2004 Volume 44 Issue 1 Pages 24-30
The exact location of the mandibular canal and mental foramen should be identified before endosseous implant surgery in the mandible. In this study we used reformatted CT images to assess and classify mental foramina into several patterns based on the morphology, and estimated the length of the anterior loop of the canal. [Material & Methods] A total of 137 sites in 69 patients were examined in this study. The patients consisted of 33 males and 36 females who were referred to our Radiology Clinic for presurgical CT examination of the mandible. After the CT, reformatted images both perpendicular and parallel to the dental arch were created by the multiplanar software supplied with the CT apparatus (GE-Yokogawa, Tokyo). The vertical location of the mental foramen was determined by the distance from the mental foramen to the alveolar ridge, and the height of the mandible was also measured on MPR-CT images. Because the presence of teeth may affect the mandibular morphology around the mental foramen, the sites examined were divided into the following 3 groups: 1) those with both premolar (s) and molar (s), 2) those with premolar (s) but without molar (s), and 3) those without either premolars or molars. Also, the morphology of the mental foramen was classified by shape into four types on MPR-CT images. Then, a total of 80 canals of 40 patients were examined. The length of the anterior loop was calculated from measurements in the MPR-CT images both perpendicular and parallel to the dental arch, and the length of the anterior loop was measured on panoramic images. [Results] Regarding the distance from the alveolar ridge to the mental foramen in the mental foramen area, the male's were larger than the female's. Moreover, when a residual tooth was present in a molar position, this value increased. In the mental foramen areas, the path of the mandibular canal varied, and it was confirmed that the length of the anterior loop also showed individual differences. These findings showed that the both the path and morphology of the mandibular canal and the mental foramen vary widely. [Conclusion] These findings may assist surgeons in planning the surgical approach for placement of the implants, reducing the risk to the inferior alveolar nerve and vessels, especially in the anterior region.
