Effect Of pH&Temperature On Roughness And Ion Release Of Ceramics

Materials&Methods:Twenty ceramic disks (8x2mm) were fabricated (EmpressII, Zirkonzahn, Noritake CerabienZR, Finesse, Vita VM7) in a special mold and divided into 2 groups of autoglaze and polishing(n=10). Surface roughness (Ra) of each specimen was evaluated using a profilometer before and after corrosion tests. The specimens were then subjected to in vitro corrosion (pH4,5-pH7-pH9 in water at 37±2°C for 18 h and 4% acetic acid solution pH=2,4 at 80±2°C for 18 h). Ion release was analyzed with inductively coupled mass spectroscopy. The major leaching elements (in ppb) were sodium (1254±279), potassium (3308±388), magnesium (1783±45), silicon (3358±138), and aluminum (3931±359) both in acid and water corrosion experiments, and, on a lower scale, yttrium (274±16), calcium (394±87), and chromium (144±55). Scanning Electron Microscopy(SEM) was performed before and after corrosion tests. The data were statistically analyzed by ANOVA and Bonferroni Test (á=0.05). Multiple comparisons of Ra between pH groups of each ceramic were computed by t-test.

Results:No significant differences in dissolution were found among ceramic groups. Ra values were significant among ceramic groups at different pH values (p<0.05). All groups demonstrated a smoother surface (Ramean=0,36±0,14) or just a minor increase in surface roughness. SEM revealed smoother surfaces in all groups.

Conclusion:Composition and microstructure alone did not provide a full explanation for the individual differences in surface corrosion when exposed to comparable environmental conditions. None of the dental ceramics studied are chemically inert in an aqueous environment. Smoother surfaces were obtained after corrosion in all ceramic groups however corrosion resistance in progressive environment might be further studied.