Color shifting at the border of resin composite restorations in human tooth cavity

The purposes of this study were to evaluate color shifting at the boarder of resin composite restorations after placement in human tooth cavities in vitro.

Twenty extracted human premolars with an A2 shade were used in this study. Cylindrical shaped cavities (3.0mm or 1.5mm depth; 2.0mm diameter) were prepared in the center of the crowns. One of four resin composites of A2 shade (Clearfil AP-X, AP; Clearfil Majesty, MA; Tetric N Ceram, TNC; Ceram X mono, CX) was placed in the cavity, and the color was measured at four points (0.4mm × 0.4mm) on the restored teeth (area 1: tooth area 1.0mm away from the border of resin composite restoration; area 2: tooth border area 0.3mm away from margin of resin composite restoration; area 3: resin composite border area 0.3mm away from margin of resin composite restoration; area 4: resin composite area at the center of resin composite restoration) using a spectrophotometer (Crystaleye). The color of each area was determined according to the CIELAB color scale. Color differences (ΔE*) between the areas of 1 and 2, 2 and 3, 3 and 4, and 1 and 4 were calculated, and also the ratio of ΔE*23 to ΔE*14 as a parameter of the color shifting at the border of resin composite restoration, was determined. The data were statistically analyzed using two-way ANOVA, and Dunnett's T3 and t-test for the post hoc test.

For all materials, the Δ*23 were significantly lower than ΔE*14, in which ΔE*23 were significantly influenced by the materials although there were no significant differences in the ΔE*14 between the materials. Additionally, ΔE*12 were significantly higher than ΔE*34. For the 3.0mm cavity depth group, the lowest ΔE*23/14 ratio was seen in CX =

All resin composite restorations in the tooth cavities produced the color shifting of resin composite and tooth at the border. For deep cavity, resin composites with higher diffused light transmission property showed higher color shifting at the border, while for shallow cavity, the straight-line as well as diffused light transmission of resin composite affected the color shifting at the border. Clinically, diffused light transmission property of resin composites may contribute to the color shifting at the border of resin composite restoration regardless of cavity depth, resulting in better color matching.