抄録
The placement of dental implants in the molar region of the maxilla is often difficult due to the presence of the maxillary sinus. Therefore, the placement of implants in the pillar of bone consisting of the maxillary tuberosity, pterygoid process of the sphenoid bone, and pyramidal process of the palatine bone, which is located at the posterior part of the maxilla, is attempted for maintenance and stabilization of prostheses. In this study, We morphometricaly examined the internal structure of the pillar of bone comparing its changes after missing teeth.
The posterior part of the maxilla, including pterygoid process of the sphenoid bone and pyramidal process of the palatine bone were embedded in polyester resin. Then serial transverse sections with 500 μm thickness were prepared, and soft X-ray photographs were taken. The ante-posterior length, bucco-lingual length and trabecular structure were measured at 3 horizontal planes of the pillar of bone (upper, middle and lower planes) using an image analyzer. Three-dimensional images of the pillar of bone were reconstructed from the contour in the soft X-ray images, and the height, inclination angles and volume of the pillar of bone were measured.
In dentulous specimens, the ante-posterior length was larger at the lower than the other planes of the pillar of bone. At the upper planes, the length under 4 mm was appeared in about 70% of the specimens. The bucco-lingual length was the greatest at the middle planes. The width of trabecular bones was greater at the lower than the other planes. The pillar of bone in the posterior part of the maxilla was inclined ante-posteriorly at an angle of 73.0 ±3.3 degrees from the anterior to posterior direction in relation to the Frankfurt horizontal plane and bucco-lingually at 18.9±1.9 degrees to the medial direction in relation to the sagittal plane.
In edentulous specimens, the ante-posterior length was greater at all planes of measurement than in dentulous specimens, but the length less than 4 mm was observed in about 40% of the specimens at the upper planes. Both the number and width of trabecular bones were smaller at all planes compared with dentulous specimens. The pillar of bone was inclined ante-posteriorly at 61.8±5.5 degrees in relation to the Frankfurt horizontal plane and bucco-lingually at 15.4±1.9 degrees in relation to the sagittal plane. The volume of the pillar of bone was greater in comparison with dentulous specimens.
