Evaluation of Branemark protocol prostheses bars obtained by conventional casting, rapid prototyping and milling using CAD-CAM technology

Abstract

Initially reported in 1969, the rehabilitation of total edentulous patients by Brånemark protocol prostheses has been shown highly viable and with high success rate. In addition, changes in the number and positioning of the implants in initial protocol have been carried out, enabling them to remain effective rehabilitation even when supported by a lower number of implants. Despite this, the description of mechanical failures associated with these prostheses is recurrent, among them, fracture and loosening of screws and prosthetic components or even a fracture of the bars. The loosening of the screws has been associated with the misfit between implant/abutment and abutment/prosthesis interfaces, which invariably occur during the clinical and laboratory procedures of rehabilitation treatment. This condition becomes even more disturbing in most extensive prostheses, because they are more susceptible to higher distortion than the unitary prostheses. The fracture of the bars may occur due to incorrect dimension of their contour, as well as when the lever arm of the cantilever extends excessively, besides laboratorial failures. In order to reduce these misfits and improve the standardization of infrastructures, the implant supported prostheses made by CAD-CAM technology has been shown excellent clinical performance in short-term. However, there are little scientific evidences that prove their long-term success, besides the high cost attributed to this technique. Therefore, the objective of this study is to verify the fracture resistance and the effects on marginal adaptation and loosening of the bars in Brånemark protocol prostheses under thermomechanical cycling. For this, two groups will be made, the first with five parallel implants between mentual foramen and the second using the concepts of "All-on-four" technique, which will be compared the CAD-CAM technology by rapid prototyping to the milled system and the conventional casting method. The stress distribution in the different groups will be performed by digital image correlation (AU)