Prior studies have shown that sputter-deposited thin-film coatings can improve the fracture resistance of dental ceramics.  In this modification, an important consideration is to enhance mechanical behavior without sacrificing advantageous ceramic characteristics.  Esthetics is one outstanding clinical feature of dental ceramics that should not be compromised.  Objectives: The purpose of this study was to investigate the effect of sputter deposited zirconia thin-films on color determinants of dental porcelain.  Methods: Thirty-two porcelain plates (10x12x1mm, Vita MkII, shade A2, Vita Zahnfabrik) were polished through 1200-grit SiC abrasive on one side and grit-blasted (50μm alumina) on the other.  Groups (n=8/group) were modified on the roughened side as follows: no modification (control); silane + resin-bonding agent (Prime & Bond NT, Dentsply, coating 1); 2μm partially-stabilized zirconia film, 25˚C, 0% background-oxygen (coating 2); 2μm partially-stabilized zirconia film, 300˚C, 5% background-oxygen (coating 3).  The reflectance spectrum was measured for each specimen using a UV-vis spectrophotometer (Lambda 900, Perkin Elmer).  L*a*b* values were calculated for each plate and used to determine the difference in color (ΔE) of each group relative to the control.  Results were analyzed using t-tests (p<0.05).  Results:  Superscript letters (a, b) in the table represent statistically equivalent means.

Specimen	L*	a*	b*	ΔE
Control	69.48±0.59	-1.14±0.04	5.18±0.14	-
Coating 1	67.73±0.30	-1.10±0.04	5.03±0.10	1.76±0.30a
Coating 2	69.23±1.02	1.30±0.38	6.07±0.80	2.88±0.41b
Coating 3	71.36±0.59	-1.01±0.12	6.70±0.12	2.44±0.46b

Conclusion: Previous experiments (Ruyter et al., 1987) have shown that ΔE £ 3.3 is clinically undetectable.  Based on this standard, surface modifications analyzed in this study produce color changes in relation to the control group that are below the threshold for human detection.  The results of this study indicate that application of a sputter-deposited zirconia thin-film should not adversely affect the optical characteristics of dental porcelain.  This study supported by NIH 5R01DE013511-02.