Influence of different shades on light transmission through different composites

Abstract Objective: This study evaluated the influence of different composite resins shades on light transmission through the composite and the difference in percentage of the decrease in Knoop hardness between bottom and top (DKH). Methods: Two restorative composites with shades A1 and A3.5 were used (Esthet X and Filtek Z350). The irradiance of the light curing unit was measured (780 mW/cm2). Twenty-five specimens were made for each shade for both composites. Light transmission test: The irradiance of light that passed through the composite was measured (n=10). Knoop Hardness test: The DKH of the same specimen was calculated (n=10). Scanning Electron Microscopy (SEM): Five specimens from either Filtek Z350 or Esthet-X composites were observed under SEM. Results: The irradiance of light that passed through shade A1 composite was statistically higher than shade A3.5 for both composites (p=0.00001). For Esthet X, the DKH of shade A3.5 was statistically higher than for shade A1; however, there was no statistically significant difference for Filtek Z350 (p=0.03035). Representative areas showing the filler particles were photographed at 1,000x magnification. Conclusion: Different composites influenced both light transmission and DKH. Darker shades allowed lower light transmission, but could not establish a relation between dark shades and DKH.