the remaining 90 cases, anatomical changes were observed relating to this canal, indicating that the prevalence of this condition in this sample was 30%. The prevalence of retromolar canals was observed in 15 patients (5.0%), of which 06 were in males and 09 in females. Conclusion The importance of a full knowledge on the anatomy of the retromolar region is herein reiterated due to the high prevalence of surgical procedures in the posterior region of the mandible, which could optimize predictability at treatment planning as well as anesthetic and surgical outcomes, thus minimizing anesthetic failures and surgical accidents.

Correlating the clinical assessment of impacted mandibular third molars with panoramic radiograph and intraoral periapical radiograph

Aims And Objectives:

This study was conducted to compare the clinical assessment of impacted third molars of mandible with panaromic radiograph (OPG) and intraoral periapical radiograph (IOPA) and to assess the efficacy of IOPA and. Moreover, we corroborated the OPG and IOPA findings of impacted mandiblar third molar root apex to inferior alveolar canal.

Materials and Methods:

A total of 200 patients with pericoronitis were examined who were indicated for surgical extraction, among which 50 patients were selected for the study. All the patients underwent a radiographic survey with a digital OPG and IOPA of impacted mandibular third molars, along with clinical survey for anatomic relationship, type of impaction, space available, position in relation to second molar, number of roots, root curvature, and proximity of nerve canal. The data was subjected to statistical analysis. The Statistical Package for Social Sciences version 4.0.1 software was used for analyzing the collected data.

Results:

The study revealed that IOPA was more accurate in determining a majority of the factors affecting the third molar surgery, including relationship of the external oblique ridge (IOPA vs OPG = 96%:90%), anteroposterior relation with ramus (IOPA vs OPG = 70%:66%), vertical depth of impaction (IOPA vs OPG = 72%:68%), number of roots (P = 0.013), morphology of roots (IOPA vs OPG = 96%:90%); however, OPG was found to be accurate in evaluating the type of impaction (IOPA vs OPG = 88%:94%), canal relation, along with root of impacted molar (IOPA vs OPG = 74%:86%).

Conclusion:

To conclude, although IOPA has a marginal angle over OPG in assessing various parameters, only the number of roots have a greater accuracy (P < 0.0013) in IOPA than with OPG. However, the OPG is the better choice to be considered when the patient is associated with trismus.

Classifications of mandibular canal branching: A review of literature

AIM: To gather existing radiographic classifications of mandibular canals branching, considering the criteria on which these were based.

METHODS: The search for studies on mandibular canals based on imaging exams included literature reviews, epidemiological studies of prevalence, descriptive studies, or case reports. An electronic search in the MEDLINE (OvidSP), PubMed, EMBASE (OvidSP), Web of Science (Thompson Reuters), and Scopus (Elsevier) databases was performed, as well as a manual evaluation of the references of the selected articles. Combinations of key words were placed in each database. No restrictions were imposed regarding the year of publication or language. References collected in duplicate were removed by the authors. A table was drawn up, containing the included studies and respective interest data.

RESULTS: Six classifications of mandibular canals branching were selected for the present literature review. Four were based on two-dimensional radiographic exams, and two were performed based on three-dimensional tomographic exams. Three-dimensional classifications were determined based on the analysis found in the least number of exams, comparatively to two-dimensional studies. The prevalence of mandibular canal branching varied from 0% to 38.75% in the works based on two-dimensional exams, while those found in three-dimensional exams ranged from 15.6% to 65%. The studies were mostly referred to branches that began in the mandibular ramus. Just one classification considered the branches that began in the mandibular body region.

CONCLUSION: Three-dimensional exams appear to be the best method to view mandibular canal branching. Further studies are warranted to determine its true prevalence and questions concerning to associations.

Anatomical variations of mandibular canal detected by panoramic radiography and CT: a systematic review and meta-analysis

OBJECTIVES

To investigate the anatomical variations of the mandibular canal through assessment in situ, panoramic radiography, CT or CBCT and assess their frequency.

METHODS

Articles were selected from databases (Cochrane Library, LILACS, ProQuest, PubMed, Scopus, Web of Science and Google Scholar), articles without limitations of language, in which the main objective was to evaluate the frequency of bifurcation of the mandibular canal through assessment in situ, panoramic radiography, CT or CBCT were selected. A meta-analysis of prevalence using random effects was performed.

RESULTS

Using a selection process in two phases, 15 articles were identified, and a meta-analysis was conducted. The results from these meta-analyses showed that the overall prevalence of anatomical variations for in situ studies was 6.46%, and through assessment of panoramic radiography and CT or CBCT the overall prevalence shown was 4.20% and 16.25%, respectively.

CONCLUSIONS

There are two types of variations of the mandibular canal: the retromolar canal and bifid mandibular canal. The frequency variations through assessing in situ, panoramic radiography and CT or CBCT were 6.46%, 4.20% and 16.25%, respectively.