An evaluation of the effects of different polishing materials and glazing techniques on the fracture toughness of dental porcelain

Abstract EN

Background : As there is an increase in the importance of measuring the fracture toughness of dental porcelain, different methods and materials were supposed.

The aim of this study was to compare the fracture toughness of feldspathic porcelain with different polishing materials and glazing techniques. Materials and methods : Forty-nine metal-ceramic discs (width = 10 mm, height = 5 mm) were fabricated and randomly divided into seven groups (n = 7) ; group one was left intact and considered as a control group, other groups’ surfaces were treated with autoglaze only, applied glaze only, polished with ceramic rubber wheel only, polished with Dentaurum universal polishing paste only, polished with paste then autoglazed, and polished with paste followed by applied glaze respectively.

Porcelain fracture toughness (KIc) for each specimen was measured by a Micro-Vickers Hardness Tester then the mean KIc for each group was determined.

The data were analyzed by using analysis of variance (ANOVA) followed by Least Significant Difference (LSD). Results : Mean porcelain fracture toughness of all groups were 1.320, 0.665, 1.469, 1.319, 1.480, 1.108, 1.548 MN / m-3 / 2 respectively.

Very high significant differences were found between the groups (P < 0.001).

The highest mean of KIc value was recorded in group VII which represented the toughest group while the lowest mean value was represented by group II. Conclusions : Surface treatment of feldspathic porcelain restorations with polishing paste and applied glaze showed highly significant increase in fracture toughness.

Polishing unglazed porcelain using ceramic rubber wheel and Dentaurum universal polishing paste showed no significant differences compared with specimens treated with applied glaze only.