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Aim: This study aimed to assess if the addition of origanum oil to denture materials could decrease microorganisms counts and biofilm formation without changing their mechanical/surface properties., Materials and Methods: A total of 66 resilient denture liner discs (SoftConfort, Dencril Comércio de Plásticos Ltda, SP, Brazil) were prepared with fixed dimensions of 10 × 3 mm for biofilm assay ( n = 36) and 12 × 2 mm for sorption-solubility tests ( n = 30) containing three oil concentrations - 0, 2.5 and 5%, thereby n = 12 per each group samples for biofilm assay and n = 10 per each group for sorption-solubility test respectively. While the microcosm biofilms of Streptococcus mutans, Candida species, and total microorganisms formed on denture liner were counted and expressed as colony-forming units per disc surface area, the water sorption (WS) and solubility (SL), was calculated by weighing the samples with an analytical balance at different intervals after storing them in a desiccator and distilled water alternatively. Data was recorded and statistically analyzed., Results: Surface roughness increased in all groups after biofilm formation ( p < 0.001), with the most significant change observed in the 2.5% oil group. The tested oil concentrations did not result in sorption changes, but a 5% oil concentration resulted in higher solubility ( p < 0.001). A reduction of total microorganisms and S. mutans was seen after 24 hours for all concentrations ( p < 0.05). No significant reduction was found for Candida (C.) albicans after 24 hours, whilst 2.5% oil concentration presented lower counts of C. albicans in comparison to the 5% group after 24 hours ( p < 0.05)., Conclusions: Incorporating 2.5% origanum essential oil into resilient denture liners seems to reduce microorganisms count in a complex biofilm model. These results need to be confirmed in future studies., Clinical Significance: The addition of natural products like origanum oil into denture-based materials can help manage biofilm onset and development while offering a simple and effective approach for maintaining denture hygiene. This strategy enhances the antimicrobial properties of denture liners without significantly altering their mechanical and surface characteristics, potentially improving patient outcomes. How to cite this article: Feitosa MÁL, Poletto-Neto V, Maske TT, et al. Surface Modifications and Antifungal Efficacy of Origanum Oil Incorporation in Denture-based Materials: An In Vitro Study. J Contemp Dent Pract 2024;25(9):878-884.

Fungal colonization of the soft denture liner is the first step in the development of denture-induced stomatitis. The study aims to assess apigenin and seashell nano-additives for their antifungal efficacy and their impact on the surface roughness of a soft denture liner. The study was accomplished in the Colleges of Dentistry in Duhok, Mosul and Hawler Medical Universities. The  Antifungal efficacy against Candida albicans was performed by the minimum inhibition concentration (MIC), for apigenin the MIC was determined by agar well diffusion and set at (0.25%, 0.5% and 1%) while for seashells, MIC was determined by broth dilution and set at (1.25%, 2.5% and 5%). Fungal adhesion was conducted on seven groups (unmodified soft liner and six groups of the modified liner with the antifungal concentrations (three for each nanoparticle). A total of forty-nine square-shaped specimens (10*10*2mm) of (GC, Super-soft, heat-cured, USA) soft liner were prepared, the adherent fungal cells were enumerated under a light microscope for each specimen in four fields and the results were expressed as fungal cells/mm2. For the surface roughness, forty-nine specimens of (20*10*3 mm) of the soft liner were prepared and the average surface roughness was obtained in µm using a profilometer (Talysurf, Taylor Hobson, UK). Apigenin and seashell-modified soft liner observed a significant decrease in both fungal adhesion and surface roughness compared to the unmodified liner and the reduction was related directly to the concentration of both additives. Apigenin and seashell nano-additives were effective as antifungal agents beside improving the surface roughness of the soft liner.

Aim: The present study aimed to assess the effect of PDT, herbal and chemical disinfectants on the dental pathogen adherence to soft denture liner colonized with E. coli, C. Albicans, S.aureus, and S. mutans., Material and Methods: A total of 20 samples of soft-lined removable acrylic complete dentures were fabricated and subjected to the American Type Culture Collection (ATCC) for the inoculation of E.coli, C.albicans, S.mutans and S.aureus in an in-vitro setup. The samples were then randomly divided into four groups and immersed in group 1: 5 µm of Rose Bengal (RB), group 2: Neem extract, group 3: Tea tree oil (TTO), and group 4: 0.12% CHX solutions respectively. Statistical analysis was accomplished by the SPSS 10 statistical software for Windows at a significance level p< 0.05. Two-way ANOVA and Tukey's multiple comparison test were used to analyze the data and compare the means and standard deviation values of CFU/mL (log10) for exposed E. coli, C. albicans, S aureus, and S. mutans., Results: Intragroup comparison indicated E.coli and C.albicans did not unveil a decrease in reduction CFU/mL (log10) when SDL irradiated with RB 5 µm. Whereas, CFU/mL (log10) values of S.aureus; 2.62±0.68 CFU/mL and S.mutans: 3.41±0.13 CFU/mL plunged significantly (p<0.05). Likewise, S. aureus and S. mutans CFU/mL (log10) strain values display reduction when treated with all four disinfectants while the count of C.albicans unveiled a significant plunge with CHX, TTO and neem extract except RB (p<0.05) CONCLUSION: 0.12% CHX and TTO have enhanced antimicrobial efficacy in reducing adhered bacterial colonies of E.coli, C.albicans, S.aureus, and S.mutans (CFU)/mL on a denture soft liner., (Copyright © 2022. Published by Elsevier B.V.)

Herein, we investigated the surface characterization and biocompatibility of a denture-lining material containing Cnidium officinale extracts and its antifungal efficacy against Candida albicans . To achieve this, a denture-lining material containing various concentrations of C. officinale extract and a control group without C. officinale extract were prepared. The surface characterization and biocompatibility of the samples were investigated. In addition, the antifungal efficacy of the samples on C. albicans was investigated using spectrophotometric growth and a LIVE/DEAD assay. The results revealed that there was no significant difference between the biocompatibility of the experimental and control groups ( p > 0.05). However, there was a significant difference between the antifungal efficiency of the denture material on C. albicans and that of the control group ( p < 0.05), which was confirmed by the LIVE/DEAD assay. These results indicate the promising potential of the C. officinale extract-containing denture-lining material as an antifungal dental material.

Purpose: The objective of this systematic review is to compare results concerning the properties of adhesion, roughness, and hardness of dental liners obtained in the last ten years., Methods: Searches on the databases LILACS, PubMed/Medline, Web of Science, and Cochrane Database of Systematic Reviews were supplemented with manual searches conducted between February and April of 2018. The inclusion criteria included experimental in vitro and in vivo , clinical, and laboratory studies on resilient and/or hard liners, assessment of hardness, roughness, and/or adhesion to the denture base, and physical/mechanical changes resulting from the disinfection process and changes in liners' composition or application., Results: A total of 406 articles were identified and, from those, 44 are discussed. Twenty-four studies examined the bond strength, 13 surface roughness, and 19 the hardness. Of these 44 studies, 12 evaluated more than one property. Different substances were used in the attempt to improve adhesion. Considering roughness and hardness, the benefits of sealants have been tested, and the changes resulting from antimicrobial agents' incorporation have been assessed., Conclusion: Adhesion to the prosthesis base is improved with surface treatments. Rough surfaces and changes in hardness compromise the material's serviceability.

This study investigated the antimicrobial efficacy and mechanical strength of hard and soft denture liners modified with benzalkonium chloride (BAC). The specimens (1 mm thickness, 8 mm diameter) were prepared by mixing 0.5, 1, 2 and 5 wt% BAC with soft (Sofreliner Medium, Tokuyama) and hard (Rebase II, Tokuyama) denture liners (n = 5/group). BAC was not added to the controls. Candida albicans ATCC 28366 (A 550  = 0.5) and Streptococcus mutans Ingbritt suspensions (A 550  = 0.35) were pipetted onto the specimens, and incubated for 4 h. The viable cells were collected, and determined by plate-culturing (CFU). The tests were repeated after the specimens were soaked in distilled water for 7 days. The mechanical strengths were evaluated by tear and 4-point flexural strength tests for soft and hard liners, respectively. The data were analyzed with ANOVA and Tukey's HSD tests at p = 0.05. C. albicans viability was lost in all groups of BAC-modified soft liners (p < 0.001), and S. mutans viability was reduced (p < 0.01), except of soaked BAC 0.5 wt% group (p > 0.05). For the hard liner, BAC 5 wt% killed the C. albicans and S. mutans cells both before and after soaked in water (p < 0.001). BAC 2 wt% showed comparable tear strength with the soft liner control (p > 0.05). BAC did not reduce the flexural strength of the hard liner (p > 0.05), except of BAC 5 wt% group (p < 0.01). BAC can be a promising agent reducing the C. albicans and S. mutans viability on the soft and hard denture liner surfaces.

Statement of Problem: The colonization of Candida albicans on soft liners causes the deterioration of material surface properties and denture stomatitis., Purpose: The purpose of this in vitro study was to investigate the effect of incorporating seed oil on the antifungal properties, surface roughness, wettability, weight changes, and glucose adsorption/absorption of a soft liner., Material and Methods: Centratherum anthelminticum, Ocimum sanctum Linn, and Linum usitatissimum seed oils were incorporated into a soft liner, and the diameter of the inhibition zone (DIZ) was calculated relative to the growth of C albicans at 24, 48, and 72 hours and 7 days. The effect of incorporating oil on wettability was evaluated with the contact angle analyzer, and effect on surface roughness was evaluated with scanning electron microscopy. Weight changes and absorption/adsorption of glucose to the soft liner were estimated. Data were analyzed by using paired Student t tests and 2-way ANOVA (α=.01)., Results: Soft liner with 800 μL each of C anthelminticum and O sanctum oils showed complete inhibition at 72 hours; the DIZ on day 7 were 31.66 ±1.20 mm and 29.66 ±1.46 mm, respectively. The change in weight between time intervals differed significantly between conditions (P<.01). The addition of oils decreased the surface roughness and improved wettability significantly for O sanctum and C anthelminticum specimens (P<.01). At 72 hours, 5.5 mg of glucose was detected in the positive control, whereas no glucose was detected in the oil specimens., Conclusions: The addition of the seed oils of C anthelminticum and O sanctum to the soft liner significantly reduced the growth of C albicans, improved wettability, reduced surface roughness, and minimized the absorption and adsorption of glucose., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Fungal biofilms may contribute to the occurrence of denture stomatitis. The objective of the study was to investigate the biofilm formation and morphology of Candida albicans in biofilms on the surface of denture base materials. Specimens were prepared from different denture base materials. After determination of surface properties and salivary pellicle formation, mono- and multispecies biofilm formation including Candida albicans ATCC 10231 was initiated. Relative amounts of adherent cells were determined after 20, 44, 68 and 188 h; C. albicans morphology was analysed employing selective fluorescence microscopic analysis. Significant differences were identified in the relative amount of cells adherent to the denture base materials. Highest blastospore/hyphae index suggesting an increased percentage of hyphae was observed in mono- and multispecies biofilms on the soft denture liner, which did not necessarily respond to the highest relative amount of adherent cells. For both biofilm models, lowest relative amount of adherent cells was identified on the methacrylate-based denture base material, which did not necessarily relate to a significantly lower blastospore/hyphae index. The results indicate that there are significant differences in both biofilm formation as well as the morphology of C. albicans cells in biofilms on the surface of different denture base materials., (© 2015 Blackwell Verlag GmbH.)

Aim: This study aimed to evaluate the influence of surface free energy (SFE) of denture base and liner materials on Candida albicans biofilm development., Methods: Discs were fabricated using poly(methyl methacrylate) acrylic resin and poly(ethyl methacrylate) denture liner, according to the manufacturers' instructions. For SFE test, discs were pellicle-coated with saliva alone, saliva + blood plasma, or blood plasma alone. Candida albicans biofilms were allowed to form on pellicle-coated discs for 48 h. Biofilms were evaluated for cell counts, metabolic activity, and structural characteristics at adhesion phase (after 1.5 h of development) and at biofilm maturity (after 48 h of development). Data were analyzed by anova and Tukey tests using a significance level of 5%., Results: Saliva + blood plasma pellicles had a higher SFE compared to pellicles of saliva or blood plasma alone (P < 0.001). Differences in SFE by pellicle-coating did not affect the cell counts, metabolic activity, or structure at the adhesion phase (P > 0.05). In contrast, the presence of blood plasma resulted in higher cell counts, biovolume, and thickness of mature biofilms on both materials (P < 0.001)., Conclusions: Increases in SFE from pellicle-coating leads to robust mature C. albicans biofilms on both denture materials., (© 2014 Wiley Publishing Asia Pty Ltd.)

Purpose: The purpose of this study was to evaluate, in situ, the initial adhesion of microorganisms to as well as the surface roughness and chemical composition of ProBase Hot (Ivoclar Vivadent), a hard acrylic resin, and Vertex Soft (Vertex-Dental), an acrylic-based soft liner, used in removable dental prostheses., Materials and Methods: Equal sized disks of ProBase Hot and Vertex Soft were prepared and polished according to the recommended procedures for clinical use. Two disks of each material were mounted in individual oral splints and exposed for 4 hours to the oral cavities of 15 participants. The microbial adhesion to each material's surface was measured with the pour plate technique using rich and selective growth media. Statistical analysis was performed using the Student t test. Scanning electron microscopy and chemical composition analyses obtained through electron probe radiographic microanalysis of sample disks also were performed., Results: In comparison to ProBase Hot, Vertex Soft presented higher microbial adhesion, namely regarding total aerobes, anaerobes, streptococci, and mutans streptococci (P < .05). Also, Vertex Soft presented higher surface roughness. Differences in the chemical composition of the two materials also were found., Conclusions: The Vertex Soft liner has been found to be more susceptible to microbial adhesion than the acrylic resin ProBase Hot, probably due to its greater surface roughness. The application of Vertex Soft liner to a hard denture base may lead to a higher risk of oral and systemic infections for patients, highlighting a greater need for plaque control, especially for more susceptible individuals.

Objective: The antimicrobial action of five drugs incorporated in temporary denture relines on the fungal biofilm was evaluated., Materials and Methods: A Candida albicans biofilm (SC5314) was formed on specimens (10 × 1 mm) of materials (Trusoft and Softone) modified or not (control) by the drugs (nystatin, miconazole, ketoconazole, itraconazole, and chlorhexidine diacetate). Cell viability was determined spectrophotometrically by the tetrazolium salt reduction assay (XTT) after 24 h, 48 h, and 7 and 14 days of incubation. The minimum inhibitory concentrations (MICs) were those which inhibited 90% or more of fungal growth. Fungal susceptibility was confirmed by confocal laser scanning microscopy analysis., Results: The MICs of drugs incorporated in the materials were 0.032, 0.256, 0.128, 0.256, and 0.064 g ml(-1) for nystatin, miconazole, ketoconazole, itraconazole, and chlorhexidine, respectively. Images from nystatin, chlorhexidine, and ketoconazole demonstrated no viable cells., Conclusions: The antimicrobials incorporated in the resilient materials inhibited fungal growth during 14 days, with lower MICs for nystatin and chlorhexidine., (© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The effect of Candida albicans biofilms and methyl methacrylate (MMA) pretreatment on the bond strength between soft denture liners and polymethyl methacrylate (PMMA) resin was analyzed. Specimens were prepared and randomly divided with respect to PMMA pretreatment, soft liner type (silicone-based or PMMA-based), and presence or absence of a C. albicans biofilm. Samples were composed of a soft denture liner bonded between two PMMA bars. Specimens (n = 10) were incubated to produce a C. albicans biofilm or stored in sterile PBS for 12 days. The tensile bond strength test was performed and failure type was determined using a stereomicroscope. Surface roughness (SR) and scanning electron microscopy (SEM) analysis were performed on denture liners (n = 8). Highest bond strength was observed in samples containing a silicone-based soft liner and stored in PBS, regardless of pretreatment (p < 0.01). Silicone-based specimens mostly underwent adhesive failures, while samples containing PMMA-based liners predominantly underwent cohesive failures. The silicone-based specimens SR decreased after 12 days of biofilm accumulation or PBS storage, while the SR of PMMA-based soft liners increased (p < 0.01). The PMMA-based soft liners surfaces presented sharp valleys and depressions, while silicone-based specimens surfaces exhibited more gentle features. In vitro exposure to C. albicans biofilms reduced the adhesion of denture liners to PMMA resin, and MMA pretreatment is recommended during relining procedures.

Objectives: The aim of this study was to evaluate Candida colonisation in the dentures with silicone soft liner in diabetic and non-diabetic patients and to assess the antifungal efficacy of chlorhexidine gluconate on Candida colonies., Materials and Methods: Thirty patients with resorbed ridges, fifteen each in the diabetic and non-diabetic group, were selected. The mandibular denture of each patient was lined with heat-polymerised silicone resilient liner. Patients were instructed to clean the dentures with soap water and brush. Samples from the fitting surface of mandibular dentures were collected at 15, 21 and 30 days. Subsequently, samples were collected at 15, 21 and 30 days, after cleaning the dentures with a detergent solution of 4% chlorhexidine gluconate, and incubated for the evaluation of Candida growth. These data were subjected to statistical analysis by Mann-Whitney U-test., Results: Normal oral flora in diabetics and non-diabetics showed no difference (p > 0.05). The density of colonies increased after 21 and 30 days in diabetic patients (p < 0.05). Number of Candida colonies significantly reduced in both the groups after 21 and 30 days of cleaning the dentures with 4% chlorhexidine gluconate (p < 0.05)., Conclusion: Dentures with silicone resilient liner exhibit increased Candida growth in diabetic patients. Four per cent chlorhexidine gluconate solution effectively disinfects these dentures., (© 2012 John Wiley & Sons A/S and The Gerodontology Society. Published by John Wiley & Sons Ltd.)

Statement of Problem: Denture liners are well known for their poor physical properties that favor the accumulation of plaque and colonization by Candida species, which can irritate the oral tissues and lead to denture stomatitis., Purpose: A systematic review was conducted to determine the feasibility of a prevention protocol for Candida colonization in denture liners and an effective treatment after the fungi has colonized the material., Material and Methods: Clinical and in vitro investigations that assessed the treatment and/or prevention of Candida colonization and biofilm formation in denture liners were selected according to the PRISMA statement. Seven electronic databases were searched from 1950 to April 2012 with the keywords "denture liner" OR "reline*" OR "tissue conditioner" AND "Candida" OR "denture stomatitis" OR "oral candidiasis" OR "antifungal agents" OR "denture clean*"., Results: The incorporation of nystatin (in general, 500 000 units) into tissue conditioners to prevent the onset of the disease and immersion in sodium hypochlorite for disinfection were the methods most often described in this systematic review, and both methods were able to prevent or inhibit Candida colonization, depending on their concentrations. The 0.5% sodium hypochlorite concentration can disinfect tissue conditioners and denture liners. Microwave irradiation has also been described an alternative method of disinfection. Because of a lack of standardized results (especially with regard to the method used to perform microbial counts), a meta-analysis could not be performed., Conclusions: The literature suggests that the use of 0.5% sodium hypochlorite can help disinfect denture liners and tissue conditioners. The incorporation of nystatin in those materials is also able to treat or prevent oral candidiasis. However, as most of the studies were in vitro, there is insufficient reliable evidence to truly provide recommendations regarding the ideal cleaning method or whether the addition of antifungal agents is worthwhile. Well-designed randomized controlled trials are needed to provide answers to these questions., (Copyright © 2013 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)

Objectives: This randomised clinical trial assessed how biofilm development and composition is affected by time and denture material type in denture wearers with and without denture stomatitis., Methods: Specimens of acrylic resin (control) and denture liners (silicone-based or acrylic resin based, depending on the experimental phase) were inserted into the surface intaglio of 30 denture wearers. Biofilm was formed in two phases of 21 days, and counts of viable micro-organisms in the accumulating biofilm were determined after 7, 14 and 21 days of biofilm formation. Data were analysed by three-way ANOVA followed by Tukey test to assess differences among health condition (healthy or with denture stomatitis), materials and time point., Results: Non-albicans Candida species counts were higher in diseased patients with silicone-based denture liners (p=0.01). Denture stomatitis patients showed higher mutans streptococci counts after 7 days (p=0.0041)., Conclusions: Longer biofilm formation time periods did not result in differences on biofilm composition. The denture liners evaluated in this study accumulate greater amount of biofilm, and therefore their use should be carefully planned., Clinical Significance: The silicone-based denture liner tested should be used cautiously in patients with denture stomatitis as it showed increased non-albicans species counts, known to be difficult to treat., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Objective: This study evaluated the influence of surface characteristics of various denture lining materials on the adherence of Candida albicans., Materials and Methods: Four different types of materials (tissue conditioners, acrylic and silicone soft liners and hard reline materials) were selected. Disk-shaped material specimens were prepared and their surface roughness values (R(a) ) measured using a profilometer. The contact angles of four reference liquids were measured on the material surfaces and surface energy parameters (total surface energy, acid and base components, degree of hydrophobicity/hydrophilicity) of the materials were calculated in accordance with acid-base theory. Specimens were incubated with C. albicans and adhering fungi quantified using the colony counting method. Data were statistically analyzed using a one-way ANOVA with Games-Howell post-hoc test (α = 0.05). Pearson correlation analysis was applied to detect correlations between surface characteristics and Candida adhesion., Results: Significant differences in the surface roughness of the materials were found (p < 0.001). The acrylic soft liners were more hydrophilic than the other materials. Overall, the acrylic soft liners and tissue conditioners showed significantly greater Candida adhesion than silicone soft liners and hard reline materials (p < 0.05). The Pearson correlation analysis indicated that the base component and degree of hydrophobicity/hydrophilicity of the materials (p = 0.005/0.008), rather than the total surface energy and the surface roughness (p = 0.093/0.057), affected C. albicans adherence in a statistically significant way., Conclusions: The adhesion of C. albicans to denture lining materials can be accounted for in terms of interfacial acid-base interactions.

Denture liners (DL) are easily colonized by Candida spp. In an attempt to prevent biofilm colonization, manufacturers have incorporated undecylenic acid (UDA) into DL. In this in vitro study, the effects of UDA released from DL on Candida biofilms were investigated. The concentrations of UDA released from commercial DL were determined by gas chromatography-mass spectrometry (GC-MS). Minimum inhibitory concentration (MIC) and minimum fungistatic concentration (MFC) tests were performed for C. albicans or C. glabrata, with UDA for comparison with the concentrations released from DL. Specimens of DL with (experimental group) and without UDA (control group) were fabricated, and Candida biofilms were developed on DL surfaces. Biofilms were evaluated by cell counts, metabolic activity, structure, and secretion of proteinase or phospholipase. The concentrations of UDA released were within the MIC and MFC ranges. In the presence of UDA, C. albicans biofilms were thinner and had lower numbers of viable and active cells, although no significant enzymatic changes were observed relative to the control group (p > 0.05). In contrast, C. glabrata biofilms exhibited higher cell counts and greater metabolic activity and also increased proteinase activity in the presence of UDA relative to the control group (p < 0.05). Overall, UDA did not prevent Candida biofilm formation.

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., (© 2011 The Gerodontology Society and John Wiley & Sons A/S.)

Objectives: This in vivo study evaluated the influence of controlled diabetes on biofilm formation on a soft denture liner in elderly patients., Background: Soft denture lining materials are more susceptible to microbial colonisation than denture base acrylic resins. Especially in the elderly, several predisposing factors may accumulate leading to an increased probability of biofilm development that may result in candidiasis, a significant clinical oral disease., Materials and Methods: Volunteers wearing complete dentures were divided into two groups (n = 20): diabetic patients with controlled glycaemia, and healthy patients. In both groups, a silicone-based soft liner was placed in a recess created at the base of the maxillary dentures. Subjects cleaned the prosthesis three times a day. Biofilm formed on the liner was quantified at various time points (baseline, two, four and six weeks). Data were analysed by two-way repeated measures ANOVA and Tukey's test (α = 0.05)., Results: There was no statistical difference in biofilm formation for any of the time points between controlled diabetes patients and healthy patients., Conclusion: The results suggest that the control of diabetes in elderly patients provides the same levels of biofilm formation when compared to healthy individuals., (© 2010 The Gerodontology Society and John Wiley & Sons A/S.)

We tried to find the effects of the application of the antibacterial solution containing silver ions on the surface of the denture soft lining material. We selected the right concentration of the silver-containing solution and coated a soft lining material with the solution so that the soft lining material could be antibacterial. The antibacterial solution containing silver ions was prepared by sol-gel method. MIC of C. a and S. a were tested by broth dilution test. The surface property and thickness were tested after coated. The in vitro antibacterial ratio against C. a and S. a were demonstrated by the method of plate-counting. A film was formed after coating, while the adequacy was not changed. Antibacterial ratio of 0.64 mg/ml group against C. a was 90.82%, and that against S. a was 94.96% in 24 hours, respectively. It was found that the antibacterial property of the soft lining material can be acquired by coating this antibacterial solution with silver ion, without changing the adequacy.

Objectives: Microorganisms may colonise polysiloxane soft liners leading to bio-deterioration. The aim of this study was to investigate in vitro adhesion and in vivo biofilm formation of Candida species on polysiloxane surfaces., Methods: The materials used in this study were Molloplast B, GC Reline soft, Mollosil Plus, Silagum Comfort and Palapress Vario. The in vitro retention of clinical isolates of Candida albicans to the relining and denture-base materials by microscopic (scanning electron microscopy, SEM), conventional culturing methods and antimicrobial properties of these materials were studied. Candida found on materials and mucosa following long-term use were identified and quantified, and biofilms covering the surfaces were investigated by SEM., Results: There was a significant decrease in the number of cells attached in vitro to saliva-coated surfaces compared with non-treated surfaces. An oral Candida carriage of 78% was found. Candida albicans, C. glabrata, C. intermedia and C. tropicalis were identified. In vivo biofilm formation on the liners appeared as massive colonisation by microorganisms., Conclusions: The results of the in vitro experiments suggest that salivary film influences early colonisation of different C. albicans strains. The film layer also minimises the differences among different strains. The Candida carriage of these patients was similar to denture-wearing patients without soft liners., (© 2009 The Gerodontology Society and John Wiley & Sons A/S.)

Objective: This study evaluated the in vitro adherence of pathogenic micro-organisms, Candida albicans, Staphylococcus aureus and Pseudomonas aeruginosa, to soft lining materials and their inhibitory effect on these micro-organisms., Materials and Methods: To measure adherence, specimens of Molloplast B and Ufi Gel P were inoculated [10(7 )colony-forming units per millimetre (cfu/ml)] with TSB media containing the micro-organisms. To determine the number of micro-organisms in the 10(-2)-10(-5) dilutions, 25 microl of the suspension were transferred to plates of selective media. Colony counts of each specimen were quantified (cfu/ml). The surface roughness was measured with a perfilometer to assess the relationship between the adherence of micro-organisms and surface roughness of each material. For the inhibition test, specimens of materials were placed in agar plates inoculated individually with the micro-organisms. After 48 h, the inhibition zones around the specimens were measured., Results: None of the materials exhibited inhibition zones. The number of cfu/ml of S. aureus and P. aeruginosa were significantly greater than C. albicans for both materials. The Ufi Gel P exhibited greater adherence of C. albicans than Molloplast B. No correlation was observed between the adherence of micro-organisms and surface roughness., Conclusion: The surface roughness of the materials is not the only factor governing micro-organism adherence.

Purpose: The aim of this study was to evaluate if the use of a varnish on a tissue conditioner would affect biofilm adhesion., Background: After the surgery has been performed, before the delivery of a complete denture, it is often necessary to use materials such as tissue conditioners on the surgical wound. However, these materials present deficient physico-mechanical properties, which allow biofilm development., Methods: Forty elderly volunteers wearing complete maxillary dentures were selected. They were randomly allocated into two groups (n = 20), G1 and G2. In both groups, a silicone-based tissue conditioner was placed in a recess created at the base of the denture, according to the manufacturer's guidelines. In group G1, a varnish was applied to the tissue conditioner, while in group G2, no treatment was applied. All volunteers performed daily hygiene of the prosthesis with a soft toothbrush, and toothpaste. Quantification of the mean score values of biofilm formed at different time points (baseline, 1 week and 3 weeks) was statistically analysed using anova (alpha = 0.05)., Results: Group G2 (1.6 +/- 1.2) showed the lowest mean score values of biofilm formation and there was a statistical difference between the groups (p = 0.03). The highest mean score values were found after 3 weeks (2.7 +/- 1.4) and were statistically different from the other time points studied (baseline and 1 week)., Conclusion: The use of a varnish had a detrimental effect on the tissue conditioner studied, allowing higher biofilm formation.

This study evaluated the long-term efficacy of denture cleansers against Candida spp. biofilm recolonization on liner surface. Specimens were fabricated of a poly(methyl methacrylate)-based denture liner and had their surface roughness evaluated at baseline and after cleansing treatments. C. albicans or C. glabrata biofilms were formed on liner surface for 48 h, and then the specimens were randomly assigned to one of cleaning treatments: two alkaline peroxides (soaking for 3 or 15 min), 0.5% sodium hypochlorite (10 min) or distilled water (control; 15 min). After the treatments, the specimens were sonicated to disrupt the biofilm, and residual cells were counted (cell/mL). Long-term effectiveness of the cleaning processes was determined by submitting a set of cleaned specimens to biofilm growth conditions for 48 h followed by estimation of cell counts. The topography of specimens after cleaning treatments was analyzed by SEM. Data were analyzed by ANOVA and Tukey's test (α; = 0.05). Results of cell count estimation showed significant differences in cleanliness among the treatments (p < 0.001), and it could be observed by SEM. However, no significant difference (p > 0.05) was observed among the Candida species regarding the recolonization condition. Alkaline denture cleansers showed similar cleaning performance and both differed from the control (p < 0.001). Sodium hypochlorite was the only treatment that removed biofilm efficiently, since no viable cells were found after its use. In conclusion, alkaline peroxide denture cleansers were not effective in removing Candida spp. biofilm from denture liner surfaces and preventing biofilm recolonization.

This study assessed how biofilm composition is affected by both time and denture material in complete denture wearers. Biofilm was formed during two phases of 14 days on acrylic resin and denture liner specimens mounted on the buccal surface of the mandibular dentures of 21 patients. Specimens were removed randomly on days 2, 7, and 14. Higher counts of Candida glabrata, total streptococci, Actinomyces, total microorganisms, and percentage of Actinomyces were observed after 7 and 14 days (P < .05). C glabrata was the only species to show progressively rising counts from day 2 to 14, while no difference was found in biofilm composition among the materials tested.

This study investigated the C. albicans adhesion to cold- and heat-polymerized soft lining materials that were initially incubated in two different artificial body fluids, namely saliva and nasal secretion, and examined the surface roughness the materials (cold and heat polymerized soft liner) tested in vitro. Cold (Visco Gel) and heat-polymerized (Molloplast B) soft liner specimens (N=32, n=8 per group) (10x10x1.5 mm) were randomly produced to express the relationship between surface roughness and contamination, and influence of body fluids, and incubated in 1.5 ml contaminated solutions for 2 h. After fixation, all of materials were evaluated under optical microscope (x400) and SEM. Surface roughness measurements were examined with profilometre for each material. Data were analyzed using two-way ANOVA, Tukey's HSD and Dunnett T3 tests (alpha=0.05). Material type (p<0.05) and contamination media (p<0.05) showed a significant influence on the C. albicans adherence. The surface roughness of cold polymerized soft liner (Visco Gel) was significantly higher than heat-polymerized soft liner (Molloplast B) (p<0.05).

Background: Soft denture lining-materials are more susceptible to microbial adhesion than hard denture base acrylic resin. Poor oral hygiene and Candida albicans infection are common among elderly denture wearers as these patients usually have difficulty in keeping them clean., Purpose: To evaluate the influence of the oral hygiene methods on the formation of a biofilm over a soft denture-lining material., Material and Methods: Twenty volunteers were randomly separated into two groups: G1 and G2. Ten volunteers performed daily hygiene of the prostheses with a soft toothbrush and toothpaste. The G2 performed a treatment identical to G1 but also immersed the prostheses in sodium hypochlorite 0.5% for 20 min, once a week. Quantification of the mean score values of biofilm formation at different times were statistically analysed using analysis of variance and Tukey's test (alpha = 0.05)., Results: G1 (0.65 +/- 0.52) showed the lowest mean score values of biofilm formation. There was statistical difference between G1 and G2. The highest mean score values were found at 6 weeks (1.3 +/- 1.08) and were statistically different from other times., Conclusion: The oral hygiene methods had a significant effect in the formation of the biofilm over a soft denture-lining material.

As poor denture hygiene is related to Candida colonisation, disinfectant solutions have been proposed as an effective method of preventing denture stomatitis. This study assessed the efficacy of denture cleansers on Candida albicans and Candida glabrata adherence on denture liners. Another aim was to correlate materials' surface roughness (Ra) to Candida adherence. Specimens of three denture liners (soft and hard polymethyl methacrylate (PMMA)-based and soft silicone-based) were prepared and had their Ra measured. Specimens were randomly divided to adherence assays with C. albicans or C. glabrata. After contamination with the fungi, specimens were treated with an enzymatic cleanser solution, a cleanser solution or a 0.5% NaOCl solution by soaking for 3, 15 or 10 min, respectively. Control group specimens were soaked in distilled water for 15 min. Number of remaining Candida cells after treatment was determined by light microscopy (x400). Analysis of variance (alpha = 0.05) showed that Ra of the silicone-based liner was lower than that of the PMMA-based liners (p < 0.05). The overall results showed high C. glabrata adherence (p < 0.001), while the lowest levels of remaining Candida cells were found for the treatment with 0.5% NaOCl (p = 0.0019). No difference among denture cleansers and control was found (p = 0.19). There was no correlation between Ra and C. albicans or C. glabrata adherence in all materials tested. The only treatment able to reduce both Candida species adherence on all materials tested was 0.5% NaOCl solution.

Purpose: The objective of the present study was to evaluate surface roughness and adherence of Candida albicans and to determine the effectiveness of denture cleansers in the disinfection of silicone-based soft lining materials., Materials and Methods: Two types of silicone-based soft lining materials (four room temperature polymerised soft lining materials [RTPSLM]: Ufi Gel P, Ufi Gel C, Mollosil and Soft-Liner; and two high temperature polymerised soft lining materials [HTPSLM]: Moloplast B and Luci Soft) and seven denture cleansers (Efferdent, Polident, Steradent, Corega, Denclen, Klorhex and Axion) were tested in the present study. For each soft lining material, 56 samples (10 mm x 10 mm x 3 mm) were prepared. Surface roughness measurements were made using a profilometer with an optical scanner probe. All samples were ultrasonically cleaned in water for 15 s, autoclave sterilised and contaminated with C. albicans solutions for adherence assay evaluation. After the evaluation, the samples were immersed in seven different denture cleansers. The results were expressed as the ratio of cells remaining after each cleanser in comparison with the control group., Results: HTPSLM showed a lower surface roughness value (2.21 +/- 0.30 lm) than RTPSLM (2.39 +/- 0.40 lm), but these differences were not statistically significant (P > 0.05). Also, HTPSLM showed lower adhesion of C. albicans (mean ranks 136.35) than RTPSLM (mean ranks 138.64), but the differences were not statistically significant (P > 0.05, one- or two-way analysis of variance). In the C. albicans removal test, all denture cleansers showed a strong effect on both silicone-based soft lining materials. HTPSLM showed lower removal activity (mean ranks 30.01) than RTPSLM (mean ranks 25.86), but these differences were not statistically significant (P > 0.05). Although there were no significant differences between disinfectants on both silicone-based soft lining materials, Axion was found to be the most effective disinfectant. Corega, Polident, Denclen, Steradent and Efferdent showed the most effective cleansing, respectively., Conclusions: RTPSLM and HTPSLM did not show significant differences in the surface roughness value; also they showed no significant differences in the adhesion rate of C. albicans. All tested silicone-based soft lining materials showed adherence of C. albicans after contamination procedures, and removal activity for C. albicans was observed in all tested silicone-based soft lining materials after disinfection procedures.

Purpose: This study evaluated the effectiveness of different exposure times of microwave irradiation on the disinfection of a hard chairside reline resin., Materials and Methods: Sterile specimens were individually inoculated with one of the tested microorganisms (Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Bacillus subtilis) and incubated for 24 hours at 37 degrees C. For each microorganism, 10 specimens were not microwaved (control), and 50 specimens were microwaved. Control specimens were individually immersed in sterile saline, and replicate aliquots of serial dilutions were plated on selective media appropriate for each organism. Irradiated specimens were immersed in water and microwaved at 650 W for 1, 2, 3, 4, or 5 minutes before serial dilutions and platings. After 48 hours of incubation, colonies on plates were counted. Irradiated specimens were also incubated for 7 days. Some specimens were prepared for scanning electron microscopic (SEM) analysis., Results: Specimens irradiated for 3, 4, and 5 minutes showed sterilization. After 2 minutes of irradiation, specimens inoculated with C. albicans were sterilized, whereas those inoculated with bacteria were disinfected. One minute of irradiation resulted in growth of all microorganisms. SEM examination indicated alteration in cell morphology of sterilized specimens. The effectiveness of microwave irradiation was improved as the exposure time increased., Conclusion: This study suggests that 3 minutes of microwave irradiation can be used for acrylic resin sterilization, thus preventing cross-contamination.

Colonization of denture lining materials by microorganisms including Candida albicans can result in deterioration of the material, as observed by a previous in vitro study by the authors. The current in vivo study monitored the microbial colonisation and penetration of five types of denture liners and their topography over six months. There was no significant difference in the microbial colonisation on the denture liners and no penetration observed, indicating a slower rate of deterioration of materials in vivo. However the surface roughness of all materials increased during use, which might alter susceptibility to subsequent microbial colonisation.

Objective: The aim of this study was to rank 10 denture disinfection methods according to their efficacy in reducing Candida albicans (C. albicans) colonization on soft denture relining material., Material and Methods: Circular specimens (diameter 8 mm) were made of soft denture relining material (Mucopren E, Kettenbach) and thermally aged. Specimens were incubated with C. albicans (strain 1386, DSMZ) followed by 1 of 10 disinfection procedures (6 soaks, 2 microwave irradiation regimes, 1 effervescent commercial cleansing product, and denture left dry overnight). Incubation with phosphate buffered saline (PBS) served as a control. Adhering fungi were quantified using a bioluminometric assay in combination with an automated plate reader for cell quantification. Scanning electron micrographs (SEMs) were made for validation., Results: Low median luminescence intensities indicated the presence of a few viable fungi after the soaking of specimens in sodium hypochlorite (10 relative luminescence units (rlu)), microwave irradiation immersed in water (8 rlu), and application of effervescent cleansing tabs (22 rlu). No statistically significant difference (p>0.05) to control PBS (200 rlu) was found after immersion in hydrogen peroxide (172 rlu), glutaraldehyde (103 rlu), household vinegar (196 rlu), Listerine coolmint (194 rlu), Plax (222 rlu), dry microwave irradiation (221 rlu) and specimens left dry overnight (165 rlu). SEM displayed C. albicans monolayers with different morphologic forms on each surface investigated., Conclusions: Only soaking in sodium hypochlorite (1%; 10 min), microwave irradiation immersed in water (800 W; 6 min), and application of effervescent cleansing tabs (Blend-a-dent tabs; 10 min) proved to be effective against C. albicans colonization on soft denture relining material.

Objective: The aim of the present study was to evaluate the clinical performance of four denture soft liners up to 12 months., Materials and Methods: Thirty-three edentulous patients who experienced difficulties when using hard denture bases because of changes in denture-supporting tissues were accepted for the study and randomly received Molloplast B, GC Reline Soft, Silagum Comfort, or Mollosil Plus relines. Performance of the materials was evaluated using nine criteria at 3, 6, and 12 months: physical integrity, surface detail, adhesion, color, odor, plaque accumulation, resilience, hygiene, and mucosal condition. A four-point categorized scale (1=poor, 2=fair, 3=good, 4=excellent) was used. Unscheduled maintenance events and the presence of fungal colonization were also recorded., Results: The percentage of patients available at 3, 6, and 12 months were 91%, 91%, and 66%. Main reasons for dropouts and discontinuation were fractured dentures and patient dissatisfaction. At 6 months, 96% of the performance scores were good or excellent and the largest changes were observed for physical integrity, surface detail, color, and fungal colonization. Fungal colonization was the most commonly observed problem and was the only reason of failure at 12 months., Conclusions: The clinical performance of all soft liners was slightly impaired over the 12-month observation. Except for cases showing extensive fungal colonization, the observed changes in clinical performance did not necessitate remaking of the dentures. Mollosil Plus showed a performance comparable to that of Molloplast B, and the other materials had slightly lower performance especially in terms of fungal colonization.

The aim of the study was to compare the adhesion of oral microorganisms to different types of soft liner and acrylic resin surfaces. Three different soft lining materials were applied to cavities formed on the fitting surfaces of prostheses in 17 patients. On days 1, 7 and 14, the specimens were taken out and immediately processed for bacteriological evaluation. The numbers of adhering microorganisms were calculated and the specimens were compared among each other and also with a control group (acrylic resin). Data were analyzed by two-way ANOVA and least squares differences at a significance level of P < 0.05. Among the four materials tested the total number of oral microorganisms adhering to Softliner material was the greatest after each of the time periods tested. Higher numbers of oral bacteria and Candida were shown to adhere to soft lining materials than to acrylic resin. Microbial coverage increased continuously with time and the differences between days 1 and 14 were statistically significant (P < 0.05). Temporary soft lining materials are not resistant to adhesion and possible surface damage caused by oral bacteria, and therefore their use should be limited to short-term periods.

Despite therapeutic progress, opportunistic oral fungal infectious diseases have increased in prevalence, especially in denture wearers. The combination of entrapment of yeast cells in irregularities in denture-base and denture-relining materials, poor oral hygiene and several systemic factors is the most probable cause for the onset of this infectious disease. Hence colonization and growth on prostheses by Candida species are of clinical importance. The purpose of this review is to critically discuss several key factors controlling the adhesion of Candida species which are relevant to denture-associated stomatitis. Although there is some consensus on the role of surface properties, studies on several other factors, as the use of denture liners, salivary properties and yeast-bacterial interactions, have shown contradictory findings. A comprehensive fundamental understanding is hampered by conflicting findings due to the large variations in experimental protocols, while other factors have never been thoroughly studied. Surface free energy and surface roughness control the initial adherence, but temporal changes have not been reported. Neither have in vivo studies shown if the substratum type is critical in dictating biofilm accumulation during longer periods in the oral environment. The contribution of saliva is unclear due to factors like variations in its collection and handling. Initial findings have disclosed that also bacteria are crucial for the successful establishment of Candida in biofilms, but the clinical significance of this observation is yet to be confirmed. In conclusion, there is a need to standardize experimental procedures, to bridge the gap between laboratory and in vivo methodologies and findings and--in general--to thoroughly investigate the factors that modulate the initial attachment and subsequent colonization of denture-base materials and the oral mucosa of patients subjected to Candida infections. Information on how these factors can be controlled is required and this may help to prevent the disease. The societal impact of such information is significant given the magnitude of the candidosis problem worldwide.

This study evaluated the surface roughness and Candida albicans adherence on denture base acrylic resins and silicone-based resilient liners with different surface finishes. Four commercial denture base acrylic resins (three heat polymerized and one room temperature polymerized) and five silicone-based liner materials (two heat polymerized and three room temperature polymerized) (10 x 10 x 2 mm) were tested in this study. The materials were processed against glass or plaster or finished with a tungsten carbide bur. Surface roughness measurements were made using a profilometer with an optical scanner probe. All specimens were ultrasonically cleaned in water for 15 s, autoclave sterilized, and contaminated with C. albicans solution for adherence assay evaluation. The materials processed against the glass surface showed significantly lower surface roughness values (0.11 +/- 0.1-1.66 +/- 1.1 microm) than those of the materials processed against the dental plaster (2.61 +/- 0.2-6.12 +/- 2.8 microm) or roughening with a bur (1.48 +/- 0.2-7.05 +/- 1.2 microm; p < 0.05, one- or two-way analysis of variance). Also, the materials processed against the glass surface showed lower C. albicans adhesion (mean ranks 120.36) than those of the materials processed against the dental plaster (mean ranks 139.77) or roughening with a bur (mean ranks 143.06), but the differences were not statistically significant (p > 0.05, Kruskal-Wallis and Mann-Whitney). In all types of surface finishes, C. albicans adhesion on denture base acrylics was significantly less (mean ranks 90.18-90.40) than those of silicone liners (mean ranks 119.38-205.18; p < 0.01, Kruskal-Wallis).

Aim: Candida albicans (C. albicans) has been widely associated with the etiology of denture-related stomatitis and has been found on soft denture lining materials. The aim of this study was to examine the surface roughness and adherence of C. albicans to saliva coated and non-coated soft lining materials by subjecting them to an in vitro accelerated aging test., Methods and Materials: Samples were prepared from three soft lining materials (Visco Gel, Ufi Gel P, Molloplast B). Surface roughness measurements and adhesion of C. albicans were examined before and after an aging process. The stimulated human whole saliva was used to assess its effect on adhesion., Results: The aging process promotes the surface roughness of soft lining materials. The aging surface roughness of Visco Gel was significantly higher than Ufi Gel P and Molloplast B. No significant difference was observed between non-aged and uncoated materials, but aged and uncoated soft lining materials showed a greater adherence of C. albicans. No significant difference was observed between non-aged and saliva coated materials, but aged and saliva coated soft lining materials showed a greater adherence of C. albicans., Conclusions: Candidosis induced by C. albicans is the most common fungal infection. Awareness of susceptibility of soft lining materials to the adherence of C. albicans is an important factor in their selection. The use of soft lining materials with smooth surfaces minimizes the adherence of C. albicans.

This study aimed to determine the influence of surface roughness (Ra), surface free energy (SFE), saliva, and bacteria on Candida adhesion to denture materials. The Ra and SFE of 2 acrylic resin specimens and 2 denture liner specimens were measured and assayed in a flow chamber for bacteria culture perfusion plus Candida albicans or C glabrata cultures. Adhesion was determined by counting under light microscopy. Candida adhesion showed significant differences depending on the factors involved. The overall colonization was significantly decreased by saliva and influenced by bacteria. Candida adhesion was strongly affected by Ra, saliva, and bacteria, but not by SFE.

Resilient denture linings cannot be used for extended periods due to the loss of softness and the adhesion of microorganisms on their surfaces. This study investigated the hardness and microbiologic adherence of four permanent soft denture lining materials. In addition, the adherence of Candida albicans and Staphylococcus aureus was studied in vitro by quantitative culture method and scanning electron microscopy (SEM). Surface properties of the materials also were observed with SEM. The hardness of all materials increased throughout the study. Molloplast-B was the most adequate permanent soft lining material for clinical use under these laboratory conditions.

Objectives: Colonization of denture soft lining materials by Candida albicans can result in clinical problems, and deterioration of the material. This study aimed to monitor this interaction by comparing the short-term adhesion of C. albicans to six denture lining materials and to monitor any longer term penetration of material by the yeast., Methods: Denture lining materials (Molloplast B, Flexor, Permaflex, Luci-soft, Eversoft and Ufi Gel hard C) were processed against glass slides or dental stone. Adhesion of yeast to surfaces was monitored after one hour incubation (37 degrees C) of standardized (2.8 x 10(6) cfu/ml) washed cell suspension with test materials. Attached cells stained with acridine orange were counted microscopically. Penetration of yeast into materials bonded onto acrylic after six weeks incubation (culture medium was replaced weekly) was observed through sections stained using acridine orange. Hyphal and yeast penetration was estimated (qualitatively and quantitatively, respectively) for three levels of the liner (subsurface, central section and adjacent to lining-acrylic junction)., Results: None of the materials produced a zone of inhibition when compared with the nystatin control. There was no significant difference (p>0.5) in cell numbers on any of the smooth surfaces. Significantly, (p<0.001) higher numbers of cells were observed on roughened surfaces. Both hyphal and yeast forms were observed when penetration was monitored. Penetration was greatest into Ufi Gel hard C (no hyphae observed), but not at the acrylic-liner junction and least into Eversoft., Significance: Different denture lining materials exhibit different properties in terms of susceptibility to yeast penetration, although the initial attachment is comparable. Smoother surfaces retain fewer cells. The selection of appropriate materials for a given function, and their fabrication may affect performance.

Purpose: The purpose of this study was to count and to speciate Candida isolated from 2 resilient denture liners, Molloplast-B and MPDS-SL., Materials and Methods: A group of 20 patients each had 1 maxillary denture and 2 mandibular dentures fabricated. One mandibular denture was lined with Molloplast-B, and 1 was lined with MPDS-SL. Each denture was used for 3 months. At the end of the 3-month period, the mandibular denture was surrendered, and a 5 x 5-mm circular resilient liner sample was obtained from the tissue surface of the lingual flange. Samples were processed, and Candida was isolated and counted. Speciation of Candida was performed using CHROMagar Candida and API 20C AUX strips., Results: Molloplast-B had, on average, 5 times as many CFU/sample as MPDSL-SL, but this difference was not significant (p = 0.26). A sign test gave a similar nonsignificant trend (p = 0.057). CHROMagar identified several Candida species, and confirmation was made using API 20C AUX strips. One patient was lost to follow-up. Of 19 Molloplast-B samples, 7 had no growth, 4 grew C. albicans, 3 grew C. parapsilosis, 2 grew C. glabrata, 1 grew C. tropicalis, 2 grew a Trichosporon spp., and 2 grew a nonidentifiable colony. The analogous counts for 19 MPDS-SL samples were 10, 4, 1, 3, 0, 1, and 1 (p = 0.45 for culture positively, exact McNemar test)., Conclusions: Candida growth on Molloplast-B was not significantly different from growth on MPDS-SL. Several yeast species were cultured from each material. The rates of culture-positive testing did not differ between the 2 resilient denture liners.

Candidal colonization and subsequent biofilm formation on denture materials are important in the development of pathogenesis, such as denture stomatitis. Routine use of denture cleansers is one of the most effective methods of denture plaque control, although the incompatibility of soft liners and denture cleansers cause damage to the materials. The present study, biofilm formation of Candida albicans on the surfaces of soft denture lining materials, immersed in denture cleansers for 180 days were studied. Seven commercially available soft denture lining materials, were artificially deteriorated by immersion into three commercially available denture cleansers for 180 days, and subsequent fungal growth and biofilm formation were studied by measuring pH of the media and by the use of adenosine triphosphate (ATP) analysis. Fungal biofilm formation on the deteriorated soft liners varied depending upon the combination of the soft liners and denture cleansers. Several combinations of soft liners with denture cleansers exhibited the significantly high colonization capacity as compared with each sample immersed in distilled water, used as individual controls. The relationship between the biofilm formation on the samples of each material and the surface roughness of the soft lining materials was analyzed. However, no significant correlation was observed. The results, taken together, suggested that fungal colonization could be predominantly regulated by the combination of lining material with denture cleansers. In clinical terms, our findings suggests that daily cleansing of soft lining materials with mismatched denture cleansers promoted the subsequent biofilm formation of fungi on the materials.

This work has dealt with the in vitro physicochemical, elastic, and microbiological properties of polymer lining materials used in dental prosthetics. Representatives of two soft polymer groups were analyzed: Vertex Soft NF, a plastified acrylic polymer, and Molloplast B, a silicon elastomer. Vertex Rapid Simplified and Triplex--two acrylic polymers routinely used at the Department of Prosthetic Dentistry were chosen as representatives of rigid acrylic material. The laminar plates of the denture are lined with elastic material to reduce wear discomfort and eliminate symptoms associated with compression of the oral mucosa by the denture. Wear-dependent deterioration in physicochemical, elastic, and microbiological properties presents as prosthetic stomatopathies due to the combined action of mechanical lesions, fungal growth, and toxicity of components of the denture, necessitating replacement of the denture. Samples used in this study were prepared at the Department of Dental Prosthetics, Pomeranian Academy of Medicine. The process of polymerization was carried out strictly as recommended by the manufacturers. The in vitro analyses were done at the Polymer Institute, Technical University of Szczecin, and the Department of Microbiology and Immunology, Pomeranian Academy of Medicine. A special system was used to reproduce conditions in the oral cavity and study their effects on the elastic liners. Samples were placed in the chamber for varying periods, depending on the type of test and material. Thermodynamic analysis was done to confirm proper polymerization and hardening. Time-dependent loss of contact between the elastic liner and rigid denture under tangential (shear) and normal (tear) stress applied to the liner-denture interface was examined. Resistance was studied using INSTRON model 4206-006 universal testing machine. Compressive changes in elastic properties of the soft materials were examined by calculating Young's modulus. Changes in viscoelastic properties of the materials depending on temperature and frequency were followed using dynamic mechanical thermal analysis (DMTA). A precision microbalance from Sartorius (+/- 0.00001 g) was used to measure time-dependent changes in weight and sorption of water. Adhesion of Candida albicans to the rigid and soft acrylic materials was determined after incubation for 3, 6 or 24 h at 37 degrees C. The study has shown that adhesive strength is much greater for acryl-acryl than acryl-silicon interface. Elastic properties of Molloplast B are very stable and superior to those of Vertex Soft NF. Time-dependent sorption of water and changes in weight have confirmed the stable nature of Molloplast B. Adhesion of Candida albicans to Vertex Soft NF was less noticeable.

Purpose: This in-vivo investigation evaluated the effect of 2 denture sealer agents on the microbial colonization of a newly placed soft interim denture liner during a period of 14 days., Materials and Methods: An interim soft denture liner (Coe-Soft; GC America, Alsip, IL) was coated with 2 different denture surface sealants (Palaseal [Heraeus Kulzer, Irvine, CA] and Mono-Poly [Plastodent, New York, NY]). Three rectangular wells of 1 cm wide x 2 cm long x 2 mm deep were placed in the intaglio of 10 maxillary complete dentures and filled with the soft liner material. The soft liner surface was treated with Palaseal (first well) and Mono-Poly (second well), and the unsealed (third well) was used as a control. These were exposed to the oral cavity for 14 days. The effect the sealant had in the prevention of Candidal colonization in vivo of the soft liner material was evaluated. Microbiological specimens were recovered from all samples and cultivated. Microbiological data from the control and 2-test samples in each denture were tabulated, and statistical analyses were performed., Results: This investigation showed clear differences (p <.001) between the sealed and unsealed soft liners. The sealed material showed significantly less colonization by yeast and bacteria. Intercomparison of the surface denture sealers, Palaseal versus Mono-Poly, showed no statistically significant differences (p < .005) in total yeast or bacterial colonization., Conclusion: Coating of Coe-Soft denture liner with either Palaseal or Mono-Poly significantly decreased yeast and bacterial colonization. ., (Copyright 2000 by The American College of Prosthodontists.)

Resilient liners are frequently used to treat denture stomatitis, a condition often associated with Candida albicans infections. Of 10 liners tested, 2 were found to inhibit the switch from the yeast form to hyphae and a third was found to stimulate this switch. The inhibitor was determined to be undecylenic acid.

Purpose: Surface properties of denture materials are of clinical importance since they may affect plaque accumulation and staining. This in vitro study investigated the roughness of 20 commercially available denture materials., Materials and Methods: Four denture base resins, nine hard lining materials, and seven soft denture lining materials were evaluated for roughness. Roughness measurements were made using a Mitutoyo Surftest SV-400, and the mean arithmetic roughness values (Ra) obtained were used for the comparisons., Results: The overall Ra values ranged from 0.7 to 7.6 microns. The denture base materials group exhibited Ra values from 3.4 to 7.6 microns, whereas the hard liners were from 0.7 to 4.4 microns. The autopolymerized and visible light-cured soft liners presented Ra values from 0.7 to 3.5 microns, while the heat-cured soft liners ranged from 3.5 to 4.0 microns., Conclusion: The roughness exhibited by all of the materials tested (Ra values greater than 0.7 micron) indicates that there is a possibility for plaque accumulation, since 0.2 micron is considered the threshold below which no further bacterial adherence can be expected.

In the present study, the growth of a single isolate of Candida albicans on saliva-, serum-coated or protein free (uncoated), thermocycled (4-70 degrees C for 1 min, respectively; 0, 1000 and 10 000 times) seven commercial soft lining materials were investigated, by adenosine triphosphate (ATP) analysis. In the case of control resilient liners (not thermocycled and uncoated), the fungal colonization appeared to depend upon the type of commercial resilient liner used. Thus, the lowest colonization was observed with fluoric and heat-cured silicone materials, cold-cured silicone materials, except for one product, and heat-cured acrylic resin exhibited the highest colonization capacity, and cold-cured acrylic resilient liners exhibited the intermediate. However, the fungal colonization on the materials was significantly promoted both by thermal cycling (ANOVA, P<0.01) and a layer of protein coating (saliva, P<0.01; serum, P<0.01). These results, taken together, suggest that the ageing of the materials and the biological fluids of the host promote yeast colonization on resilient lining materials.

In the present study, the growth of a single isolate of Candida albicans on seven saliva-, serum-coated or protein free (uncoated), thermocycled (4-70 degrees C for 1 min, respectively; 0, 1000 and 10 000 times) commercial resilient lining materials was investigated by monitoring pH changes in growth media. The inhibitory effect of the tissue conditioners on fungal growth was observed using three parameters, i.e. (i) the delay in the onset of the rapid decline in pH, (ii) the reduction in the rate of pH change and (iii) the pH minima reached. In the case of control soft liners (not thermocycled and uncoated), the antifungal effect appeared to depend upon the type of commercial soft liner used. Thus, an initial delay in pH decline and a very high pH minima were observed with fluoric and heat-cured silicone materials. High pH minima were also observed with cold-cured acrylic soft liners, whereas cold-cured silicone materials did not significantly differ from heat-cured acrylic resin (P>0.05). However, the antifungal effect of the materials was significantly reduced both by thermal cycling (ANOVA, P<0.01) and a layer of protein coating (saliva, P<0.05; serum, P<0.01). These results, taken together, suggest that the ageing of the materials and the biological fluids of the host, particularly serum, promote yeast growth on soft lining materials.

Statement of Problem: Infection of denture materials with Candida albicans is common and contributes to denture stomatitis., Purpose: This 3-phase investigation examined: (1) the efficacy of microwave irradiation against C albicans colonized on 3 soft denture liners and 1 heat-polymerized denture base resin, and (2) the effect of this irradiation on the hardness of the materials tested., Material and Methods: In phase 1, an experimental protocol was developed. Sterilized specimens from 2 denture base soft liners and 1 heat-polymerized acrylic resin denture base material (n = 45 each) were inoculated with C albicans. Two thirds of the specimens were irradiated in a 60 Hz microwave oven for 5 minutes (dry). C albicans growth was then assessed with streaked blood agar plates and thioglycollate broth. One third of the specimens were not irradiated and served as controls. Pretest and posttest Shore A hardness values were obtained and compared. For phase 2, 15 specimens from each material group were subjected to irradiation (while immersed in water) for 5 minutes; and, 15 from each material were subjected to 10- and 15-minute irradiation (dry), with subsequent sterility and change in hardness assessments completed as described in phase 1. In phase 3, 15 specimens from each material group were subjected to repeated 5-minute irradiation cycles (while immersed in water), and changes in hardness were examined., Results: Only the 5-minute irradiated specimens immersed in water were effectively sterilized, as verified by the thioglycollate assay. The effect of repeated 5-minute irradiation cycles resulted in a significant change in hardness of the PermaSoft specimens., Conclusions: Five-minute irradiation, while immersed in water, killed all C albicans present on the materials tested; and, repeated 5-minute irradiation significantly affected the hardness of only the PermaSoft material.

The aim of this paper is to review our understanding of the mechanisms and clinical significance of adhesion of C. albicans to denture-base materials in relation to denture plaque and denture-related stomatitis. Earlier reports in the literature of a 65% prevalence level of denture-related stomatitis seem to be exaggerated. More recent studies indicate that denture-related stomatitis is considerably less common, particularly in normal healthy subjects. The etiology of the condition is discussed in this review, and although much of the literature supports the view that the condition is strongly associated with C. albicans, this is not always so. In some subjects, the cause appears to be related to a non-specific plaque. This review also considers the role of denture plaque in the pathogenesis of denture-related stomatitis, the sequential development of denture plaque, and its colonization by Candida organisms. Designing controlled in vivo studies is difficult, and as a consequence, many investigators have had to resort to in vitro studies. The majority of these studies have attempted to investigate the hydrophobicity of C. albicans, relating the surface free-energy of denture-base materials, particularly acrylic resin, to that of the organism. Surprisingly little work has been directed at surface roughness and how it affects retention of organisms. Further, no attention has been paid to the properties and character of the surface, other than average surface roughness, as it affects adhesion. A comparison of results from in vitro studies on the effect on adhesion of pre-coating the surfaces of denture-base materials with saliva has produced equivocal conclusions. This is largely due to little standardization of experimental protocols between studies, particularly in the collection and handling of the saliva used. In conclusion, the review strongly supports the suggestion that adherence of C. albicans to denture-base materials in vitro is related to the hydrophobicity of the organism. The clinical significance of the observation and the mechanisms for the development and maturation of denture plaque are yet to be understood. There is a clear need for further investigation of other factors that may moderate the adhesion of organisms and subsequent colonization of denture-base materials.