Impact of apigenin and seashell nano-additives on the antifungal and roughness behavior of a soft denture liner

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.

Soft Denture liner and microbial disinfection with contemporary and conventional agents

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.

Influence of surface characteristics on the adhesion of Candida albicans to various denture lining materials

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.

[A preliminary study of application of the antibacterial solution containing silver ion to the surface of soft lining material]

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.

Temporal changes of denture plaque microbiologic composition evaluated in situ

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.

The effect of surface roughness of silicone-based resilient liner materials on the adherence of Candida albicans and inhibition of Candida albicans with different disinfectants

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.

Colonization and deterioration of soft denture lining materials in vivo

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.

Surface roughness and adherence of Candida albicans on soft lining materials as influenced by accelerated aging

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.

In vitro Candida colonization on acrylic resins and denture liners: influence of surface free energy, roughness, saliva, and adhering bacteria

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.

Adherence of Candida albicans to denture base acrylics and silicone-based resilient liner materials with different surface finishes

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).

Comparison of the hardness and microbiologic adherence of four permanent denture soft liners

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.

Colonization and penetration of denture soft lining materials by Candida albicans

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.

Clinical evaluation of resilient denture liners. Part 2: Candida count and speciation

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.

Biofilm formation of Candida albicans on the surfaces of deteriorated soft denture lining materials caused by denture cleansers in vitro

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.

[Comparative analysis of elastic materials for lining of removable dental prosthesis in vitro]

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.

Candida albicans colonization of surface-sealed interim soft liners

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. .

Undecylenic acid inhibits morphogenesis of Candida albicans

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.

Denture plaque and adherence of Candida albicans to denture-base materials in vivo and in vitro

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.

Roughness of denture materials: a comparative study

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.

Interactions between thermal cycled resilient denture lining materials, salivary and serum pellicles and Candida albicans in vitro. Part II. Effects on fungal colonization

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.

Interactions between thermal cycled resilient denture lining materials, salivary and serum pellicles and Candida albicans in vitro. Part I. Effects on fungal growth

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.

Microwave disinfection of denture base materials colonized with Candida albicans

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.

Effectiveness of chlorine dioxide in disinfection on two soft denture liners

STATEMENT OF PROBLEM

Soft tissue denture liners frequently require replacement that necessitates complete removal from the denture base. A high speed lathe located in a "clean laboratory" is often used to facilitate removal of these materials, but it is unclear whether routine disinfection procedures reduce bacterial contamination sufficiently to prevent contamination of the laboratory.

PURPOSE

The first phase of this study evaluated the effectiveness of 3-minute chlorine dioxide spray and immersion disinfection procedures on 2 denture liners (Coe Soft and Coe Comfort) and stainless steel specimens used as controls. The second phase evaluated the effectiveness of spray disinfection at time intervals of 1, 3, and 10 minutes.

MATERIAL AND METHODS

Specimens made of soft denture liners attached to acrylic resin bases (10 per group) were contaminated with Escherichia coli, Staphylococcus aureus, and Candida albicans. Colony-forming units were counted after different disinfection techniques were applied. Kruskal-Wallis 1-way analysis of variance on ranks and an all pairwise multiple comparison procedures (Dunn's method) were used to test for significant differences among test groups at the P <.05 level of significance.

RESULTS

Chlorine dioxide was effective against nonporous stainless steel specimens but was inadequate for denture liners at the recommended 3-minute time of disinfection. The immersion technique was more effective than the spray technique, but the difference was not significant. Increasing the time of disinfection did not significantly reduce the numbers of microorganisms.

CONCLUSION

Coe Soft and Coe Comfort denture liners should be removed before entering the laboratory. These materials contain sufficient viable bacteria after routine disinfection procedures to cause contamination of the "clean laboratory."

Adherence of Candida albicans to denture-base materials with different surface finishes

OBJECTIVES

To assess the in vitro adherence of Candida albicans to heat-cured hard and soft denture-base materials with varying surface roughness, and to observe the effect of a mixed salivary pellicle on candidal adhesion to these surfaces.

METHODS

In vitro adhesion assays on heat-cured acrylic resin (Trevalon), Molloplast B and Novus using the type strain of C. albicans (NCPF 3153A). Surfaces for the assays were prepared using clinically appropriate rotary instruments. Unstimulated, pooled and clarified whole saliva was used to assess its effect on adhesion.

RESULTS

Significantly greater adhesion of C. albicans to rough rather than smooth surfaces was found (P < 0.001), as well as increased adhesion to the machined soft lining materials compared with acrylic. Pre-coating denture-base materials with saliva reduced candidal adhesion on all materials.

CONCLUSIONS

Rough surfaces on denture-base materials promote the adhesion of C. albicans in vitro. However, saliva reduces adhesion of C. albicans and thus diminishes the effect of surface roughness and free surface energy differences between materials.

Candida-associated denture stomatitis. Aetiology and management: a review. Part 2. Oral diseases caused by Candida species

Certain systemic conditions and/or defects in the immune system may predispose the host to oral candidal infection and the commonest form of oral candidosis is candida-associated denture stomatitis. Until recently there has been controversy concerning the aetiology of the disease. Although some earlier investigators linked denture stomatitis with trauma or bacterial infection, others had isolated Candida albicans from the mouths of patients with the condition. Current studies indicate that denture stomatitis lesions are associated with the detection of candida species while other factors such as denture hygiene, trauma, systemic diseases and deficiencies of the immune system may be involved.

Use of microwave energy to disinfect a long-term soft lining material contaminated with Candida albicans or Staphylococcus aureus

STATEMENT OF PROBLEM

Soft lining materials have been found to be more susceptible to microbial adhesion than acrylic resin base materials. Denture hygiene is essential to maintain the serviceability of the denture, and microwave energy has been suggested for denture disinfection.

PURPOSE

The purpose of this study was to determine the effectiveness of microwave energy in the disinfection of a long-term soft lining material.

MATERIAL AND METHODS

A long-term soft lining material was contaminated with known microorganisms and the reduction of organism counts after test disinfection regimes calculated. The disinfection regimes were microwaving for 5 minutes, leaving dry overnight, and soaking overnight in a dilute sodium hypochlorite solution. The test microorganisms were Candida albicans or Staphylococcus aureus.

RESULTS

For both organisms, soaking in sodium hypochlorite reduced the number of viable adherent microorganisms recovered significantly more than exposure to microwave energy, which led to greater reduction than leaving the lining material dry overnight (p < 0.001, Wilcoxon nonparametric signed rank test).

CONCLUSION

With reference to the tested microorganisms, disinfection of Molloplast-b soft lining material in dilute sodium hypochlorite solution proved to be more effective than exposure to microwave energy, which in turn was more effective than leaving the lining dry overnight.

Evaluating the effect of soft lining materials on the growth of yeast

STATEMENT OF PROBLEM

Soft lining materials continue to have a place in clinical removable prosthodontics. However, there is an increased probability of yeast colonization on soft lining materials.

PURPOSE

This study (1) assessed a method of evaluating the effect of long-term soft lining materials on the growth of yeast and (2) investigated the effect five soft lining materials had on the growth of three species of yeast.

MATERIAL AND METHODS

Coe Supersoft, Novus, and three experimental soft lining materials were investigated together with Candida albicans, Candida tropicalis, and Issatchenkia orientalis (formerly Candida krusei) yeasts. Strips of soft lining material incubated on blood agar plates were examined for inhibition of the growth of yeast. Soft lining materials soaked in sterile trypticase soya broth or water were inoculated with yeast and incubated. The change in colony forming units per milliliter from the initial load of yeast at 3 days was measured. Statistical analysis was performed with an independent paired Student t test.

RESULTS

Inhibition of yeast growth occurred for two soft lining materials. Despite the presence of sufficient viable organisms, differences between the initial load of yeast and the 3-day results were mostly small, both for the test and control groups, suggesting that the material does not support the growth of the tested yeast during this period.

CONCLUSIONS

The often described increased prevalence of yeast associated with soft lining materials in the oral environment is likely related to readily available nutrients in the mouth and the difficulty in maintaining and cleaning these materials.

In vivo and in vitro study of fungal presence and growth on three tissue conditioning materials on implant supported complete denture wearers

In this study three type of tissue conditioning materials were used in vitro and in vivo to investigate the presence and growth of Candida albicans, considered to be the pathogenic member of the genus. In vitro test results of different tissue conditioners showed that they have a tendency to have an inhibiting effect on C. albicans at the third day of incubation. For the in vivo tests tissue conditioners were placed in existing maxillary prosthesis of 21 patients who had been treated with endosseous dental implants (seven in each group). The results showed that yeast forms were observed after 3 days in two patients' dentures which were relined with Fitt. Yeasts forms were also seen in three patients' dentures after 6 days, two of them relined with Fixo-gel and the other one relined with Visco-gel. The hyphal form of Candida was seen in four patients' dentures, relined with Fitt, and also in three patients' dentures, relined with Fixo-gel and Visco-gel.