Effect of bone quality, implant design, and surgical technique on primary implant stability

Objective: Adaptation of the surgical protocol and implant selection depending on bone quality has been advocated. It was the goal of this in-vitro study to quantify the effect of implant geometry and implant site preparation on micromotion at the implant-bone interface. Method and Materials: A parametric study was conducted with implants differing in shape, length, and diameter placed in polyurethane foam material differing in density and structure following various methods of implant site preparation. Measurement parameters included bone quality in the cervical and apical area, insertion torque, implant stability, and implant displacement under load application. Statistical analysis was based on ANOVA and Pearson's product moment correlation with the level of significance set at α = .05. Results: Compressive testing of bone allowed different bone densities (P = .000) to be distinguished. Minor changes in bone density caused by implant site preparation with osteotomes could not be detected (P > .05). Undersized drilling (P = .001), the presence of a cortical layer (P = .000), and the use of osteotomes (P = .000) led to a significant increase in implant insertion torque. Thread cutting reduced insertion torque (P = .000) whereas the use of short (P = 1.000) and wide diameter (P = .235) implants had no effect. Implant stability measurements did not always allow for differentiation of implants varying in shape and placed with different protocols. Increasing bone density led to a general reduction in maximum implant displacement under loading. Significant correlations between all parameters were found, with the exception of residual implant displacement, which only correlated with compressive bone testing in the cortical (P = .0341) and trabecular (P = .0359) areas. Conclusion: Compressive testing of bone seems to allow the prediction of implant performance. Keywords: bone quality, compressive testing, implant-bone interface, micromotion, primary stability