Improvement of a four-implant retained bridge for totally edentulous patients

摘要

Several techniques for the treatment of edentulous patients have been developed during the last 10 years. The technique proposed by Malo et al. (2003, 2005), called AU-on-4, is a four-implant retained bridge: its advantages are that it is less expensive and less invasive than global (8-10 implants) rehabilitation treatments. Moreover, this technique can be applied when bone is resorbed in the molar region and when implants cannot be placed because bone height is not sufficient: the four implants are located anterior to the mental foramen and support a fixed complete arch superstructure, with two anterior implants placed in the right and left lateral incisor areas and two additional posterior implants inclined by about 40° to the occlusal plane. Nevertheless, several cases of early fractures have been reported in the literature (Agliardi et al. 2010); recent numerical analyses have shown that the current design of the prosthesis is not optimal concerning the capacity of all metallic parts to support loads (Bonnet et al. 2009), and the use of inclined implants is thought to affect stress distribution in the bone, which may cause bone resorption and loss of osseointe-gration (Sasaki et al. 2008). The study presented in this paper is the first step of a global research programme, for which the aim was to improve the mechanical behaviour of the maxilla-prosthesis structure, according to the patient-specific data (bone density and geometry, maximal occlusal forces). This will be carriedout through an optimisation of the design and materials of the prosthesis. To attain this objective, a comprehensive study of the mechanical stimuli induced in the peri-implant bone should be achieved: those stimuli must lie within physiological limits to prevent the loosening of the implants and subsequently of the prosthesis.