The bone stiffness affects the stability of immediately loaded implant

Objectives: The objective of this study was to evaluate the effect of various bone stiffness on the initial stability of the immediately loaded dental implant using three evaluation indexes included peak insertion torque value (ITV), implant stability quotient (ISQ), and Periotest values (PTV). Methods: Five artificial Sawbones models (Pacific Research Laboratories Inc., WA, USA) with different elastic modulus, including four specimens for presenting the normal trabecular bone structure and one for the osteoporosis, were used to evaluate the implant stability. The titanium implants (3i Implant Innovations, FL, USA) were inserted into each specimen, and the ITV, ISQ and PTV were measured from the torque meter, Osstell resonance frequency analyzer and Periotest electronic device. In addition, the bone-implant contact percent (BIC%) of each specimen were calculated based on the images of micro CT. Results: In general, the data of ITV, PTV, and ISQ were raised by increasing the elastic modulus of the Sawbones models. The ISQ for all specimens were higher than 60 except for the osteoporotic bone specimen. Moreover, the ITV and PTV data of the osteoporotic specimen showed more unstable than the normal trabecular bone group. The coefficients of determination between the elastic modulus of specimen and ITV, ISQ, and PTV are 0.94, 0.52, and 0.48 respectively. Furthermore, the BIC% value was higher for the specimen with larger elastic modulus. Conclusions: The experimental results show that the data of ITV is more sensitive in terms of revealing biomechanical properties of bone as compared with ISQ and PTV. However, the resonance frequency and Periotest measurements could provide a useful advantage for long-term follow-up. The results also indicated that the implant stability was greatly affected by the interfacial condition between the implant and host bone, such as the bone-implant contact percentage.