Effectiveness of experimental dentifrices based on essential oils on biofilm on complete dentures: an in vitro study.

Specific products containing natural resources can contribute to the innovation of complete denture hygiene. OBJECTIVE: To conduct an in vitro evaluation of experimental dentifrices containing essential oils of Bowdichia virgilioides Kunth (BvK), Copaifera officinalis (Co), Eucalyptus citriodora (Ec), Melaleuca alternifolia (Ma) and Pinus strobus (Ps) at 1%. METHODOLOGY: The variables evaluated were organoleptic and physicochemical characteristics, abrasiveness (mechanical brushing machine) simulating 2.5 years, and microbial load (Colony Forming Units - CFU/mL), metabolic activity (XTT assay) and cell viability (Live/Dead® BacLight™ kit) of the multispecies biofilm (Streptococcus mutans: Sm, Staphylococcus aureus: Sa, Candida albicans: Ca and Candida glabrata: Cg). Specimens of heat-polymerized acrylic resins (n=256) (n=96 specimens for abrasiveness, n=72 for microbial load count, n=72 for biofilm metabolic activity, n=16 for cell viability and total biofilm quantification) with formed biofilm were divided into eight groups for manual brushing (20 seconds) with a dental brush and distilled water (NC: negative control), Trihydral (PC: positive control), placebo (Pl), BvK, Co, Ec, Ma or Ps. After brushing, the specimens were washed with PBS and immersed in Letheen Broth medium, and the suspension was sown in solid specific medium. The organoleptic characteristics were presented by descriptive analysis. The values of density, pH, consistency and viscosity were presented in a table. The data were analyzed with the Wald test in a generalized linear model, followed by the Kruskal-Wallis test, Dunn's test (mass change) and the Bonferroni test (UFC and XTT). The Wald test in Generalized Estimating Equations and the Bonferroni test were used to analyze cell viability. RESULTS: All dentifrices showed stable organoleptic characteristics and adequate physicochemical properties. CN, Ec, Ps, Pl and PC showed low abrasiveness. There was a significant difference between the groups (p<0.001) for microbial load, metabolic activity and biofilm viability. CONCLUSIONS: It was concluded that the BvK, Ec and Ps dentifrices are useful for cleaning complete dentures, as they have antimicrobial activity against biofilm. The dentifrices containing Bowdichia virgilioides Kunth showed medium abrasiveness and should be used with caution.

Synergistic antibacterial effect and mechanism between Cu2O nanoparticles and quaternary ammonium salt in moisture-curable acrylic coatings.

Combining with various antibacterial mechanisms is the preferred strategy to fabricate coatings with effective antibacterial performance. Herein, Cu2O nanoparticles and dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride, a kind of quaternary ammonium salt (QAS), were simultaneously incorporated into a moisture-curable acrylic resin in order to achieve both contact-killing and release-killing abilities for antibacterial coatings. The surface morphology, surface composition and basic properties of the coatings were thoroughly characterized. The antibacterial performance of the coatings was determined by in-vitro bacteriostatic test. Under the constant total mass fraction of antibacterial agents, both Cu2O and QAS content possessed the highest value on the coating surface at Cu2O/QAS mass ratio of 1:1, and correspondingly, the coatings reached sterilizing rate above 99 % against both E. coli and S. loihica, indicating the existence of synergistic effect between Cu2O and QAS. The synergistic antibacterial mechanism of the coatings involved two aspects. Firstly, the combination of contact-killing and release-killing biocides resulted in high bactericidal and antibiofilm activity against different bacteria. Further, the grafting of QAS molecules on the surface of Cu2O particles brought about the spontaneous migration of nanoparticles to the coating surface. The interaction between Cu2O and QAS also inhibited the phase separation of QAS and prolonged the release of Cu2+ at the same time. The coatings, therefore, exhibited stable antibacterial performance at varied service conditions.

In vitro comparison of antifungal activity of conventional alcohol sprays and antimicrobial photodynamic therapy on acrylic denture resin.

BACKGROUND: Traditionally, alcohol sprays are used for disinfection of acrylic-base denture surfaces. A limited number of studies have assessed the role of antimicrobial photodynamic therapy (aPDT) in this regard; however, it remains debatable whether conventional alcohol sprays are superior to aPDT in terms of antifungal activity or vis versa. OBJECTIVE: The aim of the present in vitro study is to compare the antifungal activity of conventional alcohol sprays and aPDT on acrylic denture resin. METHODS: Individuals wearing complete dentures at least on one arch were included. Dentures were randomly divided into three groups. Groups 1-3 were disinfected with an alcohol-based antiseptic spray and aPDT, respectively. Assessment of oral yeast growth was done using swab samples. The culture mediums were incubated at 37∘C for 72 hours and viewed through a microscope. The numbers of colony forming units (CFU/ml) were determined. P< 0.05 were considered statistically significant. RESULTS: At baseline, the mean CFU/ml in Groups 1-3 were comparable. After disinfection, a statistically significant reduction in microbial CFU/ml was observed in Groups 1 (P< 0.05) and 2 (P< 0.05) compared with baseline. In Group 3, there was no difference in CFU/ml throughout the study. After disinfection, there was no difference in microbial CFU/ml in dentures in Groups 1 and 2. CONCLUSION: Conventional alcohol sprays are as effective as aPDT towards reducing oral yeasts CFU/ml on acrylic denture resin.

Impact of chitosan-incorporated toothpaste on roughness, gloss, and antifungal potential of acrylic resin.

This study aimed to test the efficacy of different silica-based toothpastes with or without chitosan, as a method of cleaning the acrylic surfaces of denture prostheses. Acrylic resin specimens were prepared to evaluate surface roughness and gloss (n = 10), and Candida albicans adhesion/inhibition (n = 2). Two toothpastes with different degrees of abrasiveness were used: Colgate (CT) and Elmex (EX), with or without 0.5% chitosan (Ch) microparticles (CTCh or EXCh, respectively). The negative control was brushed with distilled water. Brushing was simulated with a machine. Surface roughness and gloss were analyzed before and after brushing. Candida albicans incidence/inhibition was tested qualitatively to determine the acrylic resin antifungal activity. The roughness and gloss data were analyzed with a generalized linear model, and the Kruskal Wallis and Dunn tests, respectively (α = 5%). Brushing with toothpastes increased roughness and reduced gloss, compared with the negative control (p < 0.05). CT showed a more significantly different change in roughness and gloss, in relation to the other groups (p < 0.05). Addition of chitosan to CT reduced its abrasive potential, and yielded results similar to those of EX and EXCh. Specimens brushed with CT showed a higher potential for Candida albicans adherence, despite its higher antifungal action. Addition of chitosan to the toothpaste made both toothpaste and brushing more effective in inhibiting Candida albicans. CT had the potential to increase roughness, reduce gloss, and increase Candida albicans adherence. In contrast, chitosan added to CT showed greater antifungal potential, and a higher synergistic effect than EX.

Antimicrobial effect of phytosphingosine in acrylic resin.

This study evaluated color stability (CS), anti-adherence effect (AAE), and cell viability of microorganisms on acrylic resin (AR) surface, treated associated or not with sodium percarbonate (SP). AR specimens were prepared, and color analysis was performed before and after the treatments and the CS was calculated. For analysis of AAE, the samples were sterilized by radiation in a microwave oven. Then samples were randomly distributed: phosphate-buffered saline (PBS - control), 0.5% sodium hypochlorite (SH), phytosphingosine (PHS), and phytosphingosine + SP (PHS+Na2CO3). The specimens remained in contact with solutions for 30 minutes and were later contaminated by Candida albicans. Aliquots were seeded in Petri dishes with Sabouraud Dextrose agar and incubated at 37°C for 24 hours. After the incubation, the number of colonies was counted. The cell viability of adhered microorganisms on the AR was evaluated and 20 fields were observed under an epifluorescence microscope, and the percentage of adhered viable cells was calculated. Data were compared (One-way ANOVA, Tukey, p<.05). As for CS, PHS+ Na2CO3 (0.4±0.1) resulted in less change than PBS (0.9±0.2), similar to the other groups (SH [1.0±0.3)]; PHS [0.9±0.2)]). There was no difference for all tested solutions regarding the ability to avoid microorganism adherence (p>0.05), but PHS (11.2±4.1) resulted in a smaller area of adhered viable cells, statistically different from SH (18.2±7.6) and PBS (26.4±10.8). It was concluded that PHS resulted in lower adhered viable cells and when associated with Na2CO3, also shows a lower effect on the CS of AR.

The effect of zinc oxide (ZnO) nanoparticle concentration on the adhesion of mucin and Streptococcus mutans to heat-cured acrylic resin.

Incorporating zinc oxide (ZnO) nanoparticles as antibacterial fillers in heat-cured acrylic resin could decrease mucin and Streptococcus mutans (S. mutans) adhesion, reducing the incidence of dental caries in the baseplates of orthodontic patients. Here, ZnO nanoparticles were modified using 3-(trimethoxysilyl)propyl methacrylate with various concentrations, added to acrylic resin powder, homogenized, mixed with acrylic resin liquid, and processed. The composite systems interfered well with mucin and S. mutans adhesion. The lowest mean of the amount of mucin adhered was on heat-cured acrylic resin with 7.5% ZnO nanoparticles, with a standard deviation of 18.07±0.80 mg/mL. The ZnO nanoparticles with a concentration of 7.5% showed an 87.09±0.88% S. mutans adhesion in control groups with no additives. These composite systems were proven to have better physicochemical characteristics and antibacterial abilities. Combining ZnO nanoparticles with heat-cured acrylic resin has great potential for self-cleaning baseplates of orthodontic patients in the future.

The effect of different concentration of emodin nanoparticles, as an antibacterial agent, on the flexural resistance of acrylic resin used in orthodontics: An in vitro study.

OBJECTIVE: The aim of this study was to investigate the impact of emodin nanoparticles (n-Emo) on the flexural strength of acrylic resin used in orthodontics. METHODS: A total of 24 acrylic resin discs were prepared according to ISO:20795-1 and divided into four groups (n=6): 0% n-Emo, 0.5% n-Emo, 1% n-Emo, and 2% n-Emo. The flexural strength of each group was measured using the Universal Testing Machine. One-way analysis of variance (ANOVA) and Tukey tests were used to analyse the data. RESULTS: The highest flexural strength values were observed in the groups containing 0% and 0.5% concentrations of n-Emo, while the lowest mean flexural strength was recorded in the group containing 2% concentration of n-Emo. There were significant difference in flexural strength values between the groups containing 0% with those containing 1% and 2% concentrations (P=0.045, P=0.011, respectively), as well as between those containing 0.5% and 2% concentrations of n-Emo (P=0.041). CONCLUSIONS: The results of the study showed that the incorporation of n-Emo had a negative impact on the flexural strength of the acrylic resin utilized in orthodontics. Nonetheless, the mean flexural strength values of all groups fell within the normal range, implying that the addition of n-Emo did not jeopardize the mechanical properties of the acrylic resin. It is therefore conceivable that the use of n-Emo as an antimicrobial agent in acrylic resin could be a promising approach to reducing enamel demineralisation and dental caries, while preserving its mechanical properties. This study was approved by the ethics committee of the Tehran University of Medical Sciences (1401-2-398-54892).

Anti-multispecies microbial biofilms and anti-inflammatory effects of antimicrobial photo-sonodynamic therapy based on acrylic resin containing nano-resveratrol.

BACKGROUND: Polymethylmethacrylate (PMMA)-based removable orthodontic appliances are susceptible to microbial colonization due to the surface porosity, and accumulating the biofilms causes denture stomatitis. the present study evaluated the anti-biofilm and antiinflammatory effects of antimicrobial photo-sonodynamic therapy (aPSDT) against multispecies microbial biofilms (Candida albicans, Staphylococcus aureus, Streptococcus sobrinus, and Actinomyces naeslundii) formed on acrylic resin modified with nanoresveratrol (NR). MATERIALS AND METHODS: Following the determination of the minimum biofilm inhibitory concentration (MBIC) of NR, in vitro anti-biofilm activity of NR was evaluated. The antibiofilm efficacy against multispecies microbial biofilm including C. albicans, S. aureus, S. sobrinus, and A. naeslundii, were assessed by biofilm inhibition test and the results were measured. To reveal the anti-inflammatory effects of aPSDT on human gingival fibroblast (HGF) cells, the gene expression levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were evaluated via quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS: According to the results, the MBIC dose of NR against multispecies microbial biofilm was considered 512 µg/mL. The highest biofilm reduction activity was observed in MBIC treated with aPSDT and 2 × MBIC exposed to light emitting diode (LED) and ultrasound waves (UW). The expression level of TNF-α and IL-6 genes were significantly increased when HGF cells were exposed to multispecies microbial biofilms (P<0.05), while after treatment with aPSDT, the expression levels of genes were significantly downregulated in all groups (P<0.05). CONCLUSION: Overall, NR-mediated aPSDT reduced the growth of the multispecies microbial biofilm and downregulated the expression of TNF-α and IL-6 genes. Therefore, modified PMMA with NR can be serving as a promising new orthodontic acrylic resin against multispecies microbial biofilms and the effect of this new material is amplified when exposed to LED and UW.

Action of chitosan-based solutions against a model four-species biofilm formed on cobalt-chromium and acrylic resin surfaces.

OBJECTIVE: To evaluate the anti-biofilm action of chitosan, nanoparticulate chitosan, and denture cleanser Nitradine™ against biofilms comprising Candida albicans, Candida glabrata, Staphylococcus aureus, and Streptococcus mutans. BACKGROUND: Biofilm removal from removable partial dentures (RPD) is important for success in prosthetic rehabilitation. MATERIALS AND METHODS: The anti-biofilm action of the experimental chitosan-based solutions and Nitradine™ was evaluated on acrylic resin and cobalt-chromium alloy through assessing cell viability, cell metabolism, residual aggregated biofilm, and extracellular polymeric substance and biofilm morphology. RESULTS: Only chitosan reduced the viability of C. albicans on cobalt-chromium alloy surface, by 98% (a 1.7 log10 reduction in cfu). Chitosan-based solutions neither promoted substantial alteration of the metabolic activity of the four-species biofilm nor reduced the amount of the aggregated biofilm. After immersion in chitosan and nanoparticulate chitosan, viable microorganisms and extracellular polymeric substances distributed over the entire specimens' surfaces were observed. Nitradine™ reduced the viability and metabolic activity of biofilm grown on both surfaces, but it did not remove all aggregated biofilm and extracellular polymeric substances. After immersion in Nitradine™, approximately 35% of the specimens' surfaces remained covered by aggregated biofilm, mainly composed of dead cells. CONCLUSION: Although chitosan and Nitradine™ promoted changes in the viability of microorganisms, neither solution completely removed the four-species biofilm from the Co-Cr and acrylic resin surfaces. Thus, isolated use of hygiene solutions is not indicated for biofilm control on RPDs; this requires complementary mechanical removal.

Determining growth inhibition of Candida albicans biofilm on denture materials after application of an organoselenium-containing dental sealant.

STATEMENT OF PROBLEM: Denture stomatitis is a chronic inflammatory condition caused by the formation of Candida albicans biofilm on denture bases. It is associated with aggravating intraoral pain, itching, and burning sensations. It can also potentiate cardiovascular diseases and aspiration pneumonia. The problem has thus far eluded efficient, toxic-free, and cost-effective solutions. PURPOSE: The purpose of this in vitro study was to investigate the effectiveness of organoselenium to inhibit the formation of C. albicans biofilm on the surface of acrylic resin denture base materials when it is either incorporated into the acrylic resin material or coated on the denture surface as a light-polymerized surface sealant. MATERIAL AND METHODS: Sixty heat-polymerized polymethyl methacrylate disks were fabricated and assigned to 4 groups (n=15): disks coated with a light-polymerized organoselenium-containing enamel surface sealant (DenteShield), disks impregnated with 0.5% organoselenium (0.5% selenium), disks impregnated with 1% organoselenium (1% selenium), and disks without organoselenium (control). C. albicans biofilm was grown on each disk which had been placed in a well of the microtiter plate containing 1-mL brain heart infusion broth inoculated with C. albicans. The plates were incubated aerobically at 37 °C for 48 hours. A confocal laser scanning microscope was used to determine the biofilm thickness, biomass, and live/dead cell ratio. Biofilm morphology was examined with scanning electron microscopy, whereas microbial viability was quantified by the spread plate method. The data were analyzed by using ANOVA and Tukey-Kramer multiple comparisons (α=.05). RESULTS: The microbial viability, biofilm thickness, biofilm biomass, and live/dead cell ratio were lower (P<.001) on disks in the test groups (DenteShield, 0.5% selenium, 1% selenium) when compared with the control group, with these variables being lowest in the 0.5% selenium and 1% selenium groups. The 0.5% selenium and 1% selenium groups did not differ significantly from each other in any of the variables (P>.05). Scanning electron microscope images showed inhibition of both biofilm growth and yeast to hyphae transition in the DenteShield, 0.5% selenium, and 1% selenium groups, with visible disruption of the biofilm morphology. CONCLUSIONS: The present study demonstrated that organoselenium, whether incorporated into or coated on the surface of an acrylic resin denture base material, has the potential to inhibit Candida albicans biofilm growth on denture surfaces and as such can be clinically useful for the prevention of denture stomatitis.

Antimicrobial Activity of Experimental Chitosan Solutions on Acrylic Resin and Cobalt-Chromium Surfaces.

PURPOSE: To evaluate the application of chitosan as a cleanser in the control of biofilm formation on cobalt-chromium (Co-Cr) alloy and acrylic resin surfaces. MATERIALS AND METHODS: In total, 172 Co-Cr discs and 172 acrylic resin discs (14 mm x 3 mm) were contaminated with Streptococcus mutans, Staphylococcus aureus, Candida albicans, or Candida glabrata and incubated for 48 hours. Then, specimens were randomly divided into groups and immersed in the following solutions for 15 minutes: solution without chitosan (WC/control); chitosan solution (CH: 5 mg/mL); chitosan nanoparticle solu.on (CN: 3.8 mg/mL); and effervescent tablet (ET). Biofilm recovery rates (n = 9) were evaluated by counting the colony-forming units (CFU/mL). Biofilm morphology was evaluated using scanning electron microscopy (SEM). Data were compared using the Kruskal-Wallis or ANOVA tests followed by the Tukey post hoc test. RESULTS: For acrylic resin, ET showed the lowest number of CFU for S aureus and S mutans (P < .001). CH exhibited intermediate values for S mutans, S aureus, and C albicans; CN exhibited intermediate values for S mutans and S aureus. For C glabrata, there was no sta.s.cal difference between the solu.ons (P = .264). For Co-Cr, ET showed the highest level of antimicrobial action against all microorganisms (P < .001), and CH showed an intermediate level of action against S mutans and S aureus. Against C albicans and C glabrata, there was no significant difference among CH, CN, and WC. CONCLUSIONS: Although ET had a broader spectrum of antimicrobial action, CH showed promise as a denture cleanser. Int J Prosthodont 2023;36:e61-e73.

Zinc-modified phosphate-based glass micro-filler improves Candida albicans resistance of auto-polymerized acrylic resin without altering mechanical performance.

Colonization of auto-polymerized acrylic resin by pathogenic Candida albicans is a common problem for denture users. In this study, zinc-modified phosphate-based glass was introduced into an auto-polymerized acrylic resin at concentrations of 3, 5, and 7 wt.%. The mechanical or physical properties (flexural strength, elastic modulus, microhardness, and contact angle), surface morphology of the resultant materials, and the antimicrobial effect on C. albicans were investigated. There were no statistical differences in the mechanical properties between the control and the zinc-modified phosphate-based glass samples (p > 0.05); however, the number of C. albicans colony-forming units was significantly lower in the control group (p < 0.05). Scanning electron microscopy revealed that C. albicans tended not to adhere to the zinc-modified-phosphate-based glass samples. Thus, the zinc-modified materials retained the advantageous mechanical properties of unaltered acrylic resins, while simultaneously exhibiting a strong antimicrobial effect in vitro.

Effect of Dentin-Disinfection Chemicals on Shear Bond Strength and Microhardness of Resin-Infiltrated Human Dentin in Different Adhesive Protocols.

Background and Objectives: Bacteria and its remnants beneath the restorations predispose the tooth to secondary caries and pulpal pathology. Hence, various chemical antibacterial agents are suggested to disinfect the prepared tooth structure before the definitive restorative procedure. This study aimed to investigate the effects of chemical disinfectant solutions on the micro-shear bond strength (µSBS) and microhardness of total-etch and self-etch resin-infiltrated human dentin. Materials and Methods: 100 caries-free intact permanent third molar teeth were vertically sectioned into the buccal and lingual half. All these specimens were mounted on acrylic resin and underlying dentin surfaces were exposed by grinding. Samples were randomly divided into five groups [n = 20] following total-etch and self-etch adhesive protocol. Teeth samples were divided according to surface treatment, as Group I (Control-CNT), Group II (2% chlorhexidine-CHX), Group III (5.25% sodium hypochlorite-NaOCl), Group IV (17% ethylenediaminetetraacetate acid­EDTA) and Group V (10% povidone iodine-PVI). A randomly selected 10 samples from each subgroup were used for µSBS and microhardness tests. After surface treatment and bonding procedure, nono-hybrid composite cylinders with a 3-mm diameter and 2-mm height were directly cured over the dentin substrate. The samples for µSBS were subjected to 5000 thermocycles and tested using a universal testing machine. Microhardness was assessed using a micro-indenter instrument, data were statistically analyzed using a one-way analysis of variance and Tukey HSD tests at p < 0.05. Results: Amongst the chemical disinfectant assessed, 2% CHX did not affect µSBS and produced a marginal reduction in dentin microhardness compared to the control group. The 5.25% NaOCl and 17% EDTA significantly compromised the microhardness of the dentin substrate. Meanwhile, 10% PVI surface treatment resulted in a substantial reduction in µSBS between composite and dentin. Conclusions: CHX with preservation of bonding to dentin and insignificant negative effect on dentin microhardness is a safe option for tooth disinfection.

Effect of Different Molecular Weights of Polyacrylic Acid on Rat Lung Following Intratracheal Instillation.

BACKGROUND: We conducted intratracheal instillations of different molecular weights of polyacrylic acid (PAA) into rats in order to examine what kinds of physicochemical characteristics of acrylic acid-based polymer affect responses in the lung. METHODS: F344 rats were intratracheally exposed to a high molecular weight (HMW) of 598 thousand g/mol or a low molecular weight (LMW) of 30.9 thousand g/mol PAA at low and high doses. Rats were sacrificed at 3 days, 1 week, 1 month, 3 months and 6 months post exposure. RESULTS: HMW PAA caused persistent increases in neutrophil influx, cytokine-induced neutrophil chemoattractants (CINC) in the bronchoalveolar lavage fluid (BALF), and heme oxygenase-1 (HO-1) in the lung tissue from 3 days to 3 months and 6 months following instillation. On the other hand, LMW PAA caused only transient increases in neutrophil influx, CINC in BALF, and HO-1 in the lung tissue from 3 days to up to 1 week or 1 month following instillation. Histopathological findings of the lungs demonstrated that the extensive inflammation and fibrotic changes caused by the HMW PAA was greater than that in exposure to the LMW PAA during the observation period. CONCLUSION: HMW PAA induced persistence of lung disorder, suggesting that molecular weight is a physicochemical characteristic of PAA-induced lung disorder.

In vitro antimicrobial effects of chitosan on microcosm biofilms of oral candidiasis.

OBJECTIVE: This study assessed the effects of chitosan (CS) on microcosm biofilms derived from saliva of patients with Candida-associated denture stomatitis. METHODS: Five removable denture wearers with denture stomatitis were included in the study. The minimum inhibitory concentration (MIC) of CS against clinical isolates of Candida albicans was determined according to the broth microdilution method. Pooled saliva from the donors was used as an inoculum for the formation of biofilms, which were developed during 72 h on acrylic surfaces in the Amsterdam Active Attachment model. The biofilms were then treated with different concentrations of CS, and the antibiofilm effects were evaluated through the quantification of colony-forming units (CFUs), total biomass (TB), metabolic activity (MA), lactic acid production (LAP), and cell viability (by confocal laser scanning microscopy). Chlorhexidine, miconazole, and nystatin were tested as positive controls, while the negative control (NC) was the untreated biofilm. Data were analyzed by 1-way ANOVA and Fischer LSD's post hoc test (α=0.05). RESULTS: MIC values of CS ranged from 500 to 800 µg/mL. For CFUs, 2500 µg/mL CS was the most effective treatment in reducing total anaerobes, mutans streptococci, and Lactobacillus spp., significantly differing from the controls. For C. albicans CFUs, CS and positive controls did not differ from each other but led to significant reductions compared to NC. Regarding TB, MA, LAP, and cell viability, 2500 µg/mL CS promoted the greatest reductions compared to NC. CONCLUSION: CS has similar or superior effects to conventional active principles on important parameters of oral candidiasis microcosm biofilms. CLINICAL RELEVANCE: The antibiofilm effects of CS show that this compound has great potential to improve the clinical condition of denture stomatitis patients, and formulations containing this natural polymer could be useful for controlling oral candidiasis.

Photocatalytic effect-assisted antimicrobial activities of acrylic resin incorporating zinc oxide nanoflakes.

To overcome the deficiency of the antimicrobial effect of polymer, zinc oxide nanoparticles have been widely utilized as advanced nanofillers due to their antimicrobial and photocatalytic activity. However, the underlying antimicrobial mechanism has not been fully understood apart from topological and physical characteristics. In this study, we prepared zinc oxide nanoparticles-based acrylic resin to explore its antimicrobial mechanism under controlled mechanophysical conditions by using silane-treated zinc oxide nanoflakes (S-ZnNFs). S-ZnNFs incorporated acrylic resin (poly(methyl methacrylate), PMMA) composites up to 2 wt% were selected based on comparable mechanophysical properties (e.g., roughness, wettability, strength and hardness), possibly affecting antimicrobial properties beyond the zinc oxide nanoparticle effect, to bare PMMA. Antimicrobial adhesion results were still observed in 2 wt% S-ZnNFs incorporated PMMA using Candida albicans (C. albicans), one of the fungal infection species. In order to confirm the antimicrobial effects by photocatalysis, we pre-exposed the UV light on 2 wt% S-ZnNF composites before cell seeding, revealing synergetic antimicrobial effect via additional reactive oxygen species (ROS) generation to C. albicans over zinc oxide nanoparticle-induced one. RNA-seq analysis revealed distinguished cellular responses between zinc oxide nanoparticles and UV-mediated photocatalytic effect, but both linked to generation of intracellular ROS. Thus, the above data suggest that induction of high intracellular ROS of C. albicans was the main antimicrobial mechanism under controlled mechanophysical parameters and synergetic ROS accumulation can be induced by photocatalysis, recapitulating a promising use of a S-ZnNFs or possibly zinc oxide nanoparticles as intracellular-ROS-generating antimicrobial nanofillers in acrylic composite for biomedical applications.

Antimicrobial effects and mechanical properties of poly(methyl methacrylate) as an orthodontic acrylic resin containing Curcumin-Nisin-poly(L-lactic acid) nanoparticle: an in vitro study.

BACKGROUND: The porous surface of acrylic orthodontic removable appliances creates a niche for microbial plaque accumulation, and changes the oral flora by raising cariogenic bacteria including Streptococcus mutans. In this study, we evaluated the mechanical properties and antimicrobial activities of incorporating different concentrations of Curcumin-Nisin-poly(L-lactic acid) nanoparticle (CurNisNps) into orthodontic acrylic resin against Streptococcus mutans and Candida albicans. METHODS: Following synthesis and characterization of CurNisNps, acrylic resin specimens with different concentrations of CurNisNps (0, 1, 2, 5, and 10% w/w) were fabricated. Flexural strength values, antimicrobial effects, anti-biofilm potential, and anti-metabolic activity against S. mutans and C. albicans were assessed at different time intervals. Also, the expression of the virulence-factor-related genes of S. mutans and C. albicans was assessed by quantitative real-time polymerase chain reaction following treatment with CurNisNps. RESULTS: Acrylic resin containing 10% CurNisNps (30.76 ± 3.91 MPa) showed flexural failure in comparison with acrylic resin specimens without CurNisNps (50.67 ± 1.82 MPa) as the control group (P < 0.05). There was no significant decrease in the flexural strength values in samples containing 1, 2, and 5% of CurNisNps in comparison to the control group (P > 0.05). Acrylic resin with 5% CurNisNps showed the highest concentration of CurNisNps and clinically accepted flexural strength value (14.89 ± 3.26 MPa, P < 0.05) simultaneously. In the disc agar diffusion assay, 5% CurNisNps showed a high level of inhibitory activity for the test microorganisms. The reduction of growth inhibition zones of the different concentrations of CurNisNps against test microorganisms was positively associated with the time, in such a way that it was reduced significantly after 60 days. The anti-biofilm and anti-metabolic activities of acrylic resin specimens containing a 5% concentration of CurNisNps against S. mutans and C. albicans could significantly decrease the expression levels of gtfB (6.8-fold) and HWP (3.4-fold) in S. mutans and C. albicans, respectively. CONCLUSIONS: Our data support that 5% (w/w) of CurNisNps can serve as an excellent orthodontic acrylic resin additive against S. mutans and C. albicans biofilm without adverse effects on its mechanical property.

Efficacy of chemical and photoactivated disinfectants against Candida Albicans and assessment of hardness, roughness, and mass loss of acrylic denture base resin.

AIM: The present study aimed to assess the antimicrobial efficacy of hematoporphyrin derivative, sodium hypochlorite (NaOCl), glutaraldehyde (GaH), and a chlorhexidine (CHX) on mass loss (ML), microhardness, and surface roughness (Ra) of acrylic denture base colonized with C. Albicans. MATERIAL AND METHODS: A total of 40 heat cure acrylic resin dentures were fabricated and inoculated by the American Type Culture Collection (ATCC) of C. Albicans in an in-vitro situation. Specimens were divided into four groups (n = 10) based on the method of disinfection. Hematoporphyrin derivatives, 1% NaOCl, 2% GaH, and 4% CHX.The pre and post candida (CFU/ml) counts were recorded before and after immersion. ML, microhardness, and Ra of acrylic denture were also assessed. Statistical analysis was executed for CFU/mL (log10) for exposed C. Albicans by two-way ANOVA and Tukey's multiple tests (p > 0.05). For normality of the data, Dunnet's Simultaneous test was performed. RESULTS: In terms of candida strain analysis, pretreatment to posttreatment comparisons revealed a reduction in mean Candida count in all groups (p < 0.05). The highest ML value after post candida disinfection of acrylic denture was observed in 2% GaH (1.587 ± 0.25) treated specimens. The least microhardness value was found in group 1 when treated with hematoporphyrin (0.97 ± 0.22 VHN) which was significantly different from other groups (p < 0.05). Group 1 surface treated with hematoporphyrin derivate (1.84 ± 0.22 µm) showed the highest Ra values (p < 0.05). CONCLUSION: Acrylic denture base resin colonized with C. Albicans when treated with a chemical disinfectant of 4% chlorhexidine displayed the highest antimicrobial efficacy with reduced mass loss, less surface roughness, and maximum denture hardness.

Anticandidal efficacy on polymide based denture resin using Photodynamic therapy, chemical and herbal disinfectants and their effect on surface roughness and hardness.

AIM: The present study aimed to evaluate the anticandidal effectiveness of PDT, DL, Triphala, CHX, and NE and their effects on Ra and the hardness of polyamide denture base colonized with C. Albicans. MATERIAL AND METHODS: A total of 50 thermo-injected polyamide denture resins were constructed and inoculated by the American Type Culture Collection (ATCC) of C. albicans in an in-vitro setup. The specimens were arbitrarily allocated into five groups, pre-candida count was measured then subjected to the diverse polyamide denture disinfection methodologies: Group 1: PDT, Group 2: Diode Laser, group 3: Triphala, group 4: 0.12% CHX (Control) and group 5 Neem extract. After disinfection protocol, post-candida count (CFU/ml) was assessed. Surface roughness and surface hardness of polyamide dentures were evaluated and statistical differences in the Ra and Vickers hardness was also assessed. Statistical analysis was performed for CFU/mL (log10) for exposed C. albicans by two-way ANOVA and Tukey's multiple test (p>0.05). For normality of the data, Kolmogorov Smirnov test was executed. RESULTS: The highest anti-microbial efficacy against Candida colonies was displayed by chemical control group 0.12% CHX (11.39 ± 1.8 CFU/ml). This was comparable to herbal NE (12.45 ± 2.9 CFU/ml) (p>0.05). There was no statistical difference found in the surface hardness values among the disinfected groups. Group 2: DL (1.32 ± 0.13 µm) showed the highest Ra value comparable to group 1: PDT (1.21 ± 0.22 µm) CONCLUSION: Polyamide denture base colonized with C. Albicans and disinfected with 0.12% Chlorhexidine and Neem extract demonstrated the highest antimicrobial efficacy with decreased surface roughness and no alteration in denture hardness.

Geraniol and thymoquinone inhibit Candida spp. biofilm formation on acrylic denture resin without affecting surface roughness or color.

PURPOSE: This study was designed to investigate the in vitro effects of geraniol (GE) and thymoquinone (TQ) on Candida biofilms on denture acrylic and any accompanying changes in acrylic surface roughness or color. METHODS: The susceptibility of Candida species to GE and TQ was determined using the broth microdilution method and time-kill assay. A minimum biofilm eradication concentration (MBEC) assay was performed using 7-day Candida biofilms grown on denture acrylic. RESULTS: The minimum inhibitory concentration (MIC) of GE and TQ for Candida spp. was 256 and 32 µg/mL, respectively. The Candida strain complete kill rates for GE and TQ at 5-fold MIC were determined after 1 h of incubation. At 5-fold MIC, GE and TQ inhibited the preformed biofilm activity (MBEC80) of all Candida strains on denture acrylic by more than 80% after treatment for 3 h. At sub-MIC levels, GE and TQ prevented the development of C. albicans and C. tropicalis hyphae. SEM images demonstrated that GE and TQ damaged the fungal cell membrane and induced cell lysis. On the other hand, GE and TQ at 10-fold MIC did not alter the surface roughness or color of the denture acrylic. CONCLUSION: GE and TQ are interesting natural substances that could be developed as promising disinfectants for removable dentures.