[Comparison among three translucency parameters].

OBJECTIVE: This study aims to compare the three commonly used translucency parameters in prosthodontics: transmittance (T), contrast ratio (CR), and translucency parameter (TP).

METHODS: Six platelet specimens were composed of Vita enamel and dental porcelain. The initial thickness was 1.2 mm. The specimens were gradually ground to 1.0, 0.8, 0.6, 0.4, and 0.2 mm. T, color parameters, and reflection were measured by a spectrocolorimeter for each corresponding thickness. T, CR and TP were calculated and compared.

RESULTS: TP increased, whereas CR decreased, with decreasing thickness. Moreover, 
T increased with decreasing thickness, and exponential relationships were found. Two-way ANOVA showed statistical significance between T and thickness, except between T and the 1.2 mm and 1.0 mm enamel porcelain groups. No difference was found among the coefficient variations (CV) of T, CR and TP. Curve fitting indicated the existence of exponential relationships between T and CR and between T and TP. The values for goodness of fit with statistical significance were 0.951 and 0.939, respectively (P<0.05).

CONCLUSIONS: Under the experimental conditions, T, TP and CR achieved the same CV. T and TP, as well as T and CR, were found with exponential relationships. The value of CR and TP could not represent the translucency precisely, especially when comparing the changing ratios.