COMPOSITE MICROFILLER CONTENT AND ITS EFFECT ON FRACTURE-TOUGHNESS AND DIAMETRAL TENSILE-STRENGTH

Previous studies have examined the relationship between total filler c ontent in hybrid restorative composites and some of their mechanical p roperties. This investigation evaluated the effect of varying the amou nt of microfiller in an experimental hybrid composite on fracture toug hness (single edge-notch technique) and diametral tensile strength. Th e microfiller content in the experimental hybrid composite was varied from 0-44 wt% for seven specimen groups, while the total filler conten t ranged from 77-84 wt%. It was found that 9 wt% microfiller loading p roduced the highest mean fracture toughness (1.33 MPa.m1/2) and 44 wt% loading produced the lowest mean value (0.80 MPa.m1/2). Only the 9 wt % microfiller content group differed significantly in fracture toughne ss from the other specimen groups. The diametral tensile strength disp layed only small differences for the range of microfiller content stud ied, with mean values ranging from 42.1-49.6 MPa. Additional research on the viscoelastic properties of these heavily filled hybrid composit es may provide some insight into the differences for the fracture toug hness and diametral tensile strength results.