Development of remineralizing, antibacterial dental materials

Abstract

Light curable methacrylate dental monomers containing reactive calcium phosphate filler [monocalcium phosphate monohydrate (MCPM with particle diameter 29 or 90 μm) and -tricalcium phosphate (-TCP) at 1:1 weight ratio] in powder : liquid ratio (PLR) 1:1 or 3:1 and Chlorhexidine Diacetate (0 or 5 wt%), were investigated. Upon light exposure, approximately 90 % monomer conversion was gained irrespective of the formulation. Increasing PLR promoted water sorption by the set material, induced expansion and enhanced calcium, phosphate, and chlorhexidine release. Concomitantly, a decline in compressive and biaxial flexural strengths occurred. With a reduction in MCPM particle diameter, however, calcium and phosphate release was reduced and less deterioration in strength observed. After 24 hours, remaining MCPM had reacted with water and -TCP forming, within the set materials, brushite of lower solubility. This provided a novel means to control water sorption, component release and strength properties. Measurable chlorhexidine release was observed for 6 weeks. Both diffusion rate and total percentage of chlorhexidine release decreased with lowering the PLR or adding buffer to the storage solutions. Higher chlorhexidine release was associated with reduced bacterial growth on agar plates and in a biofilm fermenter. In cell growth media, brushite and hydroxyapatite crystals precipitated on the composite material surfaces. Cells spread on both these crystals and the exposed polymer composite surfaces indicating their cell compatibility. These formulations could be suitable antibacterial, biocompatible and remineralizing dental adhesives/liners.