Análise de tensões pelo método de elementos finitos em próteses dento-implanto-suportadas: Influência da extensão da prótese e diâmetro do implante

Abstract

The impossibility of using implants as independent supports of the prosthesis in the patients treatment partially edentulous, mainly in cases of anatomical limitations, makes possible for the implants to be added to the natural teeth, characterizing the tooth-implant-supported prosthesis. The conditions for it to be a viable prosthetic option, justifies knowing its mechanical behavior in order to realize its indication and the cares that should be associated in this prosthesis. The objective of this study was to evaluate the distribution of stress in the support and prosthetic structures in the tooth-implant-supported fixed prosthesis and implant-supported by the finite elements method. A laboratorial model of tooth-implanted-supported prosthesis of four elements, considering the abutments a first inferior premolar and the implant of 3.75 x 10.0 mm inserted in the area of the second inferior molar, was used to the making of eight twodimensional mathematical models of both types of prostheses. Four models were made of tooth-implant-supported (PIDS) prostheses and four of implantsupported (PIS) prostheses, having as variations the number of pontics (prosthesis of three and four elements) and the distal implant diameter (3.75 x 10.0 mm or 5.0 x 10.0 mm). All models were submitted to the same type of occlusal load. The occlusal load was applied on the first third of the slopes mesial and distal of each peak, in each prosthetic element, simulating the occlusal physiologic load. The value of this applied load was 5% of the physiologic masticatory load value. The images plotted were qualitatively analyzed. For the quantitative analysis, points on the implant, cortical bone and structures of the prosthesis from all models were selected. Both analyses were made in Ansys 9.0 software, using the von Mises criterion for the tension distribution analysis. The largest stress concentrations occurred in the implant and in the bone cortical interface with neck of the implant, in all the eight models. In both type of fixed prosthesis, the four elements ones had a lot of concentrated tension among the pontics and in the mesial region of the implant s body, positioned in the second molar region. The fixed prosthesis with the implant of larger diameter (5.0 x 10.0 mm) and smaller extension (fixed prosthesis of three elements), presented more favorable results, considering the stress better distributed by the structures of the prosthesis and the ones of support. Due to the limitations of this study, it can be concluded that the prosthetic extension and the diameter of the implant influenced the distributions of the tensions in both types of prostheses. Besides, the PDIS and PIS that had the same extension (same pontics number), and the distal abutment with the same dimensions, compared by qualitative and quantitative analysis, presented similar mechanical behavior.