Hardness and Elastic Modulus of Leucite Particle and Glass Matrix in Dental Porcelain

Dental porcelains consisting of leucite particle and matrix glass are widely used in ceramic restorations. Objectives: The purpose of this study was to compare microhardness and elastic modulus of particle and glass matrix of leucite porcelain. Methods: Two leucite-containing porcelains were investigated; one commercial leucite-enriched porcelain (Empress) and one experimental porcelain containing natural leucite (Lee et al. 1998). Disk specimens of each sample were embedded in phenolic resin and received a 1-mm finishing. After etching of the porcelain surfaces with 1% hydrofluoric acid, the porcelain surfaces received further fine polishing with 0.25-mm diamond paste. Microhardness and elastic modulus of leucite and glass matrix were measured using nanoindentor (ENT-1100, Elionix, Japan) with a load of 2 gf. Results: Mean values (GPa) and standard deviation from at least five measurements of two samples each are as follows;  

Student's t-test showed that there were no significant differences in hardness between leucite and glass of two porcelain, while elastic moduli of leucite were significantly lower than those of the respective glass matrices (p<0.05). Elastic modulus of synthetic leucite particle in Empress was significantly higher than that of natural leucite.  Conclusions: Nanoindentation technique can be effectively used to micromechanical properties of components of dental porcelain. Supported by KRF grant 2001-2-F0166.