Impact of immediate and delayed light activation on self-polymerization of dual-cured dental resin luting agents

Abstract

This study investigated the impact of immediate and delayed light activation on self-polymerization of a model dual-cured luting agent. The material presented the following components: base paste – 2,2-bis[4-(2-hydroxy-3-methacryloxyprop-1-oxy)phenyl]propane/triethylene glycol dimethacrylate (TEGDMA), camphorquinone, dimethyl- p-toluidine, butylated hydroxytoluene (BHT), glass fillers; catalyst paste – bisphenol-A ethoxylated dimethacrylate/TEGDMA, benzoyl peroxide, BHT, fillers. The pastes were mixed and seven polymerization scenarios tested: immediate light activation using low (5 J cm −2) or high (20 J cm −2) energy dose; delayed light activation (after 2 min – short delay) using low or high dose; delayed light activation (after 10 min – long delay) using low or high dose; and self-polymerization only. The degree of conversion (DC) and rate of polymerization ( R p) were evaluated for 30 min by real-time infrared spectroscopy. The lowest DC was detected for the self-polymerized and immediate–low dose groups, whereas the immediate–high dose and short delay–high dose groups showed the highest values. For the self-polymerized and immediate–high dose samples, R p max was detected after approximately 7 s, whereas this took approximately 14 s for the immediate–low dose group. R p max for the immediate–high dose group was higher than for the self-polymerized sample, which in turn was higher than for the immediate–low dose group. R p max for the short delay groups was higher than for the long delay groups. In conclusion, the extent of self-polymerization was influenced by the light dose reaching the material, which was dependent on high radiant exposure for optimal polymerization and the moment at which the light was applied; the short delay increased the DC for lower doses, while also generally decreasing the R p for all scenarios.