Effect of resin and type of surface treatment on the flexural strength of cracked feldspathic porcelain

Porcelain restorations are often ground for clinical adjustment and this removes the surface glaze layer and introduces flaws that can grow in wet environments due to stress-corrosion، reduce the strength of porcelain and limit restoration lifetime. The aim of this study was to introduce some surface treatment methods to control the flaws of ceramic restorations external surface and improve their strength.

40 feldspathic discs were prepared and divided into 4 groups (n=10): not indented (group 1) and others indented by vickers with 29. 4 N and received different treatments: no treatment (group 2)، polished (group 3) and polished-silane-resin (group 4). Biaxial flexural strength of discs was tested after water storage. Data were analyzed using one-way ANOVA.

The mean flexural strength of specimens in group 1 (134. 49±12. 60)، 2 (94. 81±15. 41)، 3 (89. 20±16. 22) and 4 (80. 67±12. 01) were measured. Group 1 (not indented) revealed significantly higher strength (P<0. 001) than that of indented groups (2، 3 and 4). There was no significant difference between group 2 (no treatment) and 3 or 4 (treated) and between treatment methods (3 and 4) (P=0. 136).

The strength of porcelains is dependent on presence of cracks. With the limitations of this study، none of the treatment methods could strengthen the cracked ceramic.