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.

Summary: The mylohyoid nerve (MN) displays several branches in the posterior, intermediate, and anterior region of the mylohyoid muscle (MM) as it courses on the internal surface of the mandibular body. Branches in the intermediate region were found in 66% of the cases (272 out of 413 sides). In the submandibular triangle, one or two large branches of the MN communicated with the lingual nerve at submandibular triangle and submental triangle in 1.45% of the cases (6 out of 413 sides). These distributions of nerve supply are an important in the operations of radical neck dissection on the submandibular triangle.The mandibular nerve divides into two branches, the lingual nerve (LN) and the inferior alveolar nerve (IAN), at the mandibular notch. The IAN descends to the mandibular nerve branches on the inner mylohyoid muscle (MM). Mandibular nerve has anastomotic branches connecting to the lingual nerve (LN) after leaving laterally from the foramen ovale (Clemente, 1985). Chorda tympani join the LN in the deep region behind the lateral pterygoid muscle. The IAN is also branched into the mylohyoid nerve (MN) at the mandibular foramen. There are a few communications between the MN and the LN in the submental triangle. Kameda (1952) has reported the MN communicated with the LN in 46.3% (74 out of 160 sides) of the cases.The communication rate of the LN and the MN in Kameda reports (1952) is high in compared to that of our data, however, this reports is no detailed in course, supply, and any region in two nerves. Radical neck dissection needs the detailed information of nerve supply in the submandibular triangle (Beahrs, 1977;Swift, 1970;Feldman and Applebaum, 1977). Trail and Lubritz (1974) also indicated complete removal of tumors on the submandibular gland required radical excision of tissue around them, including neck dissection. Therefore we observed nerve supply on submandibular triangle and submental triangle in detail. Materials and MethodsWe examined the mylohyoid nerve branches under a binocular microscopy, 413 sides of 272 mandibles from adult Japanese cadavers (161 males and 111 females; 141 both sides, 60 right side only and 71 left side only) for passage and supply. We also observed the communications between the mylohyoid nerve (MN) and the lingual nerve (LN) in the submandibular triangle and submental triangle. Using forceps, we removed the entire mucous membrane, the connective tissues of the mylohyoid muscle (MM), parts of the ramus of the submental arteries, and veins at submandibular triangle and submental triangle. In each case, the communications between the MN and the LN and their distribution were analyzed and photographed. ResultsWe observed the course and the communications between the mylohyoid nerve (MN) and the lingual 45 * Correspondence to: Iwao Sato,

An abnormal cleidohyoid muscle, an excess anterior belly muscle of the digastric and a levator thyroid gland muscle are reported in the suprahyoid and infrahyoid musculature of Japanese male cadavers (Case A) 65 years and (Case B) 46 years old. The muscle weight, cross-sectional area of the transverse muscle section, number of muscle fibers per mm2 and the average size of the muscle fibers of these abnormal muscles were compared with simmilar parameters of normal suprahyoid and infrahyoid muscles.

Detailed observation of the structure of filiform papillae (FP) and microvasculature of those papillae in Japanese Azuma mole were described. In the anterior and medial regions, FP was cylinder in shape with two processes. In the posterior region, it had a long, sharp conical shape. The microvascular casts showed two types of hairpin-shaped capillary loops on three regions of the tongue. In the anterior and medial regions, the end of the capillary loops were shaped like a spoon. In contrast, in the posterior region, it was knot-like end of capillary loop. Since the shape of capillary loop was more complex in the anterior and medial regions than that in the posterior region, it was speculated that the spoon-like end of capillary loops of the FP in the anterior and medial regions supply nutrients to the filiform papillary cells and may be related to the movement of the tongue during mastication in Japanese Azuma mole.

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