To evaluate implant primary stability, the correlation between implant insertion torque and implant stability quotient (ISQ) was measured using human cadaver mandible. The implant was inserted at 10, 20, 30, 40, and 50 Ncm into the bilateral mandibular canines to the molar region with sufficient buccolingual bone height (n＝5). ISQ showed a significant correlation with insertion torque when the buccolingual bone height was maintained (condition Full, p＝0.0004), whereas all individual cadaver mandibles showed no significant correlation with ISQ. After the buccal bone wall was removed (condition Hemi), ISQ still showed a significant correlation with insertion torque (p＝0.0023) when all cadaver data were collected. Similarly, individual cadaver ISQ showed no significant correlation (p＞0.05). After the buccolingual bone wall was removed (condition Apex), the correlation between insertion torque and ISQ was lost (p＝0.9683), and also no correlation was observed for each individual cadaver. There was no significant difference in ISQ between values at any insertion torque under the Full and Hemi conditions (p＞0.05). However, condition Apex showed significantly lower ISQ value than conditions Full and Hemi at all insertion torques (p＜0.05).
When an implant is inserted in the presence of buccolingual bone, a higher torque results in a higher ISQ as a general tendency. A similar phenomenon was observed even when buccal bone was lost, and the ISQ was higher when inserted with a higher insertion torque. From these results, it is considered that it is difficult to use ISQ to detect buccal bone wall resorption, and it was found that ISQ tends to be maintained until the buccolingual bone wall is lost.