Bonding efficiency of single-bottle enamel/dentin adhesives

To compare the bond strength to dentin of the single-step enamel-dentin adhesive Etch & Prime 3.0 (EP3) to that of two-step systems Clearfil Liner Bond 2 (CL2), which includes a self etching primer and Gluma One Bond (GL1), a one-bottle bonding agent, intended for use with the total etch technique.

Shear bond strength after a 24-hour water storage was determined for 10 specimens each bonded with the three adhesives. Maximum, gap widths were recorded microscopically after a 10-minute water storage along the margins of resin-based composite restorations bonded with each adhesive in cylindrical dentin cavities (3.5 mm wide and 1.5 mm deep). Marginal micro-morphology of the specimens bonded with EP3 was observed with the SEM.

EP3 had an enamel bond strength similar to that of the other materials, but its bond strength to dentin was approximately only 50% of the bond strength of the two other adhesives. Similarly, the marginal performance of resin restorations bonded with EP3 in cylindrical dentin cavities was poor (average maximum gap width 5 microns) irrespective of the curing conditions tested with EP3. CL2 showed significantly smaller gaps (2 microns) along the cavity margin than EP3, whereas in the GL1 group in 7 of the 10 restorations inspected perfect gap-free margins were observed. An SEM investigation of different steps throughout the EP3 application and processing gave evidence that the product apparently conditions and wets enamel and dentin quite effectively, and that an approximately 0.5 micron thick hybrid layer is formed as a coupling zone between dentin (intertubular and peritubular) and restorative resin.