In vivo and in vitro studies on soft denture materials: microbial adhesion and tests for antibacterial activity

Medication-related osteonecrosis of the jaw: Prosthodontic considerations

Medication-related osteonecrosis of the jaw (MRONJ) can be triggered by several antiresorptive and antiangiogenic medications, including bisphosphonates (BRONJ), denosumab (DRONJ), and other agents used to treat osteoporosis and metastatic bone cancer. Prosthodontists and surgeons continue to face new challenges because of this condition. Despite the current evidence showing that extensive surgical intervention and laser surgery have the highest healing rates, surgical reconstruction is not always possible for large jaw defects requiring prosthetic reconstruction. Moreover, surgical treatment may not be an option in some patients because of other medical conditions. In these patients, MRONJ may develop into a chronic disease with limited resolution and they may seek prosthetic rehabilitation for aesthetic and functional reasons. Therefore, prosthetic intervention may be necessary for some patients with MRONJ even in the absence of a surgical defect. Denture trauma has been reported to be a risk factor for MRONJ, and few reports have discussed the prosthodontic considerations needed for patients with this condition. The aim of this review is to highlight the prosthodontic considerations that would decrease the risk of triggering MRONJ in susceptible patients.

Controlled release, antimicrobial activity, and oral mucosa irritation of cetylpyridinium chloride-montmorillonite incorporated in a tissue conditioner

This study examined the controlled release of cetylpyridinium chloride (CPC) from a tissue conditioner (TC) containing CPC-montmorillonite (CPC-Mont), the associated antimicrobial activity, and oral mucosa irritation. The CPC release test was performed daily for 28 days in three test solutions: distilled water, 0.2 M NaCl, and 0.2 M HCl. The antimicrobial activities for 7, 14, 21, and 28 days against Candida albicans, Staphylococcus aureus, and Streptococcus mutans were assessed according to the JIS Z 2801/ISO 22196 standard. An oral mucosa irritation test was conducted using cheek pouches in five male hamsters according to the ISO 10993-10:2010 standard. The amount of CPC released each day and the cumulative amount released over 28 days (6.12 mg) were less than the daily safe maximum of sore throat medicines (8 mg). Additionally, TC with CPC-Mont could sustain antimicrobial activity against adherent bacteria for 14 days and has no oral mucosa irritation potential.

The prosthodontic management of medication-related osteonecrosis of the jaw: a case report

Medication-related osteonecrosis of the jaw (MRONJ) has clear staging and management guidance from the American Association of Oral and Maxillofacial Surgeons. There is, however, less guidance on the prosthodontic rehabilitation for this cohort of patients. This paper aims to bring increased understanding on the staging of MRONJ as well as approaches to its prosthodontic management. This case report outlines a removable prosthodontic method that successfully rehabilitated a patient suffering from MRONJ. This case is well documented with the use of clinical photography. The article demonstrates techniques in overcoming the challenges of necrotic bone in the denture-bearing area, and how such methods can improve both tissue health and patient symptoms.

Mechanical and Surface Properties of Resilient Denture Liners Modified with Chitosan Salts

Chitosan (CS) and its derivatives show antibacterial and antifungal properties and could help treat and prevent denture stomatitis (DS). Mechanical and surface properties of resilient denture liners were evaluated when modified with CS salts. CS-hydrochloride (CS-HCl) and CS-glutamate (CS-G) were added to resilient denture liners Ufi Gel P and Coe-Soft at four different concentrations (0.1%, 0.2%, 0.4%, 1% w/w) from which specimens were produced, as well as a control group of each material with no added CS salt. Ten specimens per group (Ø 35 mm, height 6 mm) were manufactured. They were stored in distilled water at 37 °C for a total of 30 days (d). Shore A hardness (SHA) and surface roughness (Ra) were evaluated after 24 h (T1), 7 d (T2), 14 d (T3) and 30 d (T4). Kruskal-Wallis and U-test (Bonferroni-Holm adjusted) were used for statistical analysis (p ≤ 0.05). Ra increased significantly once CS salts were added. SHA increased significantly for some groups, but all specimens fulfilled requirements set by ISO 10139-2:2016. Modification with CS salts does not influence the mechanical properties of the modified resilient denture liners in a clinically relevant manner. Despite the increased roughness, the concept is suitable for further studies. Especially antimicrobial/antibiofilm studies are needed.

Knowledge and attitude about relining of complete dentures in clinical practice: A cross-sectional study

Background

Residual ridge resorption is crucial sequelae of tooth loss. Complete dentures are the most common way of rehabilitating edentulous patients. However, with continuing residual ridge resorption, dentures tend to become loose and unstable causing discomfort, chewing disability, and speech problems. Denture relining is an economical means of improving a denture's stability and retention. An understanding of the clinical indications and limitations of these materials and procedures is crucial for clinical success.

Aim and Objective

The purpose of this survey was to assess knowledge, attitude, and practice in relining dentures among dental practitioners.

Materials and Methods

The cross-sectional survey was conducted using a validated questionnaire on 200 (n = 200) dental practitioners in Nagpur city, Maharashtra. Data analysis was done using proportion test with SPSS EPI INFO software.

Results

Although all 200 practitioners were aware of the relining procedure and were routinely carrying out the procedure in their dental clinics, 50% of the practitioners were unaware of the correct relining step by step procedure and were also not sure about the antimicrobial properties of the relining material available in the market.

Conclusion

Awareness and scientific knowledge about the relining materials and procedure should be enhanced within general dental practitioners through CDE program and workshops. Steps should be taken to include relining procedure as a part of undergraduate clinical curriculum as well as internship program.

Silver nanoparticles in dental biomaterials

Silver has been used in medicine for centuries because of its antimicrobial properties. More recently, silver nanoparticles have been synthesized and incorporated into several biomaterials, since their small size provides great antimicrobial effect, at low filler level. Hence, these nanoparticles have been applied in dentistry, in order to prevent or reduce biofilm formation over dental materials surfaces. This review aims to discuss the current progress in this field, highlighting aspects regarding silver nanoparticles incorporation, such as antimicrobial potential, mechanical properties, cytotoxicity, and long-term effectiveness. We also emphasize the need for more studies to determine the optimal concentration of silver nanoparticle and its release over time.

Effectiveness of coating acrylic resin dentures on preventing Candida adhesion

PURPOSE

The aim of this study was to prevent the adhesion of C. albicans on acrylic resin dentures by modifying their surfaces.

MATERIALS AND METHODS

Ninety acrylic resin plates were divided into three groups. Group I: conventionally processed acrylic resin plates. Group II: plates painted with 2-Octyl Cyanoacrylate adhesive. Group III: plates painted with Adper Single Bond Adhesive. All specimens were immersed separately in containers filled with artificial saliva that contained C. albicans and then incubated for 11 days at 37°C. Three methods of evaluation were used to count the adhered Candida: direct culture, slide count, and serial dilutions.

RESULTS

C. albicans in 1/10, 1/10², and 1/10³ dilutions showed overgrowth in group I, while overgrowth was noted only with 1/10 dilution in group III. For group III, mean colony numbers of 123, 22, 3.4, and 0 were found for the 1/10², 1/10³, 1/10⁴, and 1/10⁵ dilutions, respectively. Regarding the slide counts, group I showed a mean fungal count of 166 compared to 40 for group III with 1/10 dilution, 21 compared to 9 with 1/10³ dilution, 8.6 compared to 0.7 with 1/10³ dilution, and 1.2 compared to 0 with 1/10⁴ dilution. No plates in group II showed any candidal colonies regardless of the method of evaluation (0%). These differences were statistically significant (p < 0.0001).

CONCLUSION

Coating the acrylic resin dentures with Adper Single Bond Adhesive was effective in reducing C. albicans adhesion to dentures, while coating with 2-Octyl Cyanoacrylate adhesive completely inhibited such adhesion.

Antifungal activity, biofilm-controlling effect, and biocompatibility of poly(N-vinyl-2-pyrrolidinone)-grafted denture materials

Colonization and biofilm-formation of Candida species on denture surfaces cause Candida-associated denture stomatitis (CADS), a common, recurring disease affecting up to 67% of denture wearers. We developed poly(N-vinyl-2-pyrrolidinone)-grafted denture materials that can be repeatedly recharged with various antifungal drugs to achieve long-term antifungal and biofilm-controlling effects. The monomer, N-vinyl-2-pyrrolidinone (NVP), was grafted onto poly(methyl methacrylate) denture resins through plasma-initiated grafting polymerization. The physical properties and biocompatibility of the resulting resins were not negatively affected by the presence of up to 7.92% of grafted poly (N-vinyl-2-pyrrolidinone) (PNVP). Miconazole and chlorhexidine digluconate (CD) were used as model antifungal drugs. PNVP grafting significantly increased the drug absorption capability of the resulting denture materials. Further, the new materials showed sustained drug release and provided antifungal effects for weeks (in the case of CD) to months (in the case of miconazole). The drug-depleted resins could be recharged with the same or a different class of antifungal drug to further extend antifungal duration. If needed, drugs on the PNVP-grafted denture materials could be "washed out" (quenched) by treating with PNVP aqueous solutions to stop drug release. These results point to great potentials of the new materials in controlling biofilm-formation in a wide range of device-related applications.

Evaluation of Candida albicans adherence on the surface of various maxillofacial silicone materials

OBJECTIVES

Fungal infection resulting from Candida adherence on material surface is one of the most important medical risks for maxillofacial prosthesis wearers. Despite wide usage, there is a sparse data evaluating C. albicans adherence on various commercial maxillofacial silicone materials that have different surface contact angles. The objective of this study was to investigate the relationship between surface contact angle and fungal adherence on widely used maxillofacial silicone materials.

MATERIALS AND METHODS

Three maxillofacial silicone materials titled VST-50, A-2006, and A-2186F were used for fabrication of disc-shaped specimens. Surface contact angle of specimens were measured by the goniometric method. Adhesion quantity of two different C. albicans strains was evaluated with a colorimetric method using XTT/Coenzyme Q0. The Kruskal-Wallis and Mann-Whitney U tests were used for statistical analysis of data.

RESULTS

The lowest surface contact angle values with the highest Candida adhesion quantity were measured on the specimens fabricated with A-2006 silicone material. Statistically significant differences were found among three maxillofacial silicone materials in terms of both surface contact angle values and adhesion quantity (P<0.01).

CONCLUSION

There is a close relationship between surface contact angle and quantity of Candida adherence. However, it should be noted that various factors arising from material properties may affect the complex nature of the Candida adhesion process.

Candida colonisation and the efficacy of chlorhexidine gluconate on soft silicone-lined dentures of diabetic and non-diabetic patients

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.

Resilient liners: a review

Resilient liners when used intelligently are an excellent adjunct in removable prosthodontics. However, currently they have to be best considered as temporary expedients because none of the advocated permanent liners have life expectancy comparable to resin denture base. This article reviews the literature regarding their composition, functions, gelation characteristics, bond strength and influence on denture bases. It also presents their drawbacks and attempts made to extend their longevity. A Medline search was completed for the period from 1986 to 2007, along with a manual search, to identify pertinent English peer-reviewed articles and textbooks.

Current perspectives of nanoparticles in medical and dental biomaterials

Nanotechnology is gaining tremendous impetus due to its capability of modulating metals into their nanosize, which drastically changes the chemical, physical and optical properties of metals. Nanoparticles have been introduced as materials with good potential to be extensively used in biological and medical applications. Nanoparticles are clusters of atoms in the size range of 1-100 nm. Inorganic nanoparticles and their nano-composites are applied as good antibacterial agents. Due to the outbreak of infectious diseases caused by different pathogenic bacteria and the development of antibiotic resistance, pharmaceutical companies and researchers are searching for new antibacterial agents. The metallic nanoparticles are the most promising as they show good antibacterial properties due to their large surface area to volume ratios, which draw growing interest from researchers due to increasing microbial resistance against metal ions, antibiotics and the development of resistant strains. Metallic nanoparticles can be used as effective growth inhibitors in various microorganisms and thereby are applicable to diverse medical devices. Nanotechnology discloses the use of elemental nanoparticles as active antibacterial ingredient for dental materials. In dentistry, both restorative materials and oral bacteria are believed to be responsible for restoration failure. Secondary caries is found to be the main reason to restoration failure. Secondary caries is primarily caused by invasion of plaque bacteria (acid-producing bacteria) such as Streptococcus mutans and lactobacilli in the presence of fermentable carbohydrates. To make long-lasting restorations, antibacterial materials should be made. The potential of nanoparticles to control the formation of biofilms within the oral cavity is also coming under increasing scrutiny. Possible uses of nanoparticles as topically applied agents within dental materials and the application of nanoparticles in the control of oral infections are also reviewed.

Study of the elution of fluconazole from a self-polymerizing acrylic resin and its activity against resistant Candida albicans

The study aimed, firstly, to monitor the release of an antifungal drug, fluconazole, from a self-polymerizing poly(methyl methacrylate) (PMMA) denture base resin in artificial saliva and comparing it with the release in water; and secondly, to investigate the effect of the released drug on the growth of resistant and standard strains of Candida albicans. A high-performance liquid chromatography-ultra-violet (HPLC-UV) method was used in the analysis of the released eluates into distilled water from self-polymerized PMMA discs doped with the 10% fluconazole antifungal drug. The efficacy of the released drug against resistant and standard strains of C. albicans was monitored, using agar diffusion method. The results showed that fluconazole, can be successfully incorporated with the self-polymerized PMMA. The findings suggest that the drug leaches steadily out of the PMMA resin into artificial saliva and distilled water at mouth temperature and that sustained drug release continued throughout the 28 days test period. It was shown that the released drug demonstrated antifungal activity against both standard and resistant C. albicans. The findings of this investigation have a clinical value in terms of their significant contribution to the treatment of fungal infections of the oral cavity. The sustained release of antifungal drug from the PMMA resin clearly constitutes a new dosage form of the drug via the poly(methyl methacrylate) delivery system.

Experiments on in vivo biofilm formation and in vitro adhesion of Candida species on polysiloxane liners

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.

In vitro antimicrobial effect of the tissue conditioner containing silver nanoparticles

PURPOSE

The aim of this study was to identify in vitro antimicrobial activity of the tissue conditioner containing silver nanoparticles on microbial strains, Staphylococcus aureus, Streptococcus mutans and Candida albicans.

MATERIALS AND METHODS

Experimental disc samples (20.0×3.0 mm) of tissue conditioner (GC Soft-Liner, GC cooperation, Tokyo, Japan) containing 0.1 - 3.0% silver nanoparticles (0%: control) were fabricated. Samples were placed on separate culture plate dish and microbial suspensions (100 µL) of tested strains were inoculated then incubated at 37℃. Microbial growth was verified at 24 hrs and 72 hrs and the antimicrobial effects of samples were evaluated as a percentage of viable cells in withdrawn suspension (100 µL). Data were recorded as the mean of three colony forming unit (CFU) numerations and the borderline of the antimicrobial effect was determined at 0.1% viable cells.

RESULTS

A 0.1% silver nanoparticles combined to tissue conditioner displayed minimal bactericidal effect against Staphylococcus aureus and Streptococcus mutans strains, a 0.5% for fungal strain. Control group did not show any microbial inhibitory effect and there were no statistical difference between 24 hrs and extended 72 hrs incubation time (P > .05).

CONCLUSION

Within the limitation of this in vitro study, the results suggest that the tissue conditioner containing silver nanoparticles could be an antimicrobial dental material in denture plaque control. Further mechanical stability and toxicity studies are still required.

Prosthodontic treatment of a patient with bisphosphonate-induced osteonecrosis of the jaw using a removable dental prosthesis with a heat-polymerized resilient liner: a clinical report

Bisphosphonate-induced osteonecrosis of the jaws (BONJ) is reported frequently in patients receiving oral or intravenous bisphosphonates. To minimize potential complications, dental treatment must be performed with care. There are invasive and noninvasive treatment options for patients with active BONJ or a history of this complication. This clinical report describes the prosthodontic treatment of a patient who developed BONJ after receiving intravenous bisphosphonates (pamidronate). Because of the recurrent incidence of BONJ, noninvasive prosthetic therapy with telescopic overdentures and a heat-polymerized resilient liner was provided. After 2 years, there were no biological or technical complications.

Comparative effects of two different artificial body fluids on Candida albicans adhesion to soft lining materials

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).

Candida albicans adherence on silicone elastomers: effect of polymerisation duration and exposure to simulated saliva and nasal secretion

OBJECTIVES

The surfaces of maxillo-facial prostheses made of silicone elastomers exposed to soft tissues may interact with saliva and nasal secretion. These body fluids may lead to colonisation of microorganisms on their surfaces leading to their degradation or infection. This study investigated Candida albicans adhesion onto commercial maxillo-facial silicone elastomers based on different polymerisation processes.

METHODS

Room-temperature polymerised maxillo-facial silicone elastomers (N=48) (10 mm x 10 mm x 2 mm) processed at different durations [VerSilTal VST-30 (20 min), VST-50 (12h overnight), VST-50F (6h)] were studied. C. albicans was chosen as a model organism for this study. The specimens were randomly divided into two subgroups and incubated in either 1.5 ml simulated saliva or nasal secretion containing C. albicans (ATCC 60193, set to 0.5 OD, 540 nm in advance) for 2h. Candida assays and adherence assays were made by inoculating C. albicans into Mueller Hinton Broth, Fluka added 500 mmol sucrose overnight. After fixation, specimens were stained by using sterilised Methylene Blue stain (Merck) and evaluated under optical microscope and SEM. For each material, on each specimen 15 different areas (mm(2)) were counted. Data were analysed using one-way ANOVA, paired sample t-test and Tukey's HSD (alpha=0.05).

RESULTS

Material type (p<0.05) and exposure media (p<0.05) showed a significant influence on the C. albicans adherence. VST-30 material showed the most C. albicans adherence in both saliva and nasal secretion (mean rank: 99.84 and 53.47, respectively) (p<0.05) and VST-50 had the least colonisation in both media (10.35 and 5.57, respectively). Microscopic evaluation showed clusters of blastospore cells of C. albicans being more spread out on VST-30 whereas cells were more localised on VST-50 and VST-50F.

SIGNIFICANCE

Among the tested materials, 12h room-temperature polymerised silicone elastomer resulted in less C. albicans adherence in both artificial saliva and nasal secretion.

Efficacy of denture disinfection methods in controlling Candida albicans colonization in vitro

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.

Effect of Disinfection Treatments on the Hardness of Soft Denture Liner Materials

PURPOSE

To evaluate the effects of disinfection treatments with chemical solutions (2% glutaraldehyde, 5% sodium hypochlorite, and 5% chlorhexidine) and microwave energy on the hardness of four long-term soft denture liners.

MATERIALS AND METHODS

Forty rectangular specimens of four soft lining materials (Molloplast-B, Ufi Gel P, Eversoft, and Mucopren soft) were made for each material. Ten samples of each material were immersed in different disinfectant solutions for 10 minutes or placed in a microwave oven for 3 minutes at 500 W. The hardness values were obtained with a Shore A durometer, before the first disinfection cycle (control), and also after two cycles of disinfection. Data were submitted to analysis of variance and Tukey's test (p < 0.01).

RESULTS

The highest value of hardness was obtained for Molloplast-B, independent of the disinfection technique. Mucopren soft demonstrated intermediate values and Ufi Gel P and Eversoft the lowest values of Shore A hardness. For Molloplast-B, the disinfection using glutaraldehyde demonstrated the highest value of hardness. The number of disinfections had no effect on the hardness values for all the materials studied and disinfection techniques.

CONCLUSIONS

The application of two disinfection cycles did not change the Shore A hardness values for all the materials. The glutaraldehyde solution demonstrated the highest values of Shore A hardness for the Molloplast-B, Mucopren soft, and Ufi Gel P materials, while Eversoft did not present any differences in hardness when submitted to different disinfection treatments.

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).

Surface modification of an experimental silicone rubber aimed at reducing initial candidal adhesion

Silicone rubber, which is a widely used biomaterial, is often used to make soft liners for permanent denture. Colonization of denture soft lining materials by Candida albicans can result in clinical problems. The aim of this study was to chemically modify the surface of an experimental silicone rubber in order to produce a silicone that was less susceptible to candidal colonization. Surface modification was carried out with the use of argon-plasma bombardment followed by silane treatment, which caused the incorporation of either hydrophilic or hydrophobic functional groups onto the surface. Changes in water contact angles and chemical analysis of the materials with scanning ion mass spectroscopy confirmed surface changes. In vitro assays were carried out using C. albicans to measure levels of adherence to the surface-modified silicone after 1 h. C. albicans exhibited very low adherence to all silane-treated surfaces, whether hydrophobic or hydrophilic. This led to the conclusion that incorporated long-chain functional groups were inhibiting the adherence of the yeast, possibly by the formation of a barrier between the surface of the material and the yeast. In conclusion, silane surface treatment of an experimental silicone rubber has been successful in reducing candidal adherence.

Oral candidal infections and antimycotics

The advent of the human immunodeficiency virus infection and the increasing prevalence of compromised individuals in the community due to modern therapeutic advances have resulted in a resurgence of opportunistic infections, including oral candidoses. One form of the latter presents classically as a white lesion of "thrush" and is usually easily diagnosed and cured. Nonetheless, a minority of these lesions appears in new guises such as erythematous candidosis, thereby confounding the unwary clinician and complicating its management. Despite the availability of several effective antimycotics for the treatment of oral candidoses, failure of therapy is not uncommon due to the unique environment of the oral cavity, where the flushing effect of saliva and the cleansing action of the oral musculature tend to reduce the drug concentration to sub-therapeutic levels. This problem has been partly circumvented by the introduction of the triazole agents, which initially appeared to be highly effective. However, an alarming increase of organisms resistant to the triazoles has been reported recently. In this review, an overview of clinical manifestations of oral candidoses and recent advances in antimycotic therapy is given, together with newer concepts, such as the post-antifungal effect (PAFE) and its possible therapeutic implications.

The effect of two different coatings on the surface integrity and softness of a tissue conditioner

STATEMENT OF PROBLEM

When they are used to treat inflamed, irritated, or distorted tissues or in implant therapy, tissue conditioners are required to function over relatively long time periods. Most presently available materials have a short life span (3 to 4 days).

PURPOSE

This study evaluated the effects of 2 different coatings on the surface integrity and softness of a tissue conditioner over a 4-week period.

MATERIAL AND METHODS

Ten subjects with a complete maxillary denture and a functioning mandibular dentition were included in the study. Each maxillary denture had 3 troughs filled with a tissue conditioner (Coe Comfort). One trough was coated with Monopoly and one with Permaseal; the third trough was left uncoated (control). The specimens were tested at insertion and at 1 week, 2 weeks, and 4 weeks post-insertion for softness with a durometer and for surface integrity with a scanning electron microscope. Statistical differences were determined with analysis of variance (P<.05).

RESULTS

At the end of 4 weeks, the mean and standard deviation of softness on the ASTM scale was 85.1 (4.2) for the control, 81.6 (3.9) for Monopoly, and 77.9 (5.0) for Permaseal. The difference between the control and Permaseal was significant (P<.0042). Qualitatively, SEM analysis indicated that the control deteriorated by the end of the first week, whereas both Monopoly and Permaseal coatings remained intact for up to 2 weeks. All groups showed some conditioner deterioration by 4 weeks. The tissues under the denture-bearing areas remained healthy during the study period.

CONCLUSION

Within the limitations of this study, the application of Permaseal or Monopoly coatings significantly reduced the loss of tissue conditioner softness. Permaseal-coated conditioner remained the softest over the length of the study.

Effects of triclosan on the cytotoxicity and fungal growth on a soft denture liner

STATEMENT OF PROBLEM

Contamination of removable prostheses with microorganisms, particularly Candida albicans, is a common clinical problem. Microban, a broad-spectrum antimicrobial containing triclosan, recently has been proposed to inhibit microbial growth.

PURPOSE

This study aimed to determine whether the addition of Microban to PermaSoft denture liner prevents the growth of C albicans and affects the cytotoxicity of the PermaSoft material.

MATERIAL AND METHODS

Experimental specimen disks (5 x 1 mm each) with and without incorporated Microban were fabricated aseptically (n = 6) against polyester film to produce a smooth surface. To assess the cytotoxic effect of Microban, the MTT assay was used. To determine the effect of Microban on the growth of C albicans, disks were placed in Transwell dishes, covered with Sabouraud's broth containing an ATCC strain of C albicans, and incubated at 37 degrees C for 24 hours. Wells containing fluorocarbon resin disks or broth alone served as controls. The disks were rinsed to remove unattached C albicans and then sonicated in sterile water to remove surface organisms. Serial dilutions of the water extracts were plated on Sabouraud's agar and returned to the incubator for 24 hours. Colonies were counted with a Brunswick Colony Counter. Growth of C albicans in the internal aspects of the specimens was determined in a manner as previously described, with the exception that the specimens were sonicated to remove surface organisms, minced, and sonicated once more before making serial dilutions. The results were compared with ANOVA and Tukey intervals (alpha=.05).

RESULTS

The number of colonies formed ranged from 17 to 31 x 10(5) (mean = 23 +/- 4 x 10(5)) and 14 to 69 x 10(5) (mean = 32 +/- 20 x 10(5)) for the PermaSoft with and without Microban groups, respectively. There was no statistically significant difference between PermaSoft with and without Microban.

CONCLUSION

The addition of Microban did not significantly alter the cytotoxicity of the PermaSoft denture lining material or reduce the adherence of viable C albicans to the surface of PermaSoft material after 24 hours.

Oral colonization by Candida albicans

Candida albicans is a commensal yeast normally present in small numbers in the oral flora of a large proportion of humans. Colonization of the oral cavity by C. albicans involves the acquisition and maintenance of a stable yeast population. Micro-organisms are continually being removed from the oral cavity by host clearance mechanisms, and so, in order to survive and inhabit this eco-system, C. albicans cells have to adhere and replicate. The oral cavity presents many niches for C. albicans colonization, and the yeast is able to adhere to a plethora of ligands. These include epithelial and bacterial cell-surface molecules, extracellular matrix proteins, and dental acrylic. In addition, saliva molecules, including basic proline-rich proteins, adsorbed to many oral surfaces promote C. albicans adherence. Several adhesins present in the C. albicans cell wall have now been partially characterized. Adherence involves lectin, protein-protein, and hydrophobic interactions. As C. albicans cells evade host defenses and colonize new environments by penetrating tissues, they are exposed to new adherence receptors and respond by expressing alternative adhesins. The relatively small number of commensal Candida cells in the oral flora raises the possibility that strategies can be devised to prevent oral colonization and infection. However, the variety of oral niches and the complex adherence mechanisms of the yeast mean that such a goal will remain elusive until more is known about the contribution of each mechanism to colonization.

Efficacy of antifungal agents in tissue conditioners in treating candidiasis

Chronic atrophic candidiasis is prevalent in up to 72% of institutionalized geriatric populations and is causally associated with Candida albicans. Topical antifungal treatments are difficult to implement in some geriatric patients due to cognitive impairment, reduced motor dexterity and memory loss.

OBJECTIVE

This in vitro study incorporated antifungal agents into tissue conditioners to investigate the effectiveness of this method of drug delivery.

DESIGN

Combinations of nystatin, fluconazole, itraconazole and Coe Soft, Viscogel, Fitt were tested at 1, 3, 5, 7, 9 and 11 wt/wt%, with and without sterilized saliva. 6 mm diameter cores were punched in Sabouraud plates pre-grown with standardized C. albicans. Antifungal agents plus tissue conditioner mixtures were injected into each core. Inhibition diameters were measured for 14 days.

RESULTS

Cores with only tissue conditioners acted as negative control and showed no significant inhibition activity (ANOVA, p > 0.05). Peak activity was between 65 to 89 hours; followed by a plateau. Itraconazole had greater fungicidal activity than fluconazole; while nystatin was found to have the least fungicidal activity (ANOVA, p < 0.05). The most effective concentration for nearly all combinations was 5% wt/wt (ANOVA, p < 0.05). Specimens with saliva showed greater antifungal activity than those without (t-test, p < 0.001). Itraconazole altered the physical properties of Viscogel hence this combination is not recommended for clinical use.

CONCLUSION

The treatment of chronic atrophic candidiasis by incorporation of antifungal drugs into tissue conditioners is efficacious. 5% wt/wt itraconazole mixed with Coe Soft or Fitt is recommended for clinical study where compliance of patient or care giver cannot be relied upon. Peak antifungal activity at 3 days suggests that mixtures prepared for clinical study may be replaced soon after this time for maximum effectiveness.

Dynamic viscoelastic properties of antimicrobial tissue conditioners containing silver-zeolite

OBJECTIVES

The purpose of this study was to determine the effects of including the antimicrobial silver-zeolite (SZ) on the dynamic viscoelastic properties of various tissue conditioners.

METHODS

The dynamic viscoelastic properties of five commercially available tissue conditioners: Visco-gel (VG), GC Soft-Liner (SL), FITT (FT), SR-Ivoseal (IV) and Shofu Tissue Conditioner (TC) containing SZ were evaluated after 1 and 28 days of water- and artificial saliva immersions with the use of complex modulus and loss tangent parameters. Values for these two parameters for each tissue conditioner were statistically analyzed by one- and two-way ANOVA and Bonferroni's test.

RESULTS

Complex modulus and loss tangent values of TC were not significantly different among specimens containing 0, 2, 5 and 10 wt.%-SZ, respectively. In FT and TC containing 2 wt.%-SZ, these values were not significantly different between 1 and 28 days in both water- and saliva immersions.

CONCLUSION

The results suggest that incorporating SZ does not affect TC's inherent dynamic viscoelastic properties, while the other tissue conditioners investigated may be found to have changed viscoelastic properties as a consequence of the inclusion of SZ.

Measurement of adsorption of salivary proteins onto soft denture lining materials

STATEMENT OF PROBLEM

The adhesion of Candida albicans to soft liners is a major causative factor in denture stomatitis. It has been suggested that salivary proteins play an important role in this candidal adhesion.

PURPOSE

This study measured the adsorption of salivary proteins on soft liners.

MATERIAL AND METHODS

Five commercial materials and 1 experimental material were immersed in saliva, albumin solution, or milk. Proteins adsorbed on the material surfaces were measured by ATR/FT-IR spectroscopy.

RESULTS

The amount of proteins adsorbed to the 6 materials varied considerably. Protein adsorption was significantly lower in the experimental fluoropolymer and polyphosphazene, and higher in acrylic resin and silicone.

CONCLUSION

Different soft liners promote adsorption of varying amounts of protein.

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."

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.

Prolonged antimicrobial effect of tissue conditioners containing silver-zeolite

OBJECTIVES

The purpose of this study was to elucidate the in vitro antimicrobial effect of tissue conditioners containing silver-zeolite on Candida albicans and nosocomial respiratory infection-causing bacteria, Staphylococcus aureus and Pseudomonas aeruginosa.

METHODS

Five commercially available tissue conditioners were selected: Visco-gel (VG), GC Soft-Liner (SL), Fitt (FT), SR-Ivoseal (IV) and Shofu Tissue Conditioner (TC). Samples, 10 x 10 x 2.5 mm in size, contained silver-zeolite (SZ sample) and no SZ (N sample). The antimicrobial effects of these two samples were evaluated as a percentage of viable cells (CFU) in a microbial suspension (100 microliter) in phosphate-buffered saline with or without immersion in artificial saliva for four weeks. The borderline of the antimicrobial effect was determined at 0.1% viable cells.

RESULTS

With the SZ samples, all tested microbes were killed under both conditions of no immersion and immersion in saliva. In non-immersed N samples, however, no cells of C. albicans (except with VG) and S. aureus survived, whereas the percentage of viable cells of P. aeruginosa was similar to that found in the control. However, with immersion in saliva, viable cells of C. albicans in some N samples (VG, SL and TC) increased compared with non-immersion samples by more than 0.1%.

CONCLUSION

Tissue conditioners containing SZ have been shown to have antimicrobial effects for four weeks on C. albicans and nosocomial respiratory infection-causing bacteria in saliva in vitro.

Growth patterns of Candida albicans in relation to radicular dentin

Candida albicans is the most common fungal pathogen isolated from the oral cavity. The role of this organism as an endodontic pathogen is poorly understood.

OBJECTIVES

The aim of this study was to observe the interaction of C. albicans with root canal walls and the growth patterns of this microorganism in relation to radicular dentin.

STUDY DESIGN

Fifteen root sections were infected with C. albicans grown in calf serum and incubated for various periods. The sections were fixed in glutaraldehyde, split into two halves, and evaluated by scanning electron microscopy.

RESULTS

Blastospores and hyphal structures were observed on the root canal walls of all specimens. Filamentous hyphal form was dominant in 5-day specimens. Most of the hyphae and blastospores showed penetration into dentinal tubules. The body of germinating mother cells and hyphae demonstrated collapsed cell walls as a result of vacuole formation.

CONCLUSIONS

With this invasive affinity to dentinal structures, C. albicans may be considered a dentinophilic microorganism.

Colonization of Candida albicans on cleaned human dental hard tissues

Candida albicans is a fungus that commonly infects oral mucosal surfaces. Limited data exist on biofilm formation by C. albicans on dental surfaces. Human premolar teeth were infected with C. albicans for 10 days and hard-tissue surfaces were examined with a scanning electron microscope. Enamel, cementum and dentine, in the absence or presence of a smear layer, were readily colonized by this micro-organism. Hyphae penetrated into cracks, followed the ridges of the cavities and migrated into dentinal tubules. Blastospores and hyphae were embedded in an extracellular material. These findings suggest that dental hard tissues may be invaded by C. albicans and thus can potentially present a reservoir for disseminating candidal infections.

Retention of Candida albicans on acrylic resin and silicone of different surface topography

STATEMENT OF PROBLEM

The adhesion of microorganisms to a denture surface is a prerequisite for colonization.

PURPOSE

This study compared the retention of Candida albicans on smooth and rough acrylic resin and silicone surfaces after a washing procedure to determine the effect of surface roughness on prosthesis infection and hygiene.

MATERIAL AND METHODS

Standardized cell suspensions of C. albicans were incubated with smooth and rough acrylic resin and silicone surfaces for 1 hour at 24 degrees C. After washing, cells that had been retained on the surface were stained with acridine orange and examined with incident beam fluorescent microscopy.

RESULTS

There was no significant difference in cell numbers on either of the smooth surfaces. Significantly higher numbers of cells (p > 0.0005) were observed on roughened surfaces (silicone > acrylic resin) than on smooth surfaces. The fitting surface of the maxillary denture was not polished.

CONCLUSIONS

Silicones used in prostheses were processed against dental stone. The resultant surface roughness may facilitate microbial retention and infection and should therefore be kept to a minimum.

Adherence of Candida albicans to experimental denture soft lining materials

STATEMENT OF PROBLEM

Colonization of denture soft lining materials by Candida albicans can result in clinical problems. Two experimental silicone soft lining materials have been developed and demonstrate good physical properties.

PURPOSE OF STUDY

The aim of this study was to determine the extent of candidal adherence to these materials compared with a commercially available soft lining material and an acrylic resin denture base.

MATERIAL AND METHODS

The experimental materials were constructed in a stainless-steel mold, and their surface energies were determined with a dynamic contact angle analyzer. The adherence of three strains of C. albicans was determined with an in vitro assay. In addition, one test strain was used to determine the effect on adherence of precoating the materials with whole saliva.

RESULTS

Adhesion to all materials was strain variable, with the lowest adherence recorded for the two experimental materials. Decreased adherence was also apparent after precoating the materials with saliva. Correlation between surface energy of the material and the degree of candidal adhesion was seen for one strain, but no correlation was seen for the other two strains.

CONCLUSION

Adherence of C. albicans to the two experimental silicone soft lining materials was significantly less than that for an acrylic resin denture base and a commercially available soft lining material.

Wettability of denture soft-lining materials

Data on the wettability of long-term resilient denture base lining materials have previously been obtained by static methods. This study determined the dynamic contact angle of a range of long-term resilient lining materials and the surface free energy properties of these materials. This method was a rapid and convenient method for determining wettability parameters. The equilibrium contact angle revealed the Flexor and Novus materials to be the least wetted with the Molloplast-B material, and CoeSuper-Soft material was wetted similarly to Trevalon material. The contact angle hysteresis indicated that all the soft-lining materials tested would improve denture stability under dislodgment forces. The surface-free energies appeared to be similar for all the soft-lining materials but were significantly lower than that of Trevalon.