In maxillary molar region implant therapy, support is sometimes obtained from trabecular bone comprising the maxillary tuberosity, pterygoid process of the sphenoid bone, and pyramidal process of the palatine bone. Great care is necessary in such cases due to the presence of the greater palatine canal, which forms a passageway for the greater palatine artery, vein, and nerve. However, clinical anatomical reports envisioning embedding of pterygomaxillary implants in this trabecular bone region have been limited in number. In this study, the 3-D morphology of the greater palatine canal region, including the maxillary tuberosity region and points requiring particular care in pterygomaxillary implantation, were therefore investigated. Micro-CT was used to image 20 dentulous jaws (40 sides) harvested from the dry skulls of Japanese individuals with a mean age of 28.2 years at time of death. The skulls were obtained from the Jikei University School of Medicine cadaver repository. Three-dimensional reconstruction of the trabecular bone region, including the greater palatine canal, was performed using software for 3-D measurement of trabecular bone structure. Trabecular bone region morphometry was performed with the hamular notch-incisive papilla (HIP) plane as the reference plane. The results showed a truncated-cone structure with the greater palatine foramen as the base extending to the pterygopalatine fossa. This indicates the need for care with respect to proximity of the dental implant body to the greater palatine canal and the risk of perforation if it is embedded in the maxillary tuberosity region at an inclination of 60° toward the lingual side. Moreover, caution must be exercised to avoid possible damage to the medial wall of the maxillary sinus if the inclination of the embedded dental implant body is almost perpendicular to the HIP plane.

Although the risk of injuring the lingual nerve in the mandibular molar area during dental treatment is high, it can be repaired by nerve grafting. However, from the perspective of clinical dentistry, the pathway and histomorphometric characteristics of this nerve remain to be documented in detail. The purpose of the present study was to morphologically elucidate the pathway of the lingual nerve to clarify its significance in a clinical setting. A histomorphometric analysis was also performed in consideration of nerve grafting. The vertical distance between the occlusal plane and the superior margin of the lingual nerve showed a gradual decrease from the premolar toward the distal molar area. This suggests that the risk of injuring the lingual nerve increases gradually toward the distal area. The average total fascicular area of the lingual nerve was 1.90 mm 2 , which was larger than that of the sural nerve. It is the first-choice donor nerve for grafting. Therefore, even though the total fascicular area of the donor nerve is a little smaller than that of the recipient nerve, nerve grafting should be successful.

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