Stresses were generated after screw tightening of the frameworks, increasing when a load was applied and when a vertical gap was present. Angled implants resulted in oblique stress patterns, which were not transferred with homogeneity to the polymeric model.

bone-resorption may occur. The loading threshold tolerated by the bone is not well-known and the failure of osseointegration can be caused by bone resorption as a result of unfavorable stress concentrations 11 . In accordance to Kohn 16 (1992), tension distribution is one of the important factors related to implant success; the tensions should be transferred to the adjacent bone, preferentially in an orientation and magnitude that keep the tissues viability near a physiologic state. * Graduate Students; **Assistant Professors -Department of Prosthodontics, School of Dentistry, University of São Paulo. ABSTRACT:The longevity of implant-supported prosthetic rehabilitation depends largely on how the masticatory forces are transferred to the implants and surrounding bone. Anatomical conditions, bone morphology and aesthetics usually dictate implant placement in less than ideal positions for prosthetic rehabilitation and sometimes it is possible to find them with different inclinations. The purpose of this paper was to compare, through photoelastic analysis, the stress distribution in a fixed prosthesis with 3 parallel implants, to the stress distribution in the same prosthesis in the existence of an angled central implant. Two photoelastic resin models were made and a polariscope was used in the visualization of isochromatic fringes formed in the models when axial loads of 2 kg, 5 kg and 10 kg were applied to a unique central point of the prosthesis. The presence of inducted tensions (preloads) was observed in the models after applying torque to the retention screws. Preloads were intensified with the incidence of occlusal forces. In the parallel implants, the force dissipation followed the long axis. The angled implant had a smaller quantity of fringes and the stresses were located mostly around the apical region of the lateral implants. DESCRIPTORS: Dental implantation, endosseous; Prosthesis implantation. RESUMO:A longevidade das reabilitações orais implanto-suportadas depende, em grande parte, de como as forças mastigatórias são transferidas aos implantes e ao osso que os circunda. Condições anatômicas, morfologia óssea e estética muitas vezes ditam a colocação de implantes em posições que não são ideais para a reabilitação protética, e podemos encontrá-los com diferentes inclinações. A proposta deste trabalho foi comparar, através de análise fotoelástica, a dissipação de tensões em uma prótese fixa com 3 implantes paralelos entre si com a dissipação de tensões na mesma prótese na existência do implante central angulado. Foram confeccionados dois modelos de resina fotoelástica. Utilizou-se um polariscópio para visualização das franjas isocromáticas que se formaram nos modelos fotoelásticos quando cargas axiais de 2 kg, 5 kg e 10 kg foram aplicadas em um mesmo ponto central da prótese. Verificou-se a indução de tensões (pré-tensões) nos modelos após o apertamento dos parafusos de retenção das próteses. As pré-tensões foram agravadas com a incidência de forças oclusais. Nos implantes paralelos, a dissipação de for...

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