Influence of Layer Thickness and Shade on the Transmission of Light through Contemporary Resin Composites

Background: Material-dependent parameters have an important impact on the efficiency of light polymerization. The present in vitro study aimed to investigate the influence of the increment thickness and shade of nano- and nanohybrid resin composites on the transmission of curing light.

Methods: Three contemporary resin composites were evaluated: Tetric EvoCeram^® (TEC); Venus Diamond^® (VD); and Filtek Supreme XTE^® (FS XTE). Light transmission (LT) was recorded in accordance with the sample thickness (0.5 to 2.7 mm) and the shade. Polymerized samples were irradiated for 10 s each using the high-power LED curing light Celalux 2 (1900 mW/cm²). LT was simultaneously recorded using the MARC Patient Simulator (MARC-PS).

Results: LT was strongly influenced by the composite layer thickness. For 0.5 mm-thick samples, a mean power density of 735 mW/cm² was recorded at the bottom side. For the 2.7 mm samples, a mean power density of 107 mW/cm² was measured. Only LT was markedly reduced in the case of darker shades. From A1 to A4, LT decreased by 39.3% for FS XTE and 50.8% for TEC. Dentin shades of FS XTE and TEC (A2, A4) showed the lowest LT.

Conclusions: The thickness and shade of resin composite increments strongly influences the transmission of curing light. More precise information about these parameters should be included in the manufacture manual.