Denture disinfection by microwave irradiation: a randomized clinical study

Effects of disinfectants on physical properties of denture base resins: A systematic review and meta-analysis

STATEMENT OF PROBLEM

The disinfection of removable dental prostheses and orthodontic appliances is essential to preventing transmission of pathogens. However, whether different disinfection solutions and durations affect the physical properties of denture base resins is unclear.

PURPOSE

The purpose of this systematic review and meta-analysis was to statistically analyze the influence of disinfectants on the physical properties of denture base resins.

MATERIAL AND METHODS

A systematic search in Medline, Embase, PubMed, and Cochrane Library databases was conducted to evaluate the effects of chemical disinfection on the physical properties of denture base resins such as surface morphology, roughness, hardness, and flexural strength. Of 1909 studies, 44 studies were included in the systematic review and 41 in the meta-analysis. Heterogeneity was analyzed by using I2 statistics. The influence of different disinfection solutions and durations on the physical properties was further analyzed, and the risk of bias evaluated. Statistical analyses were performed by using the RevMan 5.4 software program with the standardized mean differences (SMDs) and 95% confidence intervals (CIs).

RESULTS

Of the 44 included studies, 40 studies were assessed as having a low risk of bias, and 4 had an unclear risk of bias. Meta-analysis results showed that compared with the control, disinfection could not significantly affect surface roughness and hardness within 60 minutes of immersion in disinfectant solutions or flexural strength within 30 minutes (roughness: P=.79, I2=0%; flexural strength: P=.08, I2=0%; hardness: P=.05, I2=19%). In addition, the physical properties were not significantly affected when glutaraldehyde, chlorhexidine, and peracetic acid were repeatedly used for more than 30 minutes.

CONCLUSIONS

Most of the disinfectants did not reduce the physical properties of denture base resin within 30 minutes of immersion. Glutaraldehyde, chlorhexidine, and peracetic acid are recommended if longer immersion or repeated disinfection is required.

Anti-biofilm effectiveness of protocols for cleaning complete dentures in hospitalized patients: a randomized controlled trial

BACKGROUND

Denture biofilm acts as a potential reservoir for respiratory pathogens, considerably increasing the risk of lung infections, specifically aspiration pneumonia, mainly 48h after hospital admission. The establishment of a straightforward, affordable, and applicable hygiene protocol in a hospital environment for the effective control of denture biofilm can be particularly useful to prevent respiratory infections or reduce the course of established lung disease.

OBJECTIVES

To evaluate the anti-biofilm effectiveness of denture cleaning protocols in hospitalized patients.

METHODOLOGY

The maxillary complete dentures (MCDs) of 340 hospitalized participants were randomly cleaned once using one of the following 17 protocols (n=20): brushing with distilled water, toothpaste, or neutral liquid soap (controls); immersion in chemical solutions (1% sodium hypochlorite, alkaline peroxide, 0.12% or 2% chlorhexidine digluconate), or microwave irradiation (650 W for 3 min) combined or not with brushing. Before and after the application of the protocols, the biofilm of the intaglio surface of the MCDs was evaluated using two methods: denture biofilm coverage area (%) and microbiological quantitative cultures on blood agar and Sabouraud Dextrose Agar (CFU/mL). Data were subjected to the Wilcoxon and Kruskal-Wallis tests (α=0.05).

RESULTS

All 17 protocols significantly reduced the percentage area of denture biofilm and microbial and fungal load (P<0.05). The highest percentage reductions in the area of denture biofilm were observed for 1% hypochlorite solution with or without brushing and for 2% chlorhexidine solution and microwave irradiation only in association with brushing (P<0.05). The greatest reductions in microbial and fungal load were found for the groups that used solutions of 2% chlorhexidine and 1% hypochlorite and microwave irradiation, regardless of the association with brushing (P<0.05).

CONCLUSIONS

A single immersion for 10 min in 1% sodium hypochlorite, even in the absence of brushing, proved to be a straightforward, rapid, low-cost, and effective protocol for cleaning the dentures of hospitalized patients.

Microwave disinfection of facial silicone prostheses, part 2: Mechanical properties

STATEMENT OF PROBLEM

Part 1 of this 2-part study determined that microwave disinfection did not degrade the color stability of facial silicone prostheses. However, investigations on the effects of microwave disinfection on the mechanical properties of different silicone elastomers are lacking.

PURPOSE

The purpose of this in vitro study was to examine the mechanical properties of commonly used colored facial silicone elastomers before and after microwave disinfection over a simulated 1.5-year period.

MATERIAL AND METHODS

Six commonly used facial silicone elastomers: MDX4-4210, MDX4-4210/Type A, M511, A-2186, VST-50, and A-2000 were combined with functional intrinsic silicone pigments and opacifier (red, yellow, blue, and white). A total of 288 specimens were fabricated (n=12). Half of the specimens were tested for mechanical properties as the baseline, while the other specimens were tested after microwave disinfection. Microwave disinfection was performed with 660 W, 6 minutes of exposure time, and microwaved for 18 cycles to simulate 1.5 years of usage (one 6-minute exposure monthly). For mechanical property testing, all specimens were tested for tensile strength and percentage elongation (ASTM D412), tear strength (ASTM D624), and hardness (ASTM D2240). For each property, a 2-way ANOVA (silicone type and microwave disinfection factors) and Tukey multiple comparison test were performed using the R statistical software program (α=.05).

RESULTS

Following microwave disinfection, tensile strength and percentage elongation of A-2000 increased significantly (P<.05). MDX4-4210, MDX4-4210/Type A, and A-2000 showed significant increases in their hardness (P<.001). Tear strength also increased significantly for MDX4-4210 and VST-50 (P<.05). Among the materials tested (ranked from highest to lowest value,=not statistically significant different), for tensile strength, VST-50>A-2186=A-2000>MDX4-4210/Type A=M511=MDX4-4210 (P<.05). For percentage elongation, VST-50>MDX4-4210/Type A>A-2186>M511=A-2000=MDX4-4210=M511 (P<.05). For hardness, A-2000=A-2186>M511=VST-50>MDX4-4210>MDX4-4210/Type A (P<.05). For tear strength, VST-50>A-2186>A-2000>M511>MDX4-4210/Type A=MDX4-4210 (P<.05).

CONCLUSIONS

Overall, the mechanical properties of all the silicones tested were not adversely affected by microwave disinfection. VST-50 showed the best mechanical properties among the materials tested both before and after microwave disinfection. Microwave energy is a safe method of disinfecting the silicone elastomers tested in this study.

Comparative effectiveness of interventions for the treatment of denture stomatitis: A systematic review with network meta-analysis

STATEMENT OF PROBLEM

Symptomatic denture stomatitis (DS) is a painful oral mucosal disorder that can impair quality of life in denture wearers. A complete cure of DS is difficult to achieve, and the most efficacious regimen to treat DS has not yet been conclusively established.

PURPOSE

The purpose of this network meta-analysis was to assess the comparative efficacy of interventions used for the treatment of DS.

MATERIAL AND METHODS

A search was conducted for trials published in Medline, Scopus, PubMed, and Cochrane Central Register of Controlled Trials from inception until February 2022 (PROSPERO Reg no: CRD42021271366). Network meta-analysis was performed on data from randomized controlled trials that assessed the comparative efficacy of any form of intervention for the treatment of DS in denture wearers. Agents were ranked according to their effectiveness in the treatment of DS based on outcomes using surface under the cumulative ranking (SUCRA).

RESULTS

A total of 25 articles were included in the quantitative analysis. Topical antifungal agents (risk ratio [RR]=4.37[95% confidence interval [CI]: 2.15,8.90), topical antimicrobial agents used along with systemic antifungal agents (RR=4.25[95% CI: 1.79,10.33]), systemic antifungal agents (RR=4.25[95% CI: 1.79,10.10]), photodynamic therapy (RR=4.25[95% CI: 1.75,8.98]), and topical plant products (RR=3.40[95% CI: 1.59,7.26]) were found to effectively improve DS. Microwave disinfection concurrently administered with topical antifungal agents (RR=7.38(95% CI: 2.75,19.81), microwave disinfection 7.38[95% CI: 2.75,19.81]), topical antifungal agents (RR=4.88[95% CI: 1.92,12.42]), topical plant products (RR=4.49[95% CI: 1.70,11.82]), systemic antifungal agents together with topical antimicrobial agents (RR=3.85[95% CI: 1.33,11.10]), topical antimicrobial agents (RR=3.39[95% CI: 1.17,9.81]), systemic antifungal agents (RR=3.37[95% CI: 1.21,9.34]), and photodynamic therapy or photochemotherapy (PDT) (RR=2.93[95% CI: 1.01,8.47]) were found to effectively resolve mycological DS. Topical antifungals ranked highest in the SUCRA ranking for clinical improvement, whereas microwave disinfection concurrently administered with topical antifungal agents ranked highest for mycological resolution. None of the agents demonstrated significant side effects except for topical antimicrobial agents which demonstrated altered taste and staining of oral structures.

CONCLUSIONS

Available evidence suggests that topical antifungals, microwave, and systemic antifungals are effective in the treatment of DS, but confidence in these findings is low because of the limited number of studies and a high risk of bias. Additional clinical trials are needed on photodynamic therapy, topical plant products, and topical antimicrobials.

CLEANING OF REMOVABLE DENTAL PROSTHESES - A SYSTEMATIC REVIEW

Objectives The aim of this systematic review was to provide an overview of the scientific evidence available from prospective clinical studies regarding denture hygiene interventions. Therefore, investigations addressing the efficacy of removing microorganisms and biofilms formed on the surface of removable dental prostheses (RDPs) and denture base materials in situ and their impact on the properties of denture base materials, such as color stability, surface roughness, and dimensional stability, were included. Methods A systematic literature search was conducted from June 1975-May 2020 and included articles published in English that have been indexed in the digital archives of PubMed and Cochrane (including PubMed, Embase, ICTRP, CT.gov). A complementary manual search of the initially retrieved studies was conducted. Inclusion criteria comprised prospective clinical trials with a minimum of ten participants investigating (1) approaches and methods to remove biofilms formed on the surface of RDPs and denture base materials in situ and/or (2) the influence of these biofilms on denture base materials. A total of forty-four studies were included in this systematic review, which was registered in the PROSPERO database (CRD42020189649). Results and Conclusions Data gathered from the systematic review indicate that the combined use of chemical and mechanical denture hygiene interventions is significantly more effective than single cleaning approaches. Only limited evidence is available from clinical studies regarding the effect of denture hygiene interventions on the properties of denture base materials.

Is there an optimal method to detach Candida albicans biofilm from dental materials?

Introduction. Candida albicans can produce a complex, dynamic and resistant biofilm on the surface of dental materials, especially denture base acrylic resins and temporary soft liners. This biofilm is the main aetiological factor for denture stomatitis, an oral inflammatory condition characterized by chronic and diffuse erythema and oedema of the denture bearing mucosa.Gap Statement. There is no consensus in the literature regarding the best method to detach biofilms from dental materials. In order to assess the antifungal efficacy of new materials and treatments, the biofilm needs to be properly detached and quantified.Aim. This study compared different methods of detaching C. albicans biofilm from denture base acrylic resin (Vipi Cril) and temporary soft liner (Softone) specimens.Methodology. Specimens of each material were immersed in an inoculum of C. albicans SC5314 and remained for 90 min in orbital agitation at 75 r.p.m. and 37 °C. After the removal of non-adherent cells, the specimens were immersed in RPMI-1640 medium for 48 h. Biofilm formation was evaluated with confocal laser scanning microscopy (n=5). Then, other specimens (n=7) were fabricated, contaminated and immersed in 3 ml of sterile phosphate-buffered saline (PBS) and vortexed or sonicated for 1, 2, 5, or 10 min to detach the biofilm. The quantification of detached biofilm was performed by colony-forming unit (c.f.u.) ml^-1 count. Results were submitted to one-way analysis of variance (ANOVA)/Tukey HSD test (α=0.05).Results. A mature and viable biofilm was observed on the surfaces of both materials. For both materials, there was no significant difference (P>0.05) among detachment methods.Conclusion. Any of the tested methods could be used to detach C. albicans biofilm from hard and soft acrylic materials.

The effectiveness of microwave disinfection in treating Candida-associated denture stomatitis: a systematic review and metaanalysis

OBJECTIVE

To evaluate the effectiveness of microwave disinfection in treating Candida-associated denture stomatitis (CADS).

MATERIALS AND METHODS

The PubMed/MEDLINE, Embase, and Scopus databases were searched for reports on randomized clinical trials (RCTs) published in English until May 2020 (PROSPERO CRD42020192062) that evaluated the treatment of CADS by using microwave disinfection. The main outcomes were the improvement of clinical signs and/or the decrease in the residual yeast present on the dentures and palatal mucosa. The mean differences, standard deviations, risk ratio, and 95% confidence interval were calculated by using the random-effects model. Heterogeneity was assessed by using Cochran's Q test and I² values. The level of significance was set at α = 0.05.

RESULTS

Five RCTs with 245 participants were included. The descriptive investigations demonstrated that microwave disinfection was as effective (p > 0.05) as 0.2% chlorhexidine, 0.02% sodium hypochlorite, and topical nystatin (100.000 IU/mL), and was superior to topical miconazole in treating CADS. The metaanalysis did not show a statistical difference between microwave disinfection and nystatin (100.000 IU/mL) treatment in terms of mycological counts, cure, and recurrence rates (p > 0.05).

CONCLUSION

Microwave disinfection showed comparable results with those of conventional therapies for treating CADS. In addition, treatment with 650 W for 3 min once a week for 14 days had better cost-effect results, indicating both the prevention and treatment of CADS.

CLINICAL RELEVANCE

Our findings provide evidence regarding the treatment of CADS using microwave disinfection, and also indicating the best cost-effective option for this treatment modality.

Long-term microwaving of denture base materials: effects on dimensional, color and translucency stability

While the combined effect of microwave irradiation with cleansing solutions on denture base materials has been investigated, the effects of only using microwave irradiation and, more importantly, in a long-term basis, was not studied yet.

Evaluation of Surface Microhardness Following Chemical and Microwave Disinfection of Commercially Available Acrylic Resin Denture Teeth

INTRODUCTION

Denture disinfection is an indispensable procedure for preventing cross contamination and the maintenance of a healthy oral mucosa in patients rehabilitated with removable dental prosthesis. Nevertheless, they are known to cause changes in the physical and mechanical properties of denture base resins and acrylic resin denture teeth following immersion of a denture in a suitable chemical disinfectant solution or by undergoing microwave irradiation. One such mechanical property indicator for artificial tooth materials is hardness.

AIM

To assess the surface hardness of acrylic resin teeth of three different commercial brands (Ivoclar, Newace, Acryrock) following chemical (2% glutaraldehyde, 1% sodium hypochlorite) and microwave disinfections.

MATERIALS AND METHODS

Ten specimens of each of the three commercial brands were made for control and each simulated disinfection type and stored in distilled water at room temperature for 24 hours. After water storage, specimens were immersed in 2% glutaraldehyde and 1% sodium hypochlorite (one and three cycles) at room temperature for 10 minutes. Irradiation with microwave (one and three cycles) was done in domestic microwave for three minutes with the specimens immersed in 150 ml of distilled water. The specimens were stored in distilled water at room temperature for seven days after each disinfection cycle. Vickers hardness measurements were made using a hardness indenter under a load of 50 g force for 10 seconds. Data was subjected to repeated measure two-way ANOVA test and Tukey's test.

RESULTS

There were statistically significant differences for the variables disinfection, tooth, and cycle (p<0.05 for teeth & disinfectant interaction, p<0.05 cycle and disinfectant interaction). The mean surface hardness following one microwave disinfection cycle was lower than control, glutaraldehyde and sodium hypochlorite. Comparison among cycles revealed that microhardness was significantly decreased for three cycles of microwave disinfection.

CONCLUSION

It was concluded that there was no significant difference in microhardness when the teeth were subjected to chemical disinfection but three cycles of microwave disinfection produced decrease in the microhardness of different types of artificial teeth.

The Effect of Repeated Microwaving Disinfection on the Dimensional Stability of Acrylic Dentures

OBJECTIVE

The aim of this study was to evaluate the effect of repeated microwave disinfections on the dimensional stability of acrylic dentures.

MATERIALS AND METHODS

Three groups of dentures made of a heat polymerized acrylic resin were tested. I: dentures kept in water (control group). II: dentures microwaved daily while being immersed into water (wet disinfection). III: dentures microwaved daily without being immersed into water (dry disinfection).
Measurements were taken across three reference points, on two occasions: after curing and immersion in water for 24 hours, and one week later.
Data obtained were analyzed using one-way analysis of variance (ANOVA) and Scheffe's multiple range test.

RESULTS

The results showed that the microwave disinfection provokes dimensional changes of the same pattern (shrinkage). The dentures which underwent wet disinfection exhibited the greatest shrinkage (p<0.05).

CONCLUSIONS

Disinfection using microwave energy may cause dimensional changes (shrinkage) of complete dentures.
The microwave "dry disinfection" method can be safely applied in everyday practice since the dimensional changes which occurred seem to be of no clinical significance.

Effect of Atmospheric-Pressure Cold Plasma on Pathogenic Oral Biofilms and In Vitro Reconstituted Oral Epithelium

Considering the ability of atmospheric-pressure cold plasma (ACP) to disrupt the biofilm matrix and rupture cell structure, it can be an efficient tool against virulent oral biofilms. However, it is fundamental that ACP does not cause damage to oral tissue. So, this study evaluated (1) the antimicrobial effect of ACP on single- and dual-species biofilms of Candida albicans and Staphylococcus aureus as well as (2) the biological safety of ACP on in vitro reconstituted oral epithelium. Standardized cell suspensions of each microorganism were prepared for biofilm culture on acrylic resin discs at 37°C for 48 hours. The biofilms were submitted to ACP treatment at 10 mm of plasma tip-to-sample distance during 60 seconds. Positive controls were penicillin G and fluconazole for S. aureus and C. albicans, respectively. The biofilms were analyzed through counting of viable colonies, confocal laser scanning microscopy, scanning electron microscopy and fluorescence microscopy for detection of reactive oxygen species. The in vitro reconstituted oral epithelium was submitted to similar ACP treatment and analyzed through histology, cytotoxocity test (LDH release), viability test (MTT assay) and imunnohistochemistry (Ki67 expression). All plasma-treated biofilms presented significant log₁₀ CFU/mL reduction, alteration in microorganism/biofilm morphology, and reduced viability in comparison to negative and positive controls. In addition, fluorescence microscopy revealed presence of reactive oxygen species in all plasma-treated biofilms. Low cytotoxicity and high viability were observed in oral epithelium of negative control and plasma group. Histology showed neither sign of necrosis nor significant alteration in plasma-treated epithelium. Ki67-positive cells revealed maintenance of cell proliferation in plasma-treated epithelium. Atmospheric-pressure cold plasma is a promissing approach to eliminate single- and dual-species biofilms of C. albicans and S. aureus without having toxic effects in oral epithelium.

FT-Raman Spectroscopy Study of the Remineralization of Microwave-Exposed Artificial Caries

Dental caries is a microbially mediated disease that can result in significant tooth structure degradation. Although the preponderance of lesions is treated by surgical intervention, various strategies have been developed for its noninvasive management. Here, we use a novel approach for noninvasive treatment based on killing Streptococcus mutans with high-frequency microwave energy (ME). The rationale for this approach is based on modulating the pH of caries to a physiological state to enable spontaneous tooth remineralization from exogenous sources. In the present study, after demonstrating that ME kills >99% of S. mutans in planktonic cultures, 8 enamel slabs were harvested from a single tooth. Baseline mineral concentration at each of 12 points per slab was obtained using Fourier transform (FT)-Raman spectroscopy. Surface demineralization was subsequently promoted by subjecting all samples to an S. mutans acidic biofilm for 6 d. Half of the samples were then exposed to high-frequency ME, and the other half were used as controls. All samples were next subjected to a remineralization protocol consisting of two 45-min exposures per 24-h period in tryptic soy broth followed by immersion in a remineralizing solution for the remaining period. After 10 d, samples were removed and cleaned. FT-Raman spectra were again obtained at the same 12 points per sample, and the mineral concentration was determined. The effect of the remineralization protocol on the demineralized slabs was expressed as a percentage of mineral loss or gain relative to baseline. The mineral concentration of the microwave-exposed group collectively approached 100% of baseline values, while that of the control group was in the order of 40%. Differences between groups were significant (P = 0.001, Mann-Whitney U test). We concluded that killing of S. mutans by ME promotes effective remineralization of S. mutans-demineralized enamel compared with controls.

Photodynamic inactivation of a multispecies biofilm using Photodithazine(®) and LED light after one and three successive applications

In this investigation, the effectiveness of successive applications of antimicrobial photodynamic inactivation (API) mediated by Photodithazine(®) (PDZ) and LED light was evaluated against a multispecies biofilm formed by Candida albicans, Candida glabrata, and Streptococcus mutans on denture base acrylic resin. Standard cell suspensions (bacteria and yeast) were inoculated on acrylic resin samples, and the biofilm was grown for 48 h (37 °C/75 rpm). API was performed by the administration of PDZ (175 and 200 mg/L) and exposure to 37.5 J/cm(2) of LED light (660 nm). Additional samples were treated with PDZ or LED light only. Untreated control samples were not submitted to light or PDZ. The conditions described were applied once or in three consecutive applications for all groups. Cell viability was determined by colony counts (CFU/mL), metabolic activity, total biomass, and confocal laser scanning microscopy (CLSM). Data were analyzed by a nonparametric two-way ANOVA and Tukey tests (α = 0.05). The results obtained demonstrated a significant effect (p < 0.05) of number of applications and treatment groups for CFU/mL, and S. mutans showed the highest susceptibility to API. The metabolic activity of the multispecies biofilm was significantly reduced (p < 0.05) after API for both numbers of applications, which were also significantly different (p < 0.05) between them. The total biomass of the biofilm was significantly different (p < 0.05) only between groups submitted to one and three API applications. CLSM showed a visual increase of dead cells after API. API-mediated PDZ was effective in reducing the cell viability of multispecies biofilm. Three consecutive applications of API were more effective for reducing the cell viability and the total biomass of multispecies biofilm.

Effectiveness of Chemical and Microwave Disinfection on Denture Biofilm Fungi and the Influence of Disinfection on Denture Base Adaptation

The aims of this study were to evaluate the effectiveness of six disinfection methods and the influence of these methods on the adaptation of maxillary dentures. Acrylic resin specimens contaminated with fungi were exposed to the following disinfection treatments: 1. microwave oven (900 W) at full power for 5 min (with soaking the specimen in 250 ml water), 2. microwave oven at medium power for 5 min (with soaking the specimen in 250 ml water), 3. sodium hypochlorite 5.25 % for 5 min, 4. diluted sodium hypochlorite 1:420 for 5 h, 5. Chlorhexidine gluconate for 5 h, 6. effervescent tablets for 15 min, 7. soaking in 250 ml tap water for 15 min. Colony forming units (CFUs) of remaining cells were counted and compared with t test (p ≤ 0.05). Dimensional stability was evaluated using aluminum die simulating the maxillary edentulous arch. Posterior palatal gaps were measured. Data were analyzed using one-way ANOVA test and t test (p ≤ 0.05). Microwave irradiation (at full or medium power) and sodium hypochlorite 5.25 % for 5 min were able to reduce the CFUs of fungi by more than 4 log10 whereas diluted sodium hypochlorite, chlorhexidine gluconate, and effervescent tablets did not achieve a reduction of >2.8, 2.68 and 1.66, respectively. For dimensional stability test, t test revealed significant difference between control group and the microwave at full power group (p = 0.000). Within the limits of this study, microwave oven at medium power and sodium hypochlorite (5.25 %) are effective and safe methods of disinfecting removable dentures.

Effects of cleansing methods on 3-D surface roughness, gloss and color of a polyamide denture base material

OBJECTIVE

The purpose of this study was to determine the effects of two denture cleansing methods on 3-D surface roughness, gloss and color of denture base materials.

MATERIALS AND METHODS

Thirty disks from nylon (Valplast) and 30 from heat-polymerized acrylic denture base material (Paladon 65) were made and 10 of each material were immersed in water (control), Val-Clean (peroxide cleanser) and Corega Extradent (peroxide cleanser) plus microwaving for a period simulating 30 days of daily cleansing. 3-D surface roughness, gloss and color parameters were measured before and after cleansing using an interferometric profilometer, a gloss meter and a colorimeter. The results were statistically analysed by regression, paired-t, Mann-Whitney and Kruskal-Wallis tests at α = 0.05 level of significance.

RESULTS

The results showed significant differences at baseline in L* and b* parameters between materials (p < 0.01), with a significantly lower gloss (p < 0.05) and higher roughness (p < 0.05) for Valplast. After cleansing, Δϵ* was significantly greater in Valplast than Paladon 65 (p < 0.05). Gloss of both materials decreased significantly within the Corega Extradent plus microwave solution (p < 0.05), while roughness increased significantly only for Paladon 65 (p < 0.05).

CONCLUSIONS

Valplast was found to have a significantly lower gloss and a higher roughness than Paladon 65 before cleansing. After cleansing, ΔE* increased more in Valplast than in Paladon 65, gloss of both materials decreased and roughness only of Paladon 65 increased within the Corega extradent plus microwaving method.

The effect of repeated microwave irradiation on the dimensional stability of a specific acrylic denture resin

PURPOSE

To determine the dimensional stability of a poly(methyl methacrylate) (PMMA) acrylic resin when subjected to multiple sessions of repeated microwave irradiation at power settings of 700 and 420 W.

MATERIALS AND METHODS

Twenty standardized denture bases were fabricated using a PMMA resin. Points of measurement were marked on each denture base with a standardized template, and the distances between points were recorded using a digital microscope. The denture bases were randomly placed into two experimental groups of 10 bases each. Individual denture bases were placed into a glass beaker containing 200 ml of room temperature deionized water and then exposed to either 700 or 420 W of microwave radiation for 3 minutes. The denture bases were allowed to cool to room temperature, and measurements between points were recorded. This process was carried out for two microwave periods with measurements being completed after each period. The data were then analyzed for any significant changes in distances between points using a Student's t-test.

RESULTS

All denture bases experienced 1.0 to 2.0 mm or approximately 3% linear dimensional change after each period of microwaving. Results were significant with all t-tests having values of p < 0.05.

CONCLUSION

This report showed that the denture bases deformed significantly under experimental conditions at either 700 W for 3 minutes in 200 ml of water or 420 W for 3 minutes in 200 ml of water.

Effect of mixing techniques on bacterial attachment and disinfection time of polyether impression material

Objective:

The aim of this study was 2-fold. The first aim was to evaluate the effects of mixing technique (hand-mixing or auto-mixing) on bacterial attachment to polyether impression materials. The second aim was to determine whether bacterial attachment to these materials was affected by length of exposure to disinfection solutions.

Materials and Methods:

Polyether impression material samples (n = 144) were prepared by hand-mixing or auto-mixing. Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were used in testing. After incubation, the bacterial colonies were counted and then disinfectant solution was applied. The effect of disinfection solution was evaluated just after the polymerization of impression material and 30 min after polymerization. Differences in adherence of bacteria to the samples prepared by hand-mixing and to those prepared by auto-mixing were assessed by Kruskal-Wallis and Mann-Whitney U-tests. For evaluating the efficiency of the disinfectant, Kruskal-Wallis multiple comparisons test was used.

Results:

E. coli counts were higher in hand-mixed materials (P < 0.05); no other statistically significant differences were found between hand- and auto-mixed materials. According to the Kruskal-Wallis test, significant differences were found between the disinfection procedures (Z > 2.394).

Conclusion:

The methods used for mixing polyether impression material did not affect bacterial attachment to impression surfaces. In contrast, the disinfection procedure greatly affects decontamination of the impression surface.

In vitro evaluation of the enzymatic activity profile of non-albicans Candida species isolated from patients with oral candidiasis with or without diabetes

OBJECTIVE

To evaluate the expression of phospholipase (PL) and secreted aspartyl proteinase (SAP) by Candida glabrata and C tropicalis obtained from the denture biofilms of healthy participants (16 isolates), patients with oral candidiasis with diabetes (10 isolates), and patients with oral candidiasis without diabetes (25 isolates).

STUDY DESIGN

After incubation, the supernatants and pellets of the isolates were used for the enzymatic assays and quantification of colony-forming units (CFU), respectively. Colorimetric tests were used with phosphatidylcholine as a substrate for PL and azocasein as a substrate for SAP, and the absorbances of the samples were measured. Enzymatic rates were calculated, and values were normalized by CFU. Results were analyzed with factorial analyses of variance (α = .05).

RESULTS

C tropicalis and C glabrata were proteolytic and phospholipolytic. The clinical sources of isolates had no significant effect on the enzymatic activities (P > .05). C tropicalis had significantly higher enzymatic activity for both PL and SAP (P < .001) than did C glabrata.

CONCLUSIONS

C tropicalis isolates produced significantly higher amounts of both enzymes than did the C glabrata isolates.

The effect of cleaning substances on the surface of denture base material

Bakcground

The aim of this study was to evaluate the effect of substances used for hygienic cleaning of dentures on the surface of the denture base material.

Material/Methods

Meliodent Heat Cure (Heraeus-Kulzer, Germany) heat-polymerized acrylic resin was used to produce plates with all the characteristics of removable denture bases (subsequently, “plates”). Oral-B Complete toothbrushes of various brush head types were fixed to a device that imitated tooth brushing movements; table salt and baking soda (frequently used by patients to improve tooth brushing results), toothpaste (“Colgate Total”), and water were also applied. Changes in plate surfaces were monitored by measuring surface reflection alterations on spectrometry. Measurements were conducted before the cleaning and at 2 and 6 hours after cleaning.

Results

No statistically significant differences were found between the 3 test series. All 3 plates used in the study underwent statistically significant (p<0.05changed) – the reflection became poorer. The plates were most affected by the medium-bristle toothbrush with baking soda – the total reflection reduction was 4.82±0.1%; among toothbrushes with toothpaste, the hard-type toothbrush had the greatest reflection-reducing effect – 4.6±0.05%, while the toothbrush with table salt inflicted the least damage (3.5 ± 0.16%) due to the presence of rounded crystals between the bristles and the resin surface. Toothbrushes with water had a uniform negative effect on the plate surface – 3.89±0.07%.

Conclusions

All substances used by the patients caused surface abrasion of the denture base material, which reduced the reflection; a hard toothbrush with toothpaste had the greatest abrasive effect, while soft toothbrushes inflicted the least damage.

Effectiveness of denture cleanser associated with microwave disinfection and brushing of complete dentures: in vivo study

Complete dentures acts as a reservoir for microbial colonization, which may lead to systemic infections. Microwave irradiation has been used as an efficient method of denture disinfection. Even though current methods eliminate denture-base microorganisms, a recurrence rate of denture stomatitis (DS) is still observed among denture-wearing patients. It was hypothesized that microwave disinfection kills microorganisms but do not remove dead bacteria from the denture surface. To test this hypothesis, the biofilm found in the dentures of 10 patients with DS was evaluated. In addition, the effects of microwave irradiation plus brushing (MW+B) on the denture biofilm and the combination of denture cleanser with microwave irradiation and brushing (MW+DC+B) for the removal of denture-accumulating microorganisms were investigated. Microbiological data were analyzed statistically by nonparametric analysis (Friedman/Wilcoxon, α=0.05). MW+B and MW+DC+B were effective in reducing the rate of microorganisms (99.2% and 99.5% respectively), but without significant difference between them (p=0.553). However, it was observed that the complete removal of microorganisms from denture surface was only possible when all regimens were combined (MW+DC+B). Microwave irradiation in combination with soaking in denture cleanser and brushing effectively disinfected the dentures and removed denture biofilm.

Effect of different energy levels of microwave on disinfection of dental stone casts

BACKGROUND AND AIMS

Current chemical methods may not efficiently disinfect dental stone casts. The aim of this study was to investigate if microwave irradiation is effective for disinfection of stone casts.

MATERIALS AND METHODS

In this laboratory study, three groups (n = 162) of prepared spherical stone beads as carriers with a diameter of 10 mm were inoculated by separately soaking in three broth culture media, each containing a study microorganism-Pseudomonas aeruginosa, Staphylococcus aureus or Candida albicans. Six inoculated carriers were used for every test, including irradiation in a household microwave oven at 300, 450, 600 or 900 W energy level, or soaking in 0.03%, 0.06%, 0.12%, 0.25% or 0.50% concentration of sodium hypochlorite solution, at 1, 2, or 3-minute test times. Positive and negative control groups were considered for each test. All treated carriers were then individually transferred to nutrient broth culture medium and one milliliter from each tube was cultured in nutrient agar media over night. Colony forming unit per milliliter (CFU/mL) was counted, and multi-factor ANOVA was used to analyze data (α = 0.05).

RESULTS

Microwave irradiation at 600 W resulted in high-level disinfection in 3 minutes. Immersion of the stone casts in hypochlorite solution at 0.06% concentration resulted in disinfection after 2 minutes.

CONCLUSION

According to the results, high level disinfection of the stone casts can be achieved by microwave irradiation at 600 W in 3 minutes, similar to a validated chemical method.

Eradication of a Mature Methicillin-Resistant Staphylococcus aureus (MRSA) Biofilm From Acrylic Surfaces

Methicillin-resistant Staphylococcus aureus (MRSA) can grow as structured biofilm in different surfaces, including oral mucosa and denture surfaces. Such biofilms can be released into the oral fluids and aspirated, causing systemic infections such as aspiration pneumonia. This study evaluated the efficacy of two disinfectant solutions and microwave irradiation in disinfecting acrylic specimens contaminated with MRSA biofilm. Thirty-six acrylic specimens were made, sterilized and contaminated with MRSA (107 cfu/mL). After incubation (37 °C/48 h), the specimens were divided into 4 groups: not disinfected (positive control); soaking in 1% sodium hypochlorite for 10 min; soaking in 2% chlorhexidine gluconate for 10 min; and irradiating by microwave for 3 min at 650 W. The viability of cells was evaluated by XTT reduction method. All specimens from the positive control group showed biofilm formation after 48 h incubation. The mean absorbance value of the control specimens was 1.58 (OD at 492 nm). No evidence of biofilm formation was observed on specimens after the disinfection methods. Disinfection by soaking in 1% sodium hypochlorite and 2% chlorhexidine gluconate and irradiating by microwaves resulted in 100% reduction of MRSA biofilm metabolism. The use of chemical solutions and microwave irradiation was shown to be effective for eradicating mature MRSA biofilms on acrylic resin specimens.

Susceptibility profile of a Brazilian yeast stock collection of Candida species isolated from subjects with Candida-associated denture stomatitis with or without diabetes

OBJECTIVE

This study investigated the susceptibility of 198 clinical isolates of Candida species against caspofungin, amphotericin B, itraconazole, and fluconazole.

STUDY DESIGN

Suspensions of the microorganisms were spread on Roswell Park Memorial Institute (RPMI) agar plates. Etest strips were placed on the plates, and the minimal inhibitory concentration (MIC) was read after incubation (48 h at 37 °C). Data were analyzed by a factorial analysis of variance and a 2 × 2 post hoc test (α = .05).

RESULTS

C glabrata showed the highest MIC values (P < .001) against caspofungin, itraconazole, and fluconazole. For amphotericin B, the MIC values of C tropicalis and C glabrata (P = .0521) were higher than those of C albicans (P < .001). Itraconazole was the least effective antifungal; 93.3% of the C glabrata isolates, 3.3% of the C albicans, and 1.3% of the C tropicalis were resistant. All microorganisms were susceptible to caspofungin and amphotericin B.

CONCLUSIONS

Caspofungin and amphotericin B should be recommended as an effective alternative for the management of oral Candida infections when treatment with topical or other systemic drugs has definitely failed.

Comparison of denture microwave disinfection and conventional antifungal therapy in the treatment of denture stomatitis: a randomized clinical study

OBJECTIVE

The aim of this study was to compare the effectiveness of denture microwave disinfection and antifungal therapy on treatment of denture stomatitis.

STUDY DESIGN

Sixty denture wearers with denture stomatitis (3 groups; n = 20 each), were treated with nystatin or denture microwave disinfection (1 or 3 times/wk) for 14 days. Mycologic samples from palates and dentures were quantified and identified with the use of Chromagar, and clinical photographs of palates were taken. Microbiologic and clinical data were analyzed with the use of a series of statistical tests (α = .05).

RESULTS

Both treatments similarly reduced clinical signs of denture stomatitis and growth on palates and dentures at days 14 and 30 (P > .05). At sequential appointments, the predominant species (P < .01) isolated was C. albicans (range 98%-53%), followed by C. glabrata (range 22%-12%) and C. tropicalis (range 25%-7%).

CONCLUSIONS

Microwave disinfection, at once per week for 2 treatments, was as effective as topical antifungal therapy for treating denture stomatitis.

Effect of microwave disinfection on compressive and tensile strengths of dental stones

BACKGROUND AND AIMS

Although microwave irradiation has been used for disinfection of dental stone casts, there are concerns regarding mechanical damage to casts during the process. The aim of this study was to evaluate the effect of microwave irradiation on the compressive strength (CS) and diametral tensile strength (DTS) of stone casts.

MATERIALS AND METHODS

In this in vitro study, 80 cylindrical type III and IV stone models (20 × 40 mm) were prepared and divided into 8 groups of 10. The DTS and CS of the specimens were measured by a mechanical testing machine at a crosshead speed of 0.5 cm/min after 7 times of frequent wetting, irradiating at an energy level of 600 W for 3 minutes and cooling. Data were analyzed by Student's t-test.

RESULTS

Microwave irradiation significantly increased DTS of type III and IV to 5.23 ± 0.64 and 8.17 ± 0.94, respectively (P < 0.01).

CONCLUSION

According to the results, microwave disinfection increases DTS of type III and IV stone casts without any effects on their CS.

Evidence-based guidelines for the care and maintenance of complete dentures: a publication of the American College of Prosthodontists

The current rates of edentulism have been estimated to be between 7% and 69% of the adult population internationally. In the United States, while the incidence of edentulism continues to decline, rapid population growth coupled with current economic conditions suggest that edentulism and conventional denture use will continue at current or higher numbers. Unfortunately, evidence-based guidelines for the care and maintenance of removable complete denture prostheses do not exist. In 2009, the American College of Prosthodontists (ACP) formed a task force to establish evidence-based guidelines for the care and maintenance of complete dentures. The task force comprised members of the ACP, the Academy of General Dentistry, American Dental Association (ADA) Council on Scientific Affairs, the American Dental Hygienists' Association, the National Association of Dental Laboratories, and representatives from GlaxoSmithKline Consumer Healthcare. The review process included the assessment of over 300 abstracts and selection of over 100 articles meeting inclusion criteria of this review. The task force reviewed synopses of the literature and formulated 15 evidence-based guidelines for denture care and maintenance. These guidelines were reviewed by clinical experts from the participating organizations and were published in February 2011 issue of The Journal of the American Dental Association for widespread distribution to the dental community. These guidelines reflect the views of the task force.

A conventional microwave oven for denture cleaning: a critical review

INTRODUCTION

Denture cleaning should be quick and easy to perform, especially in long-term care facilities. The lack of proper oral hygiene can put older adults at higher risk from opportunistic oral infections, particularly fungal. As an alternative to regular brushing, the use of a microwave oven has been suggested for cleaning and disinfecting dentures.

OBJECTIVES

To synthesise and discuss the advantages and disadvantages of the use of a conventional microwave oven for cleaning and disinfecting complete dentures.

METHODS

A brief literature search focused on papers dealing with microwave therapy for denture cleaning through PubMed Central, Cochrane Database of Systematic Reviews, Google Scholar, Ovid MEDLINE(R) In-Process, and Scifinder Scholar.

RESULTS

One hundred and sixty-seven manuscripts published in English with full text were found, and 28 were accepted and discussed in the light of the advantages and disadvantages of the use of conventional microwave oven for cleaning and disinfecting complete dentures.

CONCLUSIONS

There was no standardisation for microwave use for denture cleaning. Manual cleaning still seemed to be the optimal method for controlling fungal infection and denture stomatitis. However, such a daily routine appeared to be underused, particularly in long-term care facilities.