Evaluation of Technique Sensitivity of Bilaminar and Trilaminar Layering Systems Using Digitally Calibrated Cross-Polarized Photography

Abstract

Objectives: To compare the effect of variation of the outer enamel layer thickness on the final shade for a bilaminar versus a trilaminar technique and to compare the effect of variation of the core layers thicknesses on the final shade for a trilaminar technique. Materials and methods: 144 resin composite discs of 10mm diameter were prepared and equally divided into 24 groups (n=6) according to the three levels of the study, Level 1: Color recipe (A1, A2 and A3). Level 2: Outer enamel layer thickness (0.25 mm and 0.75 mm). Level 3: Shade combination (Bilaminar, Trilaminar-1, Trilaminar-2, Trilaminar-3). Another 72 discs of same shade combination groups with outer enamel layer thickness of 0.5mm were prepared to serve as controls (12 groups, n=6). eLAB_prime software was used to digitally calibrate the cross-polarized photographs of the discs and measure the L*, a* and b* values. CIEDE2000 color difference formula (ΔE00) was adopted. Data were analyzed using three-way ANOVA and one-way ANOVA followed by Tukey’s post hoc test. Results: The bilaminar technique (1.09±0.65) had significantly higher color change value than the trilaminar technique (0.84±0.49) (p=0.010). The trilaminar-2 technique had the least color change value (0.70±0.36) (<0.001). Conclusions: The trilaminar technique is less sensitive to minor variation in outer enamel composite layer thickness compared to the bilaminar technique. Using equal thicknesses of body and dentin composites in the trilaminar technique produces the least change in color upon minor variation in outer enamel composite layer thickness.