Abstract
This study aimed to evaluate, in vitro and in vivo, the biocompatibility of experimental methacrylate-based endodontic sealers containing α-tricalcium phosphate (α-TCP) or nanostructured hydroxyapatite (HAp). Experimental methacrylate-based dual-cure sealers with the addition of α-TCP or HAp, at 10%wt were formulated and compared to AH Plus (AHP). Cell viability was assessed by 3-(4,5-dimethyl-thiazoyl)-2,5-diphenyl-tetrazolium bromide (MTT), and sulforhodamine B (SRB). Sealers were implanted in rats' subcutaneous tissue and histologically evaluated. Bioactivity was assessed by alkaline phosphatase enzyme activity (ALP) and Alizarin Red (AR), using apical papillary cells (SCAPs), and by the bone deposition measured in surgical cavities on rats' femur filled with AH Plus or α-TCP. In both viability assays, HAp and AHP sealers were similar, and α-TCP presented lower viability compared to the others at MTT assay (p<0.05). A gradual decrease of the inflammatory response according to the periods was observed and AHP was the only that presented giant cells (7-day period). Collagen fibers condensation increased according to the periods, with no differences among sealers. There was an increase at ALP activity and mineralized nodules deposition according to periods. HAp and α-TCP presented higher values for ALP activity at 5 days and at 5, 10, and 15 days for AR and were different from AHP (p<0.05). α-TCP presented superior values at 10 and 15 days compared to HAp and AHP for AR (p<0.05). At 90 days, α-TCP and control (empty cavity) showed high bone deposition compared to AHP (p<0.05). α-TCP and HAp, in a methacrylate-based sealer, presented biocompatibility and bioactivity, with the potential to be used as endodontic sealers in clinical practice. Further investigations are required to gain information on the physicochemical properties of these sealers formulation before its clinical implementation.
Highlights
Endodontic sealers present contact with the periapical tissue when the canals are sealed, or even, may be unintentionally extruded beyond the apical foramen
After 80% confluency, cells were washed with PBS 1X (Sigma-Aldrich), separated with Trypsin-EDTA 0.25% solution (Sigma-Aldrich), re-suspended in culture medium and transferred to a Falcon tube (TPP), forming a cell suspension that was transferred to cell culture bottles (TPP) that were kept in an incubator at 37°C, 100% humidity and 5% CO2 until reaching 80% of confluence
Bioactivity Assays Bioactivity was assessed by alkaline phosphatase enzyme activity (ALP), considered a marker of osteoblastic and odontoblastic activity and Alizarin Red staining (AR), which identifies calcium and phosphate deposits in cell culture, both at the periods of 1, 5, 10 and 15 days, and by bone deposition measured in surgical cavities on rats’ femur filled only with the AH Plus and α-tricalcium phosphate (α-TCP)
Summary
Endodontic sealers present contact with the periapical tissue when the canals are sealed, or even, may be unintentionally extruded beyond the apical foramen. Studies evaluating experimental endodontic sealers with HAp demonstrated biocompatibility in the animal model [7], presented bioactivity in vitro [8,9,10,11], and showed appropriate physicochemical properties as setting time, flow, solubility, microhardness, and bond strength [8,9,10,11]. Α-tricalcium phosphate (α-TCP) is a reactive compound that presents high biodegradation rate and progressive dissolution with formation of calcium apatite [12]. These calcium phosphates could interact with surrounding tissues, increasing the mineral deposition and biological response
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