High strength re-mineralizing, antibacterial dental composites with reactive calcium phosphates

ObjectiveDevelopment of high strength dental composites with adhesive, antibacterial and re-mineralizing potential.MaterialsUrethane and triethylene glycol dimethacrylates were combined with HEMA (10 or 20 wt%) and 2MP (2 or 10 wt%), antibacterial chlorhexidine (2.5 wt%) and chemical cure initiators. Reactive mono/tri calcium phosphate (CP) mixed with silica/silicon carbide nanoparticles (S) (CP:S weight ratio 1:2 or 2:1) was added (50 wt%).ResultsDecreasing CP/S ratio and HEMA content reduced monomer conversion at 15 min from 93 to 63%. Conversely, decreasing CP/S increased initial “dry” compressive (137–203 MPa) and flexural (79–116 MPa) strength. With high HEMA content, these decreased by ∼15–20 MPa upon 24 h water storage. With low HEMA content, average decline was <8 MPa due to reduced water sorption. Early water sorption induced mass increase, volume expansion, mono calcium phosphate dissolution and chlorhexidine release, were proportional to the initial calcium phosphate content. Furthermore, they increased ∼1.5 fold upon raising HEMA wt%. These diffusion controlled processes and strength decline slowed after 24 h as phosphates reaction bound water within the materials. Increasing 2MP concentration reduced calcium release but did not affect strength. Formulations with high CP/S indicated greater antibacterial activity in agar diffusion and in vitro biofilm tests.SignificanceNew material use beneath a conventional composite could potentially reduce high failure rates associated with residual caries and bacterial microleakage.