Effect of heat treatment parameters on the crystallization of feldspathic-based dental glass-ceramics

The effects of heat treatment time and temperature on the crystallization of the feldspathic glass-ceramics produced from frit powders were investigated. Two-step heat treatment processes (nucleation and crystal growth) were applied to produce glass-ceramics. In both stages, the samples were heated at different soaking temperatures and times. Tetragonal leucite crystal nucleation and growth processes were followed by XRD, SEM and dilatometer techniques. Depending on first step heat treatment temperature and soaking time the crystallization gradually increases with increasing time and temperature. The second step heat treatment soaking times showed significant change in the coefficient of thermal expansion (CTE) of the glass ceramic samples. Biaxial flexural strength (σ) of the samples slightly increases with increasing the 2nd step soak time and all results are above the required standard value of 100 MPa for the monolithic ceramic for single-unit anterior on dental restorations.