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

Purpose: To compare the fracture strength of intact teeth with that of frac tured crowns bonded with adhesive and a resin material on either wet or dry dentin, or dried dentin rewetted with a rewetting agent for various period s of time. Materials and Methods: Sheep central incisors were divided into seven groups, each of 10 teeth. Group 1: Intact teeth tested for fracture s trength 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 paral lel to the incisal edge. The two fracture surfaces were etched with 37% pho sphoric acid for 15 s and rinsed with water for 5-6 s. Group 2: The surface s were air-dried for 2 s. Group 3: As for Group 2 but the surfaces were rew etted 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 befor e air-blasting. Group 5: As for Group 4, but the rewetting agent was applie d for 20 s. Group 6: As for Group 4, but the rewetting agent was applied fo r 30 s. Group 7: As for Group 2, but the surfaces were left moist after etc hing and rinsing by gently shaking the specimens twice. The fracture surfac es of Groups 2-7 were rebonded with All-Bond 2 adhesive system and AElitefl o composite. After 48 hrs the restored teeth were debonded in the Instron t esting machine. Fracture strengths were calculated and compared with the fr acture strength of intact teeth (control group). Results: Newman-Keuls' mul tiple range test revealed that there was a statistically significant differ ence between the control mean and the means of Groups 2 and 3. All other me ans were not significantly different. Drying of the dentin surface decrease d the bonding strength, and rewetting of the dried dentin for 2 s was not s ufficient to rewet the collapsed collagen fibers, as indicated by a decreas e of fracture strength.