A Mathematical Model for Biomechanical Evaluation of Micro-motion in Dental Prosthetics using Vibroacoustic RFA

To monitor longitudinally the development of implant stability of SLA Straumann tissue-level implants using resonance frequency analysis (RFA) and to determine the influence of instrument positioning, bone structure and implant length on the assessment of RFA. Thirty-two healthy adult patients received either 8 mm, v4.1 mm Straumann Standard Plus tissue-level implants (n=16: Group A) or 10 mm, v4.1 mm Straumann Standard Plus tissue-level implants (n=16: Group B). During healing, RFA was performed on Weeks 0,1, 2, 3, 4, 5, 6, 8 and 12. The implants were restored after 10 weeks (impression taking) and 12 weeks. In addition, probing depth, presence of plaque and bleeding on probing were assessed. Implant stability quotient (ISQ) values of Groups A and B were compared using unpaired t-tests and longitudinally applying paired t-tests between Week 0 and the subsequent time points. Positioning of the Osstell mentor device did not affect the ISQ values. Generally, ISQ values increased continuously during healing from a mean of 65.1 (SD 16.97) to 74.7 (SD 5.17) (significantly from Week 0 to Weeks 6, 8 and 12). Lower bone density (Type III or IV) resulted in significantly lower ISQ values up to Week 8. Implant length affected the increase in ISQ values over time. While no significant increase was observed with 10 mm implants, ISQ values of 8 mm implants increased significantly from Week 0 to Weeks 6, 8 and 12. Using Osstell mentor, ISQ values are reproducible irrespective of instrument positioning. ISQ values are affected by the bone structure and implant length. Hence, no predictive values can be attributed to implant stability.

In recent decades, cementless implants have been widely used in clinical practice to replace missing organs, to replace damaged or missing bone tissue or to restore joint functionality. However, there remain risks of failure which may have dramatic consequences. The success of an implant depends on its stability, which is determined by the biomechanical properties of the bone–implant interface (BII). The aim of this review article is to provide more insight on the current state of the art concerning the evolution of the biomechanical properties of the BII as a function of the implant's environment. The main characteristics of the BII and the determinants of implant stability are first introduced. Then, the different mechanical methods that have been employed to derive the macroscopic properties of the BII will be described. The experimental multi-modality approaches used to determine the microscopic biomechanical properties of periprosthetic newly formed bone tissue are also reviewed. Eventually, the influence of the implant's properties, in terms of both surface properties and biomaterials, is investigated. A better understanding of the phenomena occurring at the BII will lead to (i) medical devices that help surgeons to determine an implant's stability and (ii) an improvement in the quality of implants.