Adhesion of composite to air-abraded enamel and dentin

The purpose of this study was to compare the shear bond strength of a resin composite to air abraded and not air abraded enamel and dentin surfaces, and to evaluate the need for acid conditioning before the application of a single component adhesive. Enamel (E) and dentin (D) flat surfaces were obtained from a pool of recently extracted human teeth (30 incisors and 30 molars) and prepared with different treatments with and without the application of air abrasion (AA) and phosphoric acid (PA). Composite samples were bonded to the surfaces and stored in distilled water at 37 degrees C. After 24 hours, shear bond strength tests were carried out with an Instron machine and the results were subjected to statistical analysis. Maximum bond strength was obtained in the E + AA + PA group (34.74 MPa--2.70), followed by: E + PA (31.26 MPa--1.87); D + PA (24.09-1.72); D + AA + PA (20.61 MPa--1.79); D + AA (8.96 MPa--0.82) and E + AA (7.17 MPa--1.75). The results were significantly lower in those groups that were not acid conditioned (P < 0.01). The bond strength of composite to enamel was slightly increased as a result of the combination of AA with PA. However, the opposite effect was observed on dentin surfaces. Acid etching is a necessary clinical step even on air abraded surfaces.