Objectives: Previous studies have developed calcium phosphate and fluoride releasing composites. Other studies have incorporated chlorhexidine (CHX) particles into dental composites. However, CHX has not been incorporated in calcium phosphate and fluoride composites. The objectives of this study were to develop nanocomposites containing amorphous calcium phosphate (ACP) or calcium fluoride (CaF 2) nanoparticles and CHX particles, and investigate Streptococcus mutans biofilm formation and lactic acid production for the first time. Methods: Chlorhexidine was frozen via liquid nitrogen and ground to obtain a particle size of 0.62 μm. Four nanocomposites were fabricated with fillers of: nano ACP; nano ACP + 10% CHX; nano CaF 2; nano CaF 2 + 10% CHX. Three commercial materials were tested as controls: a resin-modified glass ionomer, and two composites. S. mutans live/dead assay, colony-forming unit (CFU) counts, biofilm metabolic activity, and lactic acid were measured. Results: Adding CHX fillers to ACP and CaF 2 nanocomposites greatly increased their antimicrobial capability. ACP and CaF 2 nanocomposites with CHX that were inoculated with S. mutans had a growth medium pH > 6.5 after 3 d, while the control commercial composites had a cariogenic pH of 4.2. Nanocomposites with CHX reduced the biofilm metabolic activity by 10-20 folds and reduced the acid production, compared to the controls. CFU on nanocomposites with CHX were three orders of magnitude less than that on commercial composite. Mechanical properties of nanocomposites with CHX matched a commercial composite without fluoride. Significance: The novel calcium phosphate and fluoride nanocomposites could be rendered antibacterial with CHX to greatly reduce biofilm formation, acid production, CFU and metabolic activity. The antimicrobial and remineralizing nanocomposites with good mechanical properties may be promising for a wide range of tooth restorations with anti-caries capabilities.
Bibliographical noteFunding Information:
We thank Dr. L.C. Chow and Dr. S. Takagi of the Paffenbarger Research Center of the American Dental Association Foundation and Dr. J.M. Antonucci of the National Institute of Standards and Technology (NIST) for discussions, and Dr. Qianming Chen at the West China School of Stomatology for help. We are very grateful to Esstech (Essington, PA) and Ivoclar Vivadent (Amherst, NY) for donating the materials. This study was supported by NIH R01 grants DE17974 and DE14190 (HX), NIDCR-NIST Interagency Agreement Y1-DE-7005-01 , University of Maryland Dental School, NIST, and West China School of Stomatology.
- Calcium fluoride
- Calcium phosphate
- Caries inhibition
- Dental nanocomposite
- S. mutans biofilm