Curing Quality of Composites as Influenced by the Filler Content, Light Source and Curing Time

Abstract

The quality of composite polymerization has been of great concern for researchers. Curing of nanocomposites under long distance (8-mm) and extended light exposure through conventional (halogen and LED) and argon laser lamps is unclear in the literature. This study evaluated the influence of curing modes and filler particle size on hardness and degree of conversion of dental composites photoactivated at an 8-mm distance. Light sources (LED 1100mW/cm2-Bluephase; LED 700mWcm2-Ultra-lume; halogen lamp 450mW/cm2-XL3000; and argon-laser 500mW/cm2-AccuCure), curing times (20 and 60 s), microhybrid (Filtek-Z250) and nanofilled (Filtek-Supreme) resins were investigated. Eighty samples (n=5) were made using Teflon molds. Hardness and degree of conversion were obtained for bottom/top surfaces of 2-mm increments. Data were submitted to ANOVA and Tukey tests (α=5%).Top surfaces showed similar hardness. A 60s exposure time increased bottom hardness and Filtek-Z250 showed higher hardness for curing units except Bluephase. Regarding degree of conversion, bottom/top surfaces showed similar means at 60s; at 20s, bottom/top surfaces revealed similar means only for Filtek-Z250 cured by Bluephase and Ultra-lume. High irradiance and extended exposure time can improve hardness and conversion on bottom surface. Microhybrid resin presented better conversion of monomers than the nanofilled composite under higher irradiance and extended exposure times.

Comparison of a Nanofiber-Reinforced Composite with Different Types of Composite Resins

“…The surface hardness of composite resins in posterior stress-bearing areas is a crucial mechanical property influenced by the effectiveness of polymerization and bonding between monomers [17]. Various factors related to resin composites, such as the size, shape, and fraction of fillers in the inorganic phase, can influence hardness.…”