Effect of light-curing units and glass fiber reinforcement on flexural strength of direct and laboratory-processed composites / Análise in vitro da resistência fluxural de uma resina composta direta e uma resina laboratorial de segunda geração associadas ou não a fibras de reforço

RESUMO

The aim of this study was to evaluate in vitro the flexural strength of direct composite resin (Z-250 FiltekTM - 3M/ESPE) and second-generation laboratory composite (II CeseaD(ST) - Kuraray) associated or not with glass fibers(Fibrex -coronal - Angelus), changing the curing light source (L.E. Demetron 1 - Kerr and Strobolux - EDG). Fifty-six specimens of the composites F and C were constucted using a stainless-steel split ring molds and divided into eight groups G1 - Composite Z-250/No fiber/LED; GII - Composite Z-250/No fiber/Strobolux (SRT); GIII - Composite Z-250/Fibrex-coronal (FBC)/LED; GIV - Composite Z-250/FBC/STR; GV - Composite CeseaD(ST) II/No fiber/LED; GVI - Composite CeseaD(ST) II/No fiber/STR; GVII - Composite CeseaD(ST) II/FBC/ LED; GVIII - Composite CeseaD(ST) II/FBC/STR. The specimens were subjected to the flexural strength in a universal testing machine equipped with a cell load of 500Kgf at a crosshead speed of 1±0.5 mm/min. The data were submitted to Tukey's Test (p = 0.01).The mean of flexural strength was in MPa G1 - 187,91 ± 32, 78; GII - 196,76 ± 31,15; GIII - 208, 27 ± 18,79; GIV - 218,02 ± 15,76; GV - 101,72 ± 11,25; GVI - 103,05 ± 9,56; GVII - 164,76 ± 12,54 e GVIII - 176,75 ± 47,03. The direct composite showed the highest flexural strength values in all groups; the light source did not affect the flexural strength of the composites; fiber reinforcemente increased the flexural strength of both composites; however this increase was statistically significant only for the laboratory-processed composite