Effect of fractured or sectioned fragments on the fracture strength of different reattachment techniques.

This study evaluated the effect of fractured or sectioned fragments on the fracture strength recovery of four techniques used for reattachment and resin composite buildups. Ninety-one sound, permanent lower central incisors were used. Half the teeth were fractured in the incisal-proximal edge; the other half had the incisal-proximal edge sectioned by a diamond saw. Teeth from each half were randomly divided into five techniques: 1) bonded only; 2) chamfer; 3) over-contour; 4) internal dentinal groove and 5) resin composite buildup. An adhesive system and dual cure resin cement were employed for the reattachment. Restored teeth were subjected to load in a specific point on the buccal surface. Based on the fracture strength of sound teeth, a fracture strength recovery was calculated for each tooth. A one-way ANOVA and Tukey's test (alpha=0.05) were used to evaluate differences between the techniques for each method of obtaining fragments. The fracture strength recovery of similar techniques was evaluated by a Student t-test (alpha=0.05). No differences could be detected among reattachment techniques when fragments were obtained by sectioning. In groups where the fragments were fractured, Techniques 3 and 4 showed the highest fracture strength recovery. The resin composite buildup provided fracture strength recovery similar to intact teeth regardless the way fragments were obtained.