Alkalinization potential is a fundamental property of endodontic epoxy-based cements containing calcium hydroxide. Studies have shown discrepant pH results for same materials at different evaluation periods. A possible reason accounting for these differences may be the assessment procedures. Objective: To evaluate the pH value of an epoxy-based cement (Sealer 26) in different periods of analysis, using two assessment methods. Material and methods: Sealer 26 was manipulated and immediately placed into polyethylene tubes (n=10, each group) and immersed in distilled water. In G1, the tubes were kept in the same water during all experiment; and in G2, the tubes were removed and placed into another flask with an equal amount of water after the pH evaluation. The pH of these solutions was measured at 24 hours, 7, 14 and 28 days. Analysis were made within the same group according to the experimental periods and between groups in each experimental period. Data were submitted to ANOVA (α = 5%) and t test, respectively. Results: For G1 and G2, all periods showed different pH values (p < 0.05), except between 14 and 28 days (p > 0.05) and between 7 and 14 days (p > 0.05), respectively. In each period, no significant differences were observed between the groups. Conclusion: The method to obtain the pH values in different experimental periods no interfered in the final results. However, difference was observed when the results were analyzed at same group.

ResumoObjetivo: Avaliar o efeito da dentina sobre o pH e a atividade antimicrobiana de formulações com hidróxido de cálcio. Material e método: O pH e a atividade antimicrobiana das formulações (G1-polietilenoglicol, G2-glicerina e paramonoclorofenol canforado ou G3-clorexidina) foram analisados nas formulações puras (G1A, G2A e G3A) ou acrescidas de dentina em pó (G1B, G2B e G3B). Tubos de polietileno foram preenchidos com uma das formulações e imersos em água destilada. O pH foi analisado após 24 horas, 7, 14 e 21 dias. A atividade antimicrobiana foi avaliada sobre Enterococcus faecalis (ATCC 29212), através do teste de difusão em ágar. Os resultados foram submetidos aos testes de ANOVA e Tukey (p=0,05). Resultado: A dentina não exerceu efeito sobre o pH das formulações, exceto ocasionando a redução em G1, no período de 24 horas (p<0,05). Nas demais formulações, não houve interferência da dentina sobre o pH (p>0,05). Quando comparados entre os grupos, em 24 horas e 7 dias, G1A e G1B apresentaram menor pH (p<0,05). Em 14 dias, G2A, G2B, G3A e G3B demonstraram similar pH (p>0,05), assim como entre G3B e G1A (p>0,05). Em 21 dias, todas as formulações demonstram semelhante pH (p>0,05). Os resultados em ordem decrescente da atividade antimicrobiana foram G2A=G2B>G3A=G3B>G1A=G1B (p<0,05). Conclusão: A dentina não interferiu no pH e na atividade antimicrobiana das diferentes formulações com hidróxido de cálcio, exceto na associação com o polietilenoglicol, em que ocasionou a redução do pH apenas no período de 24 horas. A formulação com paramonoclorofenol canforado apresentou maior atividade antimicrobiana, seguida da clorexidina e do polietilenoglicol.Descritores: Cálcio; endodontia; Enterococcus faecalis; pH. AbstractObjective: To evaluate the dentin effect on pH and antimicrobial activity of the calcium hydroxide chemical formulations. Material and method: pH and antimicrobial activity of calcium hydroxide formulations were evaluated (G1-polyethyleneglycol, G2-glycerin and camphorated paramonochlorophenol and G3-chlorhexidine). The formulations were evaluated alone (G1A, G2A e G3A) or with dentin powder (G1B, G2B and G3B). Polyethylene tubes were filled with the formulation and immersed in distilled water. After 24 hours, 7, 14 and 21 days, pH was evaluated. The antimicrobial activity was evaluated against Enterococcus faecalis by agar diffusion test. All data were submitted to ANOVA and Tukey tests (p=0.05). Result: None effect was observed on pH and antimicrobial activity by dentin on different chemical formulations, except the reduction occurred in G1 at 24 hours (p <0.05). When compared between the groups at 24 hours and 7 days, G1A and G1B had a lower pH (p <0.05). At 14 days, G2A, G2B, G3A and G3B showed similar pH (p <0.05) and between G3B and G1A (p> 0.05). At 21 days, all formulations were similar (p> 0.05). Regarding antimicrobial activity G2B G2A => = G3A G3B> = G1A G1B (p <0.05). Conclusion: The dentin did not affect the pH and antimicrobial activity of different formulations containing calcium hydroxide...