Determination of safe zone of the mandible for implant and bone harvesting (using CBCT) of mandible in a group of Sri Lankan subjects

Bone grafting procedures are required for patients with insufficient bone volumes for dental implants. The incisive mandibular nerve is more prone to iatrogenic injury during bone graft harvesting. This study aimed at examining the relative position of the mandibular canal (MC), gender Variation and to observe a safe zone for the implant and bone harvesting. Cone beam computed tomography (CBCT) scans of 200 patients (males 56 %) with age ranging from 16 to 70 years (mean age, 34.1 ± 14.5 years) were selected from the database of the Dental Imaging Unit of the National Dental Teaching Hospital of Sri Lanka. The MC length, mental foramen (MF) diameter, location and the safe zone distance for bone graft harvesting were recorded for each hemi-mandible. The mean length of left and right MC of males were 6.99 ± 0.21 cm and 6.98 ± 0.22 cm, respectively while for females the mean length was equal for both sides (6.88 cm). The mean MF horizontal length of males was 0.32 ± 0.03 cm on the left and right sides while for females it was 0.31 ± 0.03 cm on either side. The vertical length of MF was 0.25 cm for both left and right (for both genders). The mean safe zone distance of the left and right mandibles for males were 0.27 ± 0.07 cm and 0.30 ± 0.06 cm, respectively while for females the values were 0.26 ± 0.06 cm and 0.27 ± 0.06 cm, respectively. The most frequent position of the MF among males was below the second premolar on each side of the mandible. The MF of females were frequently located below and between the first and second premolar on each side of the mandible. MC and other measurements showed a high sexual dimorphism. Therefore, gender variation in MC length, diameter and location of MF should be considered during surgical interventions such as implant and bone harvesting.