Abstract
Recently, porcelain laminate veneer restorations have been widely used for esthetical improvement of discolored teeth. However, the thickness of the porcelain shell is limited to at most 0.5mm and it may cause a difficulty in achieving the natural color appearance by fully eliminating the effects of the degree of discoloration. In the present study, the background color-hiding efficiencies of a commercial and two experimental masking porcelains were colorimetrically examined. Then, the shades of porcelain laminate shells prepared with the masking and body porcelains were also evaluated on several experimental background color bases substituted for the discolored teeth. The results obtained were as follows : 1. With the commercial masking porcelain consisting 80% body and 20% opaque porcelain particles, the clinically available thickness of 0.2-0.3mm was quite insufficient to hide the background color. It was necessary to prepare shells 0.8mm or thicker for completely hiding the white background and 0.7mm or thicker for black background. 2. When the porcelain shell prepared with 0.5mm thick body porcelain only was placed on the color bases, it showed large values of color difference from the body porcelain control specimen. 3. The shell composed of 0.2mm thick masking and 0.3mm body porcelains showed a constant lightness on any base ; however, it exhibited rather larger values of color difference from the control than the 0.5mm thick body shell. 4. The experimental masking porcelain containing 5 or 10% opaque porcelain was more effective than the commercial one for significantly reducing the color difference between the shell on the color bases and the control. Especially the former seemed favorable for the slight discoloration base, and the latter for the severe or mild base. 5. In general, the porcelain shell on the color bases was similar in shade to the control specimen of one smaller shade number of body porcelain than that used for the shell. It was suggested from the foregoing results that in the porcelain laminate veneer restoration the masking porcelain should not be expected to completely hide the tooth color but to help give desirable shade of the shell. On the basis of this concept, it is recommended for esthetically better performance to use the masking porcelain containing smaller amount of opaque particles and to fabricate the shell with the porcelain material of one larger shade number than intended in the shade guide.
