Biomechanics of Cantilevered Implant-Supported Prosthesis (Biomechanics in Implant Prosthodontics)

The peculiar characteristic of an implant-supported prosthesis is the fact that its fixation is given by the connection of an alloplastic material (the implant) to a living tissue (the bone). This fixation has been defined as rigid and clinically asymptomatic and must be maintained during functional loading (Albrektsson & Zarb, 1993). Under load, bone tissue will undergo a remodeling process, which ultimately influences the long-term function of a dental implant system (Meijer et al., 1993). Bone remodelling is a complex process that involves a sequence of chemicaland mechanical-mediated biologic events known as mechanotransduction (Duncan & Turner, 1995). Because the occlusal load will be transferred to the implants and subsequently to the bone, it is believed that the biomechanics of the implant-supported prosthesis play an important role in the longevity of the bone around dental implants (Skalak, 1985). It is commonly found in the literature that, for cantilevered implant supported mandibular prosthesis, stresses tend to be concentrated at the cortical bone on the disto-lingual aspect of the implant closest to the load (Meijer et al., 1993; Murphy et al., 1995; Rubo & Souza, 2008; Sertgoz & Guvener, 1996; Weinberg & Kruger, 1995). Many researchers have focused on the steps of force transfer to gain insight into the biomechanical effect of force directions, force magnitudes, prosthesis type, prosthesis material, implant design, number and distribution of supporting implants, bone density, and the mechanical properties of the bone-implant interface (Sahin & Cehreli, 2002). The resultant stresses should be kept below the failure stress limit of the materials involved (Frost, 1994; Skalak, 1985; Wiskott & Belser, 1999). Failures in dental implant prostheses have been correlated with biomechanical complications. Overloading factors may negatively influence implant longevity (Kim et al., 2005). According to Isidor (2006), although it has been stated that occlusal forces may be associated with the loss of oral implants, a causative relationship has never been convincingly demonstrated. The related mechanisms of these displacements are still not completely understood and studies about the influences of the several biomechanical factors are inconclusive (Rangert et al., 1989). Implant failure caused by overload has been classified as a dogma and as such should be abandoned (Carlsson, 2009). There are contradictory studies regarding bone loss in overload conditions. From those studies it can be inferred that