Rare courses of the mandibular canal in the molar regions of the human mandible: a cadaveric study

The inferior alveolar artery, vein and nerve send some branches to the molar teeth via the mandibular canal to the mental foramen. The present study attempted to define the presence and course of the mandibular canal in the mandible with the alveolar process by macroscopic cadaveric dissection and computerized tomography (CT) in order to provide information that might prevent injuries to vessels and nerves at risk during root canal treatment. We identified the position of the mandibular canal within a 30% ratio of the distance from inferior border of mandible to the apices of the root for 39 out of 131 sides (mesial root of first molar, 20%; distal root of first molar, 22.6%; mesial root of second molar, 27.8% and distal root of second molar, 47%) on panoramic X-ray observation. In one cadaver (male, 64 years old), the root apex of the second molar was in close proximity to the upper bony mandibular canal. Macroscopic dissection and computerized tomography showed that the main trunks of the inferior alveolar artery, vein, and nerve were in tight contact with the apex of the second molar. These observations of the anatomic course of the mandibular canal will be important to consider during root canal treatment of mandibular teeth.     

Morphological studies of the altered pulps of the New Zealand white rabbit after resection of the inferior alveolar nerve and/or the superior cervical ganglion

This study was carried out to determine the effects of denervation of the pulp organs of teeth, particularly on the odontoblasts and their processes. Therefore, resection of the inferior alveolar, cervical sympathetic, or a combination of both types of nerves supplying the mandibular incisor teeth of New Zealand white rabbits was performed and the results compared to adjacent, unaltered teeth. Neural stains were used to evaluate the presence or absence of nerve elements, while histochemical and titrametric methods were employed to determine the presence, location and concentration of cholinesterase enzymes in these teeth. Dilation of blood vessels was noted after cervical sympathetic resection and larger nerve trunks as well as peripherally located fine fibers were absent in the pulps following inferior alveolar nerve resection. Further, irregular dentin formation and associated small openings in the tips of the teeth were observed after nerve resection. Titrametric analysis indicated a significant decrease in the concentration of cholinesterase in the pulp organ of incisors 15–19 days after resection of either the inferior alveolar nerve or both inferior alveolar and cervical sympathetic nerves. Only a slight decrease in the concentration of cholinesterase was noted after removal of the cervical sympathetic nerve alone. Histochemical results confirmed a decrease in cholinesterase after resection of the inferior alveolar, cervical sympathetic or both nerves. The concentration of the oxidative enzyme, succinic dehydrogenase, however, increased after all three types of nerve resection. This increase was apparent particularly in the odontoblastic cells underlying the predentin.     

下颌骨血供及血管构筑的临床解剖学研究

目的：研究下颌骨血供及其血管构筑，为下颌骨截骨术提供形态学基础。方法：15例新鲜头颈部标本，其中8例经颈总动脉注入红色过氯乙烯填充剂，经腐蚀后制成头部血管铸型标本；2例去除部分内侧骨皮质，显示下牙槽动脉的分支分布情况；其余5例注入5％明胶墨汁，经脱钙、漂白、乙醇梯度脱水和二甲苯透明后，用水杨酸甲酯继续透明和保存，观察下颌骨膜和骨内的血管构筑。结果：下颌骨内部主要由下牙槽动脉供血；下颌骨表面及骨膜则由下颌骨骨膜动脉和肌动脉骨穿支营养；下颌骨骨膜动脉和肌动脉骨穿支经过下颌骨副孔穿入下颌骨内，与下牙槽动脉分支互相吻合，使下颌骨骨内与骨周围软组织间构成丰富的血管交通构筑。结论：下颌骨截骨手术后移动骨块和施行骨内固定时，要尽量少剥离下颌骨周围的软组织，以避免下颌骨发生坏死。     

下颌骨血供系统的研究及其临床意义

目的：研究下颌骨的血供，为有关下颌骨的外科临床提供解剖学基础。方法：将6例墨汁灌注的新鲜下颌骨标本制作成透明标本，对其血供系统的分布、走行及吻合情况进行观测分析。结果：下牙槽动脉自上颌动脉发出后，由下颌孔进入下颌骨，走行于下颌管内，营养下颌骨体部和下颌孔以下的升支部分。每侧下牙槽动脉共发出6条分支来营养牙齿和牙周组织。下颌骨表面骨膜内有大量的血管网，以嚼肌及翼内肌附丽部分最为丰富。下颌孔以上升支部分，包括髁突和冠突则完全由来自于骨膜的血管网营养。结论：下颌骨血供主要由下牙槽动脉以及骨膜动脉网分布，两者之间存在丰富的吻合，为下颌骨炎症扩散以及口腔癌的下颌骨骨转移提供了血管途径；骨膜动脉网的存在亦是正颌外科中下颌骨游离骨段的营养保证。     

下颌管与下颌后牙的位置关系及临床意义

目的: 为下颌牙种植术等临床口腔外科提供解剖学基础。方法：选取新鲜下颌骨标本10例、成人全牙下颌骨标本18例和20名全牙志愿者,分别暴露出下牙槽神经血管束、下颌管与下颌后牙牙根和CT连续扫描后进行三维重建。观察下牙槽神经、血管的排列关系,用游标卡尺和CT三维重建工作站分别测量下颌后牙牙根至下颌管上壁的距离。结果：下颌管自牙槽窝下方走行,其舌侧骨板较厚;下颌管内的下牙槽血管位于下牙槽神经上方。下颌磨牙的远中根至下颌管的距离均较近中根近。在标本及影像上的第1前磨牙、第2前磨牙、第1磨牙、第2磨牙、第3磨牙牙根至下颌管上壁的距离分别为(8.36±2.34)　mm和(8.42±2.42)mm、(7.36±2.21)mm和(7.52±2.18)mm、(3.22±1.40)mm和(3.36±1.85)mm、(2.96±1.54)mm和(2.84±1.55)mm、(3.64±1.72)mm和(3.88±1.76)mm。结论：（1）下颌后牙至下颌管的距离以第2磨牙最近,由近及远依次为第2磨牙、第1磨牙、第3磨牙、第2前磨牙和第1前磨牙。（2）对选择适宜长度的牙种植体,避免牙种植体损伤下牙槽神经等具有重要意义。     

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。     

Unique origin of the inferior alveolar artery

The inferior alveolar artery is the major blood supply to the mandible and mandibular teeth. This artery has a very consistent path, originating from the maxillary artery and passing inferiorly until it enters the mandibular foramen, accompanied by the inferior alveolar nerve and vein. During routine dissection of a 90-year-old female cadaver, a unique origin of the inferior alveolar artery was observed on the left side. The artery branched off the external carotid artery, just superior to the stylohyoid and posterior belly of the digastric muscle in the posterior region of the submandibular triangle. From its starting point the artery passed superiorly in the stylomandibular fascia and made a curving arch into the pterygomandibular space to enter the mandibular foramen with the inferior alveolar nerve. The position and branching pattern of the maxillary artery were otherwise typical. The inferior alveolar artery on the right side displayed a normal branching pattern within the infratemporal fossa. Results of surgical procedures in this area, such as sliding osteotomy of the mandible, could be impacted by this anomaly.     

Sensory innervation of mandibular teeth by the nerve to the mylohyoid: implications in local anesthesia

Traditionally, the nerve to the mylohyoid has been considered a motor nerve. However, dissection and clinical studies have challenged this dogma implicating the nerve to the mylohyoid as a nerve of accessory sensory innervation to mandibular teeth. Within the infratemporal fossa, the nerve to the mylohyoid branches from the inferior alveolar nerve and may be anesthetized with an inferior alveolar nerve block. However, because of the variability in location of branching and the potential barriers formed by both the pterygomandibular fascia and the sphenomandibular ligament, the nerve to the mylohyoid may escape anesthesia in an inferior alveolar nerve block. This may prevent profound local anesthesia of the mandibular teeth and may account, at least in part, for the high failure rate of the inferior alveolar nerve block. Alternative local anesthesia procedures may be employed to ensure adequate anesthesia of the nerve to the mylohyoid is achieved. This review provides a background of anatomical and clinical research of the nerve to the mylohyoid and outlines techniques suggested for providing a neural blockade of the nerve to the mylohyoid.     

Extramandibular position of the inferior alveolar nerve. Analysis and review of the literature

We report a highly unusual case of unilateral absence of the mental foramen, with the inferior alveolar nerve exiting the mandible via an orifice situated on the lateral surface of the angle of the mandible. However, the teeth on this side of the dental arch had normal sensitivity, and the mandible had grown correctly. Despite the absence of intraosseous course, the inferior alveolar nerve seems to keep its neural and guide roles.     

Evidence for the persistence of axons at the apex of the cat's lower canine tooth after section of the inferior alveolar nerve

The aim of this investigation was to establish the degree of denervation produced by inferior alveolar nerve section and to provide histological evidence for the presence of pulpal nerve fibres supplying the teeth which do not travel with the inferior alveolar nerve. Four adult cats were used. Each stage of the experiment was carried out under general anesthesia. The left inferior alveolar nerve was exposed and sectioned near the mandibular foramen. After 56 hours and 7 days, respectively, the jaw opening reflex to electrical stimulation of each lower canine was tested. Recordings were made from the left canine during electrical stimulation of the ipsilateral inferior alveolar nerve central and peripheral to the site of section as well as from the ipsilateral and contralateral inferior alveolar nerve during electrical stimulation of the left canine. Recordings were also made from the lingual nerve. After the recordings were completed two animals were perfused 56 hours after inferior alveolar nerve section, two more 7 days after section. Ultrathin sections of the apices of the lower canine teeth were examined in the electron microscope and each nerve fibre photographed. Each axon was examined to determine whether it was degenerating or normal. A jaw-opening reflex could not be elicited by stimulation of the left canine either 2 or 7 days after nerve section, whereas a normal response was evoked by stimulation of the right, control canine. At 2 days small responses could be recorded from the left canine teeth during stimulation of the left inferior alveolar nerve peripheral to the point of section. In one 2-day animal, responses could be recorded in the lingual nerve during stimulation. No pulpal fibres could be recorded in the inferior alveolar nerve central to the point of section nor from the contralateral inferior alveolar nerve. No pulpal fibres supplying the left canine could be recorded in any of the nerves examined at 7 days. Extensive degeneration was seen histologically even at 2 days. The canine pulp on the operated side contained only 31%, in one animal, and 26% in the other, of the number of axons of normal appearance that were present on the control side. At 7 days the number of remaining normal axons on the operated side were 5% and 13% of the numbers on the control side. All the axons of normal appearance were nonmyelinated. It is possible that the remaining axons represent fibres carried by the lingual nerve or some other alternative pathway that could not be detected electro-physiologically. Alternatively they may be a collateral innervation from adjacent tissues.     

上、下颌骨的CT影像与断层标本对照研究及临床意义

目的:为牙种植术等临床口腔外科提供解剖学基础.方法:选取成人全牙上、下颌骨标本和志愿者全牙CT重建影像各20例,观察上颌窦下壁的凸起结构和下颌管的走行,测量上颌窦下壁、下颌管上壁至牙根的距离.结果:上颌窦系呈三边形或四边形的锥形腔隙,其下壁常有凸起的骨隔.在标本及影像上的上颌窦下壁至第1前磨牙、第2前磨牙、第1磨牙、第2磨牙、第3磨牙牙根的距离左、右分别为(9.30±2.64)mm和(9.50±2.72)mm、(4.50±1.98)mm和(4.60±1.95)mm、(2.02±0.91) mm和(2.18±0.96)mm、(2.06±1.04) mm和(2.26±1.20)mm、(3.74±1.73)mm和(3.82±1.84)mm.下颌管自牙槽窝下方走行,其舌侧骨板较厚.在标本及影像上的下颌管上壁至第1前磨牙、第2前磨牙、第1磨牙、第2磨牙、第3磨牙牙根的距离左、右分别为(8.36 +2.34) mm和(8.42±2.42)mm、(7.36±2.21)mm和(7.52±2.18)mm、(3.22±1.40)mm和(3.36±1.85)mm、(2.96±1.54)mm和(2.84±1.55)mm、(3.64±1.72) mm和(3.88±1.76)mm.结论:上颌窦、下颌管至牙根的距离测量,对选择适宜长度的牙种植体,避免牙种植体误入上颌窦和损伤下牙槽神经等具有重要意义.     

上颌窦与上颌后牙的位置关系及临床意义

目的为上颌牙种植术等临床口腔外科提供解剖学基础。方法选取新鲜上颌骨标本10例20侧、成人全牙上颌骨标本18例36侧和20名全牙志愿者,分别暴露出上颌窦粘膜、上颌窦与上颌后牙牙根和CT连续扫描后进行三维重建。观察上颌窦的形态及其下壁的骨性和粘膜结构,用游标卡尺和CT三维重建工作站分别测量上颌后牙牙根至上颌窦下壁的距离。结果上颌窦呈三边形或四边形的锥体形腔隙,其下壁常有凸起的骨隔和粘膜隔。上颌磨牙的近中颊根至上颌窦的距离均较舌根、远中颊根近,由近及远依次为近中颊根、舌根和远中颊根。在标本及影像上的第1前磨牙、第2前磨牙、第1磨牙、第2磨牙、第3磨牙牙根至上颌窦下壁的距离分别为(9.30±2.64)mm和(9.50±2.72)mm、(4.50±1.98)mm和(4.60±1.95)mm、(2.02±0.91)mm和(2.18±0.96)mm、(2.06±1.04)mm和(2.26±1.20)mm、(3.74±1.73)mm和(3.82±1.84)mm。结论(1)上颌后牙至上颌窦的距离以第1磨牙最近,由近及远依次为第1磨牙、第2磨牙、第3磨牙、第2前磨牙和第1前磨牙。(2)对选择适宜长度的牙种植体,避免牙种植体误入上颌窦等具有重要意义。     

Bone formation as a potential motive force of tooth eruption in the rat molar

The objectives of this anatomical study were to (1) determine if significant bone growth occurs in the base of the alveolar bony crypt of the first mandibular molar to move the tooth through the eruption pathway; (2) determine if the osteogenesis in the crypt correlates with the published chronological gene expression of bone morphogenetic protein-2 (BMP-2) in the dental follicle; and (3) determine chronologically and regionally the crypt bone activity. To accomplish this, the alveolar bony crypts of rat mandibular molars from postnatal days 3 to 18 were processed and examined by scanning electron microscopy (SEM). In addition, mandibles and teeth of ages 12-18 were prepared for light microscopy. SEM demonstrated that bone formation occurs in the basal (apical) portion of the alveolar bony crypt at day 3, whereas bone resorption concurrently is ongoing in the coronal region of the crypt. By day 9, the crypt is beginning to be reduced in depth as the result of basal bone formation, and by day 14, the base of the crypt immediately under the tooth is almost completely filled with bone to form the interradicular septum. At day 18, the tooth erupts as bone formation likely elevates the molar. Bone growth in the basal area of the crypt correlates with a previous study showing enhanced BMP-2 expression in the dental follicle. Thus, SEM indicates that the motive force of tooth eruption likely is bone formation at the base of the alveolar crypt and this osteogenesis may relate to BMP-2 production in the dental follicle.     

下颌管的应用解剖及临床意义

目的:为下颌牙种植术等临床口腔外科提供解剖学基础.方法:选取下颌骨标本10例、新鲜下颌骨标本10例和成人全牙下颌骨标本20例,分别暴露出下颌管截面、下牙槽神经血管束和下颌管与下颌后牙牙根.观察下颌管的形态、走行和下牙槽神经、血管的排列关系,用游标卡尺测量下颌后牙牙根尖至下颌管上壁的距离.结果:下颌管呈椭圆形,自磨牙牙根尖舌侧和前磨牙牙根尖颊侧的下方走行;下颌管内的下牙槽血管位于下牙槽神经上方.下颌后牙牙根至下颌管的距离以第2磨牙最近,由近及远依次为第2磨牙、第1磨牙、第3磨牙、第2前磨牙和第1前磨牙;下颌磨牙的远中根至下颌管的距离均较近中根近.第1前磨牙、第2前磨牙、第1磨牙、第2磨牙、第3磨牙牙根至下颌管上壁的最短距离分别为(8.19±0.87) mm(左)和(8.29±0.88) mm(右)、(7.38±0.85) mm、(3.30±0.66) mm、(2.98±0.77) mm(左)和(2.92±0.75) mm(右)、(3.82±0.63) mm(左)和(3.86±0.64) mm(右).结论:下颌管的应用解剖对选择适宜长度的牙种植体,避免牙种植体损伤下牙槽神经等具有重要意义.     

Mesencephalic trigeminal nucleus neurons with collaterals to both the masseter and the inferior alveolar nerves. A fluorescent double-labeling study in the rat.

After fluorescent tracers were applied to the inferior alveolar nerve and the masseter nerve on the same side of the rat, double-labeled neurons were observed in the caudal part of the mesencephalic trigeminal nucleus (Vme), reflecting simultaneous innervation of both the periodontal ligaments and masseter muscle spindles by collaterals of peripheral processes of single Vme neurons.     

The course, relations and distribution of the inferior alveolar nerve and its branches in the cat

The course, relations and distribution of the inferior alveolar nerve and its branches in the cat are described. The nerves have been studied by dissection, histologically and by using electrophysiological techniques. Dissection revealed a basic pattern on which some individual variation was superimposed. The inferior alveolar nerve has three branches supplying the alveolar process (alveolar branches), one branch supplying the canine and incisor region (canine/incisor branch) and four mental branches (posterior, main and 2 anterior). Fibres supplying the teeth were found in all except the mental branches. Pulpal, periodontal and buccal gingival margin fibres from an individual tooth generally travelled together, but often in more than one branch. Branched axons supplying both tooth pulp and an area of mental skin were found. The axons branched at the point of separation of the appropriate mental nerve from the main trunk. A cutaneous midline overlap of 1-2 mm was found, but there was no transmedian innervation of tooth pulps.     

Menopause-related oral alveolar bone resorption: a review of relatively unexplored consequences of estrogen deficiency.

OBJECTIVE: The alveolar processes of the maxilla and mandible provide the bony framework for tooth support. Osteoporotic changes of these bones may directly affect tooth stability and retention. This report reviews studies that have evaluated the relationship between systemic osteoporosis and oral alveolar bone mass as well as the effect of estrogen use on oral alveolar bone and tooth retention. DESIGN: Ten years (1989-1998) literature review. RESULTS: Studies reviewed demonstrate a positive correlation between systemic bone mass and systemic osteoporosis to oral bone resorption. Estrogen replacement therapy affects oral bone in a manner similar to the way it affects other sites. CONCLUSIONS: It is evident that postmenopausal estrogen users may retain more teeth after menopause. Sustained oral health and better tooth retention are potentially additional benefits for hormone replacement therapy users after menopause.     

固定桥基牙牙槽骨三侧吸收对基牙应力分布的影响

目的:研究双端固定桥基牙牙槽骨三侧吸收对基牙应力分布的影响。方法:采用螺旋CT扫描获取健康人下颌骨、牙齿及牙周支持组织的二维图像,通过图像合成软件建立三维数字模型,并应用三维有限元分析软件生成下颌后牙三单位固定桥的三维有限元分析模型。在相同垂直和水平载荷情况下,分析基牙牙槽骨三侧吸收时固定桥各基牙的应力分布。结果:当前磨牙端基牙牙槽骨三侧吸收达15%、磨牙端基牙牙槽骨无吸收时,前磨牙端基牙开始出现应力集中;当磨牙端基牙牙槽骨三侧吸收达25%、前磨牙端基牙牙槽骨无吸收时,磨牙端基牙开始出现应力集中。结论:下颌后牙固定桥基牙牙槽骨吸收形式的不同直接影响着其应力分布,基牙牙槽骨三侧吸收的程度对基牙应力分布的影响强于单侧和多侧吸收时。     

Transverse cervical nerve: Implications for dental anesthesia

The inferior alveolar nerve block (IANB) has the highest failure incidence of any dental anesthetic technique. Many authors have outlined potential reasons for these failures in permanent lower molars, including accessory innervations from the mylohyoid and mental foramen. However, the potential accessory innervation of posterior mandibular teeth from the transverse cervical nerve (TCN), a branch of ventral rami from the C2–C3 spinal nerves from the cervical plexus (CP), has been difficult to assess as a result of the small size and thickness of the mandibular accessory foramina and nerve branches, as well as due to the dissection technique performed. The goal of this study was to identify and trace the CP branches from fresh human cadaver tissue samples using the Sihler's technique. Two fresh human cadaver samples were used. Samples were fixed in neutralized formalin, macerated in potassium hydroxide, decalcified in acetic acid, stained in Ehrlich's hematoxylin, destained in acetic acid, and cleared in glycerin. Both specimens skin was dissected. The Sihler's technique delineated all nerves three dimensionally and helped to disclose structures of small size and thickness. The TCN from the CP, stained in blue, innervated the posterior mandible in one of the two samples. These results confirmed that the CP may supply accessory innervation to the inferior border of the posterior mandible through the TCN. These findings illustrate variations of anatomy that may account for IANB failures in posterior mandibular teeth and allows for clinical decisions for implementing supplemental anesthetic techniques. Clin. Anat. 26:688–692, 2013. © 2013 Wiley Periodicals, Inc.