Adherence in vitro of Candida albicans to plasma treated acrylic resin. Effect of plasma parameters, surface roughness and salivary pellicle

Assessing the suitability of fused deposition modeling to produce acrylic removable denture bases

OBJECTIVE

To study the feasibility of using poly methyl methacrylate (PMMA) filament and fused deposition modeling (FDM) to manufacture denture bases via the development of a study that considers both conventional and additive-based manufacturing techniques.

MATERIALS AND METHODS

Five sample groups were compared: heat and cold cured acrylic resins, CAD/CAM milled PMMA, 3D-printed PMMA (via FDM), and 3D-printed methacrylate resin (via stereolithography, SLA). All groups were subjected to mechanical testing (flexural strength, impact strength, and hardness), water sorption and solubility tests, a tooth bonding test, microbiological assessment, and accuracy of fit measurements. The performance of sample groups was referred to ISO 20795-1 and ISO/TS 19736. The data was analyzed using one-way ANOVA.

RESULTS

Samples manufactured using FDM performed within ISO specifications for mechanical testing, water sorption, and solubility tests. However, the FDM group failed to achieve the ISO requirements for the tooth bonding test. FDM samples presented a rough surface finish which could ultimately encourage an undesirable high level of microbial adhesion. For accuracy of fit, FDM samples showed a lower degree of accuracy than existing materials.

CONCLUSIONS

Although FDM samples were a cost-effective option and were able to be quickly manufactured in a reproducible manner, the results demonstrated that current recommended testing regimes for conventionally manufactured denture-based polymers are not directly applicable to additive-manufactured denture base polymers. Therefore, new standards should be developed to ensure the correct implementation of additive manufacturing techniques within denture-based fabrication workflow.

Impact of multiscale surface topography characteristics on Candida albicans biofilm formation: From cell repellence to fungicidal activity

While there has been significant research conducted on bacterial colonization on implant materials, with a focus on developing surface modifications to prevent the formation of bacterial biofilms, the study of Candida albicans biofilms on implantable materials is still in its infancy, despite its growing relevance in implant-associated infections. C. albicans fungal infections represent a significant clinical concern due to their severity and associated high fatality rate. Pathogenic yeasts account for an increasing proportion of implant-associated infections, since Candida spp. readily form biofilms on medical and dental device surfaces. In addition, these biofilms are highly antifungal-resistant, making it crucial to explore alternative solutions for the prevention of Candida implant-associated infections. One promising approach is to modify the surface properties of the implant, such as the wettability and topography of these substrata, to prevent the initial Candida attachment to the surface. This review summarizes recent research on the effects of surface wettability, roughness, and architecture on Candida spp. attachment to implantable materials. The nanofabrication of material surfaces are highlighted as a potential method for the prevention of Candida spp. attachment and biofilm formation on medical implant materials. Understanding the mechanisms by which Candida spp. attach to surfaces will allow such surfaces to be designed such that the incidence and severity of Candida infections in patients can be significantly reduced. Most importantly, this approach could also substantially reduce the need to use antifungals for the prevention and treatment of these infections, thereby playing a crucial role in minimizing the possibility contributing to instances of antimicrobial resistance. STATEMENT OF SIGNIFICANCE: In this review we provide a systematic analysis of the role that surface characteristics, such as wettability, roughness, topography and architecture, play on the extent of C. albicans cells attachment that will occur on biomaterial surfaces. We show that exploiting bioinspired surfaces could significantly contribute to the prevention of antimicrobial resistance to antifungal and chemical-based preventive measures. By reducing the attachment and growth of C. albicans cells using surface structure approaches, we can decrease the need for antifungals, which are conventionally used to treat such infections.

Anti-Microbial Effect of AgBr-NP@CTMAB on Streptococcus Mutans and Assessment of Surface Roughness Hardness and Flexural Strength of PMMA

Purpose

To investigate the inhibition of Streptococcus mutans (S.mutans) and its biofilm by AgBr-nanoparticles (NP) @CTMAB (cetyltrimethyl-ammonium bromide) and evaluate the changes in Polymethyl methacrylate (PMMA)'s surface roughness (Ra), microhardness, and flexural strength during prolonged immersion in AgBr-NP@CTMAB for application in the denture cleaning industry.

Patients and Methods

The antibacterial activity of AgBr-NP@CTMAB against S.mutans was measured colony formation assay, OD600 and laser confocal microscopy. Changes in the specimens' values for surface roughness, microhardness, and flexural strength (MPa) were measured after immersion solutions for 180 or 360 days.

Results

The AgBr-NP@CTMAB solution exhibited a robust antibacterial effect on planktonic S. mutans, with a minimum bactericidal concentration of 5 µg/mL. The 10 µg/mL AgBr-NP@CTMAB solution efficiently inhibited S. mutans biofilm formation. (2) No significant difference in surface roughness after immersion in AgBr-NP@CTMAB (10 µg/mL and 20 µg/mL) comparing with distilled water (P > 0.05) and Polident had significantly higher than distilled water (P < 0.05). There was a significant decrease in the surface hardness of the PMMA specimens that were immersed in the Polident compared with those in distilled water (P < 0.05). While, no significant differences in surface hardness after immersion in the AgBr-NP@CTMAB (P > 0.05). The result of flexural strength suggested that there was no statistically significant difference (P < 0.05) between AgBr-NP@CTMAB as well as Polident and water.

Conclusion

AgBrNP@CTMAB can efficiently inhibit the growth of plankton S.mutans and biofilm formation, without affecting the flexural strength, microhardness, or surface roughness of PMMA. Therefore, AgBrNP@CTMAB holds promise as a new denture cleaning agent.

Different Polymers for the Base of Removable Dentures? Part II: A Narrative Review of the Dynamics of Microbial Plaque Formation on Dentures

This review focuses on the current disparities and gaps in research on the characteristics of the oral ecosystem of denture wearers, making a unique contribution to the literature on this topic. We aimed to synthesize the literature on the state of current knowledge concerning the biological behavior of the different polymers used in prosthetics. Whichever polymer is used in the composition of the prosthetic base (poly methyl methacrylate acrylic (PMMA), polyamide (PA), or polyether ether ketone (PEEK)), the simple presence of a removable prosthesis in the oral cavity can disturb the balance of the oral microbiota. This phenomenon is aggravated by poor oral hygiene, resulting in an increased microbial load coupled with the reduced salivation that is associated with older patients. In 15-70% of patients, this imbalance leads to the appearance of inflammation under the prosthesis (denture stomatitis, DS). DS is dependent on the equilibrium-as well as on the reciprocal, fragile, and constantly dynamic conditions-between the host and the microbiome in the oral cavity. Several local and general parameters contribute to this balance. Locally, the formation of microbial plaque on dentures (DMP) depends on the phenomena of adhesion, aggregation, and accumulation of microorganisms. To limit DMP, apart from oral and lifestyle hygiene, the prosthesis must be polished and regularly immersed in a disinfectant bath. It can also be covered with an insulating coating. In the long term, relining and maintenance of the prosthesis must also be established to control microbial proliferation. On the other hand, several general conditions specific to the host (aging; heredity; allergies; diseases such as diabetes mellitus or cardiovascular, respiratory, or digestive diseases; and immunodeficiencies) can make the management of DS difficult. Thus, the second part of this review addresses the complexity of the management of DMP depending on the polymer used. The methodology followed in this review comprised the formulation of a search strategy, definition of the inclusion and exclusion criteria, and selection of studies for analysis. The PubMed database was searched independently for pertinent studies. A total of 213 titles were retrieved from the electronic databases, and after applying the exclusion criteria, we selected 84 articles on the possible microbial interactions between the prosthesis and the oral environment, with a particular emphasis on Candida albicans.

Could Helium Plasma Treatment be a Novel Approach to Prevent the Biofilm Formation of Candida albicans?

There is no definitive method to prevent Candida albicans (C. albicans) biofilm formation on polymethyl methacrylate (PMMA) surfaces. The objective of this study was to evaluate the effect of Helium plasma treatment (before the application of removable dentures to the patient) to prevent or reduce C. albicans ATCC 10,231 the anti-adherent activity, viability, and biofilm formation on PMMA surfaces. One hundred disc-shaped PMMA samples (2 mm × 10 mm) were prepared. The samples were randomly divided into 5 surface groups and treated with different concentrations of Helium plasma: G I: Control group (untreated), G II: 80% Helium plasma-treated group, G III: 85% Helium plasma-treated group, G IV: 90% Helium plasma-treated group, G V: 100% Helium plasma-treated group. C. albicans viability and biofilm formations were evaluated using 2 methods: MTT (3-(4,5-dimethyl thiazolyl-2)-2, 5-diphenyltetrazolium bromide) assays and Crystal Violet (CV) staining. The surface morphology and C. albicans biofilm images were observed with scanning electron microscopy. The Helium plasma-treated PMMA groups (G II, G III, G IV, G V) observed a significant reduction in C. albicans cell viability and biofilm formation compared with the control group. Treating PMMA surfaces with different concentrations of Helium plasma prevents C. albicans viability and biofilm formation. This study suggests that Helium plasma treatment might be an effective strategy in modifying PMMA surfaces to prevent denture stomatitis formation.

Biofilm Formation on the Surfaces of CAD/CAM Dental Polymers

Dental polymers are now available as monolithic materials which can be readily used in computer-aided design and computer-aided manufacturing (CAD/CAM) systems. Despite possessing numerous advantages over conventionally produced polymers, the polymers produced by either of these systems fail to exhibit immunity to surface microbial adhesion when introduced into the oral environment, leading to the development of oral diseases. The aim of this study was to analyze the biofilm formation of six microorganisms from the oral cavity and its correlation to the surface characteristics of CAD/CAM dental polymers. A total of ninety specimens were divided into three groups: resin-based composite, polymethyl methacrylate, and polyether ether ketone. The experimental procedure included surface roughness and water contact angle measurements, colony forming unit counting, and scanning electron microscopy analysis of biofilm formed on the surface of the tested materials. The data were analyzed using the Kruskal-Wallis test, with a Dunn's post hoc analysis, and one way analysis of variance, with a Tukey's post hoc test; the correlation between the measurements was tested using Spearman's correlation coefficient, and descriptive statistics were used to present the data. Despite using the same manufacturing procedure, as well as the identical manufacturer's finishing and polishing protocols, CAD/CAM dental polymers revealed significant differences in surface roughness and water contact angle, and the increased values of both parameters led to an increase in biofilm formation on the surface of the materials. The CAD/CAM resin-based composite showed the lowest number of adhered microorganisms compared to CAD/CAM polymethyl methacrylate and CAD/CAM polyether ether ketone.

Microbial adhesion and viability on novel CAD/CAM framework materials for implant-supported hybrid prostheses

The aim of the study was to investigate the adhesion and viability of Streptococcus oralis and Candida albicans under in vitro conditions on CAD/CAM framework materials for implant-supported hybrid prostheses. Twenty-nine specimens were prepared from each of three different materials: ZR (zirconia), PEEK (polyether ether ketone) and CoCr₄ (CoCr₄ alloy). The experimental part included surface roughness (SR) and contact angle of water (CAW) measurements, followed by colony forming unit (CFU), cell viability assay and scanning electron microscopy (SEM) analyses of Strep. oralis and C. albicans biofilms on the materials' surfaces. Kruskal-Wallis and one-way analysis of variance (ANOVA) tests were used for differences between materials, and the correlation between measurements was estimated using Spearman's correlation coefficient. PEEK specimens revealed higher SR, CAW and CFU mean values, than ZR and CoCr₄ specimens. Strong positive correlation was found between SR and CFU and between CAW and CFU for both microbial species. Cell viability assay revealed similar values for both species across materials. Higher numbers of Strep. oralis and C. albicans on PEEK specimens confirm the impact of the higher surface roughness and contact angle values on the microbial adhesion and describes PEEK as less desirable than ZR and CoCr₄ from microbiological aspect.

The stain resistant effect of an ultraviolet curable coating material on denture base resin

This study aimed to evaluate the effects of an ultraviolet (UV) curable coating material on denture base resin. The results of the three-point bending test showed no significant difference between treated and untreated specimens, suggesting that the UV curable coating material did not compromise the physical strength of denture base resin. The surface free energy measurement and the surface analysis with atomic force microscopy revealed superhydrophilicity and a regularly arranged structure on the coating surface, improving wettability. Moreover, untreated specimens were significantly discolored in the staining test. However, specimens treated with the UV curable coating material showed no significant difference in color with slight staining, suggesting excellent antifouling ability. Therefore, the UV curable coating material used in this study could contribute to simplifying hygiene without altering the physical properties of denture base resins.

Prospects on Tuning Bioactive and Antimicrobial Denture Base Resin Materials: A Narrative Review

Denture base resin (DBR) materials are used in dentistry in constructing removable dentures and implant-supported prostheses. A plethora of evidence has demonstrated that DBR materials are associated with a high risk of denture stomatitis, a clinical complication where the soft oral tissues underneath the resin-based material are inflamed. The prevalence of denture stomatitis among denture wearers is high worldwide. Plaque accumulation and the infiltration of oral microbes into DBRs are among the main risk factors for denture stomatitis. The attachment of fungal species, mainly Candida albicans, to DBRs can irritate the underneath soft tissues, leading to the onset of the disease. As a result, several attempts were achieved to functionalize antimicrobial compounds and particles into DBRs to prevent microbial attachment. This review article explored the advanced approaches in designing bioactive and antimicrobial DBR materials. It was reported that using monomer mixtures, quaternary ammonium compounds (QACs), and organic and inorganic particles can suppress the growth of denture stomatitis-related pathogens. This paper also highlighted the importance of characterizing bioactive DBRs to be mechanically and physically sustainable. Future directions may implement a clinical translational model to attempt these materials inside the oral cavity.

Evaluation of the effectiveness of bioactive glass fillers against Candida albicans adhesion to PMMA denture base materials: An in vitro study

Background

Dentures with antimicrobial properties are desirable for preventing Candida albicans adhesion. This study was to assess the effectiveness of bioactive glass (BAG) on C. albicans adhesion, surface roughness, and hardness of denture base materials.

Methods

Heat-polymerized (HP) and autopolymerized (AP) acrylic resins were used to fabricate 240 disk specimens (120/material, 60/C. albicans, 60/surface roughness and hardness). Specimens were divided into five groups (n = 10) based on the BAG concentration: 0.5, 1.5, 3, 5, and 7.5 wt% of the acrylic powder, with a control group comprised of unmodified specimens. Direct culture method was used to assess C. albicans adhesion. A profilometer and Vickers hardness test were used to measure surface roughness and hardness respectively. Analysis of variance (ANOVA) and post hoc Tukey's test were used for data analysis (α = 0.05).

Results

BAG addition significantly decreased the C. albicans count when compared with the control group (P < 0.001) for both HP and AP. Regarding surface roughness, there was no change in the HP acrylic resins (P > 0.05), while the AP acrylic resins exhibited significantly higher surface roughness with BAG addition (P < 0.001). The hardness of the HP and AP acrylic resins were significantly higher with the addition of BAG (P < 0.001).

Conclusions

The addition of BAG to HP and AP acrylic resins effectively decreases C. albicans adhesion. The roughness of AP acrylic resins increases with the addition of BAG, while the hardness of both HP and AP acrylic resins increase with the addition of BAG.

Surface Characterization, Antimicrobial Activity of Nonthermal Atmospheric-Pressure Plasma Jet on Polyvinyl Siloxane Impression Materials

Background and Objectives The antimicrobial efficacy of a nonthermal atmospheric-pressure plasma jet (NAPPJ) on dental impression materials was investigated. Materials and Methods Type 3 polyvinyl siloxane was used as the impression material, and air and nitrogen NAPPJ were applied. The antibacterial effect of the NAPPJ was measured using the number of colony-forming units (CFUs) and scanning electron microscopy (SEM) images of Streptococcus mutans. Surface chemical characteristics of the impression material were examined using X-ray photoelectron spectroscopy (XPS) and contact angle measurement. Additionally, physical properties were analyzed through surface roughness measurement, detail reproduction, and strain-in-compression test. Results Compared with the control group, the plasma treatment group showed ruptured bacteria membranes, destroyed bacteria structures, a significant reduction in the number of CFUs, and a significantly reduced contact angle. Further, XPS analysis showed that their surface was significantly richer in hydroxyl groups. The surface roughness, detail reproduction, and strain-in-compression results indicated no significant differences between the plasma treatment and control groups. NAPPJ treatment could remove bacteria from polyvinyl siloxane dental impression materials without changing the surface's physical properties. Conclusion Therefore, it is considered a promising method for disinfection.

The Use of Acrylate Polymers in Dentistry

The manuscript aimed to review the types of acrylate polymers used in dentistry, as well as their chemical, physical, mechanical, and biological properties. Regarding their consistency and purpose, dental acrylate polymers are divided into hard (brittle), which includes acrylates for the production of plate denture bases, obturator prostheses, epitheses and maxillofacial prostheses, their repairs and lining, and soft (flexible), which are used for lining denture bases in special indications. Concerning the composition and method of polymerization initiation, polymers for the production of denture bases are divided into four types: heat-, cold-, light-, and microwave-polymerized. CAD/CAM acrylate dentures are made from factory blocks of dental acrylates and show optimal mechanical and physical properties, undoubtedly better monomer polymerization and thus biocompatibility, and stability of the shape and colour of the base and dentures. Regardless of the number of advantages that these polymers have to offer, they also exhibit certain disadvantages. Technological development enables the enhancement of all acrylate properties to respond better to the demands of the profession. Special attention should be paid to improving the biological characteristics of acrylate polymers, due to reported adverse reactions of patients and dental staff to potentially toxic substances released during their preparation and use.

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.

Effect of phytochemical-filled microcapsules with antifungal activity on material properties and dimensional accuracy of denture base resin for three-dimensional printing

BACKGROUND

Studies on the material properties and dimensional accuracy of three-dimensionally (3D) printed denture base containing microcapsules with antifungal phytochemicals are lacking.

METHODS

Two types of phytochemicals (phytoncide A and B) with antifungal activity were microencapsulated. The 3D-printed denture base specimens with minimum and maximum effective concentrations of microcapsules (6 and 8 wt% for phytoncide A; 15 and 25 wt% for phytoncide B) were prepared. The morphological changes of C. albicans on 3D-printed denture base with microcapsules was microscopically observed. The degree of conversion of 3D-printed denture base with microcapsules investigated. The microhardness and flexural strength values were also measured to evaluate the mechanical properties of 3D-printed denture bases. The dimensional accuracy (trueness) of the specimens with microcapsules was measured as root-mean-square values (RMS) for the whole, upper, and side surfaces of the specimens as well as their total height. For the degree of conversion, microhardness, and flexural strength values, the Kruskal-Wallis analysis and a post-hoc comparison using Mann-Whitney U test was performed. For the analysis of trueness (RMS), the one-way analysis of variance and a post-hoc comparison using Tukey's method was conducted (α = 0.05).

RESULTS

At both maximum and minimum effective concentrations of microcapsules, cell surface disruption or membrane breakdown of fungal cells were observed in the specimens. The groups with microcapsules (both phytoncide A- and B-filled) showed significantly lower microhardness and elastic modulus values than the control group (all, P = 0.001). For the trueness, all the RMS values of the whole, upper, and side surfaces of the specimens with microcapsules were less than 100 µm, although significantly higher than those without (all, P = 0.001). The mean flexural strength values of the groups with phytoncide A-filled microcapsule were higher than 65 MPa, not statistically different from that of the control group (all, P > 0.05). However, the groups with phytoncide B-filled microcapsules showed significantly lower values than the control (all, P = 0.001).

CONCLUSIONS

Within the limitations of this in-vitro study, the 3D-printed denture base containing 6 wt% of phytoncide A-filled microcapsules was clinically acceptable in terms of antifungal activity, dimensional accuracy, and flexural strength.

Hydrophobicity of denture base resins: A systematic review and meta-analysis

Objectives:

The aim of this article is to review the factors that attract Candida albicans to denture base resin (DBR) and to verify the influence of different surface treatments, chemical modification, or structural reinforcements on the properties of DBR.

Materials and Methods:

Searches were carried out in PubMed, Scopus, WOS, Google Scholar, EMBASE, and J-stage databases. The search included articles between 1999 and 2020. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. The keywords used during the search were “Candida albicans,” “Denture base,” “PMMA,” “Acrylic resin,” “Surface properties,” “hydrophobicity/hydrophilicity,” “contact angle,” and “surface free energy.” English full-text articles involving in-vitro studies with different acrylic resin modifications were included, whereas abstracts, dissertations, reviews, and articles in languages other than English were excluded. A meta-analysis was performed where appropriate.

Results:

Out of the 287 articles, 21 articles conformed to inclusion criteria. Sixteen articles were subjected to meta-analysis using random-effects model at 95% confidence interval. Results showed that DBR coatings/plasma coatings were effective methods to modify surface properties with estimated contact angle (CA) of 59.37° [95% confidence interval (CI): 53.69, 65.04]/55.87° (95% CI: 50.68, 61.06) and surface roughness (R_a) of 0.55 µm (95% CI: 0.52, 0.58)/0.549 µm (95% CI: 0.5, 0.59), respectively. Antifungal particle incorporation into poly(methylmethacrylate) DBR also produced similar effects with an estimated R_a of 0.16 µm (95% CI: 0.134, 0.187).

Conclusion:

The three properties responsible for C. albicans adhesion to DBR were R_a, CA, and surface free energy in terms of hydrophobicity. Therefore, the correlations between the hydrophobicity of DBR and C. albicans adhesion should be considered during future investigations for Candida-related denture stomatitis.

Mechanical and antimicrobial effects of riboflavin-mediated photosensitization of in vitro C. albicans formed on polymethyl methacrylate resin

PURPOSE

This study assessed the potential of riboflavin-mediated photodynamic therapy (RF-PDT) against Candida albicans (C. albicans) and compared the effects of RF-PDT with other therapeutic modalities in terms of mechanical and surface characteristics of acrylic denture base material.

MATERIALS AND METHODS

Molds (10 × 10 × 2 mm) of acrylic resin specimens were prepared and underwent artificial ageing. C. albicans were grown aerobically over the specimens and divided into four groups (n = 10/group); Group-I: no decontamination; Group-II: nystatin suspension; Group-III: riboflavin 0.1% in darkness, Group-IV: blue LED light only, and Group-V: riboflavin 0.1% for 10 minutes (pre-irradiation time) and photoactivated by the blue LED light (light dose). Fungal viability was assessed using MTT assay and characterized using scanning electron microscopy and confocal laser microscopy (CLSM). Treated specimens were subjected to surface roughness (R_a), flexural strength (FS), and flexural modulus (FM).

RESULTS

Group-I showed the highest C. albicans viability followed by Group-III. Nystatin group (Group-II) showed ∼50% of the viability while RF-PDT showed the least C. albicans viability among the four groups (p<0.05). On SEM, specimens treated with Group-IV and V showed almost clear and free from C. albicans that was evidenced on CLSM. Post-treated specimens and storage after 72 h revealed that FS was significantly higher for RF-PDT group as compared to any other group (>105.82 MPa) (p<0.05). The FM and Ra showed statistically no significant difference between the groups (p>0.05).

CONCLUSION

RF-PDT showed the highest anti-fungal capacity against C. albicans over acrylic denture surface without any surface deterioration.

Synthesis, Antifungal Activity, and Cytotoxicity of AgBr-NP@CTMAB Hybrid and Its Application in PMMA

Objective

To synthesize and determine the antifungal activity of AgBr-nanoparticles (NP) @CTMAB (cetyltrimethyl-ammonium bromide) against Candida albicans (C. albicans) for use in the field of denture cleaning.

Methods

The morphology and structure of AgBr-NP@CTMAB were characterized by IR, UV-Vis, XRD and SEM. The antifungal potential of AgBr-NP@CTMAB against C. albicans was determined by colony formation assay and growth curve analysis. PMMA containing AgBr-NP@CTMAB was prepared, and the long-term antifungal efficacy was analyzed. The effect against C. albicans biofilm was analyzed by SEM and OD600 , and the color changes of the specimens were observed by stereomicroscopy after 1 week of incubation. Cytotoxicity to human oral gingival fibroblasts and oral mucosal epithelial cells was detected by Cell Counting Kit-8 (CCK-8) in vitro.

Results

The compound showed a good crystalline phase, the presence of AgBr nanoparticles and the hybridization of CTMAB+ with AgBr-NPs. AgBr-NP@CTMAB showed significant antifungal activity against C. albicans at concentrations of 10 μg/mL and 20 μg/mL. PMMA specimens containing AgBr-NP@CTMAB showed no long-term antifungal effect against C. albicans biofilm. The clearance rate of C. albicans attached to PMMA was 44.73% after soaking in 10 µg/mL AgBr-NP@CTMAB solution for 30 min and 91.35% for 8 h. There was no significant residual cytotoxicity or visual color change after soaking.

Significance

AgBr-NP@CTMAB showed promising potential treatment for denture cleaners.

Inhibition of Candida albicans and Mixed Salivary Bacterial Biofilms on Antimicrobial Loaded Phosphated Poly(methyl methacrylate)

Biofilms play a crucial role in the development of Candida-associated denture stomatitis. Inhibition of microbial adhesion to poly(methyl methacrylate) (PMMA) and phosphate containing PMMA has been examined in this work. C. albicans and mixed salivary microbial biofilms were compared on naked and salivary pre-conditioned PMMA surfaces in the presence or absence of antimicrobials (Cetylpyridinium chloride [CPC], KSL-W, Histatin 5 [His 5]). Polymers with varying amounts of phosphate (0–25%) were tested using four C. albicans oral isolates as well as mixed salivary bacteria and 24 h biofilms were assessed for metabolic activity and confirmed using Live/Dead staining and confocal microscopy. Biofilm metabolism was reduced as phosphate density increased (15%: p = 0.004; 25%: p = 0.001). Loading of CPC on 15% phosphated disks showed a substantial decrease (p = 0.001) in biofilm metabolism in the presence or absence of a salivary pellicle. Salivary pellicle on uncharged PMMA enhanced the antimicrobial activity of CPC only. CPC also demonstrated remarkable antimicrobial activity on mixed salivary bacterial biofilms under different conditions displaying the potent efficacy of CPC (350 µg/mL) when combined with an artificial protein pellicle (Biotene half strength).

Incorporation of antimicrobial agents in denture base resin: A systematic review

STATEMENT OF PROBLEM

Denture base resins (DBRs), such as polymethyl methacrylate, are commonly used in the fabrication of removable dentures because of their physical, mechanical, and esthetic properties. However, the denture base acts as a substrate for microorganism adherence and biofilm formation, which may lead to denture stomatitis and be further complicated by fungal infections, of especial importance with geriatric and immunosuppressed patients. Therefore, methods to enhance the antimicrobial property of DBRs will be beneficial.

PURPOSE

The purpose of this systematic review was to evaluate the literature on the antimicrobial activity of DBRs incorporating antimicrobial agents or materials.

MATERIAL AND METHODS

A search of English peer-reviewed literature up to February 2019 reporting on antimicrobial activity of DBRs with respect to antimicrobial agents or materials, antimicrobial test effects and methods, and conclusion or knowledge gaps was conducted by using Embase, Google Scholar, PubMed, and Web of Science databases. Search terms included denture base resin and antibacterial, denture base resin and antifungal, and denture base resin and antimicrobial. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were applied for subsequent data analysis.

RESULTS

Of 2536 identified articles, 28 met the inclusion criteria for the systematic review. Antimicrobial materials were divided into 3 groups: antimicrobial monomer or copolymer, phytochemical or phytomedical components, and other compounds. Strategies on how to incorporate these substances into DBRs and their impact on the reduction and prevention of the growth of microorganisms were identified.

CONCLUSIONS

Although many efforts have been made to improve the antimicrobial ability of DBRs, this systematic review found that the effectiveness of incorporating of antimicrobial agents into DBRs has not been demonstrated conclusively.

Antibiofilm efficacy of tea tree oil and of its main component terpinen-4-ol against Candida albicans

Candida infection is an important cause of morbidity and mortality in immunocompromised patients. The increase in its incidence has been associated with resistance to antimicrobial therapy and biofilm formation. The aim of this study was to evaluate the efficacy of tea tree oil (TTO) and its main component - terpinen-4-ol - against resistant Candida albicans strains (genotypes A and B) identified by molecular typing and against C. albicans ATCC 90028 and SC 5314 reference strains in planktonic and biofilm cultures. The minimum inhibitory concentration, minimum fungicidal concentration, and rate of biofilm development were used to evaluate antifungal activity. Results were obtained from analysis of the biofilm using the cell proliferation assay 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) and confocal laser scanning microscopy (CLSM). Terpinen-4-ol and TTO inhibited C. albicans growth. CLSM confirmed that 17.92 mg/mL of TTO and 8.86 mg/mL of terpinen-4-ol applied for 60 s (rinse simulation) interfered with biofilm formation. Hence, this in vitro study revealed that natural substances such as TTO and terpinen-4-ol present promising results for the treatment of oral candidiasis.

Fluorinated vs. Zwitterionic-Polymer Grafted Surfaces for Adhesion Prevention of the Fungal Pathogen Candida albicans

Fluorinated (F6) and zwitterionic, as well as phosphorylcholine (MPC) and sulfobetaine (MSA), copolymers containing a low amount (1 and 5 mol%) of 3-(trimethoxysilyl)propyl methacrylate (PTMSi) were prepared and covalently grafted to glass slides by using the trimethoxysilyl groups as anchorage points. Glass-surface functionalization and polymer-film stability upon immersion in water were proven by contact angle and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) measurements. Antifouling performance of the grafted films was assayed against the yeast Candida albicans, the most common Candida species, which causes over 80% of candidiasis. Results revealed that the F6 fluorinated, hydrophobic copolymers performed much better in reducing the adhesion of C. albicans, with respect to both corresponding zwitterionic, hydrophilic MPC and MSA counterparts, and were similar to the glass negative control, which is well-known to inhibit the adhesion of C. albicans. A composition-dependent activity was also found, with the films of copolymer with 99 mol% F6 fluorinated co-units performing best.

Antimicrobial Activity of Cold Plasma Treatment on Acrylic Denture Bases: An In Vitro Evaluation

Introduction: Cross-contamination between dental office and prosthetic laboratories is of utmost importance. The dental prosthesis could harbor tones of microorganisms harmful to health staff. It has been estimated that more than 60% of the prostheses delivered to clinics from laboratories or vice versa are contaminated with pathogenic microorganisms. Several disinfection methods and chemicals have been proposed for sanitizing prostheses. Cold plasma, or nonthermal plasma, has been introduced as a new method in medical equipment disinfection. The current study aimed to compare the antimicrobial effect of cold plasma and the routinely used alcohol-based impression disinfectant ASEPTOPRINT® on disinfecting dentures. Methods: In this experimental study, 30 maxillary complete dentures were used as the microbial source. Dentures were randomly divided into 3 groups: (1) cold plasma treatment for 30 seconds, (2) cold plasma for 60 seconds, (3) ASEPTOPRINT® spray. Microbial culturing was taken before and after disinfection in each group on both Blood Agar plates and Soborou Dextrose Agar (SDA) plates. After 48 hours incubation at 37°C, the number of colonies was counted using a digital colony counter and differences between the groups were analyzed. Results: A significant reduction in microbial colonies was observed after using all disinfection methods. ASEPTOPRINT® spray showed more antimicrobial effects comparing to cold plasma. Conclusion: The antimicrobial effect of ASEPTOPRINT® spray solution is more than cold plasma application on both microbial and fungal microorganisms. The time of plasma application was not accompanied by any significant differences in the results.

Reduction of Candida albicans biofilm formation by coating polymethyl methacrylate denture bases with a photopolymerized film

STATEMENT OF PROBLEM

As Candida albicans biofilm formation is associated with severe local and systemic infections in denture-wearing patients, its prevention or reduction becomes an essential factor in the health of this population.

PURPOSE

The purpose of this in vitro study was to investigate whether 2 photopolymerized coatings of poly(acrylic acid) (PAA) and poly(itaconic acid) (PIA) can effectively reduce the adhesion of C albicans on denture base acrylic resin surfaces.

MATERIAL AND METHODS

The surface of the polymethyl methacrylate (PMMA) denture base was modified through photopolymerization of a thin film of PAA or PIA. The polymeric coatings were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), contact angle goniometry (CA), and surface roughness measurement (Ra). For biological evaluation, the coated PMMA surfaces were tested in a C albicans biofilm dynamic formation model, observed by confocal laser scanning microscopy (CLSM), and quantified by the number of colony-forming units (CFUs). The cytotoxicity of the polymeric coatings was also evaluated by using a lactic dehydrogenase-based (LDH) test. For statistical analysis, ANOVA and the nonparametric Kruskal-Wallis test were used (α=.05).

RESULTS

The PMMA resin base surfaces coated with PAA and PIA had an inhibitory effect on C albicans growth, the wettability of the coated surface, and the average roughness. The PAA and PIA coatings had no statistically significant cytotoxic effect on periodontal ligament fibroblasts.

CONCLUSIONS

PMMA acrylic resin base material was superficially modified through the incorporation of carboxylic acid groups by using PAA and PIA coatings that reduced the adherence of C albicans biofilm by 90%.

The effect of nanodiamonds on candida albicans adhesion and surface characteristics of PMMA denture base material - an in vitro study

Candida albicans is the main causative pathogen of denture stomatitis, which affects many complete denture patients. Objective: To evaluate the effect of different concentrations of nanodiamonds (NDs) added to polymethyl methacrylate (PMMA) denture base material on Candida albicans adhesion as well as on surface roughness and contact angle. Methodology: Acrylic resin specimens sized 10×10×3 mm³ were prepared and divided into four groups (n=30) according to ND concentration (0%, 0.5%, 1%, 1.5% by wt). Surface roughness was measured with a profilometer, and the contact angle with a goniometer. The effect of NDs on Candida albicans adhesion was evaluated using two methods: 1) slide count and 2) direct culture test. Analysis of variance (ANOVA) and Tukey's post hoc test were used in the statistical analyses. Results: Addition of NDs decreased the Candida albicans count significantly more than in the control group (p<0.05), with a lowest of 1% NDs. Addition of NDs also significantly decreased the surface roughness (p<0.05), but the contact angle remained the same. Incorporation of NDs into the PMMA denture base material effectively reduced Candida albicans adhesion and decreased surface roughness. Conclusion: PMMA/NDs composites could be valuable in the prevention of denture stomatitis, which is considered one of the most common clinical problems among removable denture wearers.

Antimicrobial effects of terpinen-4-ol against oral pathogens and its capacity for the modulation of gene expression

This study evaluated the antibacterial activity of terpinen-4-ol against Streptococcus mutans and Lactobacillus acidophilus and its influence on gbpA (S. mutans) and slpA (L. acidophilus) gene expression. As measured by XTT assay, the concentrations of terpinen-4-ol that effectively inhibited the biofilm were 0.24% and 0.95% for S. mutans and L. acidophilus, respectively. Confocal microscopy revealed the presence of a biofilm attached to the enamel and dentin block surfaces with significant terpinen-4-ol effects against these microorganisms. The expression of the gbpA and slpA genes involved in adherence and biofilm formation was investigated using RT-PCR. Expression of these genes decreased after 15 min with 0.24% and 0.95% terpinen-4-ol in S. mutans and L. acidophilus, respectively. These findings demonstrate the antimicrobial activity of terpinen-4-ol and its ability to modulate the expression of gbpA and slpA genes, emphasizing the therapeutic capacity of terpinen-4-ol as an alternative to inhibit adherence in biofilm.

In Vitro Evaluation of Adhesion of Candida albicans on CAD/CAM PMMA-Based Polymers

PURPOSE

To compare the amount of adherent Candida albicans to different CAD/CAM poly(methyl methacrylate) (PMMA)-based polymers and conventional heat-polymerized PMMA after long-term thermal cycling.

MATERIALS AND METHODS

The specimens were subjected to 10,000 thermal cycles (5-55°C) and divided into two groups, uncoated and pellicle-coated. Surface roughness and contact angles of the specimens were measured. The surface morphology was observed with scanning electron microscopy (SEM). An adhesion test was performed by incubating the disk specimens in C. albicans suspensions at 37°C for 2 hours, and the adherent cells were counted under an optical microscope. The data were analyzed statistically using a variance analysis and Tukey HSD post hoc comparison test. The correlation between measurements was tested using a Pearson correlation analysis (α = 0.05).

RESULTS

CAD/CAM polymers generally showed statistically significant lowest Ra and contact angle values, whereas conventional PMMA showed the highest Ra and contact angle values in the uncoated group (p < 0.05). Pellicle coating essentially increased contact angle of all materials and reduced the differences in a number of Candida cells on the materials (p < 0.05). Candida adhesion was statistically significantly greatest on conventional PMMA when compared to CAD/CAM polymers. A strong positive correlation was found between the surface roughness of the specimens (p < 0.05) and the amount of adhered cells, whereas no correlation was found between hydrophobicity of the specimens and the amount of adhered cells (p > 0.05).

CONCLUSIONS

CAD/CAM PMMA-based polymers may be preferable to reduce Candida-associated denture stomatitis in long-term use.

Incorporation of the microencapsulated antimicrobial agent phytoncide into denture base resin

BACKGROUND

This study aimed to fabricate a denture base resin (DBR) containing phytoncide microcapsules (PTMCs) and determine the mechanical properties of the resin and antifungal activity.

METHODS

Fifty-four heat-cured rectangular DBR specimens (64 × 10 × 3.3 ± 0.2 mm) containing nine concentrations of PTMC between 0 and 5% (wt/wt) were fabricated and subjected to a three-point bending test. A phytoncide release bioassay was developed using DBR containing 0% and 2.5% PTMCs (wt/wt) in a 24 well-plate assay with incubation of Porphyromonas gingivalis at 37 °C for 74 h. The antifungal activity of PTMCs against Candida albicans, in a pH 5.5 acidic environment was determined in a plate assay.

RESULTS

Flexural strength decreased with increasing PTMC concentration from 97.58 ± 4.79 MPa for the DBR alone to 53.66 ± 2.46 MPa for DBR containing 5.0% PTMC. No release of phytoncide from the PTMCs in the DBR was detected at pH 7.4. The PTMCs had a minimal inhibitory concentration of 2.6% (wt/vol) against C. albicans at pH 5.5.

CONCLUSIONS

PTMCs can be added to DBR 2.5% (wt/wt) without adversely affecting flexural strength. PTMCs released the antimicrobial agent at pH 5.5 at concentrations sufficient to inhibit the growth of the C. albicans.

Effects on cytotoxicity and antibacterial properties of the incorporations of silver nanoparticles into the surface coating of dental alloys

The aim of this study was to research the changes in cytotoxicity and antibacterial properties after silver nanoparticles (AgNPs) were incorporated into the surface coating of dental alloys. AgNPs were attached to cobalt chromium alloys and pure titanium using a hydrothermal method, according to the reaction: AgNO₃+NaBH₄→ Ag+1/2H₂+1/2B₂H₆+NaNO₃. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to evaluate the cytotoxicity of the alloys when in contact with osteogenic precursor cells (MC3T3-E1) from mice and mesenchymal stem cells (BMSC) from rats. The antibacterial properties of dental alloys incorporating three different concentrations (10, 4, and 2 μmol/L) of AgNPs were tested on Staphylococcus aureus (SA) and Streptococcus mutans (MS). High cytotoxicity values were observed for all dental alloys that contained 0% of AgNPs (the control groups). The incorporation of AgNPs reduced cytotoxicity values. No significant difference was observed for antibacterial performance when comparing dental alloys containing AgNPs to the respective control groups. The results demonstrated that the cobalt chromium alloys and pure titanium all had cytotoxicity to MC3T3-E1 and BMSC and that the incorporation of AgNPs could reduce this cytotoxicity. The concentrations of AgNPs adopted in this study were found to have no antibacterial action against SA or MS.

Effectiveness of disinfectants on the adherence of Candida albicans to denture base resins with different surface textures

The aim of the present study was to compare the effects of some disinfectants, including ethanol extract of propolis (EEP), on the adhesion of Candida albicans to denture base resins. Seventy-two acrylic resin samples were prepared, half of which was polished and the other half was roughened. C. albicans strain ATCC 10231 was incubated on Sabouraud dextrose agar (SDA) at 37°C for 48 h. The adhesion period was completed by keeping the cells in this suspension for 90 min at 37°C. Specimens were then immersed in the following solutions: 1%, 2%, and 5% sodium hypochlorite; 4% chlorhexidine gluconate; and 10% EEP. Quantification of the antifungal activity of the chemical solutions was performed using the colorimetric MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay test. One-way ANOVA and post-hoc Tukey tests were performed to evaluate the effectiveness of chemical agents. Polished and roughened surfaces were compared using independent sample t-test. The mean surface roughness value was 0.35 (±0.04) µm for the polished group and 1.2 (±0.2) µm for the roughened group. The contact angles of both surfaces showed statistically significant difference, and 10% EEP solution exhibited significantly less removal of adherent viable C. albicans cells in both groups. All forms of sodium hypochlorite solutions yielded higher efficiency than 4% chlorhexidine gluconate and EEP solutions (P < 0.05). (J Oral Sci 58, 431-437, 2016).

Effects of trimethylsilane plasma coating on the hydrophobicity of denture base resin and adhesion of Candida albicans on resin surfaces

STATEMENT OF PROBLEM

Candida-associated denture stomatitis is the most common oral mucosal lesion among denture wearers. Trimethylsilane (TMS) plasma coating may inhibit the growth of Candida albicans on denture surfaces.

PURPOSE

The purpose of this in vitro study was to investigate whether TMS plasma coatings can effectively reduce C albicans adhesion on denture base acrylic resin surfaces.

MATERIAL AND METHODS

Sixty denture base acrylic resin disks with smooth and rough surfaces were prepared and were either left untreated (control group) or coated with TMS monomer (experimental group) by using plasma. Contact angles were measured immediately after TMS plasma coating. The morphology of C albicans adhesion was observed with scanning electron microscopy (SEM). Energy-dispersive spectroscopy (EDS) was used to characterize the elemental composition of the specimen surface. An adhesion test was performed by incubating the resin disk specimens in C albicans suspensions (1×10⁷ cells/mL) at 37°C for 24 hours and further measuring the optical density of the C albicans by using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay test. One-way ANOVA and 2-way ANOVA were followed by a post hoc test analysis (α=.05).

RESULTS

The group with TMS coating exhibited a more hydrophobic surface than the control group. EDS analysis revealed successful TMS plasma coating. The difference in the mean contact angles between the uncoated group and the TMS-coated group was statistically significant (P<.05), 79.0 ±2.9 degrees versus 105.7 ±1.5 degrees for the smooth surface and 90.2 ±7.6 degrees versus 131.5 ±2.1 degrees for the rough surface. In SEM analysis, the C albicans biofilm was found to grow more on the surface of the denture base resin without the TMS coating than on the surfaces of the experimental group. In the adhesion test, the amount of C albicans adhering to the surface of denture base resin with the TMS coating was significantly less than that on the surfaces without TMS coating (P<.05).

CONCLUSIONS

TMS coating significantly reduced the adhesion of C albicans to the denture base resin and may reduce denture stomatitis.

Virulence factors of fluconazole-susceptible and fluconazole-resistant Candida albicans after antimicrobial photodynamic therapy

This study evaluated the effects of antimicrobial photodynamic therapy (aPDT) mediated by Photodithazine® (PDZ) and LED light on the virulence factors of fluconazole-susceptible (CaS) and fluconazole-resistant (CaR) Candida albicans. Standardized suspensions of strains were prepared (10⁷), and after 48 h of biofilm formation, these strains were incubated with PDZ (100 mg/L) for 20 min and exposed to LED light (660 nm, 37.5 J/cm²). Additional samples were treated with PDZ or light only, and the control consisted of biofilms that received no treatment. After aPDT, the cells were recovered and the virulence factors were evaluated. To analyze the capacity of adhesion, cells were recovered after aPDT and submitted to the adhesion process in the bottom of a 96-well plate. After this, metabolic activity tests (XTT assay) and cell viability (colony forming units per milliliter, CFU/mL) were applied. To evaluate the biofilm-forming ability after aPDT, the cells recovered were submitted to biofilm formation procedures, and the biofilm formed was evaluated by XTT, CFU/mL, and total biomass (crystal violet) tests. Lastly, the capacity for synthesizing protease and phospholipase enzymes after aPDT was evaluated by fluorimetric tests. Data were analyzed by two- or three-way ANOVA tests (p ≤ 0.05). It was verified that aPDT reduced the viability of both strains, fluconazole-susceptible and fluconazole-resistant C. albicans. It was also observed that the CaR strain had lower susceptibility to the aPDT when compared with the CaS strain. However, regarding the virulence factors evaluated, it was demonstrated that aPDT did not alter the adherence and biofilm formation ability and enzymatic production.

Efficacy of citronella and cinnamon essential oils on Candida albicans biofilms

INTRODUCTION

The discovery of new antimicrobials derived from plants could aid in the management of biofilm-associated infections, including denture-induced stomatitis (DS). DS is an oral infection caused by Candida biofilms on the surfaces of poorly cleansed dentures. Effective treatment of DS requires the use of an appropriate denture cleanser and preferably one that exhibits antimicrobial properties.

OBJECTIVE

This study aimed to evaluate the anti-Candida and anti-biofilm efficacy of two essential plant oils from Cymbopogon winterianus (citronella) and Cinnamon cassia (cinnamon).

MATERIALS AND METHODS

Minimum Inhibitory Concentrations (MICs) and Minimum Fungicidal Concentrations (MFCs) were determined by broth microdilution, whilst anti-biofilm activity was measured against mature (cultured for 72 h) biofilms on acrylic surfaces. Candida cell viability was assessed immediately (0 h) after treatment (T0) and 48 h after biofilm re-growth (T48). Biofilm structure was determined using Scanning Electron Microscopy (SEM) at T0 and T48.

RESULTS

The respective MICs of cinnamon and citronella oils were 65 and 250 μg/ml and these were also the MFC values. For anti-biofilm efficacy, both oils significantly (p < 0.05) reduced the number of viable micro-organisms and accumulation of biofilms at T0. However, at T48, there was no difference between treated and untreated biofilms.

CONCLUSIONS

It is concluded that citronella and cinnamon essential oils have potential for daily anti-candidal denture cleansing.

In vitro treatment of Candida albicans biofilms on denture base material with volume dielectric barrier discharge plasma (VDBD) compared with common chemical antiseptics

OBJECTIVES

To prevent oral candidiasis, it is crucial to inactivate Candida-based biofilms on dentures. Common denture cleansing solutions cannot sufficiently inactivate Candida albicans. Therefore, we investigated the anticandidal efficacy of a physical plasma against C. albicans biofilms in vitro.

MATERIALS AND METHODS

Argon or argon plasma with 1 % oxygen admixture was applied on C. albicans biofilms grown for 2, 7, or 16 days on polymethylmethacrylate discs; 0.1 % chlorhexidine digluconate (CHX) and 0.6 % sodium hypochlorite (NaOCl) solutions served as positive treatment controls. In addition, these two solutions were applied in combination with plasma for 30 min to assess potential synergistic effects. The anticandidal efficacy was determined by the number of colony forming units (CFU) in log(10) and expressed as reduction factor (RF, the difference between control and treated specimen).

RESULTS

On 2-day-biofilms, plasma treatment alone or combined with 30 min CHX treatment led to significant differences of means of CFU (RF = 4.2 and RF = 4.3), clearly superior to CHX treatment alone (RF = 0.6). Plasma treatment of 7-day-or 16-day-old biofilms revealed no significant CFU reduction. The treatment of 7-day-old (RF = 1.7) and 16-day-old (RF = 1.3) biofilms was slightly more effective with NaOCl alone than with the combined treatment of NaOCl and plasma (RF = 1.6/RF = 1.9). The combination of CHX and plasma increased the RF immaterially.

CONCLUSION

The use of plasma alone and in combination with antiseptics is promising anticandidal regimens for daily use on dentures when biofilms are not older than 2 days.

CLINICAL RELEVANCE

Plasma could help to reduce denture-associated candidiasis.

Antimicrobial activity of a tissue conditioner combined with a biocide polymer

BACKGROUND

The characteristics of tissue conditioners support microorganism development that can threaten the health of the dentures user.

PURPOSE

The object of this study was to evaluate the effect on antimicrobial activity, roughness and wettability surface of a tissue conditioners material combined with the antimicrobial polymer poly (2-tert-butilaminoethyl) methacrylate (PTBAEMA).

MATERIALS AND METHODS

Specimens of tissue conditioner (Coe Soft(®)) were divided into three groups, according to the concentration of PTBAEMA incorporated (0, 10 and 25%). Antimicrobial activity was assessed by adherence assay of one of the microorganisms, Staphylococcus aureus, Streptococcus mutans and Candida albicans. Roughness measurements were made using a Mitutoyo SJ-400, and the mean arithmetic roughness values (Ra) obtained were used for the comparisons. The wettability properties were determined by contact angle measurements.

RESULTS

The group containing 25% of PTBAEMA inhibited totally the S. aureus and S. mutans biofilm formation. A significant reduc tion in the S. aureus (Kruskal-Wallis, p = 0,001) and S. mutans (Kruscal-Wallis, p = 0,001) count for 10% PTBAEMA group compared with respective control group. No significant difference was found for C. albicans among PTBAEMA groups and control group (ANOVA, p > 0,05). Incorporating 10 and 25% PTBAEMA increased surface roughness and decreased contact angles (ANOVA and Tukey's post hoc tests, α = 5%).

CONCLUSION

Incorporating 10% PTBAEMA into tissue conditioner increases wettability and roughness of tissue conditioner surface; and decreases the adhesion of S. mutans and S. aureus on material surface, but did not exhibit antimicrobial effect against C. albicans.

SIGNIFICANCE

The PTBAEMA incorporated into tissue conditioner could prevent biofilm formation on elderly patient.

Toxicology of antimicrobial nanoparticles for prosthetic devices

Advances in nanotechnology are producing an accelerated proliferation of new nanomaterial composites that are likely to become an important source of engineered health-related products. Nanoparticles with antifungal effects are of great interest in the formulation of microbicidal materials. Fungi are found as innocuous commensals and colonize various habitats in and on humans, especially the skin and mucosa. As growth on surfaces is a natural part of the Candida spp. lifestyle, one can expect that Candida organisms colonize prosthetic devices, such as dentures. Macromolecular systems, due to their properties, allow efficient use of these materials in various fields, including the creation of reinforced nanoparticle polymers with antimicrobial activity. This review briefly summarizes the results of studies conducted during the past decade and especially in the last few years focused on the toxicity of different antimicrobial polymers and factors influencing their activities, as well as the main applications of antimicrobial polymers in dentistry. The present study addresses aspects that are often overlooked in nanotoxicology studies, such as careful time-dependent characterization of agglomeration and ion release.

Plasma in dentistry

This review describes the contemporary aspects of plasma application in dentistry. Previous studies on plasma applications were classified into two categories, surface treatment and direct applications, and were reviewed, respectively according to the approach. The current review discussed modification of dental implant surface, enhancing of adhesive qualities, enhancing of polymerization, surface coating and plasma cleaning under the topics of surface treatment. Microbicidal activities, decontamination, root canal disinfection and tooth bleaching were reviewed as direct applications with other miscellaneous ones. Non-thermal atmospheric pressure plasma was of particular focus since it is gaining considerable attention due to the possibility for its use in living tissues. Future perspectives have also been discussed briefly. Although it is still not popular among dentists, plasma has shown promises in several areas of dentistry and is now opening a new era of plasma dentistry.

In vitro evaluation of adherence of Candida albicans, Candida glabrata, and Streptococcus mutans to an acrylic resin modified by experimental coatings

This study evaluated the effect of experimental coatings, containing zwitterion or hydrophilic monomers, on the adherence of Candida albicans, Candida glabrata, and Streptococcus mutans to an acrylic resin. Acrylic samples (smooth or rough surfaces) were left untreated (control) or coated with one of the following experimental coatings: 3-hydroxypropylmethacrylate (HP) or sulfobetaine methacrylate (S), at concentrations of 25, 30, or 35%. Half of the specimens were coated with saliva. The adhesion test was performed by incubating specimens in C. albicans, C. glabrata, and S. mutans suspensions at 37°C for 90 min. The number of adhered microorganisms was determined by metabolic activity (XTT) and by cell viability (CFU). All coated specimens exhibited lower absorbance and CFU values compared to control specimens. Saliva and roughness did not promote microorganism adherence. An XPS analysis confirmed the modification in the chemical composition of the coatings in the experimental samples. These experimental coatings significantly reduced the adherence of C. albicans, C. glabrata and S. mutans to acrylic resin.