Storage stability of solutions of pyruvic acid/glycine used in adhesive bonding

The rate of deterioration of pyruvic acid/glycine solutions used as common pretreatment of enamel and dentin in the Gluma bonding technique was investigated. Bond strengths between composite resin and enamel/dentin were measured. The bonds were mediated by pyruvic acid/glycine solutions, applied from 0 to 6 months after the time of manufacture. Bond strengths to enamel varied between 8.6 and 13.5 MPa and to dentin between 6.2 and 18.0 MPa. The pH of the solutions rose slightly during the experimental period, but no statistically significant change in bond strengths was observed.