STRENGTH DEGRADATION UNDER 'FATIGUE' STIPULATION IN BULK-FILL COMPOSITES: AN IN VITRO APPRAISAL

Abstract

Objectives. To determine the Weibull and slow crack growth parameters of bulk-fill resin composites. The strength degradation over time of the materials was assessed by strength-probability-time analysis. Methods. Three bulk-fills and one conventional resin composite were studied. 75 disk-shaped specimens were prepared. The SCG parameters were obtained by testing ten specimens in five stress rates: 10-2 , 10-1 , 100 , 101 and 102 MPa/s. Weibull parameter were obtained by testing additional 20 specimens at 1 MPa/s. SPT diagrams were constructed by merging SCG and Weibull parameters. Results. Bulk-fill(BFL and TBF) presented higher n values. Conventional composite(Z250) showed the highest sf0 value. Weibull analysis showed m similar for all materials. SPT diagram for 5% probability of failure showed strength decrease of 18% BFL and 36% Z250, after 5 years. Significance. The reliability and decadence of strength over time for bulk-fill resin composites studied are comparable or higher to conventional composites.