Color of Indirect Resin-Composite on Resin Cements with Different Transparency

Objectives: This study examined the effect of the degree of transparency of experimental resin cements on color of overlaid indirect resin-composite.

Materials and methods: Experimental UDMA-based resin cements with five different transparencies were fabricated by adding 0.05, 0.1, 0.15 and 0.2mass% TiO2 powder. Cement without TiO2 powder served as a control. Disk specimens (10mm dia., 1mm thick) were prepared from indirect resin-composite [CERAMAGE, Shofu, CM-56 (L*=89.0±0.2, a*=-4.1±0.0, b*=12.1±0.4, translucency parameter value (TP) =26.7±0.2); CM-61 (L*=82.2±0.1, a*=2.3±0.1, b*=25.5±0.6, TP=30.6±0.2)]. CM-56 had the highest L* value, and CM-61 had the lowest L* values among the commercially available shades. Disk-shaped abutments (10mm dia., 2mm thick) were made from resin abutment materials (Die Color Checker, Shofu, DC-7). A layer of the set cement (100µm thick) was placed between the indirect resin-composite and the abutment discs. The color differences (⊿E*ab，n=6) between the specimens with and without the cement layer were determined using a spectrocolorimeter (PR650 Photo Research). The results were statistically compared using ANOVA/Scheffé's test (a=0.05).

Results: The ⊿E*ab results (mean ± sd) were as follows (control, 0.05%, 0.1%, 0.15%, 0.2% TiO2): CM-56 (0.9±0.3, 1.2±0.6, 1.9±0.5, 2.3±0.7, 2.8±0.5, respectively) and CM-61 (0.7±0.3, 1.2±0.4, 1.4±0.3, 2.0±0.4, 2.4±0.4). Significant differences in the ⊿*ab values were found between the control and the cement with 0.1% TiO2 (p<0.05) for CM-56 and 61. No significant effects (p>0.05) on ⊿E*ab value were found in the cement containing ³0.1% TiO2 for CM-56. For CM-61, the ⊿E*ab value for the cement with 0.2% TiO2 was significantly greater than with 0.1% TiO2 (p<0.05).

Conclusion: Under the present experimental conditions, cement with at least 0.1% TiO2 powder was effective at modifying the color of the abutment material. There was little shading effect when the TiO2 content increased to 0.2%, causing the overlaid composite to be less transparent.