Effect of fiber nets, application techniques and flowable composites on microleakage and the effect of fiber nets on polymerization shrinkage in class II MOD cavities.

This study evaluated the effects of fiber nets and application techniques and flowable composites as a liner on microleakage and the effects of fiber nets on polymerization shrinkage in Class II MOD cavities. Standard MOD cavities were performed in 80 extracted third molars. The teeth were randomly divided into eight groups (n=10). Group 1: Filtek Supreme XT (bulk technique) (FSB); Group 2: Filtek Supreme XT (incremental technique) (FSI); Group 3: Filtek Supreme XT Flow (FS Flow)+FSB; Group 4: FS Flow+FSI; Group 5: FS Flow+Ribbond (R)+FSB; Group 6: FS Flow+R+FSI; Group 7: FS Flow+everStick NET (E)+FSB; Group 8: FS Flow+(E)+FSI. All the teeth were then immersed in 0.5% basic fuchsin solution for 24 hours after thermocycling for 1000 cycles (5 degrees C and 55 degrees C). The teeth were sectioned longitudinally and observed under a stereomicroscope. In order to determine the polymerization shrinkage, another study was designed. In Group A, composite was applied as a bulk. In Group B, the resin composite was divided into two parts and Ribbond fiber was placed in the middle of the mass. In Group C, everStick NET fiber was placed inside the composite, as in Group B. Statistical analysis were performed by using one-way ANOVA and Tukey HSD tests for both microleakage and polymerization shrinkage (p < 0.05). Less microleakage was observed in groups where composites were applied by the incremental technique compared with those where the bulk technique was used (p < 0.05). The groups that used flowable composites showed significantly lower microleakage (p < 0.05). In groups where fiber nets were used, a significant decrease was determined in terms of microleakage (p < 0.05). Groups with fiber nets exhibited lower polymerization shrinkage (p < 0.05). Fiber nets decreased both microleakage and polymerization shrinkage. The incremental technique is an effective method for Class II composite restorations.