Implications of Implant Framework Misfit: A Systematic Review of Biomechanical Sequelae

Purpose: The objective of this study was to review all biomechanical investigations that have evaluated the implications of implant framework misfit with fixed prostheses. Materials and Methods: A detailed electronic search was conducted of PubMed (MEDLINE), Google Scholar, and Cochrane Library with the aid of Boolean operators to combine relevant key words. The search was confined to articles published in English through April 2013. The literature search was enlarged by manual searches of the peer-reviewed literature and the reference lists of the selected articles. Results: A total of 633 articles were retrieved from the initial search; however, only 28 articles met the determined inclusion criteria of the review. According to the study design, the selected articles were classified into two categories: laboratory studies (finite element analyses, actual model analyses, and screw stability analyses) and animal studies. The studies evaluated the effects of alterations in the magnitude and configuration of misfit, framework rigidity, type of retaining screws, and implant loading time. In addition to a lack of clear criteria of what constitutes an accurate implant framework fit, the biomechanical implications of framework misfit are unclear. Conclusions: Although implant framework misfit alters the biomechanical situation, negative biomechanical sequelae could not be confirmed from the included studies. Biologically, bone resorption cannot develop as a result of framework misfit. From a mechanical perspective, the framework stresses and screw stresses and instability increase with misfit, but the clinical significance of this remains unclear. Keywords: biologic complications, framework fit, mechanical complications, stress, strain