Influence of 3 different forms of a commercially available denture adhesive material on the growth of Candida species: An in vitro study

Novel antimicrobial denture adhesive containing S-PRG filler

The antimicrobial effects of denture adhesives containing novel surface pre-reacted glass-ionomer (S-PRG) fillers were assessed. We prepared denture adhesives containing S-PRG (particle sizes: 1 and 3 µm; quantities: 5, 7.5, and 10 wt%). We evaluated acid buffering capacity, ion release, and antimicrobial effects of denture adhesives with and without S-PRG. Significantly higher pH changes were observed in 1 µm S-PRG adhesives than in 3 µm S-PRG adhesives. Adhesives containing 7.5 and 10 wt% S-PRG exhibited significantly higher ion release than adhesives with 5 wt% S-PRG. The 1µm-10wt% S-PRG denture adhesive exhibited significantly lower colony-forming units on the denture adhesive contact surface than in the control group; additionally, it exhibited excellent acid buffering capacity, ion release properties, and antimicrobial effect against C. albicans, C. glabrata, S. mutans, and A. naeslundii. Longer contact periods resulted in significantly lower adhesion of Candida albicans to the denture base resin treated with denture adhesive.

Are Denture Adhesives Safe for Oral Cells?

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 Pro Plus 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-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assays), cell morphology (immunofluorescence assays), 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.

Influence of the use of complete denture adhesives on microbial adhesion and biofilm formation by single- and mixed-species

Objectives

To verify whether the Ultra Corega Cream and Corega Strip Denture Adhesive adhesives interfere in the microbial adhesion and biofilm formation by Candida albicans and Lactobacillus casei in single- and mixed-species settings, and observe whether synergistic or antagonistic relationships between these species occur.

Methods

Specimens made from heat-polymerized acrylic resin (Lucitone 550) were fabricated (n = 144) with a circular shape and standardized roughness (3.0 μm ±0.3 Ra) and were divided into three groups: Without Adhesive (WA), with Ultra Corega Cream adhesive (CA) and Corega Strips adhesive (SA). These groups were divided into three subgroups each: C. albicans single-species, L. casei single-species and C. albicans with L. casei (mixed-species). Microbial adhesion and biofilm formation assays were performed in duplicate at four distinct experimental times (n = 8 per experimental condition). The amount of each microorganism on the surfaces of the specimens was observed by counting of the Colony Forming Units (CFU) per substrate. Additional specimens were characterized by Scanning Electron Microscopy (SEM), with 18 specimens being used in this analysis (n = 18), 2 per experimental condition (n = 2). Two-way ANOVA and Tukey’s test for multiple comparisons were employed, using α≤0.05.

Results

L. casei (mixed-species) adhered more on the WA substrate than the CA, while C. albicans (single- and mixed-species) adhered more on the SA. C. albicans, both single- and mixed-species adhered more than the L. casei (single- and mixed-species), regardless of the substrate. L. casei (single-species) formed more biofilm on the WA, but in its mixed cultivation, it had no difference of growth among the tested situations. C. albicans (single- and mixed-species) formed more biofilm on the SA than the CA, and the fungus formed more biofilm when compared to L. casei. In general, whenever a species was compared in its single- and mixed-species situation, no statistically significant difference was observed. SEM of biofilm formation assays demonstrated that L. casei single-species WA formed more biofilm than when the adhesives tested were used, and C. albicans (both single- and mixed-species) formed more biofilm on the SA than on the CA.

Conclusions

(1) The two denture adhesives tested increased the adhesion of C. albicans but not of L. casei; (2) biofilm formation by C. albicans (single- and mixed-species) was increased on the SA; (3) Relations of synergism or antagonism was not observed between the two microorganisms studied.

Proinflammatory cytokine production from NOK-SI keratinocytes after exposure to denture adhesives

STATEMENT OF PROBLEM

Although the cytotoxicity of denture adhesives has been widely assessed, data on the release of proinflammatory cytokines from oral epithelial cells are still scarce.

PURPOSE

The purpose of this in vitro study was to evaluate the proinflammatory cytokines interleukin (IL) 1β, IL-6, and tumor necrosis factor α (TNF-α) released from human oral keratinocytes after exposure to denture adhesives.

MATERIAL AND METHODS

Eluates of the Ultra Corega cream, Corega powder Fixador Ultra, and Corega strip denture adhesives were created at 1% wt/vol after 24 hours of exposure in a Dulbecco modified Eagle medium culture. The release of IL-1β, IL-6, and TNF-α was measured using a sandwich enzyme-linked immunosorbent assay after the oral epithelial cells (NOK-SI) had been exposed to the eluates for 3, 6, and 24 hours (n=6).

RESULTS

IL-1β release from the strip was higher at 3 hours compared with the control (Bonferroni post hoc test, P=.016). IL-6 releases from the cream and powder denture adhesives at 6 and 24 hours were higher than for the controls (Bonferroni post hoc test, P<.05). TNF-α release was not detectable in some groups and periods.

CONCLUSIONS

In long periods, denture adhesive strips do not induce any change on cytokine release from human oral keratinocytes.