Effect of filler particles on surface roughness of experimental composite series

Objective: The purpose of this study was to evaluate the effect of different filler sizes and shapes on the surface roughness of experimental resin-composite series. Material and Methods: Thirty-three disc-shaped specimens of the series (Spherical-RZD 102, 105, 106, 107, 114 and Irregular-RZD 103, 108, 109, 110, 111, 112) were prepared in a split Teflon mold and irradiated with an halogen light-curing unit (450 mW/cm(2) for 40 s) at both top and bottom surfaces. The specimens were stored for 3 months in distilled water. The surface roughness values in form of surface finish-vertical parameter (R-a), maximum roughness depth (R-max) and horizontal roughness parameter (Sm) were recorded using a contact profilometer. The data were analyzed by one-way ANOVA and the means were compared by Scheffe post-hoc test (alpha=0.05). Results: The lowest surface roughness (R-a) was observed in S-100 (0.079 +/- 0.013), while the roughest surface was noted in I-450/700/1000 (0.125 +/- 0.011) and I-450/1000 (0.124 +/- 0.004). The spherical-shape series showed the smoothest surface finish compared to the irregular-shape ones with higher significant difference (p>0.05). The vertical surface roughness parameter (R a) values increased as the filler size increased yielding a linear relation (r(2)=0.82). On the contrary, the horizontal parameter (Sm) was not significantly affected by the filler size (r(2)=0.24) as well as the filler shape. Conclusions: Filler particle's size and shape have a great effect on the surface roughness parameters of these composite series.