Study on changing the coefficient of thermal expansion (CTE) of dental porcelain

Raising the thermal expansion coefficient (CTE) of dental porcelains is important to match the CTE of the ceramic material with the higher CTE of the metal inlay in dental restorations. The higher thermal expansion of the leucite phase increases the overall thermal expansion coefficient of the dental porcelain. Potassium nitrate (KNO3) additions in controlled percentages to the base dental porcelain formulation help in the formation of a leucite phase. The percentage added was 5,10 and 20 weight percent of leucite, respectively, to the total base frit composition. The change in CTE values was then investigated using a Linseis Dilatometer. A 20wt% KNO3 addition resulted in a CTE of 9.0 microm/m-K compared to the 7.7 microm/m-K CTE of the base composition. The microstructures observed under the scanning electron microscope (SEM) show a multiphase material with the leucite phases dispersed within a glassy matrix. The results suggest that higher CTEs in the dental porcelain are possible by increasing the KNO3- additions within the limits tested.