Effects of moisture degree and rubbing action on the immediate resin-dentin bond strength.

OBJECTIVES

To compare the effects of moisture and rubbing action on the microtensile bond strength (BS) of an ethanol/water-based (Single Bond [SB]) and an acetone-based system (One-Step [OS]) to dentin.

METHODS

On 60 human molars, a flat superficial dentin surface was exposed by wet abrasion. Two coats of the adhesives were applied on either a dry (D) or rewetted surface (W), under no rubbing action (NRA), slight (SRA) or vigorous rubbing action (VRA). After light curing (600 mW/cm2/10 s), composite build-ups were constructed incrementally and specimens were stored in water (37 degrees C/24 h). They were longitudinally sectioned in the "x" and "y" directions to obtain bonded sticks (0.8 mm2) to be tested in tension at 0.5 mm/min. Resultant BS was expressed as an index that includes bond strength values of the different fracture patterns and the specimens that failed during preparation for testing. The data were analyzed by a three-way ANOVA and Tukey's multiple comparison tests (95%).

RESULTS

The interactions moisture/agitation and adhesive/agitation were statistically significant (p < 0.05). In D groups, the highest BS was obtained under VRA (37.11 +/- 7.3). In W groups, the BS at SRA (41.82 +/- 8.4) and VRA (38.89 +/- 8.2) were similar. For SB system, the SRA (33.6 +/- 8.3) and VRA groups (41.26 +/- 5.9) yielded similar BS while for OS the VRA was essential to reach high BS (34.2 +/- 8.4).

SIGNIFICANCE

High BS to dentin can be obtained, under dry conditions, when ethanol/water and acetone-based systems, are vigorously agitated in the surface. On wet dentin, slight agitation seems to be enough to provide high BS to dentin.