The position of the mandibular canal and histologic feature of the inferior alveolar nerve

The inferior alveolar nerve is the one of the large branches of the mandibular division of the trigeminal nerve. It is vulnerable during surgical procedures of the mandible. Despite its importance, no anatomical and histological examination has been conducted to provide a detailed cross‐sectional morphology of the mandibular canal according to dental status. Therefore, the present study aimed to identify the position of the mandibular canal through direct measurement and to determine the branches of the inferior alveolar nerve through histologic examination. The area between the anterior margin of the third molar and the anterior margin of the second premolar of dentulous, partially dentulous, and edentulous hemimandible specimens (n = 49) from 26 human cadavers was serially sectioned into seven segments, and specific distances were measured using digital calipers. Following this, 5‐μm cross‐sections were prepared along the mandibular canal and mental foramen, and examined by fluorescence microscopy. The mandibular canal was located at a mean distance of 10.52 mm above the inferior margin of the mandible. The mean maximum diameters of the mandibular canal, inferior alveolar nerve, inferior alveolar artery, and inferior alveolar vein were 2.52, 1.84, 0.42, and 0.58 mm, respectively. This study found that the inferior alveolar nerve often gives rise to several branches at each level (range 0–3). To minimize the risk of injury, knowledge of the small branches of the nerve and of the detailed findings regarding the position of the mandibular canal reported here should be considered when planning mandibular surgery, especially during implant placement. Clin. Anat. 23:34–42, 2010. © 2009 Wiley‐Liss, Inc.     

Evaluation of bifid mandibular canals with cone-beam computed tomography in a Turkish adult population: a retrospective study

Purpose  

Knowing the anatomic location and also variations of the mandibular canal is especially important for surgical procedures on mandible such as dental implant surgery, impacted molar extraction and sagittal split ramus osteotomy. The purpose of this study was to clarify the incidence and location of bifid mandibular canals in an adult Turkish population to avoid complications during surgical procedures.     

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.     

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.     

面神经下颌缘支的应用解剖

目的了解面神经下颌缘支的正常层次解剖位置,为涉及面侧区和颌下区的美容外科手术提供临床应用解剖学资料。方法解剖33具（共66例）成人尸体标本的头颈部标本,观察了面神经下颌缘支的分支类型、走行、与面动脉的位置关系以及穿出腮腺处和与面动脉的交叉处的体表位置。结果面神经下颌缘支为1-2支,以单干型居多,约占58%,大多行于下颌骨下缘上方约占44%,行于骨下缘下方者占5%。未发现面神经下颌缘支不与面动脉交叉,位置在均下颌角下缘上、下方约0.5-1 cm范围内。面神经下颌缘支经过面动脉的浅面和深面者分别占89%和6%;面神经下颌缘支穿出腮腺处的体表位置分别在下颌角上方和下颌支后缘前方1 cm交点附近,面神经下颌缘支与面动脉交处距下颌支后缘约4 cm,距下颌骨下缘约1 cm。结论面神经下颌缘支的毗邻和行程关系较为复杂,了解其与周围结构的重要位置关系,可以减少美容外科手术因神经损伤造成下唇及口角功能障碍的发生。     

Prevalence of bifid mandibular canals in panoramic radiographs: a maxillofacial surgical scope

Purpose

The present study aims to estimate the prevalence of bifid mandibular canals in patients treated at the Dental Clinic of the Federal University of Paraná, Brazil.

Methods

The sample consisted of 3,024 panoramic radiographs from male (n = 1,155) and female (n = 1,869) patients (mean age 30 years). An experienced radiologist analyzed the panoramic radiographs according to the study of Langlais et al. (J Am Dental Assoc 110:923–926, 1985), which classifies bifid mandibular canals into four different types.

Results

Sixty patients (1.98 %) presented bifid mandibular canals. Specifically, 50 patients revealed bifid mandibular canals type I, while 10 patients revealed bifid mandibular canals type II. All the variations were unilateral. In addition, statistically significant results were not observed for gender distribution.

Conclusion

The present findings indicate a low prevalence of morphologic alterations of the mandibular canal in the studied population. However, the present outcome highlights the clinical relevance of investigating the radiologic morphology of the mandibular canal prior to surgical interventions.     

下颌角肥大整形术相关解剖

目的 精细解剖下颌角周围软组织结构及下颌神经管,为下颌角肥大整形术提供解剖学参考。 方法 20例大体标本,观察及测量面动静脉、面神经下颌缘支及咬肌区的血管和神经。据下颌骨表面骨性标志定位5条径线,测量该5条径线上下颌神经管在下颌骨中的位置。计算各软组织结构和下颌神经管的安全范围。 结果 面动脉距下颌角点为23.18～36.28 mm,距咬肌前缘为-9.51～9.27 mm。面静脉距离下颌角点为17.79～32.03 mm。面神经下颌缘支贴近下颌角部及下颌骨下缘走行,距离下颌角点为-8.57～10.70 mm,而咬肌前缘下颌缘支距下颌骨下缘为-8.83～11.06 mm。咬肌的血供主要有面动脉咬肌支、颈外动脉咬肌支、上颌动脉咬肌支及面横动脉咬肌支这四大来源。咬肌神经多与咬肌动脉伴行进入咬肌。下颌神经管在5个截面中距离下颌骨外侧点分别大于10.50 mm、14.72 mm、15.60 mm、8.53 mm、6.74 mm。 结论 在剥离下颌角区软组织时,注意对咬肌前缘面动脉、面神经下颌缘支及下颌角点附近面神经下颌缘支的保护。去除咬肌的最佳层次为咬肌深层中份最厚点及中下份。而在截骨或劈骨时,根据下颌神经管的安全范围,可在下颌骨颊侧骨板快速画出一条指导性的安全线。     

下颌管的观测及应用解剖

为对下颌骨矢状劈开截骨术避免损伤牙槽血管神经束提供下颌管的正常数据，为人类学积累资料，对３０个干燥下颌骨的下颌管在三个不同断面进行了下颌管的形状、直径、下颌管外侧壁至下颌骨外侧面垂直距的观测，所得数据经统计学处理分析，供临床参考。     

上下颌前牙根根管系统解剖及临床意义

目的了解上下颌前牙牙根数目,根管类型,为临床前牙根管充填提供理论依据。方法采用离体牙经透明牙标本制备,用XXT-3A连续变倍体视显微镜检测上下颌前牙根管系统。结果1973颗前牙1975支牙根的主根管类型分为六型,I型上颌前牙占100%、下颌前牙占74.97%;侧副根管分四种:根管侧支检出率17.97%,管间吻合检出率0.81%,根尖分歧检出率4.61%,根尖分叉7.39%。结论上下颌前牙根管形态及根管系统具有规律性和多变性。     

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。     

层递探查法探查下颌第一恒磨牙近中中央根管成功率的体外评价

目的探讨体外三阶段层递探查法探查离体下颌第一恒磨牙近中中央根管(MMC)的成功率,并研究下颌第一恒磨牙MMC的解剖形态学特征。方法收集近期拔除的下颌第一恒磨牙60颗,采用肉眼直视下探针探查、显微镜辅助探查、显微镜辅助超声预备三阶段层递探查法探查下颌第一恒磨牙MMC,最终对未发现MMC的离体牙采用透明牙染色法,以此为对照评价上述三阶段探查MMC的成功率;分析MMC的形态分类以及在各年龄段中的分布情况。结果层递探查法各阶段探查离体牙MMC的发现率分别为5.3%(3颗)、8.8%(5颗)、21.1%(12颗);经透明牙染色法确认后,有1颗离体牙的MMC被遗漏;体外三阶段各自的探查成功率分别为23.1%、38.5%、92.3%;第一、二阶段MMC发现率比较差异无统计学意义(P>0.05),第三阶段与第一、二阶段比较,差异均有统计学意义(P<0.05);MMC的根管解剖学分型多为融合型(3-2型、3-1型);MMC在21~40岁组中的发现率最高(33.3%)。结论体外三阶段层递探查法能有效提高下颌第一恒磨牙中MMC的发现率,在显微镜辅助超声预备下探查MMC的成功率明显较高;MMC的解剖形态相对复杂,与近中主根管间的联系紧密,且随着年龄的增长,MMC的发现率逐渐降低。     

Lingual foramina on the mandibular midline revisited: a macroanatomical study

The purpose of the present study was to determine the incidence, size, location, course, and content of the foramina and bony canals located on the lingual side of the mandibular midline. Fifty dry human mandibles were morphometrically analyzed by measuring the distances of these midline foramina from the mandibular base and the dimensions of these foramina and their bony canals. In addition, macro- and microanatomical dissection was performed on 12 intact cadaver mandibles. The macroanatomic midline foramina were classified into superior and inferior genial spinal foramina according to their vertical location with respect to the genial spines. This study showed that out of 50 dry mandibles, 49 (98%) had at least one midline lingual foramen; only one lacked a true midline foramen. Evaluation of the microanatomical dissections indicated a clear neurovascular bundle in both superior and inferior genial spinal foramina and canals. For the superior canal, the content was found to derive from the lingual artery and the lingual nerve. For the inferior canal, however, the arterial origin was submental and/or sublingual, while the innervation derived from a branch of the mylohyoid nerve. In conclusion, different kinds of lingual foramina have been identified according to their location. The superior and inferior genial spinal foramina have different neurovascular contents, determined by their anatomical location above or below the genial spines.     

Radiological and Microsurgical Anatomy for Variation of the Mandible: Comparative Study of Human and Macaca fascicularis

Recent studies using cone‐beam computer tomography (CBCT) have added to our understanding of anatomical variation in the mandible of humans. However, the distribution of nerves cannot be revealed by CBCT. There have been investigations of the distribution of nerves relating to the mandible, but some proposed causes of these variations remain controversial. In this study, we observed a total of 10 sides from five mandibles of Macaca fascicularis of unknown age and sex using CBCT and dissection under stereomicroscopy. Nine of the 10 sides had two mental foramina in each side. Innervation by the mental nerves depended on the locations of those foramina. The long branch to the mandibular angle ran with a branch of the facial artery, which joined the mental artery in all 10 sides. Five specimens had a median perforating canal in the mandibular bone. In addition, a branch of the sublingual artery, which joined with the small branches of the submental artery, entered the mandibular bone from the median lingual foramen. This foramen was located in the lower part of the mandibular symphysis and passed via the median perforating canal to exit from the median labial foramen, also located in the lower part of the mandibular symphysis. We speculate that the median perforating canal of the mandible, rarely found in humans, is the remnant of the feeding artery of the fetal mandible, and in M. fascicularis is seen in all specimens because they have no mental protuberance. Anat Rec, 300:1464–1471, 2017. © 2017 Wiley Periodicals, Inc.     

The marginal mandibular branch of the facial nerve in Koreans

The marginal mandibular branch (MMB) has a particular risk of injury during surgical procedures in the submandibular region, especially over the lower border of the mandible. The facial nerve has been described in many studies, but the MMB is dealt with generally as a branch of the facial nerve. The purpose of this study was to document the anatomy of the MMB by correlation with anatomical landmarks. Eighty‐five facial halves were examined for this study. The MMB was classified according to the number of branches and their connections with other branches, and by its relationship with landmarks of the gonion, facial artery, and retromandibular vein. The MMB showed one (28%), two (52%), three (18%), or four branches (2%) where it exited the parotid gland. Classification was based on connection with other branches. Type I (60%) did not communicate with other branches. Type II (40%) communicated with the buccal or cervical branches, or with another branch of the MMB. The cervicofacial division coursed along the lateral aspect of the retromandibular vein in 83% of specimens. The MMB passed the facial artery superficially (42%), passed it deeply in 4%, and ran on both sides of it in 54% of the facial halves. The distribution of the MMB formed a quadrilateral with angles +19.8 mm, ?8.1 mm, +30.0 mm, and ?15.3 mm measured from two sides on the inferior border of the mandible. These topographical data should help to decrease the incidence of injuries during surgery on the submandibular regions in Koreans. Clin. Anat. 22:207–214, 2009. © 2008 Wiley‐Liss, Inc.     

Endodontic treatment of a mandibular canine with two roots

Lower canine is a tooth with a robust, long root and very good implantation, making it a valuable abutment tooth for any type of prosthetic treatment. In order to treat it conservatively and to prevent its loss from the dental arch it is necessary to accomplish a correct and complete endodontic treatment, which involves knowledge of all its morphological variation. The mandibular canine usually presents one root with a single large canal centrally located. The possible anatomical variations are the existence of a single root with two canals and of two different roots, each having a canal. The incidence of lower canines with two roots is usually low, as described in various studies, but their presence in everyday practice shows that the clinician must consider them if he wants to prevent dental endodontic treatment failure. This article presents a relatively rare case of a patient whose right mandibular canine has two roots and two canals. Although the frequency of mandibular canines with two roots is very low, we must not forget that we can deal with such cases, which can obviously occur even in patients in our country, as the ones described in foreign specialty literature.     

Anastomosis between the inferior alveolar artery branches and submental artery in human mandible

The mental artery displays several branches internal to the anterior region of the mandible as confirmed by macroscopic observation and computed tomography. The inferior alveolar artery formed complex branches and divided into mental and incisive branches, which were found in the right internal side of the mandible of one male cadaver (88 years old). The branches of these two arteries ran through the bony lingual canal to the lingual foramen between the canine and premolar region of the inner surface of the mandible body, where they emerged to enter the mylohyoid and anterior belly of the digastric muscles and communicate with the submental artery. The observation of the anastomotic artery is considered important for surgical placement of dental implants in the mandibular region.     

The marginal mandibular branch of the facial nerve

The peripheral, extraparotid course and localisation of the marginal mandibular branch of the facial n. is described, with variations, based on the dissection of 40 cadaver half heads. Its anatomical relationships with the ramus of mandible and facial a. are studied and morphometric features are reported. Knowledge of the accurate course and relationship of the marginal mandibular branch should help to protect this nerve from surgical injury.     

Development of the mandibular condylar cartilage in human specimens of 10–15 weeks' gestation

This study analyses some morphological and histological aspects that could have a role in the development of the condylar cartilage (CC). The specimens used were serial sections from 49 human fetuses aged 10–15 weeks. In addition, 3D reconstructions of the mandibular ramus and the CC were made from four specimens. During weeks 10–11 of development, the vascular canals (VC) appear in the CC and the intramembranous ossification process begins. At the same time, in the medial region of the CC, chondroclasts appear adjacent to the vascular invasion and to the cartilage destruction. During weeks 12–13 of development, the deepest portion of the posterolateral vascular canal is completely surrounded by the hypertrophic chondrocytes. The latter emerge with an irregular layout. During week 15 of development, the endochondral ossification of the CC begins. Our results suggest that the situation of the chondroclasts, the posterolateral vascular canal and the irregular arrangement of the hypertrophic chondrocytes may play a notable role in the development of the CC.     

An assessment on spiral CT scan of the superior and inferior genial spinal foramina and canals

To characterise the superior as well as the inferior genial spinal foramen and their bony canal using a large CT data sample. The study included 555 mandibular spirals CT scans, taken from patients for pre-operative implant planning. Basic observation by three observers included the number of canals, their respective anatomical location and morphological variations. Furthermore, linear measurements were performed to describe the foramina and canal characteristics. On spiral CT scans, the superior and inferior genial spinal foramina were detected in 448 CT scans (81%). In 29% of the mandibular CTs, two or more midline canals were noted. 47% of the foramina were located in a position inferior to the genial spines; the others were located in a superior position. The mean (SD) lingual and buccal diameters of the canal structures were 0.73 (0.27) and 0.54 (0.29) mm, respectively with an average length of 3.94 (1.29) mm. The canal was located on average 7.40 (5.31) mm from the mandibular base at the lingual entrance and 7.96 (3.47) mm at the buccal canal end point. The average canal extended towards the buccal bone for an average 37% of the bone width. The results demonstrated the presence of both superior and inferior genial spinal foramina, with 29% of the individuals having double foramina. About 53% of the foramina was located superior to the genial spines. Considering its neurovascular content, these foramina should be carefully evaluated during pre-operative planning.     

Anatomical variations of mandibular first molar and their implications in endodontic treatment

The possible variations of anatomical and morphological characteristics of the teeth are very important especially for the endodontic practitioner. Before beginning any kind of endodontic treatment, the clinician must be always take into account the morphological variations in pulp anatomy. Among all human teeth, the mandibular first permanent molar is one of the most important. It is often affected by caries and usually needs root canal treatment, even at an early age. For the success of its endocanalicular treatment, dentists need to locate all root canals, debride them entirely, and after that fill the whole endocanalicular system with an inert root filling material. Unfilled canals, left like this because they were not detected, can compromise the longevity of the tooth, thus being a source of infection and a main cause of failure of the prosthetic treatment. This article presents two clinical cases of right mandibular first molars with two roots and four canals instead of three.