Pages 637-643, Language: EnglishWorthington, Robert B. / Murchison, David F. / Vandewalle, Kraig S.Objective: This study evaluated the effect of preparation utilization and design, and addition of resin composite to the bonding interface, on the fracture resistance of reattached incisal fragments. Method and materials: Sixty bovine incisors were distributed among 1 control group and 5 experimental groups. Experimental specimens were sectioned 3.0 mm from the incisal edge with a 0.15-mm wafering blade at a 25-degree inclination apically in a faciolingual direction. Two groups received no further preparation. Specimens in the other 3 groups received either external bevels, internal bevels, or combined external and internal bevels. One preparationless group was reattached with dentin bonding agent alone. All other fragments were reattached with a dentin bonding agent/resin composite interface. After thermocycling and 4 weeks of bond weathering, specimens were sheared to failure in a universal testing machine. Results: No significant differences in fracture strength were observed among any of the experimental groups, yet each displayed significantly less resistance to fracture than the control group. Reattachment of fragments in all groups restored approximately one half or one third the fracture strength of the control teeth for crown or root fractures, respectively. Conclusion: Compared to the simple, expedient regimen of using a dentin bonding agent alone, nonconservative tooth modification and the addition of resin composite to the bonding interface did not increase resistance to fracture and thus provided no retentive advantage.
