Publication date: Available online 4 December 2018
Source: The Journal of Prosthetic Dentistry
Author(s): Kurt Erdelt, Madalena Lucia Pinheiro Dias Engler, Florian Beuer, Jan-Frederik Güth, Anja Liebermann, Josef Schweiger
Abstract
Statement of problem
Determining the relationship between variable thicknesses and the translucency of dental ceramics is essential for optimizing esthetics in different clinical situations.
Purpose
The purpose of this in vitro study was to analyze the relationship between layer thickness and translucency of 2 multi-layered monolithic zirconia materials and to develop an equation by which the grade of translucency can be calculated dependent on the materials' layer thicknesses in advance.
Material and methods
Two semisintered multi-layered zirconia blanks, namely KATANA Zirconia Super Translucent Multi-Layered Disk (Noritake Dental Supply Co, Ltd) and Zirconia Ultra Translucent Multi-Layered Disk (UTML) (Noritake Dental Supply Co, Ltd), were sectioned (N=96) to separate the 4 layers (n=12 per layer): enamel layer, transition layer 1, transition layer 2, body layer. All specimens were sintered in a furnace (M2 Plus; Thermo-Star) at 1500°C for 2 hours and automatically polished under water cooling up to P2400 for the thicknesses of 1.6, 1.3, 1.0, 0.7, and 0.4 mm. Transmittance of visible light was measured using a spectrophotometer (Lambda 35; Perkin Elmer). Data were analyzed using the Kolmogorov-Smirnov, 2-way ANOVA, and Scheffé post hoc tests (α=.01) and curve fitting.
Results
Analyzing the fitting of the values of the 8 material groups to the linear, exponential, and logarithmic curves, 7 of the 8 groups (not UTML body layer) fitted the most (R-square value closer to 1.0) to the logarithmic curve. Constants were obtained from the distance to the x-axis and the curvature.
Conclusions
The methodology of this study provided the materials' specific constants a and b by analyzing the translucency behavior of KATANA Super Translucent Multi-Layered Disk and Ultra Translucent Multi-Layered Disk in different thicknesses, allowing further translucency calculation by applying the developed formula and the constants.
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