pH changes of self-etching primers mixed with powdered dentine

The purpose of this study was to examine the pH changes of self-etching primers mixed with dentine powder.

Four self-etching primer adhesive systems were used: Clearfil SE Bond, Imperva Fluoro Bond, Mac Bond II, and Unifil Bond. Dentine discs obtained from extracted bovine incisors were milled and pulverized into a fine powder. The dentine powder was then mixed with solutions of self-etching primers diluted with distilled water. The pH changes of the primer-dentine powder mixtures were measured by a solid-state pH sensor connected to a pH meter at time points 10, 20, 30, 60, 120, 180, 300, and 600 s after the start of mixing. Data were analyzed by the Tukey HSD test and the Dunnett test at a significance level of 0.05.

The baseline pH values of the self-etching primers ranged from 1.83 to 2.34, with Mac Bond II exhibiting a significantly lower value than the other three products. After mixing with the dentine powder, the pH values significantly increased, ranging from 6.95 to 7.37 at 600 s after mixing; there were no significant differences in these values among the self-etching primers used. An insoluble precipitate was formed in the case of Clearfil SE Bond, indicating a chemical reaction between the functional monomer and the dentine powder.

The dentine has a strong buffering capacity against the acidity of self-etching primers.