Although this study is different from the previous studies in that the thickness of the cortical bone and bone density were determined from the voxel values calculated by CBCT, a significantly positive correlation of the thickness of the cortical bone and the voxel values with ITVs and ISQ values was confirmed as in the previous studies. Furthermore, the multiple regression analysis with the ITVs and the ISQ values as the dependent variables showed that the thickness of the cortical bone as well as the voxel values had a positive influence.

Based on these results, it was revealed that the thickness of the cortical bone obtained from CBCT had a correlation with the ITVs and the ISQ values which are the indexes of the primary stability of the implant. It was also revealed that the voxel values correlated with ITVs and ISQ values. It is desirable to be able to infer the primary stability at the time of implant placement not only from the thickness of the cortical bone but also from the voxel values, if the cortical bone cannot be observed on the CT images of the extraction socket immediately after or at a certain period of time after the tooth extraction (until the maturation of the bone). Conversely, there was no statistical correlation between the voxel values and ISQ values among 5-mm-diameter, 12-mm-length implants. These ISQ values were high enough regardless of bone densities, and this caused that the correlation did not confirm between voxel values and ISQ values.

In addition, these results were confirmed by using mechanically polished surface implants. Therefore, it is thought that primary stability becomes more stable by using rough-surface implants.