Amirhossein Fathi1, Mitra Farzin2, Rashin Giti3, Mohammad Hassan Kalantari4. 1. Assistant Professor, Department of Prosthodontics, Dental Materials Research Center, Isfahan University of Medical Sciences, Isfahan, Iran. 2. Associate Professor, Department of Prosthodontics, Biomaterials Research Center, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran. 3. Assistant Professor, Department of Prosthodontics, Biomaterials Research Center, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran. Electronic address: giti_ra@sums.ac.ir. 4. Assistant Professor, Department of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
Abstract
STATEMENT OF PROBLEM: Color matching between a zirconia-based ceramic restoration and a natural tooth is a common clinical challenge. PURPOSE: The purpose of this in vitro study was to investigate the effects of the number of firings, veneer thickness, and zirconia core translucency on the final color and translucency of zirconia-based ceramic restorations. MATERIAL AND METHODS: Sixty disk-shaped zirconia specimens (10×1 mm) were prepared in high and low translucencies (n=30 per translucency group). Each zirconia group was subdivided into 3 subgroups (n=10) veneered with ceramic layers of 0.5-, 1-, and 1.5-mm thicknesses. The specimens were then subjected to 1, 3, 5, and 7 firing times. Color and translucency parameters were measured by using a spectrophotometer. Data were analyzed by using multifactorial repeated measures ANOVA and subgroup analysis (α=.05). RESULTS: The number of firings affected the L*, a*, and b* values and translucency parameter in both zirconia-based systems with different veneer thicknesses (P<.05). Increasing the veneer thickness decreased the translucency parameter and increased the L*, a*, and b* values in both zirconia-based systems (P<.05). The color difference values (ΔE) were the highest between 1 and 3, 1 and 5, and 1 and 7 firings, and the lowest between 5 and 7 firings in both zirconia systems. CONCLUSIONS: Repeated firings and porcelain veneer thickness affected the final color and translucency of both zirconia systems and, consequently, adversely influenced the esthetic outcomes. Thus, these factors should be considered in the tooth preparation and laboratory phase.
STATEMENT OF PROBLEM: Color matching between a zirconia-based ceramic restoration and a natural tooth is a common clinical challenge. PURPOSE: The purpose of this in vitro study was to investigate the effects of the number of firings, veneer thickness, and zirconia core translucency on the final color and translucency of zirconia-based ceramic restorations. MATERIAL AND METHODS: Sixty disk-shaped zirconia specimens (10×1 mm) were prepared in high and low translucencies (n=30 per translucency group). Each zirconia group was subdivided into 3 subgroups (n=10) veneered with ceramic layers of 0.5-, 1-, and 1.5-mm thicknesses. The specimens were then subjected to 1, 3, 5, and 7 firing times. Color and translucency parameters were measured by using a spectrophotometer. Data were analyzed by using multifactorial repeated measures ANOVA and subgroup analysis (α=.05). RESULTS: The number of firings affected the L*, a*, and b* values and translucency parameter in both zirconia-based systems with different veneer thicknesses (P<.05). Increasing the veneer thickness decreased the translucency parameter and increased the L*, a*, and b* values in both zirconia-based systems (P<.05). The color difference values (ΔE) were the highest between 1 and 3, 1 and 5, and 1 and 7 firings, and the lowest between 5 and 7 firings in both zirconia systems. CONCLUSIONS: Repeated firings and porcelain veneer thickness affected the final color and translucency of both zirconia systems and, consequently, adversely influenced the esthetic outcomes. Thus, these factors should be considered in the tooth preparation and laboratory phase.