How should composite be layered to reduce shrinkage stress: Incremental or bulk filling?

Objectives: The purpose of this study was to determine the effect of different layering techniques on cuspal deflection in direct composite restorations. Methods: Aluminum blocks were used to prepare MOD cavities divided into three groups. Each cavity was restored with composite using three different filling techniques. Group 1 was filled in bulk, group 2 was restored by a horizontal increment technique, and group 3 by an oblique increment technique. Cuspal deflection was measured with LVDT probes and compared among groups using ANOVA and Scheffe's post hoc test (α = 0.05). Results: The cuspal deflections in groups 1-3 were 21.6 ± 0.90 μm, 19.3 ± 0.73 μm and 18.4 ± 0.63 μm, respectively. The bulk filling technique yielded significantly more cuspal deflection than the incremental filling techniques, while there was no significant difference between the horizontal and oblique increment methods. Significance: Cuspal deflection resulting from polymerization shrinkage can be reduced by incremental filling techniques to obtain optimal outcomes in clinical situations.