Purpose: To compare the microtensile bond strengths of incremental and bulk-fill techniques under different C-factor and compliance conditions. Methods and Materials: Extracted human third molars were divided into three experimental groups. For group I, Class I cavities were prepared. For group II, MOD cavities of the same size were prepared. For group III, the cavities were prepared the same way as group II only with high compliance cavity walls. The cavity wall compliance of the specimens was evaluated. Each of these groups was divided into four subgroups. The teeth were restored using two different materials: TB (Tetric N-Ceram Bulk Fill; Ivoclar Vivadent, Hanau, Germany) and VB (Venus Bulk Fill; Heraeus Kulzer, Armonk, NY, USA), and two methods, either an incremental or bulk-fill technique. Then, the microtensile bond strengths (l-TBSs) were measured and compared. The polymerization stresses of the composites were calculated using a custom-made device. The results were statistically analyzed using the Kruskal-Wallis test and Weibull analysis. Results: In group I, the l-TBS obtained using the incremental technique was significantly higher than that obtained by the bulk-fill technique (p,0.05). In contrast, no difference of the l-TBS value was observed between the two techniques in groups II and III. The l-TBS value of group I was significantly lower than those of groups II and III (p,0.05). No statistical difference in the l-TBS was observed when the cavities were filled with either TB or VB (p.0.05). Conclusions: The incremental technique showed higher bond strength than did the bulk-fill technique in high C-factor cavities. However, no difference was found between the two techniques in the low C-factor cavities. The bond strength in the high C-factor cavities was significantly lower than that of the low C-factor cavities.
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