Double mandibular foramen leading to the accessory canal on the mandibular ramus

Purpose

The knowledge of the variation in the mandibular foramen and canal is clinically significant in surgical procedures of the mandible. This study aims to evaluate the anatomical characteristics of double mandibular foramen leading to the accessory canal on the mandibular ramus using cone beam CT.

Methods

The sagittal, cross-sectional, and three-dimensional images of cone beam CT data from 446 patients were evaluated in the presence of double mandibular foramen and the accessory canal passing through the foramen. The accessory canals were classified into two types according to the configuration (forward and retromolar type), and the location of double mandibular foramen was recorded.

Results

The eight double mandibular foramina leading to the accessory canals were observed in six patients out of 446 patients (1.35 % of population). Regarding the configuration of the accessory canal, there were two forward types and six retromolar types. All double mandibular foramina were located above the mandibular foramina on the medial aspect of the mandibular ramus.

Conclusion

Three-dimensional images of cone beam CT data are useful in confirming the presence of double mandibular foramen leading to the accessory canal. The variation may cause failure in the routine mandibular nerve block anesthesia and it is often vulnerable during surgical procedures involving the mandibular ramus. Also, double mandibular foramen is considered as an easy route for tumor cell to spread following the radiotherapy. Therefore, the variation should be carefully investigated using reconstructed cone beam CT images in planning of dental surgery or radiotherapy in the mandible.     

Mandibular lingual canals distribute to the dental crypts in prenatal stage

Purpose

To describe configurations of human prenatal mandibular, lingual canals using a limited-field cone beam computed tomography (CBCT) to examine their origin and anatomical significance.

Materials and methods

Nine fetal mandibles were examined using a CBCT. Mandibular maturity was assessed according to the mandibular size measured directly and image findings on development of dental crypts. Mandibular, lingual canals and the related foramina (mandibular, mental, and lingual foramina) were observed on axial, sagittal, and cross-sectional images. The horizontal position of mental and lingual foramina was assessed by direct observation using a loupe.

Results

In all nine mandibles, CBCT images depicted three separate mandibular canals, which individually occurred at the ramus area. One was a short canal directly connecting to the permanent molar crypt. The other two showed a parallel course, following the mandibular corpus toward the frontal area; the upper one connected to the mental foramen, and the lower one distributed anterior area of canine and incisor crypts. Lingual foramina were observed bilaterally in eight of nine mandibles, whose horizontal position was lingual against the crypt of deciduous canine. The lingual canals occurred from lingual foramina, and connected to the close deciduous tooth crypt or the mandibular canal distributing in the frontal area.

Conclusions

It was suggested human dentition could be developed by plural mandibular and lingual canals.     

Evaluation of location and dimensions of mandibular lingual foramina using cone-beam computed tomography

Objectives

The aim of this study was to assess the regional frequency and anatomical properties of mandibular lingual foramina (MLF) and their bony canals with cone-beam computed tomography (CBCT).

Materials and methods

A retrospective study was conducted by selecting images of the mandible from CBCT examination of 500 patients. MLF were located according to tooth areas and were grouped into midline, paramedian, and posterior foramina. In addition, the frequency of bony canals originating from lingual foramina was calculated, and the course and anastomoses were examined.

Results

In total, 491 areas with lingual foramina were observed. The highest regional frequency was recognized in the midline area (95.2 %), followed by left first premolar (15.1 %) area. The frequency of foramina in the midline was different from the paramedian and posterior (p < 0.01) regions. 95.6 % of lingual vascular canals originating from midline lingual foramina had a perpendicular course into the symphysis, whereas 60.3 % of canals from paramedian foramina and 83.6 % of canals from lateral lingual foramina presented with an anteriorly directed course.

Conclusions

CBCT examination easily demonstrates the presence of the lingual vascular canals. MLF are frequently present in a Turkish population; radiologists and oral surgeons should be aware of this anatomic feature and its possible implications.     

Anatomical configuration of the inferior alveolar neurovascular bundle: a histomorphometric analysis

Purpose

The inferior alveolar neurovascular bundle (NVB) is important in implant placement and many other surgeries in dentistry because it is a major supplier of sensation and blood to the mandible via the mandibular canal. The purposes of the present study were to determine the areas and diameters of the NVB, the inferior alveolar nerve (IAN), and the inferior alveolar artery (IAA), and to verify the buccolingual location of the mandibular canal.

Methods

The anatomical configuration of the NVB was examined by histomorphometrically analyzing 20 embalmed dentulous hemimandibles. The areas and maximum horizontal and vertical diameters of the NVB, IAN, and IAA were measured according to tooth region. The distances from the internal border of the mandibular canal to the outer surface of the buccal and lingual cortical plates were also measured.

Results

The areas of the vertically oval-shaped NVB and IAN appeared to be constant between the molar and premolar regions, which contain the mental branch, and decreased sharply in the lateral incisor after branching off of the mental branch via the mental canal. The mandibular canal was located close to the lingual cortical plate in the posterior tooth region before passing through the mental canal, immediately after which it was situated quite close to the buccal cortical plate, and then closer to the middle toward the anterior tooth region.

Conclusions

The findings of this study provide useful anatomical information that should help to minimize the risk of injury to the NVB during surgical procedures in the mandibular region.

     

Cone beam computed tomographic evaluation of nutrient canals and foramina in the anterior region of the mandible

Purpose

To investigate the incidence and anatomical location of mandibular nutrient canals (NCs) originating from the mandibular canal using dental cone beam computed tomography (CBCT).

Methods

CBCT images from 105 patients were examined to evaluate the presence, number, diameter, and course of NCs.

Results

NCs and their foramina were bilaterally located in 17 (16.2 %) images. The mean diameters of NCs and foramina were 0.9 ± 0.4 (range, 0.2–3.2) mm and 0.9 ± 0.4 (0.2–2.1) mm, respectively. NCs coursed through the mandibular incisor region up to the lingual surface of the alveolar bone crest.

Conclusion

The present study revealed the frequency and distribution of NCs using CBCT image analysis. NCs are important because surgical injury to the neurovascular bundle within these canals can lead to excessive bleeding and postoperative paresthesia. The identification of NC on CBCT images may be useful during the harvesting of bone blocks or placement of endosseous implants in the anterior region of the mandible.

     

Correlation of mandibular impacted tooth and bone morphology determined by cone beam computed topography on a premise of third molar operation

Purpose

To determine the width and morphology of the mandible in the impacted third molar region, and to identify the location of the mandibular canal prior to planning impacted third molar operations.

Methods

Cone beam computed tomography (CBCT) data of 87 mandibular third molars from 62 Japanese patients were analyzed in this study. The width of the lingual cortical bone and apex-canal distance were measured from cross-sectional images in which the cortical bone was thinnest at the lingual side in the third molar region. Images were used for measuring the space (distance between the inner border of the lingual cortical bone and outer surface of the third molar root), apex-canal distance (distance from the root of the third molar tooth to the superior border of the inferior alveolar canal) and the cortical bone (width between the inner and outer borders of the lingual cortical bone).

Results

The means of the space, apex-canal distance and lingual cortical width were 0.31, 1.99, and 0.68 mm, respectively. Impacted third molar teeth (types A–C) were observed at the following frequencies: type A (angular) 37 %; type B (horizontal), 42 %; type C (vertical), 21 %. The morphology of the mandible at the third molar region (types D–F) was observed as: type D (round), 49 %; type E (lingual extended), 18 %; and type F (lingual concave), 32 %.

Conclusions

The width and morphology of the mandible with impacted teeth and the location of the mandibular canal at the third molar region could be clearly determined using cross-sectional CBCT images.     

Edentulousness in relation to remodeling of the gonial angles and incisures in dentate and edentate mandibles: morphometric study using the Image J software

Purpose

The human mandible is subject to stimuli during its growth phase and also in adulthood. One of these stimuli may be absence of teeth, which gives rise to mandibular remodeling. Morphological changes may occur in different areas of this bone, such as in the gonial, condylar and ramus regions.

Objective

To investigate the influence of edentulousness on remodeling of the gonial angle of the mandible and the angle formed by the mandibular incisure.

Materials and method

Eighty-five dry mandibles from adults were examined: 42 from males and 43 from females. The mandibles were photographed using a camera coupled to a static support that was positioned 20 cm from the object to be photographed. The images were digitized and transferred to the Image J 1.42q software, in which the gonial angle of the mandible and the mandibular incisure angle were measured.

Results

There were no differences in the mandibular and mandibular incisure angles in relation to presence or absence of teeth, or between the right and left sides. The mandibular incisure angle was greater in the women.

Conclusion

Edentulousness did not cause remodeling of the gonial angle of the mandible or in the mandibular incisure angle.     

Morphometric study of mandibular foramen in macerated skulls to contribute to the development of sagittal split ramus osteotomy (SSRO) technique

Purpose

The aim of this study was to provide morphometric data, obtained from macerated mandibles, which might facilitate the topographic location of the mandibular foramen, considering aspects such as gender, age and ethnicity.

Materials and methods

One hundred and eighty-five macerated mandibles of adult black and white individuals of both sexes were analyzed. Initially, 5 points were established: MF, the lowest point of the mandibular foramen; S, greatest concavity of the mandibular notch; A, anterior margin of the ramus of mandible; P, posterior margin of the ramus of mandible; and Go, gonion. Then the following measurements were performed bilaterally: MF-S, MF-A, MF-P and MF-Go.

Results

The following mean values were found: MF-S: 21.02 mm for white females (WF) and 22.00 mm for black females (BF); 24.40 mm for white males (WM) and 24.35 mm for black males (BM); MF-A: 17.05 mm for WF and 18.09 mm for BF; 17.18 mm for WM and 18.11 mm for BM; MF-P: 11.11 mm for WF and 12.24 mm for BF; 13.10 mm for WM and 14.15 mm for BM; MF-Go: 19.00 mm for WF and 19.44 mm for BF; 23.13 mm for WM and 22.12 mm for BM.

Conclusions

The values found in this study, considering gender, age and ethnic group, can be used as a parameter to carry out the sagittal split ramus osteotomy technique, making it more predictable and with less risk of complications.     

Detection of buccal perimandibular neurovascularisation associated with accessory foramina using limited cone-beam computed tomography and gross anatomy

Purpose  

To investigate buccal perimandibular neurovascularisation associated with the mandibular accessory buccal foramina (ABF) which were detected using a limited cone-beam computed tomography (limited CBCT).     

Cone beam CT findings of retromolar canals in a Korean population

Purpose

The identification of the variation involving the mandibular canal is important during surgical procedures in the mandible. This study aims to investigate the incidence, course, width, and location of retromolar canals in a Korean population using cone beam CT.

Methods

The cross-sectional, sagittal, and three dimensional images from volumetric cone beam CT data of 446 patients were reconstructed using imaging analysis software for the presence of a retromolar canal. Retromolar canals were classified into three types according to the courses. The width and location (distance from the second molar) of retromolar canals were evaluated.

Results

A retromolar canal was observed in 8.5 % of patients (38/446). Most retromolar canals had vertically curved courses (Type 1, 66.7 %), followed by horizontally curved courses (Type 2, 20 %). Type 3 retromolar canals, which run independently from separate foramina in the mandibular ramus, were rare (13.3 %). The mean width of a retromolar canal was 1.13 mm (SD ± 0.38, 0.60–2.00), and the mean distance to the second molar was 14.08 mm (SD ± 3.85, 8.50–24.00).

Conclusions

The incidence of retromolar canals in the Korean population was lower than that reported in the investigated ethnic groups. In the presence of a retromolar canal, local anesthesia may be ineffective. The damage to a retromolar canal may be unavoidable during surgical procedures involving the mandible and may result in paresthesia, excessive bleeding, postoperative hematoma, or traumatic neuroma.     

Evaluation of the morphological changes in the mandible for dentate and totally edentate elderly population using cone-beam computed tomography

Purpose

The loss of teeth considerably modifies the mandibular shape. The aim of this study was to compare the morphological changes in the mandible for dentate and totally edentate elderly subjects using cone-beam computed tomography.

Methods

In total, 50 cone-beam computed tomography patients (25 dentate, 25 edentate) without any maxilla-mandibular dysmorphosis were analyzed retrospectively. Panoramic representations of the mandible with superimposed axial slices and cross-sectional slices were developed with the cone-beam computed tomography scans. Values of the mandibular cortical index, bone quality index, gonial angle, antegonial angle, antegonial depth and condyle angle in the left and right side were measured.

Results

There was a significant difference in the mandibular cortical index between the total edentate group and the dentate group in the left side of the mandible (p < 0.001). There was a significant difference in the bone quality index between the total edentate group and the dentate group in the right side and the left side (p < 0.001). There was a significant difference in the bone quality index between the right side and the left side (p < 0.005). When comparing gender, there was only a difference in the right side (p < 0.05).

Conclusions

Our study concluded that the mandibular basal bone morphology changes as a consequence of tooth loss. Cone-beam computed tomography is shown to be a good tool in investigating and achieving these results.     

Uncommon trajectory variations of the mandibular canal and of the mandibular incisive canal: case report

Purpose

This paper aims to report and discuss a case in which unusual anatomical variations were observed in the mandibular canal (MC) and the mandibular incisive canal (MIC) in a same patient.

Materials and methods

A 49-year-old healthy female was referred for mandibular dental implant placement. Panoramic radiography and cone beam computed tomography (CBCT) were performed. Cross-sections, axial, coronal, panoramic reconstructions and volume rendering were obtained.

Results

The panoramic radiograph did not show any evidence of abnormality. CBCT showed a bifid MC on the right side. It extended to the buccal cortex, exteriorized for 6 mm and returned to its conventional trajectory to reach the mental foramen. On the left side, the MIC initially followed its normal trajectory for 4 mm but, in the canine region, it also extended to the buccal cortex and exteriorized.

Conclusion

The advent of CBCT in Dentistry allowed a greater accuracy in the diagnosis of anatomical variations in the jaws, preventing injury to the neurovascular bundle and enabling an adequate surgical planning in the region.     

Trabecular bone ratio of the mandibular condyle according to the presence of teeth: a micro-CT study

Purpose

During mastication, mechanical pressure from the dentition is transmitted to the trabecular bone of the mandible. The occlusal forces, which could thus affect condylar growth, vary with tooth loss, age, and sex. The trabecular bone of the mandibular condyle is denser in dentate subjects than in edentate subjects. However, since the different tooth groups (incisor, premolar, and molar) have different functions, they could exert different effects on the mandibular condyle. The aim of this study was to elucidate the bone quantity of the Korean mandibular condyle according to the presence of teeth using micro-computed tomography (micro-CT), thereby clarifying the influences of tooth presence on the condylar microstructure.

Methods

Thirty-one sides were scanned and reconstructed into a 3D structure using a micro-CT system. The specimen was sectioned vertically, passing through the medial and lateral poles of the mandibular condyle (P0) to enable measurement of the trabecular bone ratio. Likewise, three additional images, parallel with P0, were acquired. Mean and standard deviation values were calculated, and the t test, one-way ANOVA and post hoc analysis were performed to examine the differences among each group, classified according to the presence of teeth and according to sex.

Results

The density of the trabecular bone of the mandibular condyle was significantly associated with the presence of the molars, but not the incisors or premolars. There were significant differences between sexes.

Conclusions

The present study has provided data regarding the bone quantity of the trabeculae of the mandibular condyle according to the presence or absence of teeth.     

Cone-beam computed tomography analysis of the shape,height, and location of the mandibular lingula

Objectives

The precise anatomic location of the lingula is clinically significant because it is subject to injury during a variety of oral and maxillofacial surgical procedures. This is the first study to identify and classify the different morphological shapes of the mandibular lingula using cone-beam computed tomography.

Materials and methods

A retrospective study was performed to evaluate the shape, height, and location of the lingula in relation to surrounding structures using cone-beam computed tomographic images. The shape of the lingula was classified into triangular, truncated, nodular, and assimilated types. The location was determined by five distances from the lingular tip to: the anterior and the posterior borders of the mandibular ramus, the mandibular notch, the distal surface of the mandibular second molar, and the occlusal plane.

Results

Nodular shape of the lingula was most commonly found [51.2 % (422)] followed by truncated [32 % (264)]. The mean height of the lingula was 7.97 ± 1.84 mm. The mean distance of lingula from the anterior and posterior borders of mandibular ramus was 16.7 ± 2.7 and 13.0 ± 2.3 mm, respectively. The lingula was located at 15.3 ± 2.4 mm from the mandibular notch and 29.4 ± 3.9 mm from the distal side of alveolar socket of mandibular second molar tooth.

Conclusion

The present study provides new information to the literature concerning the shape, height, and location of the lingula in the Turkish population. This finding may assist surgeons to localize the lingula and avoid intraoperative complications.     

Risk assessment of inferior alveolar neurovascular bundle by multidetector computed tomography in extractions of third molars

Purpose

This study aimed to assess the reliability of multidetector computed tomography (MDCT) in determining the surgical risk of the inferior alveolar neurovascular bundle in extractions of third molars.

Methods

The sample comprised thirty-three individuals (63 third molars) who underwent preoperative evaluation by MDCT before extraction of impacted mandibular third molars. MDCT was used to determine the relationship between the roots of the third molars and the mandibular canal, and the course of the mandibular canal. Inferior alveolar nerve (IAN) exposure and the presence of hemorrhage were analyzed after removal of the teeth. IAN neurosensory deficit was recorded after 7?days. Clinical and MDCT findings were compared using Fisher’s exact test (P?Results There was a statistically significant association between IAN exposure and the tomographic relationship between the roots of third molars and the mandibular canal (P?=?0.015). Conventionally, all cases of IAN neurosensory deficit and hemorrhage occurred when the roots of the third molar presented in an at-risk relationship with the mandibular canal, however, this association was not statistically significant (P?>?0.05). A statistically significant association was found between the lingual course of the mandibular canal and IAN exposure (P?=?0.03).

Conclusions

MDCT is an effective tool for determination of the surgical risk to the inferior alveolar neurovascular bundle in extraction of mandibular third molars.     

Variations in the branching pattern of posterior division of mandibular nerve: a case report

Purpose

Abnormal communications among the branches of mandibular nerve especially the posterior division are significant due to various procedures undertaken in this region. These variations are worth reporting as they pose serious implications in several interventions in this region, and may even lead to false diagnosis.

Methods

During routine dissection, the mandibular nerve and its branches were dissected in the infratemporal fossa. The branches from the posterior division of the mandibular nerve namely the inferior alveolar and auriculotemporal nerves were carefully dissected, and their abnormal branching pattern was noted.

Results

There was a communicating branch between left inferior alveolar and auriculotemporal nerve. There was also a variant recurrent branch from the left inferior alveolar nerve that supplied the lateral pterygoid muscle.

Conclusions

Such variant branches and communications between the branches of mandibular nerve as seen in this case have an embryological basis and are clinically important in this region especially for dental surgeries and anesthesia.     

Prestyloid compartment of the parapharyngeal space: a histological study using late-stage human fetuses

Purpose

Although the prestyloid space is well known, its definition still remains unclear.

Methods

Using semiserial sagittal sections of 15 late-stage human fetal heads, we studied details of the topographical anatomy.

Results

A definite posterior marginal fascia of the space was seen along the anterior aspect of the stylopharyngeus and styloglossus muscles. Inferiorly, the prestyloid space faced the bucallis and medial pterygoid muscles and the submandibular gland. The external carotid artery ran along the posterolateral side of the space. The tensor veli palatini fascia did not contribute to the posterior marginal fascia. A major supplying artery of the space was the ascending palatine artery.

Conclusions

The prestyloid compartment of the parapharyngeal space (hereafter, the prestyloid space) seems to correspond to a border between the first and second pharyngeal arch derivatives. This concept may provide a better understanding of prestyloid space.     

Clinical anatomy and surgical significance of the lingual foramina and their canals

The lingual foramina and canals can be categorized as median or lateral based on their relation to the midline of the mandible. Investigation of the mandibular lingual region is often done with gross anatomical dissections of cadavers, 2D panoramic radiographic imaging, CT, and cone beam CT (CBCT). While gross studies are the most reliable at qualifying canal contents and course, CBCT proved to be superior to other radiographic techniques for visualizing lingual foramina and canals. The submental and sublingual arteries, and their branches are found in the lingual vascular canals. There is tremendous variation between individuals in terms of the course of the lingual canals and their anastomosis with other vascular canals. Performing the dental implantation procedures in the anterior and posterior regions of the mandible can result in perforation of the lingual cortex, which could injure the arteries that lie within the lingual canal. If hemorrhage occurs, it could lead to life‐threatening upper airway obstruction. Pre‐surgical investigation to identify the diameter of the lingual foramina and canal as well as their distance from the alveolar process might be necessary to prevent hemorrhage for all patients. Clin. Anat. 30:194–204, 2017. © 2017 Wiley Periodicals, Inc.     

下颌神经管的解剖结构

背景:在下颌后牙种植术中,由于下颌神经管走行于下颌骨体内,有时可损伤下齿槽神经,因而制约了牙种植术的应用。 因此,牙种植术的应用需详细了解下颌神经管的解剖结构。 目的：观察下颌神经管在下颌骨内的走行及管内的解剖结构。 方法：共纳入15具成人牙下颌骨标本与4具新鲜下颌骨动脉灌注标本。纳入对象均牙列完整,后牙无缺失,牙槽骨无吸收。测量15具成人牙下颌骨标本下颌管走行及其管腔各径长度,包括下颌管横径与纵径,下颌管至上下内外缘距离。观察4具新鲜下颌骨动脉灌注标本管内下颌神经管内神经、血管位置关系。 结果与结论：下颌管内缘至舌侧骨板的距离比下颌管外缘至颊侧骨板距离短(P < 0.01);下颌管上缘至牙槽嵴顶的距离较下颌管下缘至下颌骨下缘的距离大(P < 0.01)。表明下颌管在下颌骨体部走行中偏舌侧、偏下颌骨下缘。下颌神经管在下颌骨体部的部分横径小于纵径(P < 0.05),亦即下颌管截面形态为上下径略长的椭圆形。神经管横纵径于前后牙位区差异无显著性意义。实验还发现在暴露的下颌管腔中下牙槽神经及伴随血管有一层被膜包绕成神经血管束,血管位于神经上方,而且位置恒定,并发出小分支包绕神经。结果提示,下牙槽血管神经束在下颌管内走行中血管位于神经之上。     

Multiple accessory foramina of the mandibular ramus: risk factor for oral surgery

A 27-year-old female was referred to our hospital with a chief complaint of removal of an impacted right mandibular third molar. Panoramic radiography showed two small circular radiolucencies on the right mandibular ramus. Computed tomography revealed that one of the radiolucencies was an accessory foramen located lateral to the mandibular ramus, and the other radiolucency was an accessory foramen located medial to the ramus; it was also connected to the mylohyoid groove. Continuity with the mandibular canal was confirmed for both accessory foramina. After explaining the risks of extraction, the patient decided against surgery and the impacted tooth was left in situ. Most patients have at least one or more accessory foramina in the mandible; however, accessory foramina of the lateral aspect of the mandibular ramus have not been reported. The high resolution of cone-beam computed tomography and three-dimensional reconstructed images enable improved detection of accessory foramina. Therefore, additional accessory foramina that are similar to those found in the present case could be found in the future using such imaging modalities.