The aims of this human cadaver study were to analyze the primary stability of dental implants inserted by using different methods of preparation and to explore correlations among the bone density, peak insertion torque and resonance frequency analysis values.

Forty-eight implants were placed into six human cadaver mandibles. The bone density of each implant recipient site was preoperatively measured by using computerized tomography (CT) in Hounsfield Units (HU). Three test groups were created according to the final drill size. The diameters of the final twist drills were 3 mm, 3.4 mm, and 3.8 mm in group T1, group T2, and group T3, respectively. The peak insertion torque and resonance frequency analysis values were recorded.

The mean bone density, insertion torque, and RFA values were 285 ± 90 HU, 42.8 ± 5 Ncm, and 74 ± 6 ISQ for all 48 implants, respectively. Statistically significant correlations were noted between bone density and insertion torque values (P < 0.05), bone density and RFA values (P < 0.01), and insertion torque and RFA values (P < 0.001). When considering the three test groups, the mean insertion torque, and RFA values were 47.1 ± 3 Ncm, and 83.1 ± 6 ISQ in Group T1, and 43.4 ± 5 Ncm and 73.4 ± 6 ISQ in Group T2, and 37.9 ± 6 Ncm, and 65.3 ± 5 ISQ in Group T3.

The results of this study suggest that undersized implant site preparations may be helpful in enhancing primary implant stability and that there are significant correlations among bone density, maximum insertion torque, and RFA values.