Synthesis and characterization of novel calcium phosphate glass-derived cements for vital pulp therapy

Evaluation of the physicochemical behavior and setting reactions of a novel inorganic pulp capping cement which makes use of the unique corrosion properties of sodium metasilicate (NaSi) glass. NaSi and calcium phosphate (CaP) glass powders were synthesized through a melt-quench method. Cements were created by mixing various amounts of the glasses with deionized water at a powder-to-liquid ratio of 2.5 g mL^-1. Working and setting times were measured using the indentation standard ISO 9917-1. Sealing ability was tested by placing set samples of each composition in methylene blue dye solution for 24 h. Set samples were also submerged in phosphate buffered saline and incubated at 37 °C for one week. X-ray diffraction was used to identify mature crystalline phases after incubation. Infrared spectroscopy and scanning electron microscopy were used to characterize cements before and after setting and after incubation. Working and setting times measured in the ranges of 2-5 and 10-25 min, respectively. Working and setting time generally decrease with increased NaSi concentration. Cements with compositions of 25 and 33 wt% NaSi were found to resist the infiltration of dye and maintain their shape. Compositions outside this range absorbed dye and collapsed. Infrared spectroscopy provided insight into the setting mechanism of these cements. After one week in vitro, cements were found to contain crystalline phases matching chemically stable, bioactive phases. The combination of NaSi and CaP glasses has favorable setting behavior, sealing ability, and mature phases for pulp capping while relying on a relatively simple, inorganic composition.