Biologic responses to substances in dental fillings: PhD defence

In vitro toxicity of filler particles and methacrylates used in dental composite materials: Cytokine release and cell death

Dental polymer-based composite materials are complex, The main components are filler particles (inorganic component) and a polymer matrix, consisting of monomers that usually are polymerized by ligh curing devices.

The polymerization process is never complete, and degradation processes may lead to release of particles and ions in addition to the organic components.  Clinical handling during placement and finishing may cause release of particulate dust to the air in dental clinics to the tissue and to the saliva of the patients. Thus, both dental personnel and patients could be exposed to components of polymer-based dental materials. 

The main objective of the thesis was to characterize the toxic potential of selected inorganic filler particles (barium glass particles and silica particles) and methacrylates (MMA, HEMA, TEGDMA, BisGMA, GDMA) commonly used in dental filling materials.  The results showed that both nano- and micro-sized filler particles could modulate the release of inflammatory mediators in vitro. The methacrylates investigated induced cytotoxicity, but the potency and the mechanism involved seemed to differ between the methacrylates.  HEMA was found to induce apoptosis and DNA damage followed by activation of DNA damage response. To address possible exposure to multiple components of polymer-based dental composite materials the effect of co-exposure to components was studied. An additive inflammatory response was observed with particles and one of the methacrylates (TEGDMA).

Studies on the mechanisms of possible adverse biological responses to substances released from polymer-based dental materials contribute to safer dental materials.

The work was performed in collaboration with the Nordic Institute of Dental Materials (NIOM).