Effect of Surface Treatments on the Biaxial Flexural Strength of High Leucite Feldspathic Porcelains


The purpose of this study was to examine the effect of altering surface topography on the biaxial flexural strength (BFS) of four dental ceramics, Mirage (MI), Flexoceram (FL), Optec-HSP (OP) and IPS Empress (EM).Twelve groups of ten discs 123mm were prepared and fired according to the manufacturers' instructions. Ten specimens of each material were subjected to three surface treatments, polished, grit blasted and etched with 10% hydrofluoric acid (HF) for 2 minutes. Some specimens were gold coated for examination under Scanning Electron Microscope (SEM). BFS was determined using Lloyd M5K universal testing machine at a cross-head speed of 0.5 mm/min. A one-way ANOVA was used to evaluate the differences between groups.The results obtained showed that the only significant difference in the BFS was the 10% HF for OP and FL (One-way Anova, P<0.05). The decrease in BFS is most likely due to an increased surface flaw size, such that surface initiated crack growth dominates over the bulk internal flaw size of the ceramics.The BFS of dental porcelain used in this study may be governed either by the internal or surface flaws depending on the manner of surface preparation. Specimens etched with 10% HF became weaker for OP and FL ceramics.