A pilot study of lactic acid as an enamel and dentin conditioner for dentin-bonding agent development

The purpose of this pilot study was to determine how lactic acid solution at various concentrations and etching times affected prepared human enamel and dentin surfaces and to assess whether it could be used in place of phosphoric or maleic acid as an etchant. The occlusal surfaces of extracted molar teeth were ground wet with 600-grit silicon carbide paper and treated with various aqueous solutions of lactic acid. Random samples were prepared for observation by scanning electron microscopy. The rest were used to determine shear bond strength of bonded dental composite cylinders. The micrographs revealed that lactic acid dissolved the smear layer with various degrees of etching and demineralization. The degree of smear layer and matrix removal was proportional to the concentration of the acid and the length of application time. A 20% lactic acid concentration applied for 10 seconds produced a clearly etched surface with minimal demineralization. A 30% concentration not only removed the smear layer and enlarged the dentin tubule orifices but also appeared to affect the collagen matrix. The shear bond strength to enamel treated with 50% lactic acid (17.5 +/- 1.5 MPa) and All-Bond 2 etchant (18.9 +/- 1.3 MPa) were not significantly different (p > 0.05). However, mean dentin bond strengths for all groups of lactic acid etchant and All-Etch etchant (10% phosphoric acid) were statistically similar.