Cytotoxicity of four denture adhesives on human gingival fibroblast cells

Quorum quenching of Streptococcus mutans via the nano-quercetin-based antimicrobial photodynamic therapy as a potential target for cariogenic biofilm

Background

Quorum sensing (QS) system can regulate the expression of virulence factors and biofilm formation in Streptococcus mutans. Antimicrobial photodynamic therapy (aPDT) inhibits quorum quenching (QQ), and can be used to prevent microbial biofilm. We thereby aimed to evaluate the anti-biofilm potency and anti-metabolic activity of nano-quercetin (N-QCT)-mediated aPDT against S. mutans. Also, in silico evaluation of the inhibitory effect of N-QCT on the competence-stimulating peptide (CSP) of S. mutans was performed to elucidate the impact of aPDT on various QS-regulated genes.

Methods

Cytotoxicity and intracellular reactive oxygen species (ROS) generation were assessed following synthesis and confirmation of N-QCT. Subsequently, the minimum biofilm inhibitory concentration (MBIC) of N-QCT against S. mutans and anti-biofilm effects of aPDT were assessed using colorimetric assay and plate counting. Molecular modeling and docking analysis were performed to confirm the connection of QCT to CSP. The metabolic activity of S. mutans and the expression level of various genes involved in QS were evaluated by flow cytometry and reverse transcription quantitative real-time PCR, respectively.

Results

Successful synthesis of non-toxic N-QCT was confirmed through several characterization tests. The MBIC value of N-QCT against S. mutans was 128 μg/mL. Similar to the crystal violet staining, the results log₁₀ CFU/mL showed a significant degradation of preformed biofilms in the group treated with aPDT compared to the control group (P < 0.05). Following aPDT, metabolic activity of S. mutans also decreased by 85.7% (1/2 × MBIC of N-QCT) and 77.3% (1/4 × MBIC of N-QCT), as compared to the control values (P < 0.05). In silico analysis showed that the QCT molecule was located in the site formed by polypeptide helices of CSP. The relative expression levels of the virulence genes were significantly decreased in the presence of N-QCT-mediated aPDT (P < 0.05).

Conclusions

The combination of N-QCT with blue laser as a QQ-strategy leads to maximum ROS generation, disrupts the microbial biofilm of S. mutans, reduces metabolic activity, and downregulates the expression of genes involved in the QS pathway by targeting genes of the QS signaling system of S. mutans.

Cytotoxic Potential of Denture Adhesives on Human Fibroblasts—In Vitro Study

(1) In recent years, there has been a significant increase in the availability of denture adhesives for stabilizing removable dentures. The aim of the present study was to assess the cytotoxicity of three denture adhesives on human fibroblasts. (2) Methods: Three denture adhesives were analyzed. Fibroblast cultures were established for the study and control groups in order to assess the incidence of necrosis and to evaluate the microscopic intracellular alterations induced. Following incubation with (study groups) or without adhesives (control group), trypan blue dye exclusion assay was used to determine the number of viable and/or dead cells. Microscopic specimens were stained with haematoxylin and eosin, scanned, digitally processed and then analyzed by a histopathologist. (3) Results: All three denture adhesives analyzed demonstrated various toxic effects in vitro on human fibroblast: quantitative evaluation—45.87–61.13% reduction of cell viability (p = 0.0001) and slight to moderate cytotoxicity in qualitative evaluation. (4) Conclusions: Denture adhesive creams demonstrated a toxic effect on human fibroblasts in vitro in quantitative and qualitative evaluation. In vivo observations are needed to find out if denture adhesives present a cytotoxic effect in patients.

Toxicity potential of denture adhesives: A scoping review

STATEMENT OF PROBLEM

Denture adhesives are widely used products, but limited evidence regarding their toxicity is available.

PURPOSE

The purpose of this scoping review was to map the existing literature on the toxic potential of denture adhesives.

MATERIAL AND METHODS

This scoping review was structured based on the 5-step methodology proposed by Arksey and O'Malley and The Joanna Briggs Institute Manual for Evidence Synthesis and followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews. The methods were registered on the Open Science Framework (<osf.io/nqryt>). The following research question was formulated: Are there any toxic effects related to the use of denture adhesives? The electronic literature search was performed independently by 2 authors in the following databases: PubMed/MEDLINE, Scopus, Web of Science, and the Cochrane Library. The inclusion criteria were in vitro and clinical studies; studies that evaluated the cytotoxic properties of denture adhesives as local or systemic implications; and studies published in English.

RESULTS

The search conducted in October 2020 provided 1099 articles. In total, 33 studies were included, 14 in vitro and 19 clinical studies. Commercially available denture adhesives have a dose-dependent cytotoxic effect on fibroblasts and keratinocytes, with poor cell recovery noted in older human fibroblasts. Patients presented different levels of neurologic or hematological alterations associated with the excessive use of denture adhesives.

CONCLUSIONS

Most commercially available denture adhesives have a dose-dependent cytotoxic effect, and the use of well-adapted removable dental prostheses, proper patient follow-ups, and correct instructions for their use when indicated should be a priority.

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.

Developing biocompatible silver nanoparticles using epigallocatechin gallate for dental use

OBJECTIVE

To develop silver nanoparticles (AgNPs) using epigallocatechin gallate (EGCG) and evaluate its biocompatibility and inhibition effect on Streptococcus mutans biofilm growth.

DESIGN

AgNPs were synthesized using EGCG as a reducing agent. Cytotoxicity was assessed using half-maximal inhibitory concentration (IC₅₀) against human gingival fibroblast (HGF-1) and stem cells from human exfoliated deciduous teeth (SHED). Antibacterial properties were evaluated with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against S. mutans. Dentine blocks were treated with AgNPs, silver nitrate (AgNO₃), or water before being incubated with S. mutans. The kinetics, morphology and viability of the biofilm at different time points were assessed by colony-forming units (CFUs), scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM), respectively. Lactic acid and polysaccharide production of the biofilm were also investigated.

RESULTS

Spherical AgNPs with diameter 17 ± 7 nm were developed. The IC₅₀ of AgNPs and AgNO₃ against HGF-1 were 44.88 ± 11.39 μg/mL and 11.53 ± 6.96 μg/mL, respectively (p < 0.001), whereas those against SHED were 68.02 ± 24.48 μg/mL and 9.54 ± 6.63 μg/mL, respectively (p = 0.02). The MIC of AgNPs and AgNO₃ were 32.22 ± 7.34 μg/mL and 48.89 ± 15.11 μg/mL, respectively (p = 0.01), whereas their MBC was 63.33 ± 11.73 μg/mL and 85.00 ± 20.77 μg/mL, respectively (p = 0.02). Log CFUs of the AgNPs group were the lowest among the groups (p < 0.001). SEM and CLSM found a confluent biofilm in AgNO₃ and water groups but not in AgNPs group. Biofilms in AgNPs group was revealed with lowest level of acidic acid and polysaccharides production (p < 0.001).

CONCLUSION

This study developed biocompatible AgNPs which inhibited the growth of a cariogenic biofilm.

Comparison of primary human gingival fibroblasts from an older and a young donor on the evaluation of cytotoxicity of denture adhesives

Denture adhesives (DA) improve the retention and stability of ill-fitting dentures, especially for older adults. These materials should be biocompatible, i.e., they cannot cause undesired biological responses and be non-cytotoxic to oral tissues. However, in vitro testing of DA biocompatibility employing primary cell culture may possibly be affected by other factors, such as the donor age.

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.

Retention of denture bases fabricated by three different processing techniques - An in vivo study

Aim:

Distortion due to Polymerization shrinkage compromises the retention. To evaluate the amount of retention of denture bases fabricated by conventional, anchorized, and injection molding polymerization techniques.

Materials and Methods:

Ten completely edentulous patients were selected, impressions were made, and master cast obtained was duplicated to fabricate denture bases by three polymerization techniques. Loop was attached to the finished denture bases to estimate the force required to dislodge them by retention apparatus. Readings were subjected to nonparametric Friedman two-way analysis of variance followed by Bonferroni correction methods and Wilcoxon matched-pairs signed-ranks test.

Results:

Denture bases fabricated by injection molding (3740 g), anchorized techniques (2913 g) recorded greater retention values than conventional technique (2468 g). Significant difference was seen between these techniques.

Conclusions:

Denture bases obtained by injection molding polymerization technique exhibited maximum retention, followed by anchorized technique, and least retention was seen in conventional molding technique.

Cytotoxic effects of one-step self-etching adhesives on an odontoblast cell line

The aim of this study was to evaluate the cytotoxic effects of one-step self-etching adhesives. Cells from an immortalized mouse odontoblast cell line (MDPC-23) were cultured with six different dental adhesive systems (diluted to concentrations of 0.5% for 4 h): Adper Easy Bond (EB), Xeno V (XV), iBond (IB), AdheSE One (AO), Clearfil SE primer (CS), and Adper Single Bond 2 (SB). MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and flow cytometric apoptosis assays were used to evaluate cell viability and the rate of apoptosis. The odontoblasts were also examined under a scanning electron microscope. While all of the cultures with adhesives showed reduced viability, the viabilities in the IB and SB groups were not significantly different from the control group. Although increased apoptosis rates were observed in all of the cultures with adhesives, the rate in the SB group was not significantly different from the rate in the control. The control group showed the lowest apoptosis rate followed by the SB, AO, IB, EB, XV, and CS groups. When examined under a scanning electron microscope, control odontoblasts and the SB group exhibited relatively large cytoplasmic extensions. In contrast, in the EB and CS groups, fewer fibroblasts remained adhered to the plate surface. Cytoplasmic membrane shrinkage and cell-free areas with residual membrane fragments from dead cells were observed. In conclusion, all cultures with one-step self-etching adhesives showed increased apoptotic activity. SB, an etch-and-rinse adhesive, was comparable to the control group, and CS and EB showed the lowest odontoblast viabilities according to the MTT assay.