Reduced polymerization stress through non-bonded nanofiller particles

The stress that results from the placement of dental composite in a confined setting compromises the integrity of the marginal seal. Dental composites which include nanofiller particles that are not treated with a functional agent to couple them to the resin matrix can result in lower stress levels. Three types of nanofillers were evaluated having either a functional silane coating, a non-functional silane coating, or no coating. These were added at five different vol% levels to a photo-sensitized mixture of three dimethacrylate monomers alone or at three different vol% levels to the same resin filled with mini-filler particles to a clinically realistic level. The stress generated by these materials when cured in a confined setting was measured in a mechanical testing machine. The effect of monomer molecular weight on the stress levels was evaluated by preparing three resin formulations with varied co-monomer levels and filling them with bonded or non-bonded nanofillers. Reductions in polymerization stress of up to 31% were achieved among both the nanofilled resins and the mini-filled composite. The materials which contained a heightened level of diluent monomer produced significantly higher stress levels (ANOVA/Tukey's test, p<0.05). Significant reductions in polymerization stress can be achieved through minor alterations in composite chemistry.