pH Changes upon Mixing of Single-step Self-etching Adhesives with Powdered Dentin

Purpose: Single-step self-etching adhesives have been developed as a bonding material that adheres to the tooth surface. The adhesives contain acidic resin monomers that penetrate the dentin but can be neutralized to stop the reaction. This study aimed to improve understanding of the pH changes that occur when self-etching adhesives are mixed with dentin powder. Materials and Methods: Dentin disks obtained from extracted bovine incisors were milled and pulverized into a fine powder. The powder was mixed with diluted self-etching adhesives, and pH changes were measured by a solid-state pH sensor connected to a pH meter at various time points after the start of mixing. Data were analyzed by Tukey's Honestly Significant Difference (HSD) test and Dunnett's test at a significance level of 0.05. Precipitates from the adhesive/ dentin powder mixture were observed by scanning electron microscopy (SEM). Results: The baseline pH values of the self-etching adhesives ranged from 0.97 to 2.83. After mixing with the dentin powder, the pH values significantly increased, ranging from 6.30 to 7.11 at 180 s after mixing. SEM observation revealed products of the reaction between dentin powder and self-etching adhesive which indicate a chemical reaction between the functional monomer and dentin. Conclusion: Dentin has a strong modulation effect against the acidity of self-etching adhesives. Keywords: dentin, functional monomer, pH, self-etching adhesive, insoluble precipitate