Optimal photoinitiator concentration for light-cured dental resins

In this paper, we study the optimal photoinitiator (camphorquinone, CQ) concentration for light-cured dental resins by combining such properties as the degree of conversion, mechanical properties, and curing depth (the depth at which the hardness is 80% of the surface hardness). The material properties of the light-cured dental resins (Bis-GMA/TEGDMA in a mass ratio of 70:30) are characterized by in-situ near-infrared (NIR) spectroscopy and nanoindentation tests. Experimental results indicate that the degree of conversion (DC) and mechanical properties such as elastic modulus and hardness increase, while the curing depth decreases with the increase of CQ concentration. However, above a certain concentration (~0.5 wt%), these properties do not benefit from the further increasing CQ concentration because of potential self-annihilation between free radicals. The presented study offers a method to determine the optimal photoinitiator concentration for light-cured resins and establishes the correlations between the photoinitiators, polymerization kinetics, and mechanical properties of the light-cured resins.