Dual-cure dental composites: can light curing interfere with conversion?

Abstract

Dual-cure composites used for dental restorations offer photo- and self-activation, promising unlimited curing depth. This study examined depth of cure with respect to light- and self-cure capabilities. Four dual-cure composites (BulkEZ; Activa; HyperFIL; Injectafil) were tested, with bulk fill (Tetric) and universal (TPH) light-cure composites as comparison. Composites were irradiated from one direction in molds. Additionally, dual-cure composites were left to self-cure without irradiation. Vickers hardness was measured up to 6 mm deep. Results were analyzed with two-way ANOVA and pairwise comparisons (α = 0.05). Hardness dropped significantly with depth in light- and dual-cured composites, except BulkEZ. Self-cured dual-cure composites achieved constant hardness throughout their depth. Only BulkEZ was unaffected by curing mode. Irradiation significantly decreased hardness in middle sections of Hyperfil and Injectafil compared with self-cured samples. Dual-cure composites cured substantially through 6 mm depths but curing behaviors differed. Whereas irradiation did not affect one dual-cure composite, in two other dual-cure composites low-density light levels interfered with the self-polymerization aspect.