Objective: To determine the effect of storage medium pH on fatigue parameters (stress corrosion coefficient: n, and scaling parameter: s_f0) of a leucite-based porcelain (Ultropaline Dentin, JenDental – UD), and a vitreous porcelain (Veneer Material 7, Vita Zahnfabrik – VM7). Methods: 150 disc specimens of each material were produced following manufacturers' firing cycles, and divided into artificial saliva solutions with the following pHs: 3.5; 7.0 and 10.0 (10 days storage/37^oC). The fatigue parameters were obtained by the dynamic fatigue test, using a biaxial flexural strength design (piston-on-three-balls) and five constant stress rates (0.01, 0.1, 1, 10, and 100 MPa/s, n=10). During the tests, specimens were immersed in the same solution they were stored at 37^oC. Fatigue parameters were determined and statistically analyzed based on equations presented in ASTM-C-1368-00. Results: The n value of VM7 did not vary significantly as a function of pH. For porcelain UD, the n value was significantly lower when specimens where stored in pH 3.5 compared to other pHs, which resulted in similar n values. For both materials, storage in basic pH resulted in a significant decrease in s_f0. VM7 also showed a decrease in s_f0 after storage in acid pH. Lifetime curves showed that the applied stress (s₁₀) calculated to obtain a time to failure of 10 years for VM7 was higher than that calculated for UD regardless of the pH. Conclusion: The effect of pH on fatigue parameters varied according to the porcelain studied. Acknowledgments: FAPESP, CNPQ and CAPES.

Porcelain	pH	n	sf0 (MPa)	s10 (MPa)
UD	3.5	26.5 ± 4.2	57.8 ± 0.02	32.9
	7.0	40.8 ± 10.2	58.3 ± 0.02	41.1
	10.0	39.6 ± 8.9	53.2 ± 0.02	36.8
VM7	3.5	29.9 ± 8.1	73.1 ± 0.03	46.6
	7.0	31.2 ± 7.1	79.6 ± 0.02	51.0
	10.0	30.4 ± 7.6	71.8 ± 0.03	46.0

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