Uncompleted polymerization and cytotoxicity of dental restorative materials as potential health risk factors

Composite materials used in dentistry indicate adverse biological effects in laboratory conditions. One reason for this activity is incomplete conversion of their polymer matrix, favoring chemical instability and release of biologically harmful components to the external environment.

The aim of the study was to assess the degree of conversion of restorative materials commonly available on the European market and to examine the cytotoxic effects of their eluates in vitro.

Using the Fournier transform infrared spectroscopy (FTIR) technique of analysis, the degree of polymer matrix conversion of 6 restorative materials was examined: Gradia Direct, Arkon, Filtek Z550, Herculite XRV, Tetric Evo Ceram, Charisma, polymerized with LED light. In order to assess the cytotoxicity of eluates of the studied materials obtained after 1 hour , 24 hours and 7 days, the MTT assay was used in cultured 3T3 cells. The results were statistically analyzed at significance level of p=0.05.

The conversion degree of the assessed polymers ranged from 31.56% for Tetric Evo Ceram to 75.84% for Arcon. The strongest (p=0.05) cytotoxic effect was demonstrated after 7-day observation of Tetric Evo Ceram eluates, reducing the metabolic activity of cells down to 56%. A positive correlation (r(x, y) = 0.62) between the degree of conversion of composite materials and cytotoxic effects of their eluates on cell cultures was confirmed.

1. Restorative dental materials are chemically unstable in the conditions of the present study. 2. Polymer-based restorative dental materials available on the European market demonstrate cytotoxic properties constituting a potential threat to the patients' health.