Cytotoxicity and effect on protease activity of copolymer extracts containing catechin

To evaluate cytotoxicity and effect on protease activity of epigallocatechin-gallate extracted from experimental restorative dental copolymers in comparison to the control compound chlorhexidine.

Copolymer disks were prepared from bis-GMA/TEGDMA (70/30 mol%) containing no compound (control) or 1% w/w of either epigallocatechin-gallate or chlorhexidine. MDPC-23 odontoblast-like cells were seeded with the copolymer extracts leached out into deionized water. Cell metabolic activity was quantified by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay at 24, 48, 72 h. Inhibition of protease activity by resin extracts was measured by a collagenolytic/genatinolytic enzyme activity assay and gelatin zymography. Data for MTT and protease inhibition were analyzed using two-way ANOVA followed by Tukey or Bonferroni post hoc tests (α=0.05).

The MTT revealed that at 72 h, extracts from control (16.7%) and chlorhexidine (22.3%) copolymers induced significant reduction in cell metabolism (p<0.05). All copolymer extracts caused enzymatic inhibition in a dose dependent manner (p<0.01). Even when highly diluted, epigallocatechin-gallate extract had a significant antiproteolytic activity (p<0.05). Zymograms showed that all extracts reduced activity of MMP-2 and MMP-9 (pro- and active forms), with MMP-9 exhibiting the highest percentage inhibition revealed by densitometry.

Epigallocatechin-gallate and chlorhexidine extracts did not exert cytotoxicity on evaluated cells when compared to control extracts. Both compounds retained antiproteolytic activity after extraction from a dental copolymer.

Once extracted from a dental copolymer, epigallocatechin-gallate is not cytotoxic and retains antiproteolytic activity. These results may allow incorporation of epigallocatechin-gallate as a natural-safe alternative to chlorhexidine in functionalized restorative materials.