Bifid mandibular canal: literature review and case report

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

PURPOSE

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).

METHODS

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).

RESULTS

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.

CONCLUSION

The results of this study highlight the importance of evaluating specific individual characteristics of a given population.

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.

Characterization of a retromolar foramen in a Chinese population: A radiographic study

BACKGROUND

Retromolar canal (RMC) arises from the mandibular canal (MC) behind the second or third molar and travels anterosuperiorly to a retromolar foramen (RMF). RMCs and RMFs have generally been ignored in anatomical textbooks and have rarely been reviewed or studied in the anatomical and dental literature until the last decades.

OBJECTIVE

This study aimed to characterize RMF in a Chinese population concerning its incidence, origin, and classification via anatomical study and periapical radiography.

METHODS

123 dry adult Chinese mandibles were collected to observe the incidence of RMFs. RMFs were determined using a steel wire 0.5 mm in diameter. The passways or origins of the retromolar canal (RMC) were determined and classified via periapical radiography. For each RMF, two dentists independently measured the diameter and its distances to the lingual cortex, the buccal cortex, and the distal edge of the last tooth (or the alveolar fossa) using a vernier caliper.

RESULTS

The incidence of RMFs was 31.71%. The average RMF diameter was 0.78 ± 0.27 mm. From RMF, the distance was 4.27 ± 1.87 mm to the lingual cortex, 8.61 ± 2.23 mm to the buccal cortex, and 7.84 ± 3.87 mm to the distal edge of the last tooth (or the alveolar fossa). RMCs were classified into MC type originating from the mandibular canal and AF type originating from the alveolar fossa. The diameters of MC ones were more significant than those of AF ones. There was no apparent correlation between the existence of the third molar and the presence of an RMF.

CONCLUSION

The incidence of RMFs in Chinese may be about one-third, which is a potential factor in the onset of surgery accidents. RMCs can be classified into two types by their origins. One of them is MC, which originates from the mandibular canal, and the other is AF, which originates from the alveolar fossa.

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.

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.

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.

Evaluation of Mandibular Third Molar Region in a Turkish Population Using Cone-Beam Computed Tomography

OBJECTIVES

To evaluate impacted mandibular third molar tooth region and obtain linear measurements using CBCT images and to assess the relationship between the impacted third molar and the mandibular canal.

METHODS

CBCT scans of 351 patients (208 females, 143 males) were assessed. Age, gender, and impaction site were recorded for each patient. The relationship of third molars with the vertical axis of second molars, 2nd molar resorption and the relationship between third molar apices and the mandibular canal were assessed. In addition, the distance between ramus and second molar, mesiodistal width of the third molar, the angle between third molar and second molar, and width of the third molar capsule were measured. Binary Logistic Regression, Chi-Square Test, and General Linear Model were used for statistical analysis.

RESULTS

The highest percentage of impaction was found for mesioangular followed by transversal and vertical. The transversal impacted third molars revealed a significant association with adjacent second molar root resorption (p<0.001). There was a statistical significance between the second molar resorption and distance between ramus and second molar (p<0.001). The mesioangular impacted third molars revealed significant relation with the mandibular canal (p<0.05). The most frequent variation found was the dental canal followed by the retromolar canal. In general, higher measurement values were obtained for men when compared to women (p<0.05).

CONCLUSION

CBCT assessment of the third molar region provided useful information regarding impacted mandibular third molar surgery operations.

Study of Normal Anatomy of Mandibular Canal and its Variations in Indian Population Using CBCT

Introduction

Identification of detailed anatomy of mandibular canal (MC) with its contents including the position, course, and morphology is extremely important for the management of various surgical procedures including dental implant placement, third molar surgery, dental anesthesia, mandibular osteotomy, bone-harvesting procedure from the ramus and body of mandible, bone plating in angle and body region of mandible, or any other surgical procedure involving the mandible.

Methods

This prospective randomized study was carried out in the Department of Oral and Maxillofacial Surgery, Saraswati Dental College, Lucknow, on 100 randomly selected cone-beam computed tomography (CBCT) mandibular views displaying the entire mandible.

Results

Various parameters of the canal were studied in detail and subjected to statistical analysis using SPSS 20 software. For all the observations, paired t test was applied to compare right and left sides and independent t test for the comparison of gender.

Conclusion

For centuries MC has been a paramount topic of discussion, and with the contraption of CBCT, we can finally decipher the canal in great detail. CBCT acts as a guide to prevent damage to the neurovascular bundle as the canal traverses its course and sometimes with certain variations.

Observation of double mandibular canals and types of bifid canals in dry skulls

Background/Aim: The aim of the present study was to assess prevalence and morphologic mandibular canal variations in dry skulls. Material and Methods: Panoramic radiographs were obtained of 57 skulls among the academic collection at the University of Pittsburgh. Orthodontic wire was inserted through the mandibular canal as a reference point at panoramic images for localization of the course of the mandibular canal. Results: Double mandibular canals were present in 2 out of 57 skulls (3,5%); one of them was unilateral the other one was bilateral. Additionally, bifurcation of the mandibular canal and different types of configurations were assessed. In five of the specimens (8,8%) bifid canals were identified. Among them, one case (1,7%) was identified as a forward type. In one case additional canal (1,7%), was detected in the retromolar region, which joined the main canal. Three of the specimens (5,3%) showed accessory canal types. These were the canals that detached from the main canal and proceeded towards the molar teeth roots (dental type). All of these bifid canal types were unilateral. Conclusions: Our results depicted the anatomical variations of the mandibular canal. Dental practitioners should be aware of this underestimated but not a rare occurrence of mandibular canal variations in order to avoid complication during surgical procedures.

A DETAILED CBCT STUDY OF 'CORONOID FORAMINA' AND ACCESSORY FORAMINA OF THE MANDIBLE: A UNIQUE ANATOMIC VARIATION

The aim of the study was to evaluate accessory foramina (AF) located on the medial aspect and to present a unique finding of 'coronoid foramina' (CF) along with AF on the mandible. The cone beam computed tomography images of the mandible in 979 patients were retrospectively evaluated for the presence of CF and AF. AF was found in 39 (3.98%) patients. AF located on the medial surface below and above mandibular foramen was found in 15.38% and 84.62% of patients, respectively. CF was confirmed in 20 (2.04%) patients. Mandibular AF is important for surgical procedures in the posterior region of the mandible and for mandibular nerve anesthesia. This study including CF will be useful for further studies due to the lack of literature on the issue.

Bilateral Bifid mandibular canals - Special relevance for a general dental practitioner. Report of 2 cases

Dental practitioners may encounter bifid mandibular canals upon radiographic assessment, and may not understand the true extent of this presentation. The presentation of a bifid mandibular canal poses difficulties when carrying out dental procedures, including administration of mandibular block anaesthesia, oral surgical procedures of the lower third molars, orthognathic surgery and implant placement. Therefore it is of paramount importance that general dental practitioners be aware of the radiographic appearance, as incorrect diagnosis of this rare presentation can lead to detrimental consequences. The purpose of the communication is to draw dental practitioner’s attention to the variations of bifid mandibular canals and ensure practitioners interpret radiograph correctly to make an informed diagnosis and eliminate the risk of damage and discomfort in the event of surgical treatment being carried out. It is advised that dental practitioners refer for further imaging such as a cone beam scan for greater understanding of the anatomical variation.

Key words:Bifid mandibular canal, inferior alveolar nerve, bilateral bifid mandibular canal.

Case-control study of mandibular canal branching and tooth-related inflammatory lesions

OBJECTIVES

Morphological variations of mandibular canals increase the risk of neurovascular damage and bleeding during surgical procedures by decreasing the predictability of the inferior alveolar neurovascular bundle location. To improve the predictability with such variations, the present study aimed to verify the possibility of a relationship between mandibular canal branches (MCBs) and tooth-related inflammatory lesions, using trough cone-beam computed tomography (CBCT) examinations.

METHODS

The sample comprised 150 age and sex-matched examinations (50 cases and 100 controls) from two databases. The CBCT examinations were grouped by the presence of MCBs starting in the mandibular body regions as the outcome variable. Tooth-related inflammatory lesions and measurements of gray levels in the posterior region of the alveolar ridge were assessed in both groups. A multiple logistic regression analysis was applied to verify the relationships between MCBs and independent variables (p < 0.05).

RESULTS

Occurrence of tooth-related inflammatory lesions increased the risk of MCBs in the mandibular body regions (p < 0.001; OR 11.640; 95% CI 4.327-31.311). High-contrast images had a weaker association with MCBs (p = 0.002; OR 1.002; 95% CI 1.002-1.003). The most frequent tooth-related inflammatory lesions in both groups were endodontic (34 lesions; 45.94% of the total lesions). Most of the tooth-related inflammatory lesions related to MCBs were endodontic (20 cases) and combined endodontic and periodontal inflammation (20 cases).

CONCLUSIONS

An association was observed between MCBs in the mandibular body regions and tooth-related inflammatory lesions. Inflammatory lesions of endodontic origin are most often associated with MCBs.

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.

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.

[Cone beam computed tomography evaluation of bifid mandibular canals in the adult population in Sichuan Province]

OBJECTIVE

To investigate the incidence of bifid mandibular canals (BMC), and analyze the types, courses, and anatomic features of the variant canals in the adult population in Sichuan Province.

METHODS

Five hundred patients (1 000 hemimandibles) underwent cone beam computed tomography (CBCT) were included in this study. The incidence, bifurcate types and courses of the BMC were evaluated.

RESULTS

The incidence of BMC was 13.8% (69/500) in the study, 9.2% in terms of total hemimandibles. The most frequently type was retromolar canals, followed by the dental and buccolingual type, meanwhile the lowest was the forward type. The mean diameter of the accessory canals was 0.90 mm and the mean length was 9.39 mm.

CONCLUSIONS

CBCT used in this study has shown that the incidence of BMC assessed by CBCT was significantly higher than panoramic radiography. Furthermore, CBCT can depict the position, course, size and the branches of the mandibular canals.
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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.

Proximity of the Mandibular Canal to Teeth and Cortical Bone

INTRODUCTION

The proximity of the inferior alveolar canal to the mandibular molar roots may pose a risk of injury during various dental surgeries. The purpose of this study was to evaluate age-related and gender-related changes by using cone-beam computed tomography images between the roots of the second molars, mandibular cortex, and the inferior alveolar canal.

METHODS

One hundred fifty-five patients (68 men, 87 women), 20 years and older, who had previous cone-beam computed tomography scans were enrolled in this study. The patients were subcategorized by gender and age (group I, <21 years; group II, 21-40 years; and group III, >40 years). Distance between the mandibular canal (MC) and the second molar distal root apex as well as the 3 mandibular cortical regions (inferior cortex, buccal cortex, and lingual cortex) were measured.

RESULTS

In men, the second molar root apex to the MC distance was significantly shorter in group I than in group III (P < .01). In women, the second molar root apex to the MC distance was significantly shorter in group I than in group II and group III (P < .05). In both men and women, the buccal cortex of the mandible to the MC distance was significantly shorter on the right side compared with the left side (P < .01).

CONCLUSIONS

Our study shows that age, gender, and region have an influence on the location of the MC in the second molar area.

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.

Anthropomorphic assessment of the retromolar foramen and retromolar nerve: anomaly or variation of normal anatomy?

The retromolar foramen, retromolar canal, and retromolar nerve constitute a variation of the inferior alveolar nerve (IAN) with a prevalence of 12-75%; this represents type 1 bifidity of the IAN. The aim of this study was to assess the prevalence of the retromolar nerve in our population and to obtain related data. One hundred and thirty-six mandibles of fresh cadavers aged 20-75 years were dissected. The buccolingual location, diameter, and distance from the third molar, and their associations with sex, were measured. The area of innervation and demographic data were also documented and analysed statistically. The retromolar foramen and retromolar nerve were observed in 55 cases (40.4%). The mean diameter of the retromolar foramen was 1.7 mm (range 1.1-2.1 mm); the mean diameter was 1.8 mm in males and 1.5mm in females. Histological findings showed that the retromolar nerve extended from the anterior border of the ramus, innervating the retromolar pad and continuing to the buccal gingiva of up to two teeth anteriorly (first molar region). This high percentage of IAN type 1 bifidity (40.4%) suggests it to be a normal anatomical variation of the IAN rather than an anomaly.

Análise das variações anatômicas do canal da mandíbula encontradas em radiografias panorâmicas

INTRODUÇÃO: No âmbito da clínica odontológica, o bloqueio do nervo alveolar inferior é o mais utilizado; todavia, diversos estudos têm mostrado as mais altas taxas de fracasso, as quais, normalmente, têm como motivo a falha na observação da posição, da forma e da anatomia dos nervos. Essas falhas decorrentes da variação anatômica do nervo alveolar inferior já vêm sendo estudadas na literatura, através de estudos com a análise de radiografias panorâmicas, como proposto neste estudo. OBJETIVO: O objetivo deste estudo foi verificar a ocorrência e a prevalência das variações anatômicas, bem como a correlação das variações do canal da mandíbula com lado e sexo, que podem ocorrer no canal mandibular, por meio de radiografias panorâmicas de pacientes atendidos no Departamento de Odontologia da Universidade Federal de Sergipe (UFS). MATERIAL E MÉTODO: Foram analisadas 1.500 radiografias panorâmicas de pacientes atendidos pelo Departamento de Odontologia da Universidade Federal de Sergipe (UFS). Imagens radiográficas foram observadas sobre um negatoscópio, utilizando-se uma máscara preta ao redor das radiografias, em ambiente com luminosidade apropriada. RESULTADO: Neste estudo, foram observados 5,3% de bifurcações do canal mandibular; 47,5% de canais altos; 16,8% de canais intermediários; 27,1% de canais baixos, e 8,6% de canais com outras variações. CONCLUSÃO: Baseando-se na altura do canal mandibular, houve maior prevalência dos canais altos do que os demais nas mulheres, sendo que não houve diferenças entre os gêneros com relação aos demais tipos e lados afetados. Na classificação dos canais bífidos, não houve diferença estatisticamente significante entre homens e mulheres. Observou-se que a maior prevalência foi para canais sem bifurcação.

Occurrence of the retromolar foramen in dry mandibles of South-eastern part of India: a morphological study with review of the literature

The retromolar foramen (RMF) is a rare anatomical structure situated in the retromolar fossa behind the third molar tooth. When it is present, the foramen is connected with the mandibular canal and is believed to transmit neurovascular structures that provide accessory source to the mandibular molars and the buccal area. Reports from the literature show that the presence of RMF could pose a challenge in complete blockage of the inferior alveolar nerve during mandibular surgeries. We report the incidence of retromolar foramen from ninety-four dry mandibles of south-eastern part of Karnataka State, India. The foramen was observed in 11 mandibles out of 94 included in the study (11.7%). In three mandibles, the foramen was present bilaterally (3.2%) and in three it was on the left side (3.2%) and in five it was on the right side (5.3%). For the first time, we also measured the dimensions of the retromolar area and distance of the foramen from third molar tooth to understand its risks during the surgical extraction of the lower third molar tooth. A thorough review of the literature has also been done to compare the present findings with the studies reported from the various populations.

Assessment of bifid and trifid mandibular canals using cone-beam computed tomography

Purpose

To investigate the prevalence of bifid and trifid mandibular canals using cone-beam computed tomography (CBCT) images, and to measure their length, diameter, and angle.

Materials and Methods

CBCT images of 500 patients, involving 755 hemi-mandibles, were used for this study. The presence and type of bifid mandibular canal was evaluated according to a modified classification of Naitoh et al. Prevalence rates were determined according to age group, gender, and type. Further, their diameter, length, and angles were measured using PACSPLUS Viewer and ImageJ 1.46r. Statistical analysis with chi-squared and analysis of variance (ANOVA) tests was performed.

Results

Bifid and trifid mandibular canals were found in 22.6% of the 500 patients and 16.2% of the 755 sides. There was no significant difference between genders and among age groups. The retromolar canal type accounted for 71.3% of the identified canals; the dental canal type, 18.8%; the forward canal type, 4.1%; and the trifid canal type, 5.8%. Interestingly, seven cases of the trifid canal type, which has been rarely reported, were observed. The mean diameter of the bifid and trifid mandibular canals was 2.2 mm and that of the main mandibular canal was 4.3 mm. Their mean length was 16.9 mm; the mean superior angle was 149.2°, and the mean inferior angle was 37.7°.

Conclusion

Bifid and trifid mandibular canals in the Korean population were observed at a relatively high rate through a CBCT evaluation, and the most common type was the retromolar canal. CBCT is suggested for a detailed evaluation of bifid and trifid mandibular canals before mandibular surgery.

Evaluation of perimandibular neurovascularization with accessory mental foramina using cone-beam computed tomography in children

OBJECTIVES

The purpose of this study was to clarify the perimandibular neurovascularization with mandibular accessory mental foramina in a children population using cone-beam computed tomography (CBCT) to avoid complications during anesthetic and surgical procedures.

METHODS

This retrospective study evaluated cone-beam CT images for bifid mandibular canals in the mandibles of 63 children (35 girls, 28 boys; age range, 7-16 years; mean age, 12.3 years). Both right and left sides were examined from CT images (n = 126), including axial, sagittal, cross-sectional, and panoramic views as well as reconstructed three-dimensional images, as necessary. The course, length, and superior and inferior angles between canals were classified and measured.

RESULTS

Bifid mandibular canals were observed in 34 (27%) of the 126 sides examined. The most frequently encountered type of bifid canal was the retromolar canal (11.1%), followed by the forward (7.14%), buccolingual (6.35%), and dental canal (2.4%). Mean lengths of bifid canals were 10.2 mm on the right side and 10.6 mm on the left side. Mean superior angles were 131 degrees on the right side and 147 degrees on the left side, whereas mean inferior angles were 47 degrees on the right side and 34 degrees on the left side. No statistically significant differences were found in the lengths or angles between the right and left sides or between boys and girls (P < 0.05). The most common position for the mental foramen was between the first and second premolars, and an accessory mental foramen was observed in 4 children (6.34%).

CONCLUSIONS

This study utilized CBCT images to identify bifid mandibular canals and accessory mental foramina in children. Cone-beam CT was found to be a useful technique for detecting secondary canals. However, despite the fact that CBCT uses less ionizing radiation than other types of three-dimensional imaging, unless the diagnostic information provided through CBCT improves treatment results, CBCT should not be recommended for use in children or adolescents.

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

OBJECTIVES

To examine the presence and morphologic characteristics of bifid mandibular canals (BMCs) and retromolar foramens (RFs) using cone beam CT (CBCT) and to determine their visualization on panoramic radiographs (PANs).

METHODS

A sample of 225 CBCT examinations was analysed for the presence of BMCs, as well as length, height, diameter and angle. The diameter of the RF was also determined. Subsequently, corresponding PANs were analysed to determine whether the BMCs and RFs were visible or not.

RESULTS

The BMCs were observed on CBCT in 83 out of the 225 patients (36.8%). With respect to gender, statistically significant differences were found in the number of BMCs. There were also significant differences in anatomical characteristics of the types of BMCs. Only 37.8% of the BMCs and 32.5% of the RFs identified on CBCT were also visible on PANs. The diameter had a significant effect on the capability of PANs to visualize BMCs and RFs (B = 0.791, p = 0.035; B = 1.900, p = 0.017, respectively).

CONCLUSIONS

PANs are unable to sufficiently identify BMCs and RFs. The diameter of these anatomical landmarks represents a relevant factor for visualization on PANs. Pre-operative images using only PANs may lead to underestimation of the presence of BMCs and to surgical complications and anaesthetic failures, which could have been avoided. For true determination of BMCs, a CBCT device should be considered better than a PAN.

Classification of bifid mandibular canals using cone beam computed tomography

The objective of this study was to classify the morphology of bifid mandibular canals and to evaluate their relationship with the roots of third molars, using cone beam computed tomography (CBCT) scans. The CBCT scans of 75 patients were analyzed and the bifurcations were classified according to Langlais et al. (1985). The relationship of bifurcation and third molars was established according to the following classification: class A--uninvolved, class B--close relationship, class C--intimate relationship and class D--absence of third molars. Data were submitted to descriptive statistics, and the results indicated that the patients' mean age was 48.2 (± 13.2) years. Unilateral bifurcation (Type 1) was the most frequent type (72.6%), followed by unilateral Type 2 (19.3%). Class D was the most frequent (57.33%), followed by class C (21.33%), class B (13.33%) and class A (8%). It could be concluded that most cases presented unilateral bifid mandibular canals extending to the third molar or adjacent regions, and when present, the roots seemed to be a continuation of the bifid mandibular canal.

The incidence and configuration of the bifid mandibular canal in Koreans by using cone-beam computed tomography

Purpose

This study was performed to investigate the incidence and configuration of the bifid mandibular canal in a Korean population by using cone-beam computed tomography (CBCT) imaging.

Materials and Methods

CBCT images of 1933 patients (884 male and 1049 female) were evaluated using PSR-9000N and Alphard-Vega 3030 Dental CT units (Asahi Roentgen Ind. Co., Ltd, Kyoto, Japan). Image analysis was performed by using OnDemand3D software (CyberMed Inc., Seoul, Korea). The bifid mandibular canal was identified and classified into four types, namely, the forward canal, buccolingual canal, dental canal, and retromolar canal. Statistical analysis was performed by using the chi-squared test and one-way analysis of variance (ANOVA).

Results

Bifid mandibular canals were observed in 198 (10.2%) of 1933 patients. The most frequently observed type of bifid mandibular canal was the retromolar canal (n=104, rate: 52.5%) without any significant difference among the incidence of each age and gender. The mean diameter of the accessory canal was 1.27 mm (range: 0.27-3.29 mm) without any significant difference among the mean diameter of each type of the bifid mandibular canal. The mean length of the bifid mandibular canals was 14.97mm(range: 2.17-38.8 mm) with only a significant difference between the dental canal and the other types.

Conclusion

The bifid mandibular canal is not uncommon in Koreans and has a prevalence of 10.2% as indicated in the present study. It is suggested that a CBCT examination be recommended for detecting a bifid canal.

Comparative analysis of mandibular anatomical variations between panoramic radiography and cone beam computed tomography

PURPOSE

The objective of this study is to compare the ability of panoramic radiography and cone beam computed tomography (CBCT) in detecting anatomical variations of the mandibular canal and mental foramen.

METHODS

One hundred twenty-seven preoperative panoramic and CBCT images were evaluated. Two oral and maxillofacial radiologists investigated the presence of bifid mandibular canals and/or additional mental foramina on the right, left, or both sides of the mandible. Intra- and interobserver reliability was determined using Cohen's kappa coefficient. McNemar's test compared the prevalence of mandibular anatomical variations between panoramic radiography and CBCT. The significance level was set at 0.05.

RESULTS

Additional mental foramen and bifid mandibular canal were detected in 1.2 and 7.4 % of the panoramic radiographs and 7.4 and 9.8 % of the CBCT images, respectively. The incidence of anatomical variations on the mandibular canal was not significantly different between both imaging modalities (P > 0.05).

CONCLUSIONS

Although CBCT provides better viewing of anatomical structures, including location, shape, and relationship with the surrounding area, panoramic radiography is a conventional imaging modality that can be used in the study of the bifid mandibular canals.

Clinical and radiological classification of the jawbone anatomy in endosseous dental implant treatment

Objectives

The purpose of present article was to review the classifications suggested for assessment of the jawbone anatomy, to evaluate the diagnostic possibilities of mandibular canal identification and risk of inferior alveolar nerve injury, aesthetic considerations in aesthetic zone, as well as to suggest new classification system of the jawbone anatomy in endosseous dental implant treatment.

Material and Methods

Literature was selected through a search of PubMed, Embase and Cochrane electronic databases. The keywords used for search were mandible; mandibular canal; alveolar nerve, inferior; anatomy, cross-sectional; dental implants; classification. The search was restricted to English language articles, published from 1972 to March 2013. Additionally, a manual search in the major anatomy and oral surgery books were performed. The publications there selected by including clinical and human anatomy studies.

Results

In total 109 literature sources were obtained and reviewed. The classifications suggested for assessment of the jawbone anatomy, diagnostic possibilities of mandibular canal identification and risk of inferior alveolar nerve injury, aesthetic considerations in aesthetic zone were discussed. New classification system of the jawbone anatomy in endosseous dental implant treatment based on anatomical and radiologic findings and literature review results was suggested.

Conclusions

The classification system proposed here based on anatomical and radiological jawbone quantity and quality evaluation is a helpful tool for planning of treatment strategy and collaboration among specialists. Further clinical studies should be conducted for new classification validation and reliability evaluation.

Number of accessory or nutrient canals in the human mandible

OBJECTIVES

The aim of the study was to assess the presence, location and the number of accessory or nutrient canals in the body of the mandible by means of cone beam CT images, obtained with the Planmeca ProMax® 3D Max device.

MATERIAL AND METHODS

Seventy-four cone beam images of the mandible from adult patients (37 males and 37 females) who were imaged for dental implantology planning or third molar extraction were used to assess the number and location of accessory or nutrient canals. All images were taken with the same machine (Planmeca® ProMax 3D Max) at 200-, 400- or 600-μm resolution. Distinction was made between canals entering or exiting the mandible superior or inferior of the inferior alveolar canal and between similar canals superior or inferior of the genial tubercula.

RESULTS

The number of accessory canals varied between nil to 11. No statistical significant difference between males and females was found with regard to the number or location of accessory canals in the mandible. Only 5.4% of patients had no accessory canals. One to five accessory canals were found in 71.6%, and 23% of patients had more than five accessory canals. The majority (81%) of patients had between two and six accessory canals.

CONCLUSION

It seems that subjects showing no accessory canals whatsoever should be considered exceptional as more subjects with than without accessory canals in the body of the mandible were found.

CLINICAL RELEVANCE

These results are clinically relevant for mandibular surgery and mandibular local anaesthesia.

Retromolar foramen and canal: a comprehensive review on its anatomy and clinical applications

The retromolar foramen (RMF) and retromolar canal (RMC) are the anatomical structures of the mandible located in retromolar fossa behind the third molar tooth. This foramen and canal contain neurovascular structures which provide accessory/additional innervation to the mandibular molars and the buccal area. These neurovascular contents of the canal gain more importance in medical and dental practice, because these elements are vulnerable to damage during placement of osteointegrated implants, endodontic treatment and sagittal split osteotomy surgeries and a detailed knowledge of this anatomical variation would be vital in understanding failed inferior alveolar nerve blockage, spread of infection and also metastasis. Although few studies have been conducted in the past showing the incidence and types in different population groups, a lacunae in comprehensive review of this structure is lacking. Though this variation posed challenging situations for the practicing surgeons, it has been quite neglected and the incidence of it is not well presented in all the textbooks. Hence, we made an attempt to provide a consolidated review regarding variations and clinical applications of the RMF and RMC.

Radiographic assessment of the mandibular retromolar canal using cone-beam computed tomography

OBJECTIVE

The 'retromolar' nerve is a collateral branch of the inferior alveolar nerve. Cone-beam computed tomography (CBCT) provides higher resolution images. This CBCT study reports the frequency of the retromolar nerve.

MATERIALS AND METHODS

From 2007-2010 the CBCT study of 233 hemi-mandibles have been examined. The CBCT study was obtained from an investigation of the posterior mandibular region in 187 patients suffering from different pathologies and it was aimed at detecting in patients the presence of a retromolar canal and foramen.

RESULTS

Thirty-four retromolar canals with a foramen were detected on 233 CBCT (14.6%) in 30 out of 187 patients (16%). In the 46 patients who underwent CBCT bilaterally, the retromolar canal was found in nine subjects (19.6%) and was present bilaterally in four subjects, for an incidence of 8.7%.

CONCLUSIONS

The results suggest that the radiological frequency of the retromolar nerve is notable, with a possible relevance in the surgical approach of the mandibular retromolar area. The presence of a retromolar canal, well detected with CBCT, may warn clinicians about the possibility of inadequate pre-surgical anaesthesia, local intra-operative bleeding and post-operative alterations of the sensation in the third molar area.

Anatomic variations of neural canal structures of the mandible observed by 3-tesla magnetic resonance imaging

OBJECTIVE

Anatomical variations of the dental canal structures are present in a small proportion of the population and often go undiagnosed. In such cases, there could be an increased risk of complications during surgery and failure of anesthesia. The aim of this study was to search for anatomical anomalies in a relatively large random population by using 3-T high-field magnetic resonance imaging (MRI).

METHODS

Sixty-four dentate patients were examined using a modified T2 space sequence. The scans were analyzed with respect to anatomical features, variations, and rarities of the mandibular canal, mental canal, incisive canal, and the nutrient canals.

RESULTS

Sixteen anatomical variations were identified in the study, and some of those images are presented.

CONCLUSION

High-resolution MRI performed on a 3.0-T system can effectively visualize variations of the inferior alveolar nerve in dentate mandible of patients. Thus, MRI can be used in dentistry and oral surgery in vague or unclear cases, which could not be clarified by orthopantomography or even a computed tomographic scan, to improve patient care.

A false presence of bifid mandibular canals in panoramic radiographs

OBJECTIVES

This study was performed in order to verify bifid mandibular canals revealed from panoramic radiographic results.

METHODS

1000 panoramic radiographs from dental patients and the panorama, cone beam CT (CBCT) and micro-CT from 40 dry mandibles were examined for bifid mandibular canals. The results were confirmed by a stereoscopic and histological examination of the cross-sectioned mandibles.

RESULTS

The prevalence of bifid canals detected from the panoramic radiographs was 0.038. The panoramic radiographs from one dry mandible showed two separate radiolucent mandibular canal-like structures delineated by radio-opaque lines. However, a stereoscopic and histological examination of a cross-section of the mandible showed that only one canal was a true canal containing neurovascular bundles: the other was false, reflecting merely a bony trabecular pattern.

CONCLUSIONS

The presence of bifid mandibular canals determined by panoramic radiography should be judged with great caution in relation to dental surgery.

A review of the mandibular and maxillary nerve supplies and their clinical relevance

Mandibular and maxillary nerve supplies are described in most anatomy textbooks. Nevertheless, several anatomical variations can be found and some of them are clinically relevant. Several studies have described the anatomical variations of the branching pattern of the trigeminal nerve in great detail. The aim of this review is to collect data from the literature and gives a detailed description of the innervation of the mandible and maxilla. We carried out a search of studies published in PubMed up to 2011, including clinical, anatomical and radiological studies. This paper gives an overview of the main anatomical variations of the maxillary and mandibular nerve supplies, describing the anatomical variations that should be considered by the clinicians to understand pathological situations better and to avoid complications associated with anaesthesia and surgical procedures.