RESUMO
To assess the clinical performance of restorative materials with respect to mechanical failure, the shape of the restoration, the strength and fatigue properties and the loading history are important. This study deals with the feasibility of a method to estimate the mechanical lifetime of dental restorations. The method takes into account that the mechanical lifetime is a stochastic quantity determined by shape, strength and fatigue properties and by the cyclic nature of the mastication forces. The general outline of the method is described and the necessary experimental data are discussed. Preliminary estimates of the lifetime of a composite and an amalgam restoration are made. The method is found to be feasible and the estimated lifetimes of the restoration are of the same order of magnitude as found clinically.
Assuntos
Resinas Compostas/química , Amálgama Dentário/química , Restauração Dentária Permanente , Dente Pré-Molar , Força de Mordida , Elasticidade , Humanos , Mastigação , Teste de Materiais/métodos , Modelos Biológicos , Modelos Estatísticos , Probabilidade , Estresse Mecânico , Resistência à Tração , Fatores de TempoRESUMO
A controlled clinical study, containing 720 posterior amalgam restorations placed in a group of 103 adult patients by three dentists, was used for examination of the influences on the incidence of occlusal and approximal bulk fractures. These fractures were evaluated from black and white photographs, taken annually, of the occlusal surface of the restorations over a 5-year period, using a three point photo-rating scale for both fracture sites. The influence of the dentist as well as the influence of the alloy and tooth type were statistically analysed. The results of these analyses demonstrated that the dentist, as well as the alloy and tooth type, have a statistically significant influence on the incidence of bulk fracture of amalgam restorations.
