Dual application of dentin bonding agents: effect on bond strength.

PURPOSE: To evaluate the effect of a dual application of dentin bonding agents (DBA) on their shear bond strength on dentin with intermediate application of a provisional cement.
MATERIALS AND METHODS: Freshly prepared flat dentin surfaces of human teeth were coated with a first layer of one of various dentin bonding agents (All-Bond 2, ART Bond, Syntac or an experimental DBA called P-Bond). After curing the DBA, a provisional cement (Temp Bond, Freegenol or Fermit, a soft provisional diacrylate) was applied to the bonded dentin surface. After 24 hours, the provisional cement was removed and the dentin surface scrubbed with pumice. A second application of the same DBA together with a composite cylinder followed. After curing and 1,500 thermal cycles with constant imitation of intrapulpal pressure, shear bond strengths were measured.
RESULTS: Compared to a single application of dentin bonding agents following Temp Bond treatment (SBS in MPa: Syntac: 0.86 +/- 1.75, ART Bond: 0.26 +/- 0.47, P-Bond: 14.90 +/- 4.51) application of DBAs prior to use of Temp Bond as well as after its removal seems to be very beneficial to shear bond strength values (SBS in MPa: Syntac:13.36 +/- 4.70, ART Bond: 16.34 +/- 5.02, P-Bond: 19.04 +/- 2.01). Independent from the provisional cement, the values after serial application of P-Bond provided consistently high bond values which were not statistically different (Kruskal-Wallis, P > 0.05) from values of P-Bond on fresh dentin (18.19 +/- 2.29 MPa). The only exception from these findings in the present study was All-Bond 2. Regardless of the provisional materials used, the bond strength values of All-Bond 2 remained low (maximum SBS with Fermit as intermediate provisional cement: 4.63 +/- 2.91 MPa).