Are denture adhesives safe for oral cells?

Abstract

Purpose: To compare the cytotoxicity of six commercially available denture adhesives on human gingival cells: Poligrip Flavour Free Fixative Cream, Fixodent Pro Duo Protection, Novafix cream, FittyDent, Polident Total Action, and Fixodent ProPlus Duo Protection. Material and Methods: Eluates of denture adhesives were brought into contact with human gingival cells and compared to untreated cells (w/o any dental adhesive elute). Cell toxicity was assessed by measuring cell viability (3-(4,5-imethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assays), cell morphology (immunofluorescenceassays), induction of apoptosis/necrosis and production of reactive oxygen species (ROS) (flow cytometry assays). In addition, the pH of each sample was determined. Data were analyzed using one-way analysis of variance (ANOVA) followed by Dunnett’s multiple comparisons test. Results: All denture adhesives tested led to a reduction in pH, especially Fixodent Pro Duo Protection and Fixodent Pro Plus Duo Protection. The cell viability assays showed that Fixodent Pro Duo Protection (1:1 72 hours, p = 3.04 × 10−6; 1:2 72 hours, p = 2.07 × 10−6; 1:4 72 hours, p = 2.04 × 10−6) and Fixodent Pro Plus Duo Protection (1:1 72 hours, p = 2.01 × 10−6; 1:2 72 hours, p = 3.03 × 10−6; 1:4 72 hours, p = 2.02 × 10−6) significantly decreased cell viability at all dilutions. Compared to the control group and the rest of the adhesives, Poligrip Flavour Free Fixative Cream (PFF 1:1 72 hours, p = 2.24 × 10−6; 1:2 72 hours, p = 2.44 × 10−6; 1:4 72 hours, p = 2.04 × 10−6) showed a significantly higher cell viability score at all dilutions. Fixodent Pro Duo Protection and Fixodent Pro Plus Duo Protection, both adhesives containing zinc salts in their composition, were responsible for necrosis, and the number of cells was much reduced, with aberrant morphology and pyknotic nucleus. Finally, Fixodent (1:2, p = 2.04 × 10−6, 1:4, p = 0.00036; 1:2, p = 8.82 × 10−6, 1:4, p = 2.30 × 10−6) products significantly promoted ROS production in gingival cells. Conclusions: The results suggest that denture adhesives containing zinc in their composition could be responsible of the decrease of cell viability, ROS production, aberrant cell morphology, and induction of apoptosis and cell death. However, other possible additional cytotoxic factors must be considered. Thus, more studies are necessary to confirm this hypothesis.