Characterization of novel dental composite materials with both antibacterial and potential re-mineralizing activities.
Methods:
Chemical curing UDMA : TEGDMA resin (1:1 by weight) was mixed with chlorhexidine diacetate (2.5 wt%), HEMA (10 or 20 wt%) and Bis (2-methacryloxyethyl) phosphate (MEP) (2 or 10 wt%). This was combined with 50 wt% filler consisting of monocalcium phosphate monohydrate : tricalcium phosphate : nano-silica-fused silicon carbide whiskers (1:1:(1 or 4) by weight). Monomer conversion was assessed via Fourier-transform infrared spectroscopy (FTIR). Kinetics of water sorption, chlorhexidine, calcium and phosphate release from set composite discs (10 mm diameter, 1 mm thick) were investigated using gravimetry, UV spectrometry and ion chromatography. Data were analyzed using factorial analysis. Antibacterial action was quantified using agar diffusion tests and a constant-depth film-fermentor.
Results:
Raising whiskers mass fraction decreased average degree of monomer conversion from 96±3 to 76±5 %. Furthermore, raised whiskers fraction reduced average maximum water sorption (at 4 weeks) and chlorhexidine release (at 6 weeks) from 4±1 and 42±3 wt% (mean±95% C.I.) to 2±0.4 and 30±2 wt%. Reducing HEMA mass fraction also decreased these properties from 3.5±0.5 and 40±2 to 2±0.5 and 35±2 wt%. Calcium and phosphate release (at 2 weeks) also decreased upon raising whiskers or reducing HEMA percentage. Increasing MEP wt% reduced levels of calcium ions release from 0.7±0.2 to 0.4±0.1 mmol/l. Formulations with faster chlorhexidine release exhibited more effective antibacterial action.
Conclusion:
Novel composites with high monomer conversion levels that subsequently release both antibacterial chlorhexidine and Calcium and Phosphate ions have been produced. Factors likely to raise mechanical properties, however, such as reduced monomer hydrophilicity and water sorption or raised reinforcing silicon carbide whiskers and MEP levels tend to reduce release kinetics of active ingredients.