Effect of light-curing distance on the degree of convergence of the top and bottom sides of flowable bulk-fill composite materials

Abstract

Background: Flow able bulk-fill materials were introduced to be used in one thick increment of an internal base underneath a conventional layer. However, complete polymerization of the whole layer, particularly the bottom surface, is essential to achieve biocompatibility and the best mechanical properties. Objective: To evaluate the effect of three light-curing distances (0, 2, and 4mm)on the degree of convergence(DC) of the top and bottom surfaces for three flowable bulk-fill composite resins; Smart dentin replacement, Opus bulk fill flow, and Tetric N flow. Methods:45 disk-shaped specimens with an internal diameter of 5 mm and a depth of4mm cured for 20 seconds were fabricated from the three composite resins (n=15). For each material, three subgroups were fabricated according to the position of the light tip from the top surface; at 0, 2, and 4mm distances. DC for the top and bottom sides of all the specimens was calculated using FTIR spectroscopy. The statistical significance for the mean values of DC% among the different groups was calculated using a one-way analysis of variance (ANOVA) and the Tukey test with a significance level of 0.05.