W M Johnston1, M H Reisbick. 1. Section of Restorative Dentistry, Prosthodontics and Endodontics, College of Dentistry, Ohio State University, Columbus, USA. Johnston.5@osu.edu
Abstract
OBJECTIVES: This study was conducted to evaluate various types of contemporary resin composites and glass ionomer restorative materials for color differences that occur during light curing and after submersion in water. Additionally, translucency was evaluated through the use of a translucency parameter for each of these materials at these times. METHODS: A translucency parameter was calculated from observed colors of 2 mm thick layers of light, medium and dark shades of popular restorative materials on black and white backings. The colors of these materials were also calculated, based on Kubelka-Munk theory, for layers on a B2 shade backing. Repeated measures analyses of variance were used to identify statistically significant factors for color differences and translucency parameters. RESULTS: A statistically significant interaction was found between the products, shades and time intervals or times studied for both color difference and translucency parameter. There is relatively high variability in both lightness and translucency changes among these popular products, with some products increasing and others decreasing in these parameters with curing and subsequent water submersion. SIGNIFICANCE: Kubelka-Munk theory can be used to calculate the color of a layer of material on a backing other than those used to determine the Kubelka-Munk coefficients, thereby increasing the efficiency of research into the optical properties of esthetic restorative materials. The relatively large optical changes which occur as popular esthetic restorative materials are cured and subsequently submersed in water indicate that these changes should be taken into account during any initial clinical appearance match at placement of the unset material.
OBJECTIVES: This study was conducted to evaluate various types of contemporary resin composites and glass ionomer restorative materials for color differences that occur during light curing and after submersion in water. Additionally, translucency was evaluated through the use of a translucency parameter for each of these materials at these times. METHODS: A translucency parameter was calculated from observed colors of 2 mm thick layers of light, medium and dark shades of popular restorative materials on black and white backings. The colors of these materials were also calculated, based on Kubelka-Munk theory, for layers on a B2 shade backing. Repeated measures analyses of variance were used to identify statistically significant factors for color differences and translucency parameters. RESULTS: A statistically significant interaction was found between the products, shades and time intervals or times studied for both color difference and translucency parameter. There is relatively high variability in both lightness and translucency changes among these popular products, with some products increasing and others decreasing in these parameters with curing and subsequent water submersion. SIGNIFICANCE: Kubelka-Munk theory can be used to calculate the color of a layer of material on a backing other than those used to determine the Kubelka-Munk coefficients, thereby increasing the efficiency of research into the optical properties of esthetic restorative materials. The relatively large optical changes which occur as popular esthetic restorative materials are cured and subsequently submersed in water indicate that these changes should be taken into account during any initial clinical appearance match at placement of the unset material.