Effect of resin thickness and light-curing irradiance on the hardness and depth of cure of short fiber-reinforced resin composite

This study analyzed the effect of short fiber-reinforced resin composite (SFRC) thickness and light-curing irradiance on the depth of cure. A total of 24 specimens of SFRC (EverX PosteriorTM) were made and divided into two different groups based on thickness: 4 and 5 mm (n = 12), formed into a cylindrical shape with a diameter of 6 mm. Each group was divided into two subgroups cured by different light-emitting diode (LED) curing units with different irradiances: 1000 and 1200 mW/cm2 (n = 6). Each specimen was cured for 20 s with a 2-mm light-curing distance. The depth of cure was measured by calculating a Vickers hardness ratio of the bottom to the top surfaces of specimens (%). Data were analyzed statistically by one-way ANOVA tests, followed by post hoc Fisher's least significant diameter (LSD) tests. The depths of cure in the 4-mm thickness groups cured by 1000 and 1200 mW/cm2 light-curing irradiance were 79.46 ± 0.85% and 80.74 ± 0.95%, respectively, compared to 49.41 ± 0.47% and 61.65 ± 0.77%, respectively, in the 5-mm thickness groups. The results showed significant differences (P < 0.05) in the depth of cure in all groups tested. It can be concluded that SFRC thickness and light-curing irradiance have a significant effect on the depth of cure. (paper)