Effect of the degree of conversion of resin-based composites on cytotoxicity, cell attachment, and gene expression

Objective This study investigated the influence of the degree of conversion (DC), resin-based composites (RBC) composition, and the effect of additional violet light from one light curing unit (LCU) on cell attachment/growth, eluate cytotoxicity, and gene expression. Methods The effect of different DC of RBCs on human gingival fibroblasts (HGFs) when cultured directly onto cured RBCs, and when exposed afterwards to eluates in cell culture medium was examined. Venus® (RBC-V; Bis-GMA-based) and Venus Pearl® (RBC-P; TCD-DI-HEA and UDMA-based) were cured using a single emission peak (blue) light, Translux Wave®; TW and a dual emission peak (blue-violet) light, Translux 2 Wave®; T2W. To determine the value of the additional violet light from the T2W, exposure times and distances were adjusted to deliver similar radiant exposures (RE) from the blue region of both lights at five different RE levels from 1.5 J/cm² to 28.9 J/cm². Results Both RBCs light-cured with the T2W at higher REs resulted in higher DC, increased cell adhesion and decreased eluate cytotoxicity. RBC-V induced greater cell adhesion, lower mRNA levels of pro-inflammatory markers, and higher mRNA levels of a proliferation marker than RBC-P. Wettability was the same for both RBCs. Toxicity decreased with increasing number of elution cycles. The initial eluates from RBC-P had a lower toxicity than from RBC-V. Significance RBCs cured with T2W (delivering both blue and violet light) at higher RE had greater DCs. The greatest DC and the least cell reactions were observed when the RE was >25 J/cm².