Comparison of porcelain surface and flexural strength obtained by microwave and conventional oven glazing

Statement of problem Although the superior qualities of microwave technology are common knowledge in the industry, effects of microwave glazing of dental ceramics have not been investigated. Purpose The purpose of this study was to investigate the surface roughness and flexural strength achieved by glazing porcelain specimens in a conventional and microwave oven. Material and methods Thirty specimens of each type of porcelain (Omega 900 and IPS d.Sign) were fabricated and sintered in a conventional oven. The specimens were further divided into 3 groups (n=10): hand polished (using diamond rotary ceramic polishers), microwave glazed, and conventional oven glazed. Each specimen was evaluated for surface roughness using a profilometer. The flexural strength of each specimen was measured using a universal testing machine. A 2-way ANOVA and Tukey HSD post hoc analysis were used to determine significant intergroup differences in surface roughness (α=.05). Flexural strength results were also analyzed using 2-way ANOVA, and the Weibull modulus was determined for each of the 6 groups. The surfaces of the specimens were subjectively evaluated for cracks and porosities using a scanning electron microscope (SEM). Results A significant difference in surface roughness was found among the surface treatments ( P =.02). Follow-up tests showed a significant difference in surface roughness between oven-glazed and microwave-glazed treatments ( P =.02). There was a significant difference in flexural strength between the 2 porcelains ( P