Cytocompatibility of Dental Composites: Effects of Conversion, Filler, and Roughness

Objective: Dental composites are complex mixtures and can be costly and time-consuming to optimize. Our objective was to utilize our gradient-based testing platform to screen rapidly the effects of degree of conversion (DC), filler type and mass fraction, and surface roughness on cell response.

Methods: Composites varying discretely in composition and continuously in irradiation were fabricated. Monomers bisphenol-A dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA), 50:50 by mass, were filled with SP 345 silane glass macro-filler (up to 65 % by mass) and fumed amorphous silica nano-filler OX50 (up to 5 % by mass) and photopolymerized. DC and surface roughness were measured using near infrared spectroscopy and confocal microscopy, respectively. Murine RAW 264.7 macrophage-like cells were cultured on the composites for 24 h. Cell viability, density, and spreading were quantified using fluorescent microscopy.

Results: DC increased and roughness decreased as irradiation increased, independent of composition. Filler content ≤ 35 % (mass fraction) resulted in reduced cell viability and density as DC decreased. This agrees with our previous studies showing that unfilled polymers reduce cell viability and density at low conversions. As the filler content increased, viability and density remained high for all DC levels. Cell spreading changed as a function of position and was affected by a combination of filler particles, DC, and roughness.

Conclusions: Cell response to dental polymeric composites is affected by a number of variables, including filler size, filler mass fraction, degree of conversion, and surface roughness. Increasing the filler content reduced the toxicity associated with low conversions. This testing platform is suitable for screening chemical, physical, mechanical, and biological properties of polymers and composites in order to accelerate the optimization of dental materials for clinical applications.

Support: NIDCR/NIST Interagency Agreement Y1-DE-7005-01.