Antioxidant in composite fillings did not improve cytocompatibility

A new study shows that adding the antioxidant N-acetylcysteine (NAC) to resin-based composites reduces oxidative stress in cells, but without clearly improving the metabolic activity of pulp cells. How NAC affects the material itself depends on which photoinitiator is used.

These were the findings in a study initiated by UCLouvain and the University of Geneva (UNIGE) where NIOM participated with analyses performed by Senior Engineer Lene A. Grutle, Senior Scientist Silvio Uhlig and CTO Hilde Molvig Kopperud.

What is this about?

Resin-based composites are the material of choice for direct fillings. However, the material never cures completely, and unreacted monomers can leach out and harm cells in the dental pulp, partly through oxidative stress. The antioxidant NAC has shown promising effects against this, and the idea is to add it directly to the material. At the same time, NAC can interfere with curing. The researchers therefore examined both biological effects and material properties in composites with two different photoinitiators: camphorquinone (CQ) and TPO.

What did the researchers find out?

In CQ-based composites, NAC interfered with the curing process. This led to a lower degree of conversion, weaker mechanical properties and, at 0.5% NAC, increased leaching of the monomer TEGDMA. In TPO-based composites, curing was largely preserved, and the degree of conversion even increased slightly with NAC.

What are the key results?

• NAC reduced the production of reactive oxygen species (ROS) in pulp cells in almost all groups.
• However, this did not lead to a consistent improvement in the cells' metabolic activity.
• The effect of NAC on the material depends on the photoinitiator system.
• Good curing and minimal monomer leaching remain the most effective route to better short-term cytocompatibility.