Flexural strength of fluorapatite-leucite and fluorapatite porcelains exposed to erosive agents in cyclic immersion

OBJECTIVE The aim of this study was to evaluate the flexural strength of two porcelain materials (IPS d.SIGN and IPS e.max Ceram) exposed to erosive agents. MATERIAL AND METHODS One hundred and twenty bar-shaped specimens were made from each of fluorapatite-leucite porcelain (IPS d.SIGN) and fluorapatite porcelain (IPS e.max Ceram) and divided into 8 groups of 15 specimens each. Six groups were alternately immersed in the following storage agents for 30 min: deionized water (control), citrate buffer solution, pineapple juice, green mango juice, cola soft drink and 4% acetic acid. Then, they were immersed for 5 min in deionized water at 37ºC. Seven cycles were completed, totalizing 245 min. A 7th group was continuously immersed in 4% acetic acid at 80ºC for 16 h. The final, 8th, group was stored dry at 37ºC for 245 min. Three-point bending tests were performed in a universal testing machine. The data were analyzed statistically by 2-way ANOVA, Tukey's HSD test and t-test at significance level of 0.05. RESULTS The flexural strengths of all groups of each porcelain after exposure to erosive agents in cyclic immersion did not differ significantly (p>0.05). For both types of porcelain, dry storage at 37ºC yielded the highest flexural strength, though without significant difference from the other groups (p>0.05). The flexural strengths of all groups of fluorapatite porcelains were significantly higher (p<0.05) than those of the fluorapatite-leucite porcelains. CONCLUSIONS This study demonstrated that the erosive agents evaluated did not affect the flexural strength of the tested dental porcelains.