Evaluation of Candida albicans adhesion and biofilm formation on a denture base acrylic resin containing silver nanoparticles

Aim: This study firstly evaluated the activity of a silver nanoparticle (AgNPs) solution against Candida albicans and then the effect of incorporation of AgNPs into a denture base acrylic resin on the material’s hydrophobicity, C. albicans adhesion and biofilm formation. Methods and Results: The AgNPs solution was synthesized by chemical reduction and characterized. Minimum inhibitory (MIC) and minimum fungicidal (MFC) concentrations for planktonic cells and sessile cells (MFCs) of the AgNPs solution against C. albicans were determined. Specimens (n = 360) of silver‐incorporated acrylic resin at concentrations of 1000, 750, 500, 250 and 30 ppm were also prepared and stored in PBS for 0, 7, 90 and 180 days. Control was acrylic resin without AgNPs (0 ppm). After the storage periods, contact angles were measured and the specimens were used for C. albicans adherence (37°C; 90 min; n = 9) and biofilm formation (37°C; 48 h; n = 9) by XTT reduction assay. MIC, MFC and MFCs values were 3·98, 15·63 and 1000 ppm, respectively. Incorporation of AgNPs reduced the hydrophobicity of the resin. No effect on adherence and biofilm formation was observed. At 90 and 180 days of storage, there was significant increase in adherence and biofilm formation. Conclusions: Although the AgNPs solution had antifungal activity, no effect on C. albicans adherence and biofilm formation was observed after its incorporation into a denture base resin. Significance and Impact of the Study: The synthesized AgNPs solution is a promising antifungal agent, warranting investigations of more efficient methods of incorporation into denture base resins.     

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.     

Antifungal drugs effect adherence of Candida albicans to acrylic surfaces by changing the zeta-potential of fungal cells

The effect of sub-inhibitory concentrations of antifungal drugs on the adherence of Candida albicans to acrylic surfaces was investigated. Among five antifungals tested, azalomycin F and aculeacin A significantly enhanced the adherence. The zeta-potential of fungal cells was affected by antifungal drugs, whereas no significant change in cell surface hydrophobicity was observed. The relationship obtained between the change in the adherence and that in zeta-potential suggests that the enhanced adherence was caused by decreased electric repulsive forces.     

Glycosaminoglycans inhibit Candida albicans adherence to extracellular matrix proteins

The ability of Candida albicans to adhere to subendothelial extracellular matrix (ECM) may be important in the pathogenesis of disseminated candidiasis. ECM proteins, such as fibronectin, laminin, and types I and IV collagen bind C. albicans avidly. These proteins all possess heparin-binding domains. The influence of the glycosaminoglycans (GAGS) including heparin, heparan sulfate and dextran sulfate on C. albicans adherence to subendothelial ECM and ECM proteins was studied. It was demonstrated that the GAGS inhibited C. albicans adherence to ECM and ECM proteins. This possibly occurred by the GAGS binding to the ECM proteins and, in so doing, masking a preferred ligand for C. albicans adherence.     

The effect of denture adhesives on Candida albicans growth in vitro

doi: 10.1111/j.1741‐2358.2011.00478.x
The effect of denture adhesives on Candida albicans growth in vitro Objective: Denture‐wearing favours the growth of Candida. In view of the fact that many denture wearers regularly use adhesives to enhance denture retention, stability and function, the aim of this work was to study the effect of denture adhesives on Candida albicans growth in vitro. Materials and methods: The denture adhesives tested were Corega^® cream, Kukident^® cream, Novafix^® cream, Polident^® cream, Protefix^® cream, Steradent^® cream, Aderyn^® powder, Corega^® ultra powder, Protefix^® powder and Corega^® strip. C. albicans growth curves were obtained in the presence or absence of a 1% solution of the denture adhesive diluted in Sabouraud broth. Macro‐ and microscopic morphological changes in C. albicans were analysed, as was microbial contamination of the denture adhesive. Results: Most of the denture adhesives studied induced morphological changes in C. albicans cells and colonies, but only two had any significant inhibitory effect on yeast growth. Kukident^® cream markedly inhibited C. albicans growth in a concentration‐dependent way, reducing the growth rate by 95%, whereas Corega^® cream also inhibited C. albicans growth but in a non‐concentration‐dependent way, reducing the growth rate by 37%. In addition, denture adhesives available as powders had detectable microbial contamination. Conclusion: Some commercially available denture adhesives showed microbial contamination and some had significant inhibitory effect on C. albicans growth.     

胡桃楸提取物对体外白念珠菌生物膜形成的影响

目的研究胡桃楸提取物对白念珠菌生物膜形成的影响。方法采用甲基四氮盐（XTT）还原法评价胡桃楸提取物对白念珠菌的生物膜形成及黏附性的影响。镜下观察胡桃楸提取物对白念珠菌生物膜的形态学影响。结果胡桃楸提取物抑制白念珠菌生物膜50％及90％的最小抑制药物浓度（SMIC50、SMIC90）分别为15．2μg、23．4μg。胡桃楸提取物作用浓度大于20μg时对该菌细胞黏附有抑制作用。30μg胡桃楸提取物可完全抑制白念珠菌生物膜的形成。结论胡桃楸提取物对体外白念珠菌生物的膜形成有较强的抑制作用。     

Effect of pre-processing methods on bond strength between acrylic resin teeth and acrylic denture base resin

doi: 10.1111/j.1741‐2358.2011.00480.x
Effect of pre‐processing methods on bond strength between acrylic resin teeth and acrylic denture base resin Objectives: This study evaluated the effects of various pre‐processing methods on the bond strength between resin and denture teeth. Backgrounds: Debonding of acrylic resin teeth from denture base material is a problem for patients wearing complete dentures. Materials and Methods: Four experimental groups (n = 30) were investigated by subjecting tooth–resin bonding to tensile loading. Specimens were prepared and tested according to the methods of the International Standards Organization (ISO 22112:2005) using a special assembly. Four pre‐processing surface treatments of teeth were applied: (i) ST₁, no treatment applied (control); (ii) ST₂, wax solvent (Dewaks, Faber Kimya & Ilaç, Turkey); (iii) ST₃, boiling water followed by conditioning with methyl methacrylate (MMA) monomer (Meliodent, Bayer Dental, Germany); (iv) ST₄, boiling water followed by wax solvent agent and finally MMA monomer application. Bond strength test was performed using a universal testing machine. Results: All the strength values of the test groups were within clinically acceptable limits. The lowest values were from the ST₁ group and the highest values were in the ST₄ group. Conclusions: Wax elimination methods affected bonding strength. Application of wax solvent and MMA monomer to the ridge lap surfaces of the teeth gave the best results. In clinical practice, this application procedure may decrease the bonding failure of denture teeth.     

3种义齿清洁剂对3种活动义齿材料表面白色假丝酵母菌抑菌效果的比较

目的比较保丽净、高乐氏、洗必泰对不同活动性义齿表面白色假丝酵母菌的抑菌效果。方法分别制备带白色假丝酵母菌的钴铬基托试件、纯钛基托试件、热凝树脂基托试件,并分别浸泡于洗必泰、保丽净、高乐氏溶液中6h,评价上述3种义齿清洁剂的抑菌效果。结果同一清洁剂的不同基托间比较细菌下降率差异无统计学意义(F=0.02,P0.05);同一基托经过不同清洁剂处理,细菌下降率差异有统计学意义(F=8.04,P0.05);钴铬基托、纯钛基托、热凝树脂基托的除菌效果均为保丽净最高,洗必泰最低,差异均有统计学意义(P0.05)。结论保丽净可有效减少细菌滋生,可作为理想的活动性义齿清洁剂长期使用。     

Fungicidal effect of human lactoferrin against Candida albicans

Human lactoferrin (LF) in its iron-free state (apo LF), killed Candida albicans in a time- and dose-dependent way. The lethal effect was stronger at pH 7.0 than at pH 5.5 and maximum inhibition at neutral pH was achieved in 25 min when the fungal cells were exposed to LF in 0.05 mM KCl at 37 degrees C. Fe(3+)-saturated LF had no fungicidal activity. Apo LF-mediated killing was also temperature-dependent with enhanced inhibition at higher temperatures (37 degrees, 42 degrees C). The presence of 1 mM D-glucose did not affect the candidacidal activity of apo LF but both phosphate and bicarbonate ions at physiological salivary concentrations completely blocked the anti-fungal effect. Therefore it seems unlikely that LF belongs to the major host defence factors against oral candidosis.     

Effect of reline material and denture base surface treatment on the impact strength of a denture base acrylic resin

doi:10.1111/j.1741‐2358.2009.00292.x
Effect of reline material and denture base surface treatment on the impact strength of a denture base acrylic resin Objective: In this study, the effect of relining and surface treatment on the impact strength (IS) of a heat‐polymerising denture base acrylic resin (Lucitone 550‐L) was evaluated. Materials and methods: Rectangular bars of L were made (60 × 6 × 2 mm) and relined (2 mm) with the relining resins Ufi Gel Hard (UH) and Tokuso Rebase Fast (TR). Specimens relined with L and intact L, TR and UH specimens were also made (60 × 6 × 4 mm), for comparison. Before relining, the L surface was left untreated or wetted with methyl methacrylate monomer and/or the bonding agents (BA) supplied by manufacturers of the reline resins. V‐notches were machined at the midpoint of the length of all specimens. The notches were made either across the width (Nw) or across the thickness of the specimens (Nth). The Charpy impact test was performed using a 0.5‐J pendulum, which had been specially designed and constructed. Data were analysed separately for each notch position using one‐way analysis of variance and Tukey honestly significant difference post‐hoc test (p = 0.05). Results: The IS of L was similar to that of L/L. For the Nw notch, treating the denture base L with TR BA and relining with TR reline material produced the highest IS. Conclusion: The IS of specimens made from heat polymerising acrylic resin Lucitone 550 was increased after relining using the hard chairside reline resin TR with its proprietary BA.     

Candida albicans biofilm formation on soft denture liners and efficacy of cleaning protocols

doi: 10.1111/j.1741‐2358.2011.00485.x
Candida albicans biofilm formation on soft denture liners and efficacy of cleaning protocols Objective: The aim of this study was to investigate Candida albicans biofilm formation on denture liners and to analyse the efficacy of cleaning protocols. Material and methods: Specimens were prepared from four silicone‐based soft denture liners. After artificial ageing and surface free energy determination, specimens were incubated with saliva (2 h) and Candida albicans ATCC 10231 for either short‐ (2.5 h) or long‐term (24 h) biofilm formation. Adherent cells were determined either after incubation of specimens with Candida albicans or after treatment with different denture cleaning protocols. Statistical analysis was performed using one‐way anova and the Games–Howell test (α = 0.05). Results: For both short‐ and long‐term biofilm formation, similar amounts of Candida albicans cells were found on the surface of the different liners (p = 0.295 and 0.178, respectively). For both short‐ and long‐term biofilm formation, the highest cleaning efficacy was observed for sodium hypochlorite (NaOCl; p < 0.01). The efficacy of the chemical denture cleaner in removing long‐term Candida albicans biofilms was significantly lower than the efficacy of removal by brushing (p < 0.001). Conclusion: Different silicone‐based soft denture liners yield similar Candida albicans biofilm formation on their surface. The highest efficacy for the removal of Candida albicans biofilms was identified for NaOCl. Chemical denture cleaners appear to have rather low efficacy to remove mature Candida albicans biofilms.