How light sources and distance of the light tip influence water sorption, solubility, and biaxial flexural strength of a composite resin.

This study evaluated the water sorption (WS), solubility (SL), and biaxial flexural strength (BFS) of a resin composite based on different polymerization units, storage permeants (distilled water and 75% ethanol), and distances between the light's tip and the composite resin. Using a stainless steel mold, 80 specimens were made and separated in two independent groups, according to the duration of storage (7 days or 60 days). The specimens were photocured using either a QTH or LED light (both used at 600 mW/cm2 for 40 seconds), with the light's tip guide either 0 mm or 2 mm from the surface of the resin. In general, the 75% ethanol produced higher WS and SL values but lower BFS values compared to water. Both distances influenced the WS and SL values, especially when 75% ethanol was used (p < 0.05), although neither distance affected BFS values (p > 0.05). For nearly all groups, the WS, SL, and BFS in different solvents and at different distances for photocuring of the tested resin were not affected by the curing light used.