Bonding of composite to water aged composite with surface treatments

Objective The purpose of this study was to determine the shear bond strength of new composite to water aged composite with and without interfacial surface treatment. Methods Two hundred and eighty cylindrical samples were prepared for each of three resin composites (Spectrum, Dentsply; Durafill, Kulzer; Herculite, Kerr). Seventy samples of each material were bonded immediately and the remaining were stored in water. After 1, 4 and 12 weeks 70 samples were removed and the surface treated prior to bonding a second fresh increment. The treatments were: (1) no treatment, (2) abrasion with pumice, (3) a layer of Prime and Bond (Dentsply), (4) abrasion + Prime and Bond, (5) a layer of Optibond Solo Plus (Kerr), (6) abrasion + Optibond and (7) a layer of bis-GMA/TEGDMA. The specimens were loaded to failure in shear mode with a crosshead speed of 50 mm/min until fracture. The fracture surface of a number of specimens were examined in a scanning electron microscope. Results At all time intervals the treatment that resulted in the highest bond strengths (>20 MPa) was treatment with the dentine bonding agents (DBS) Prime and Bond or Optibond Solobond Plus. No treatment or abrasion alone resulted in very low bond strengths even after 1 week in water. When used in conjunction with DBSʹs abrasion did not increase the bond strength over the use of the DBS alone. The bis-GMA/TEGDMA was not as effective as the DBSʹs. Significance When bonding new composite to composite that has been underwater it is essential to treat the original composite surface. The results of this study indicated that the application of a dentine bonding agent significantly enhanced the bond. Abrasion alone did not produce an adequate bond.