12 Months Results of Bond Strength and Endogenous Enzymatic Activity of Radicular Dentin Obturated With Bioceramic Sealer

Purpose: Evaluation of radicular bond strength and dentinal matrix metalloproteinases (MMPs) activity with different endodontic sealers (traditional vs bioceramic), filling techniques (warm vs cold), and adhesive protocols (self-etch vs etch-and-rinse), after 24 hours and after one year (T0 vs T1).
Materials and Methods: 96 extracted, caries-free, single-rooted teeth were selected and shaped with Proglider, ProTaper Next X1-X2. Samples were randomly divided into four groups: warm filling with ZOE sealer; cold filling with resin-based sealer; cold filling with bioceramic sealer; warm filling with bioceramic sealer. After 7 days, a 10 mm post space was prepared using dedicated drills, and each group was divided into two subgroups according to the adhesive procedure (self-etch vs etch-and-rinse, SE vs ER) employed for fiber post cementation with dual resin cement. Samples were analyzed with push-out tests at T0 and T1. 16 additional non-carious multirooted teeth were prepared following the described groups and subgroups for in-situ zymography analysis at T0 and T1. A four-way ANOVA, post-hoc Tukey was used to test the four factors and one-way ANOVA to evaluate the differences within each variable (α = 0.05).
Results: Bioceramic sealer showed significantly higher bond strength than traditional sealer (P 0.05), especially when associated with the warm filling technique. SE adhesive protocol performed significantly better (P 0.05) independently of the sealer used, the filling technique, and the aging time. Greater endogenous collagenolytic activity was identified within the hybrid layer of ER-treated samples compared to SE independently from the other variables tested. In addition, warm technique proved to significantly reduce MMPs activity compared to the cold technique.
Conclusion: The results showed that bioceramic sealers should guarantee better results in radicular dentin bond strength, without altering the endogenous enzymatic activity. The heat produced during the root canal obturation might reduce the internal enzymatic activity but, in association with bioceramic sealers, after 12 months, it produces higher bond strength. Heat reduces the difference between the two adhesive systems. ER technique and aging increase enzymatic activity. Aging tends to increase bond strength, especially in traditional sealers groups associated with ER protocol. Keywords: bioceramic, bond strength, matrix metalloproteinases, push-out, in-situ zymography