Influence of cavity wall thickness on the color adjustment potential of single-shade resin composites

Background. The color adjustment potential of resin composites depends on the specific characteristics of the surrounding structures. The authors evaluated the influence of cavity wall thickness on CIEDE2000 color adjustment potential (CAP00) of single-shade composites using the CIEDE2000 color difference (Delta E-00) formula. Methods. Two types of specimens were produced: single, using Vittra APS color DA3 (FGM posites; and dual, using Vittra APS color DA3, but with cavity wall thicknesses of 3, 2, or 1 mm, restored with VU or Omnichroma. CIEL*a*b* color coordinates were obtained from digital photographs of the specimens at different locations, and AE00 and CAP00 were calculated. Statistical analysis included 2-way analysis of variance, Kruskal-Wallis, Holm-Sidak, Student-Newman-Keuls, Wilcoxon signed rank, and paired t tests (a 1/4 5%). Results. Cavity walls 1-mm-thick had higher AE00 values and lower CAP00 values, particularly for VU (P < .05). Restorations matched better with the control at the periphery than the central area (P < .001). Overall AE00 means exceeded the color perceptibility threshold (ie, 0.8) and the acceptability threshold (ie, 1.8). Color differences (between center of restoration and control composite) were moderately unacceptable for 3-mm and 2-mm thicknesses and extremely unacceptable for 1-mm thickness. Both composites had a AE00 color shift predominately determined by means of the lightness difference. Positive CAP00 values were found for VU and Omnichroma. Conclusions. Wall thickness, especially at 1 mm, negatively impacted the color of single- shade composites. This effect was more pronounced for VU, affecting mainly the restoration's central area. Practical Implications. Color matching ability depends on the structural and material characteristics, and clinicians should be attentive to these factors when using single-shade resin composites.