Objectives:The aim of this study is to optically evaluate dental all-ceramic restorations.

Methods:(1) Light transmission was measured for alumina plates, Vintage AL porcelain(VAL, Shofu Inc.), zirconia plates and Vintage ZR porcelain(VZR, Shofu Inc.).

(2) Tristimulus values(Y) were measured for specimens prepared with VAL and VZR opaque liner porcelains. Contrast ratio(C) was calculated, where Y_b was the value measured for the black background, Y_W for the white background, and L for thickness, as follows:

C= 1-(1-Y_b/Y_W)^1/L

(3) Values a* and b* were measured for specimens prepared with VAL and VZR enamel porcelains. Opal index(OI) was calculated, where a*_b,b*_b was the value measured for the black background, and a*_w,b*_w was for the white background, as follows:

OI= [(a*_w-a*_b)²+(b*_w-b*_b)²]^1/2

(4) Test crowns were prepared with VAL and VZR built up in the same layer structure onto each frame and fired. Colors of the crowns(shade:A₂, A₃, A_3.5) were then measured. Color difference DE was calculated as follows:

DE=[(L*_VAL-L*_VZR)²+(a*_VAL-a*_VZR)²+(b*_VAL-b*_VZR)²]^1/2

Results:(1) At 0.2mm thickness, alumina plates showed a higher light transmission(40.9%) compared to zirconia plates(37.6%). VAL and VZR showed similar light transmissions: 14.5%(VAL), 14.0%(VZR) for opaque liner porcelain; 45.5%(VAL), 45.9%(VZR) for body porcelain; and 79.0%(VAL), 79.9%(VZR) for enamel porcelain.

(2) Contrast ratios for both VAL and VZR depended on thickness (correlation coefficient:-0.999). VAL and VZR showed similar opacifying properties.

(3) The values of OI for enamel porcelain were 10.8(VAL) and 10.6(VZR), respectively.

(4) DE between VAL and VZR were: 0.82 for A₂, 0.38 for A₃, and 0.66 for A_3.5. Visual evaluation results also showed an excellent color match.

Conclusion: VAL and VZR are equivalent in opacifying properties for opaque liner porcelain, optical transparency for body porcelain, optical transparency and opal property for enamel porcelain. It is thus suggested that all-ceramic crowns fabricated using these porcelains can also reproduce equivalent colors intraorally.

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