The influence of porcelain layer thickness and color on the final shade of ceramic restorations

Seong, Dong Hwan; Lee, Im Gi; Sohng, Jin Won; Bok, Won Mi; Ahn, Seung Geun; Park, Charn Woon

Abstract

STATEMENT OF PROBLEM: Ceramic restorations should be made of porcelain layers of different opacity, shade, and thickness in order to provide a natural appearance. Lithium disilicate glassceramic system has superior color reproducibility, because it uses the ceramic ingot which is similar to teeth shade and uses the staining technique and layering technique. However, staining technique has a fault of discoloration. Also, porcelain is divided core and dentin layer, it is not enough to study about the influence of porcelain layer thickness and shade on the shade of ceramic restorations. PURPOSE: The purpose of this study was to evaluate the influence of porcelain layer thickness and color on the final shade of ceramic restorations. MATERIALS AND METHOD: The CIE L*a*b*(CIELAB) values of 72 assembled specimens, each consisting of 3 discs (enamel porcelain 0.2 mm/dentin porcelain - 1.2, 0.9, 0.7, 0.5 or 0.3 mm/ceramic core - 0.3, 0.5, 0.7, 0.9 or 1.2 mm, diameter is 1.0 mm) were evaluated with a spectrophotometer (Model Chromaview 300, Spectron Tech Co, Korea) for the shade A1, A2, A3 and A4. Distilled water (refractive index: 1.7) was used to attain optical contact between the layers. White, white gray, and white brown backgrounds were used to assess the influence of the background on the final shade. And the mean color difference value(delta E) was calculated. RESULTS AND CONCLUSION: The results obtained from this study were as follows. 1. There was a significant correlation between the thickness ratio of the ceramic core/dentin porcelain system and L*, a* and b* values when the total thickness of specimen combination was smaller than 1.4 mm( p<0.05). 2. The specimen which the ceramic core thickness was more than 0.7 mm had the best masking effect against background colors. 3. The mean color difference value(delta E) is smaller than 2 (delta E<2) when the ceramic core thickness was larger than 0.7 mm and the total thickness of specimen was more than 1.4 mm.