Influence of restorative technique, beveling, and aging on composite bonding to sectioned incisal edges

The aim of this study was to evaluate the effect of material technique, bevel placement, and aging on the fracture resistance of composite restorations bonded to sectioned incisal edges.

For the retention test, the incisal thirds of 80 mandibular human incisors were sectioned. Ten sound incisors were used as a control group. Teeth were divided into two groups according to storage time (24 h and 180 days with 1000 thermal cycles). In each group, subgroups were randomly formed as follows: beveled or nonbeveled direct resin composite restorations (Adper Single Bond/Filtek Z250) and beveled or nonbeveled indirect composite restorations (prepolymerized Filtek Z250 cemented with Adper Single Bond/Rely X ARC). For each experimental group, 20 specimens were prepared (10 tested after 24 h and the remaining after 180 days). The specimens were subjected to shear testing in a universal testing machine with a crosshead speed of 0.5 mm/min. Failure patterns were analyzed by stereomicroscopy (30X). Data were statistically analyzed with ANOVA and Tukey's and Student's t-tests for retention resistance, and with Fisher's exact test for fracture patterns at the 0.05 level of significance for all tests.

After 24 h, beveled restorations exhibited higher fracture strength values than nonbeveled restorations and showed resistance similar to the sound teeth. After 6 months, beveled restorations still presented better results than nonbeveled restorations. Thermal cycling and water storage decreased the fracture resistance in the majority of the groups. Adhesive failures were mainly observed in nonbeveled restorations and mixed failures in beveled restorations.

Within the limitations of the study, it was concluded that storage with thermal cycling decreased fracture resistance, beveling improved fracture resistance, and indirect restorations had a fracture resistance similar to direct restorations.