Effect of Polywave and Monowave Light Curing Units on Color Change of Composites Containing Trime-thylbenzoyl-Diphenyl-Phosphine Before and After Aging

The use of traditional camphorquinone (CQ) photo-initiators in dental composites may cause undesirable yellow discoloration. An alternative photo-initiator called lucirin trimethylbenzoyl-diphenyl-phosphine oxide (TPO) was recently introduced which exhibits minimal color change (ΔE). This study evaluated the color change of TPO-containing composites cured by different types of light-curing units, after accelerated artificial aging (AAA).  

In this in vitro experimental study, specimens were fabricated from Tetric N-Ceram and Vit-l-escence TPO-containing composites with 10 mm diameter and 2 mm thickness (n=10) and light-cured by Bluephase G2 polywave and Bluephase C5 monowave curing units. The samples were polished with Sof-Lex discs and underwent initial colorimetry by a spectrophotometer after 24 hours. Aging was performed for 384 hours in a weathering chamber and final colorimetry was then performed. The results were analyzed by two-way ANOVA.

The interaction effect of light curing unit and composite type on ΔE was not significant (P=0.53). The mean ΔE of Vit-l-escence and Tetric N-Ceram cured with Bluephase G2 and Bluephase C5 light-curing units was 1.67±0.48 and 1.62±0.45, and 2.59±0.29 and 2.69±0.26, respectively. Tetric N-Ceram demonstrated significantly greater ΔE than Vit-l-escence (P=0.001). Light curing units had no significant difference in ΔE (P=0.80).

The ΔE of TPO-containing composites does not depend on the type of light curing unit but depends on the type of composite. Aging caused discoloration of the composites but this discoloration was clinically acceptable (ΔE<3. 3).