A strontium and amorphous calcium phosphate dipped premixed injectable calcium silicate-based ceramic for dental root canal sealing

Abstract

A type of strontium and amorphous calcium phosphate dipped premixed injectable tricalcium silicate-based dental root canal sealer was developed as the following protocols. A powder mixture containing tricalcium silicate, strontium carbonate (6, 8, 10, and 12 wt%), zirconia (20 wt%), calcium chloride (6 wt%), and amorphous calcium phosphate (ACP) (5 wt%) was mixed with liquid polyethylene glycol 400 (PEG 400) at a liquid-to-powder ratio of 0.5 mL/g and mechanically ground using a planetary ball to obtain the premixed injectable calcium silicate-based sealer. The sealer’s physicochemical property and cytocompatibility were evaluated in vitro. Quantitative data were expressed as mean ± standard deviation, and Student's t-test or a one-way analysis of variance (ANOVA) test were carried out at significant differences with P < 0.05. All the sealer groups had suitable flowability (21.3–33.3 mm, n = 3), setting time (241.87 ± 32.72–299.00 ± 26.05 min, n = 8) and radiopacity basically according to ISO 6876-2012 standard. The pH value generally stabilized between 10 and 12 (n = 5) when the sealer was immersed into deionized water or phosphate buffered solution. The sealing property of root canal sealer was evaluated by dye penetration, 6% strontium groups had the best root canal sealing property among all the groups (1.21 ± 0.17–5.75 ± 0.97) mm, n = 10, P < 0.05). 6% strontium groups bonded together to the dental root canal wall, penetrated the dentinal tubule to occlude the dentinal tubules, formed calcium–silicate–hydrate (C–S–H) network structure, induced a layer of nano hydroxyapatite crystal grown on its surface in simulated body fluid (SBF), showing good biomineralization activity. It also had osteogenic differentiation activity cultured with rat bone marrow mesenchymal stem cells (n = 5, P < 0.05). This sealer provided a potential new filling material for root canal therapy and has promising application prospects.