Polymerisation and Stability of Remineralising, Antibacterial Dental Composite Pastes

Objectives: The aim was to produce dental composites with potential to reduce bacterial micro-leakage through use of: a higher molecular weight diluent Poly(Propylene glycol) Dimethacrylate monomer (PPG), remineralising mono/tri Calcium Phosphate (CaP) and antibacterial Polylysine (PLS). Objectives were to assess how varying these additives, polymerisation initiator (CQ) and activator (DMAEMA) influence maximum polymerisation (required for good mechanical / cytocompatibility properties) and potential long-term paste stability.
Methods: Urethane Dimethacrylate, conventional diluent monomer Triethyleneglycol Dimethacrylate (TEG) or PPG, CQ and DMAEMA were combined with a dental glass containing Polylysine and CaP. Monomer conversion (MC) of the resultant pastes was calculated from FTIR spectra at 37°C upon 40s light exposure before and after 70 days of accelerated paste aging at 60°C (n=3, SD=2%).
Results: Replacement of TEG by PPG enabled >10% increase in initial MC without significant increase in estimated polymerisation shrinkage. Simultaneously increasing CQ and reducing CaP and/or DMAEMA enabled maintenance or increase in initial conversion whist enhancing paste stability. Decrease in polylysine level also reduced decline in MC with aging (see Table 1).
Conclusions: Monomers containing PPG can achieve higher MC than those containing TEG without enhancing shrinkage which enables bacterial microleakage. Level of DMAEMA, CaP and PLS should be kept low to maintain stability of dental composite pastes.