Adhesive bonding of fractured anterior teeth: effect of wet technique and rewetting agent

To compare the fracture strength of intact teeth with that of fractured crowns bonded with adhesive and a resin material on either wet or dry dentin, or dried dentin rewetted with a rewetting agent for various periods of time.

Sheep central incisors were divided into seven groups, each of 10 teeth. Group 1: Intact teeth tested for fracture strength in an Instron testing machine and used as controls. Groups 2-7 were sectioned in a vice equipped with sharp blades, 2.5 mm away from and parallel to the incisal edge. The two fracture surfaces were etched with 37% phosphoric acid for 15 s and rinsed with water for 5-6 s. Group 2: The surfaces were air-dried for 2 s. Group 3: As for Group 2 but the surfaces were rewetted with Aqua-Prep for 2 s and immediately air-blasted to remove excess. Group 4: As for Group 3, but the rewetting agent was applied for 10 s before air-blasting. Group 5: As for Group 4, but the rewetting agent was applied for 20 s. Group 6: As for Group 4, but the rewetting agent was applied for 30 s. Group 7: As for Group 2, but the surfaces were left moist after etching and rinsing by gently shaking the specimens twice. The fracture surfaces of Groups 2-7 were rebonded with All-Bond 2 adhesive system and Aeliteflo composite. After 48 hrs the restored teeth were debonded in the Instron testing machine. Fracture strengths were calculated and compared with the fracture strength of intact teeth (control group).

Newman-Keuls' multiple range test revealed that there was a statistically significant difference between the control mean and the means of Groups 2 and 3. All other means were not significantly different. Drying of the dentin surface decreased the bonding strength, and rewetting of the dried dentin for 2 s was not sufficient to rewet the collapsed collagen fibers, as indicated by a decrease of fracture strength.