Objectives: To evaluate the effect of layering technique and cavity dimension on the fatigue behavior and marginal adaptation of bulk fill (BF) restorations in extensively damaged teeth.
Methods: Seventy-two premolars received class II cavities (MOD) followed by endodontic treatment. Half sample had 1/3 of their palatal cusp removed. Teeth were restored using three techniques: (I) incremental, with conventional resin composite (RC); (C) combined, using BF flow and RC, (B) bulk fill, with regular BF. Specimens were subjected to fatigue (80 N, 2 Hz, 37° C water) for 1 million cycles (n = 12). The test was interrupted every 250,000 cycles to evaluate tooth integrity, restoration fracture and adaptation using FDI criteria. Images of the proximal surfaces were obtained before and after the cycling to measure the gap. Restoration fatigue survival and success were analyzed using Weibull distribution and Maximum Likelihood Estimation. Gap thickness was analyzed with Kruskal-Wallis and Student-Newman-Keuls tests (α = 0.05).
Results: For the survival analysis, Weibull modulus (β) and characteristic lifetime (η) were similar among groups. Yet, for the success analysis, in which only restorations that were free of technical complications were ranked as success, the bulk-fill technique resulted in higher β, while the combined technique produced restorations with higher η, for teeth that had their cusp removed. C-technique also resulted in smaller gaps than I and B.
Significance: The effect of the layering technique on the success of restorations was dependent on the cavity extension. The combined technique favors the adaptation and the longevity of extensively damaged teeth.
Keywords: Endodontics; Fatigue; Permanent dental restoration; Resin composite.
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