Effectiveness of a combination denture-cleaning method versus a mechanical method: comparison of denture cleanliness, patient satisfaction, and oral health-related quality of life

Efficacy of ultrasonic home-care denture cleaning versus conventional denture cleaning: A randomised crossover clinical trial

OBJECTIVE

To compare the efficacy of test (ultrasonic cleaner combined with immersion in denture cleanser solution) and control (immersion in denture cleanser solution followed by conventional brushing) denture cleaning interventions in enhancing denture cleanliness, reducing denture stomatitis, and improving patient satisfaction.

METHODS

A prospective, single-blind, block-randomised, two-period crossover, superiority-controlled clinical trial was conducted of a 3-month intervention. The study design included a pre-intervention period (2 weeks), intervention period one (3 months), washout period (2 weeks), and intervention period two (3 months). A total of 56 community-dwelling elders were block-randomized into either sequence Test/Control or sequence Control/Test. The intervention, period, and carryover effects for the changes in the cleanliness of extensive partial and complete acrylic dentures, denture stomatitis, and changes in patient satisfaction were estimated using Generalized Estimating Equations models.

RESULTS

Percentage plaque area coverage, patient satisfaction, and denture stomatitis were significantly improved for both intervention and control arms after 3 months (P < 0.05). The intervention arm was found to significantly improve denture cleanliness (P < 0.001) and patient satisfaction (P = 0.002) more than the control arm. Denture-wearing habits and denture age were also significantly associated with the changes in denture plaque coverage (P < 0.05). However, the effect of the test intervention on denture stomatitis was not significantly different compared to the control arm (P = 0.284).

CONCLUSION

This study revealed that the test intervention group was significantly more effective than the control group in improving denture cleanliness and patient satisfaction among community-dwelling elders. This test intervention is recommended for maintaining optimum denture hygiene among older adults.

CLINICAL SIGNIFICANCE

Removable dentures can harbor opportunistic pathogens, emphasizing the need for effective denture hygiene intervention using ultrasonic cleaner combined with immersion in denture cleanser solution to eliminate denture biofilm in community-dwelling elders.

Scientific evidence on the efficacy of effervescent tablets for cleaning removable prostheses. A systematic review and meta-analysis

STATEMENT OF PROBLEM

Scientific evidence to determine the optimal method of cleaning and disinfecting removable prostheses is lacking.

PURPOSE

The purpose of this systematic review and meta-analysis was to evaluate the effectiveness of effervescent tablets in the cleaning and sanitizing of removable prostheses compared with other chemical and physical methods by assessing the reduction of biofilm, microbial levels, and material stability.

MATERIAL AND METHODS

A systematic literature search and meta-analysis was conducted in August 2021 in the MEDLINE/PubMed, Cochrane, Embase, Scopus, and Web of Science databases. Randomized and nonrandomized controlled clinical trials published in English were included without publication year limits. A total of 23 studies were included in the systematic review and 6 in the meta-analysis, which had been registered in the international prospective register of systematic reviews (PROSPERO) database (CRD42021274019). The Cochrane Collaboration tool was used to assess the risk of bias of randomized clinical trials. The physiotherapy evidence database (PEDro) scale was used to analyze the internal validity of clinical trials by assessing the quality of the data obtained. The studies included in the meta-analysis were combined by using a random-effects model with the inverse variance method. Publication bias was analyzed by using the Duvall and Tweedie trim-and-fill method.

RESULTS

With regard to biofilm reduction, the standardized mean difference estimated with the 4 studies combined in the meta-analysis was P=.012: mean difference=-1.92; 95% confidence interval=-3.45 to -0.38, indicating a "large" effect of the combination of brushing and effervescent tablet versus brushing alone. To estimate the reduction in the total bacteria levels in the 3 combined studies, a "large" effect size was obtained for the combination of brushing and using an effervescent tablet versus brushing alone, P<.001: mean difference=-4.43; 95% confidence interval=-8.29 to -0.55. Finally, when the 3 studies were combined to assess the reduction of Candida or fungal infection, a "moderate" effect size was obtained for the combination of brushing combined with the use of an effervescent tablet, P<.001: mean difference=-0.78; 95% confidence interval=-1.19 to -0.37.

CONCLUSIONS

The combination of brushing and the use of effervescent tablets versus brushing alone had a significantly higher effect on reducing biofilm and bacterial counts and a moderate effect on reducing Candida. Regarding color and dimensional stability, few studies were found, with the results depending on the concentration of the product and the immersion time of the device.

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.

Denture Plaque Biofilm Visual Assessment Methods: A Systematic Review

Denture plaque, a biofilm that develops on denture surfaces, could contribute to many oral and systemic afflictions. Hence, a quantitative assessment of denture plaque is important to evaluate the denture hygiene of denture wearers, particularly to prevent plaque biofilm-associated diseases. The aim of this systematic review, therefore, was to review and summarize the visual denture hygiene assessment methods using denture plaque indices and with planimetries published in the literature. English language studies published up to March 2022 in four electronic databases, PubMed, Medline, Embase, and Cochrane Library, were searched, followed by a manual search of Google Scholar by two assessors. The review followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) whenever possible. Details of the visual assessment methods, including the types of denture assessed, its materials and its surfaces, as well as the use of a disclosing agent, were the main outcomes. Of 492 screened studies, 74 were included per the inclusion and exclusion criteria. Of these, 60 studies utilized various denture plaque indices while 18 used planimetries. 43 out of 60 studies with indices and 17 out of 18 studies with planimetries used disclosing agents for visual evaluation of plaque. A total of 21 indices were described in the included studies, of which seven graded a divided denture surface, while the remainder graded entire denture surface. Of the 18 planimetric assessments, one study quantified squares of the disclosed plaques on denture images, 16 studies quantified such pixels with computer programs, and a single study quantified points, pixels, and contour of plaque areas. In summary, denture plaque indices appear to be popular in denture plaque assessment due to their simplicity. Computerized planimetric assessment, though more time-consuming, provides a more accurate assessment of plaque load as it is less prone to subjectivity and assessor errors.

Relation between the risk factors for the severity of denture stomatitis and quality of life of complete edentulous individuals: a cross-sectional study

OBJECTIVE

To assess the association between risk factors for developing denture stomatitis (DS) and oral health-related quality of life (OHRQoL) in complete denture wearers.

METHODOLOGY

Participants of both sexes, wearing complete dentures, were classified using the modified Newton classification for the absence or the severity of DS and allocated to groups Normal or zero, IA, IB, II, and III. Lifestyle, oral and denture history, and medication use were assessed using specific questionnaires; clinical parameters such as anatomical characteristics of support were evaluated with the Kapur classification; salivary flow (SF) was calculated by the volume of unstimulated saliva per minute; and microbial load was determined by counting colony forming units (CFU) of target microorganisms present in the biofilm collected from dentures and palate. OHIP-EDENT assessed the OHRQoL. Kendall's tau_b and Spearman tests were applied with a significance level of 5%.

RESULTS

184 patients (143 female and 41 male) aged 65.5 ± 6.8 years were evaluated. Positive correlations were found for sex (women; p=0.013, r=0.16), individuals who started to consume alcoholic beverages as a young adult (18-27 years) (p=0.008, r=0.22), CFU of Candida spp. (p<0.001, r=0.27 denture; p<0.001, r=0.31 palate); Candida albicans (p=0.004, r=0.22 denture; p=0.003, r=0.25 palate), and Candida glabrata (p=0.004, r=0.22 denture; p=0.001, r=0.27 palate). Moreover, negative correlations with DS were found for CFU of Staphylococcus spp. (p=0.004, r=-0.20 palate) and enterobacteria (p=0.002, r=-0.24 palate), as well as a negative correlation between SF (p=0.009, r=-0.193) and DS. The CFU of Staphylococcus spp. and enterobacteria on the palate significantly correlated with OHRQoL.

CONCLUSION

Being female, consuming alcoholic beverages as a young adult, CFU of Candida spp., Candida albicans, Candida glabrata, and salivary flow may be the most significant risk factors for DS. The microbial load of Staphylococcus spp. and enterobacteria seems to influence the quality of life for complete denture wearers.

Effects of two novel denture cleansers on multispecies microbial biofilms, stain removal and the denture surface: an in vitro study

BACKGROUND

The continuously increasing demand for removable denture appliances and the importance of adequate denture cleaning have led to the development of various denture cleansing products. The aim of this study was to evaluate the efficacy of two novel denture cleansing agents (GE and TM) and three commonly available cleansers (0.5% sodium hypochlorite; NaClO, 0.12% chlorhexidine gluconate; CHX, and Polident®; POL) on multispecies microbial biofilm formation, stain removal and physical properties of dentures.

METHODS

The antimicrobial activities of denture cleansing agents were determined against major oral opportunistic pathogens including Streptococcus mutans, Staphylococcus aureus, Escherichia coli and Candida albicans, using time-kill assays. Multispecies microbial biofilms grown on acrylic resins for 72 h were generated to determine the antibiofilm effects of cleansing agents by confocal laser scanning microscopy (CLSM). Evaluations of the tea and coffee stain removal properties and the alterations in the physical properties of dentures were also performed. The toxicity of cleanser residues released from denture acrylics to fibroblast cells was investigated using MTT assay.

RESULTS

All denture cleansing agents tested could effectively kill oral bacteria and Candida albicans. Furthermore, after immersion for more than 3 h, the cleansers Polident®, GE and TM could efficiently penetrate and inhibit multispecies denture biofilms with effects similar to 10 min of immersion in 0.5% NaClO. However, immersion in 0.12% CHX for 20 min showed less antibiofilm activity. The NaClO solution had the highest efficacy for removing stains from the artificial teeth. Conversely, the CHX solution enhanced tea and coffee staining, and the teeth immersed in this solution showed clinically unacceptable colour changes (ΔE > 5.5). However, the colour differences of teeth stained and immersed in POL, GE and TM cleansers were in the clinically acceptable range. There was no significant difference among the POL, GE and TM cleansers in terms of stain removal efficacy. The cleansers GE and TM did not alter the surface roughness and colour of the materials, moreover the residues of both cleansers did not exhibit cytotoxicity.

CONCLUSION

Two novel denture cleansing agents containing natural products, GE and TM exhibited effective antimicrobial activity, antibiofilm and stain removal capabilities without toxicity or disturbance of the physical properties of acrylics.

Agreement in quantification of removable prosthesis plaque area coverage using a semi-automated planimetric assessment method

OBJECTIVES

To determine the agreement of removable dental prosthesis cleanliness as assessed by a semi-automated planimetric method between images captured by a digital single-lens reflex camera (DSLR) and smartphone.

METHODS

A total of 97 participants with removable prostheses were recruited for the quantification of the prosthesis plaque area coverage. The colour images of stained prosthesis plaque were obtained using both a DSLR camera and a smartphone. The prosthesis plaque area coverage was analysed in two ways: (i) prosthesis cleanliness index (PCI) and (ii) percentage plaque area coverage (PPC). The PPC (continuous data) was converted to the PCI (categorical data) to provide prevalence ordinal scales and the agreements in PCI ratings were determined using weighted Kappa statistics. Agreement of PPC scores was determined through assessing directional, standardised directional, and absolute differences and correlation analyses.

RESULTS

Weighted Kappa values of agreement between PCI categories were excellent (> 0.80) for all comparisons. The mean PPC was 24.79 % as determined by DSLR and 25.37 % as determined by smartphone. There was no statistically significant difference in the means of PPC between the DSLR and smartphone (P = 0.149). The standardised directional difference was 0.15 ('small'). The mean absolute difference was 2.77. The interclass correlation coefficient was 0.98 ('excellent').

CONCLUSIONS

This method showed almost perfect agreements and allowed for threshold-based plaque segmentation on the removable prostheses. There was substantial agreement between DSLR and smartphone assessment of prosthesis plaque area coverage as determined by a semi-automated planimetric assessment.

CLINICAL SIGNIFICANCE

This semi-automated planimetric assessment method has implications for monitoring removable prosthesis hygiene initiatives by offering a valid, reliable, and quantitative method of assessment with potential use in managed care and community settings.

Could Helium Plasma Treatment be a Novel Approach to Prevent the Biofilm Formation of Candida albicans?

There is no definitive method to prevent Candida albicans (C. albicans) biofilm formation on polymethyl methacrylate (PMMA) surfaces. The objective of this study was to evaluate the effect of Helium plasma treatment (before the application of removable dentures to the patient) to prevent or reduce C. albicans ATCC 10,231 the anti-adherent activity, viability, and biofilm formation on PMMA surfaces. One hundred disc-shaped PMMA samples (2 mm × 10 mm) were prepared. The samples were randomly divided into 5 surface groups and treated with different concentrations of Helium plasma: G I: Control group (untreated), G II: 80% Helium plasma-treated group, G III: 85% Helium plasma-treated group, G IV: 90% Helium plasma-treated group, G V: 100% Helium plasma-treated group. C. albicans viability and biofilm formations were evaluated using 2 methods: MTT (3-(4,5-dimethyl thiazolyl-2)-2, 5-diphenyltetrazolium bromide) assays and Crystal Violet (CV) staining. The surface morphology and C. albicans biofilm images were observed with scanning electron microscopy. The Helium plasma-treated PMMA groups (G II, G III, G IV, G V) observed a significant reduction in C. albicans cell viability and biofilm formation compared with the control group. Treating PMMA surfaces with different concentrations of Helium plasma prevents C. albicans viability and biofilm formation. This study suggests that Helium plasma treatment might be an effective strategy in modifying PMMA surfaces to prevent denture stomatitis formation.

Effect of Particle Sizes and Contents of Surface Pre-Reacted Glass Ionomer Filler on Mechanical Properties of Auto-Polymerizing Resin

Herein, the mechanical properties of an auto-polymerizing resin incorporated with a surface pre-reacted glass ionomer (S-PRG) filler were evaluated. For this, S-PRG fillers with particle sizes of 1 μm (S-PRG-1) and 3 μm (S-PRG-3) were mixed at 10, 20, 30, and 40 wt% to prepare experimental resin powders. The powders and a liquid (powder/liquid ratio = 1.0 g/0.5 mL) were kneaded and filled into a silicone mold to obtain rectangular specimens. The flexural strength and modulus (n = 12) were recorded via a three-point bending test. The flexural strengths of S-PRG-1 at 10 wt% (62.14 MPa) and S-PRG-3 at 10 and 20 wt% (68.68 and 62.70 MPa, respectively) were adequate (>60 MPa). The flexural modulus of the S-PRG-3-containing specimen was significantly higher than that of the S-PRG-1-containing specimen. Scanning electron microscopy observations of the specimen fracture surfaces after bending revealed that the S-PRG fillers were tightly embedded and scattered in the resin matrix. The Vickers hardness increased with an increasing filler content and size. The Vickers hardness of S-PRG-3 (14.86–15.48 HV) was higher than that of S-PRG-1 (13.48–14.97 HV). Thus, the particle size and content of the S-PRG filler affect the mechanical properties of the experimental auto-polymerizing resin.

Effects of disinfection with a vinegar-hydrogen peroxide mixture on the surface composition and topography of a cobalt-chromium alloy

STATEMENT OF PROBLEM

Choosing the best disinfection agent for removable partial dentures may be challenging since most commercially available disinfection solutions alter the properties of the metal framework.

PURPOSE

The purpose of this in vitro study was to analyze the changes in the surface topography and elemental composition of a cobalt-chromium (Co-Cr) alloy when immersed in a vinegar-hydrogen peroxide mixture.

MATERIAL AND METHODS

Disk-shaped specimens (N=50) were fabricated with Co-Cr alloy and randomly distributed into 5 groups (N=10) according to the immersion solutions: distilled water (control) (W); 0.5% sodium hypochlorite (H); 3% hydrogen peroxide and water in a 1:1 ratio (HP); vinegar and water in a 1:1 ratio (V); and vinegar and 3% hydrogen peroxide mixture in a 1:1 ratio (VHP). The immersions simulated 90 uses of 10 minutes each. The surface topography and the elemental composition were analyzed with scanning electron microscopy and energy-dispersive spectroscopy, before (T0) and after (T1) the immersions. The 2-way ANOVA for repeated measures was used for statistical comparisons (α=.05).

RESULTS

The tested mixture (VHP) did not change the metal surface topography or increase the oxygen proportion, indicating that no corrosion occurred. Similarly, groups W, HP, and V had no topographic changes and nonsignificant statistical differences at T1 for elemental composition (P>.05). However, the specimens immersed in sodium hypochlorite (H) showed staining, surface irregularity, composition change, with an appearance of 22.56% more oxygen, 41% less chromium, and 28.77% less cobalt at T1 (P<.05).

CONCLUSIONS

The immersion of Co-Cr alloy in a vinegar-hydrogen peroxide mixture did not change the surface structure of the metal.

Properties and characteristics of foam denture cleaners as denture adhesive removers

The need for denture adhesives is increasing worldwide, but few denture-care products target denture adhesive users. Foam denture cleaners have been recently marketed to assist brush denture cleaning, but there is a lack of objective evaluation. In this study, we compared the detergency of denture adhesives using six commercial foam-denture cleaners. For removing the adhesives, most of the tested cleaners were effective in immersion experiments, and three cleaners were more effective in the denture cleaning experiment compared to control water. However, only one could effectively remove the slime that is derived from the adhesive and detergency of artificial dirt. The surface roughnesses of the denture base and the relining material revealed that prolonged immersion in some cleaners could be affected. The results suggest that different commercial foam denture cleaners have different detergency levels, and that some cleaners may affect the properties of denture materials upon long-term use.

Bacterial Disinfection of Polymethyl Methacrylate (PMMA) Resin Polymer Using Low Level Microwave Irradiation and Denture Cleaning Agent

The aim was to evaluate the disinfection of E. coli, S. aureus and S. mutans cultured on Polymethyl Methacrylate (PMMA) resin polymer using microwave disinfection and sodium perborate (DC). Biofilms of E. coli, S. aureus and S. mutans were cultured on the PMMA denture base for 24, 36, 48 and 96 h. Specimens were subjected to three disinfection protocols, including microwave disinfection in distilled water (MW-DW), sodium perborate (denture cleaning tablet) with distilled water (DC-DW) and a combination of MW-DC-DW for 1 to 5 min. Colony-forming units among the study groups were analyzed using Kruskal–Wallis and Mann–Whitney tests. For E. coli and S. aureus cultured on PMMA, the MW-DC-DW group displayed complete disinfection at 2 min of exposure. However, for both bacteria, the MW-DW disinfection group showed zero CFU at 3 min. DC disinfection for E. coli and S. aureus displayed zero CFU at 5 min of exposure (p ≤ 0.05). For S. mutans, MW-DC-DW and MW-DW displayed zero CFU count at 1 min and 2 min, respectively. In DC-treated samples, CFU were significantly zero at 4 min when compared with the control at each growth time. A combination of MW irradiation with DC (sodium perborate) showed higher disinfection percentage of bacterial species on PMMA polymer denture bases compared to MW and DC alone. PMMA disinfection using DC displayed a lower antimicrobial disinfection percentage than the combined use of MW and DC as well as MW alone at 1 min or 2 min disinfection for E. coli, S. aureus and S. mutans.

Effect of Denture Hygiene Protocols on Patient Satisfaction, Oral Health-Related Quality Of Life, and Salivary Parameters: A Randomized Clinical Trial

PURPOSE

This randomized controlled trial compared four denture hygiene protocols in terms of patient satisfaction, oral health-related quality of life (OHRQoL), and salivary parameters in complete denture wearers with denture stomatitis.

MATERIAL AND METHODS

For this randomized, double-blind controlled clinical trial, 108 participants were assigned to soak their dentures in one of the following solutions: (1) 0.25% sodium hypochlorite (positive control), (2) 0.15% Triclosan, (3) denture disinfecting tablets, or (4) denture disinfecting tablets plus palatine mucosa brushing solution. The outcomes of patient satisfaction, OHRQoL, and salivary parameters (salivary flow rate and pH) were measured at baseline and after 10 days. Results were compared by Kruskal-Wallis, between-group by the Dunn test, and Wilcoxon tests between times (α = 0.05).

RESULTS

After the hygiene protocols, and when compared with baseline, the overall patient satisfaction, maxillary denture satisfaction, maxillary denture comfort, and maxillary denture retention were ameliorated. A significant improvement was noted in OHRQoL in 3 of 4 domains evaluated (orofacial pain and discomfort, masticatory discomfort and disability, and psychological disability and discomfort). The salivary flow rate (unstimulated and stimulated); and pH were not significantly affected at the times evaluated.

CONCLUSIONS

Complete denture wearers may feel more satisfied with their complete dentures when treated for denture stomatitis. The tested treatments lead to similar improvement in terms of patient satisfaction and OHRQoL. This article is protected by copyright. All rights reserved.

Development of a United Kingdom-centric cost-effectiveness model for denture cleaning strategies

STATEMENT OF PROBLEM

Denture stomatitis is a prevalent condition in denture wearers. Economic evaluations of health care can help stakeholders, including patients, make better decisions about treatments for a given condition. Economic models to assess the costs and benefits of different options for managing denture stomatitis are lacking.

PURPOSE

The purpose of this study was to explore the feasibility of developing a cost-effectiveness model to assess denture cleaning strategies aimed at preventing denture stomatitis from a denture-wearer perspective in the United Kingdom.

MATERIAL AND METHODS

A model was developed to identify and estimate the costs and effects associated with 3 denture cleaning strategies. These were low care (LC)-cleaning by brushing and soaking overnight in water; medium care (MC)-brushing with toothpaste and soaking overnight in water; and optimum care (OC)-brushing and soaking overnight in water and antimicrobial denture cleanser. Costs, outcome measures (denture stomatitis-free days), and probabilities (incidence of stomatitis, unscheduled dentist visits, prescription charges, self-medication) associated with each strategy were defined. A sensitivity analysis was used to identify key drivers and test the robustness of the model.

RESULTS

The model showed that the total costs for 2015 ranged from £1.07 (LC) to £18.42 (OC). Costs associated with LC were derived from unscheduled dentist visits and use of medication and/or prescription charges. Incremental costs per denture stomatitis-free day were £0.64 (MC) and £1.81 (OC) compared with LC. A sensitivity analysis showed that varying either or both key parameters (baseline incidence of denture stomatitis and relative effectiveness of MC and OC strategies) had a substantial effect. Incremental cost-effectiveness ratios ranged from £4.11 to £7.39 (worst-case scenario) and from £0.21 to £0.61 (best-case scenario).

CONCLUSIONS

A model was developed to assess the relative cost-effectiveness of different denture cleaning strategies to help improve denture hygiene. An important finding of the study was the lack of evidence on the relative effectiveness of different cleaning strategies, meaning that several assumptions had to be incorporated into the model. The model output would therefore likely be considerably improved and more robust if these evidence gaps were filled.

Low Concentrations of Chlorhexidine Inhibit the Formation and Structural Integrity of Enzyme-Treated Multispecies Oral Biofilms

The self-produced matrix of biofilms, consisting of extracellular polymeric substances, plays an important role in biofilm adhesion to surfaces and the structural integrity of biofilms. In dentistry, biofilms cause multiple diseases such as caries, periodontitis, and pulpitis. Disruption of these biofilms adhering to dental hard tissues may pose a major challenge since biofilms show higher tolerance to antimicrobials and antibiotics than planktonic cells. In this study, the effect of low concentrations of chlorhexidine (CHX) on enzyme-treated multispecies oral biofilm was investigated in an in vitro model. Six-species biofilms were enzymatically treated by anaerobic growth in a medium containing DNase I and proteinase K. Biofilms were exposed to a low concentration of CHX at defined time points. After 64h, biofilms were either harvested and quantified by cultural analyses or stained for confocal laser scanning microscopy (CLSM) analyses using either Live/Dead kit or different fluorescent dyes. A mixture of YoPro1 and SYTOX^™ Green, Fluorescent Brightener 28 (Calcofluor), and SYPRO^™ Ruby Protein Gel Stain was used to stain total DNA, exopolysaccharides, and extracellular proteins, respectively. Extracellular DNA (eDNA) was visualized via an indirect immunofluorescence assay (Mouse anti-DNA IgG, Goat anti-Mouse IgG, Streptavidin-Cy3). Overall, the total colony-forming units significantly decreased after combined treatment with a low concentration of CHX and enzymes compared to the group treated with CHX alone (p<0.001). These findings also apply to five species individually (Streptococcus mutans, Streptococcus oralis, Actinomyces oris, Veillonella dispar, and Candida albicans) occurring in the biofilms, with Fusobacterium nucleatum being the only exception. Furthermore, CLSM images showed less dense biofilms and a reduction in cell numbers after combined treatment compared to the group without enzymes. The combination of enzymes capable of disturbing the matrix integrity with antimicrobial agents thus appears to be a promising approach for biofilm disruption and killing.

Characterization and evaluation of a novel silver nanoparticles-loaded polymethyl methacrylate denture base: In vitro and in vivo animal study

The aim of this study was to optimize the preparation method of polymethyl methacrylate (PMMA) denture base loaded with nano silver (NAg), to more effectively and safely impart sustainable antibacterial functions. NAg solution was synthetized and mixed with acrylic acid and methyl methyacrylate (MMA) monomer in order to prepare a new type of NAg solution (NS)/polymer methyl methacrylate denture base specimens (NS/PMMA). The surface morphology, mechanical strength, antimicrobial activity, anti-aging performance, cytotoxicity and biocompatibility of NS/PMMA denture base were evaluated in comparison with specimens fabricated using traditional NAg adding methods and NAg-free denture base. The aesthetic characteristics and mechanical strength of NS/PMMA denture base met the clinical application requirements. Meanwhile, NS/PMMA denture base showed better antibacterial activity, anti-aging properties, no cytotoxicity and displayed exceptional biocompatibility. NS/PMMA denture base thus has great potential for clinical application.

Oral Candidiasis and COVID-19 in Users of Removable Dentures: Is Special Oral Care Needed?

Elderly patients with systemic disorders and immunocompromised patients seem to have a higher risk of developing morbidity from COVID-19. Candida albicans (C. albicans) is a potentially dangerous pathogen for these patients, especially for denture wearers with prosthetic stomatitis who require mechanical ventilation. C. albicans infection, the main candidiasis infection associated with denture wear, can complicate COVID-19 and increase the associated morbidity and mortality. Therefore, early diagnosis of C. albicans infection in COVID-19 patients is important to establish more effective antifungal treatment methods and prophylaxis strategies. Hospitalized COVID-19 patients should undergo an oral examination to assess their oral health, and those with poor oral health should receive the appropriate care and monitoring.

Effect of a vinegar-hydrogen peroxide mixture on the surface properties of a cobalt-chromium alloy: A possible disinfectant for removable partial dentures

STATEMENT OF PROBLEM

A vinegar-hydrogen peroxide mixture has been reported to be effective in eliminating Candida albicans and Staphylococcus aureus from acrylic resin, and its action has been reported to be comparable with that of sodium hypochlorite or peracetic acid. However, the effects of this mixture on cobalt-chromium alloys remain unknown.

PURPOSE

The purpose of this in vitro study was to evaluate the surface roughness, Knoop microhardness, surface free energy, and wettability of a cobalt-chromium alloy when exposed to a vinegar-hydrogen peroxide mixture.

MATERIAL AND METHODS

Fifty specimens of cobalt-chromium alloy were fabricated and immersed for 900 minutes, simulating 3 months of a daily 10-minute immersion in the following chemical agents (n=10): distilled water (W); 0.5% sodium hypochlorite (H); 3% hydrogen peroxide and water dilution in 1:1 ratio (HP); white-wine vinegar and water dilution in 1:1 ratio (V); and vinegar and hydrogen peroxide mixture in 1:1 ratio (VHP). Surface roughness, Knoop microhardness, surface free energy, and wettability were measured with single blinding before and after immersions. Data were statistically analyzed by using 2-way repeated measures ANOVA (α=.05).

RESULTS

The vinegar-hydrogen peroxide mixture did not affect the surface roughness or Knoop microhardness. However, 0.5% sodium hypochlorite significantly increased the roughness and decreased microhardness. Surface free energy and wettability increased after immersions, regardless of the types of solution.

CONCLUSIONS

Immersion in a vinegar-hydrogen peroxide mixture did not affect the surface characteristics of a cobalt-chromium alloy.

Applications of bioluminescence in biotechnology and beyond

Bioluminescent probes have hugely benefited from the input of synthetic chemistry and protein engineering. Here we review the latest applications of these probes in biotechnology and beyond, with an eye on current limitations and future directions.

Effect of toothbrush/dentifrice abrasion on weight variation, surface roughness, surface morphology and hardness of conventional and CAD/CAM denture base materials

We evaluated the effect of toothbrush/dentifrice brushing on the weight variation and surface properties of different denture bases. Four denture base materials (conventional heat cure, high impact, CAD/CAM, and polyamide resins) were subjected to toothbrushing abrasion (50,000 strokes). The weight value, surface roughness, and topography of each group were determined before and after toothbrushing. The hardness was measured by the Vickers hardness test. Data were analyzed using ANOVA and Bonferroni tests. After toothbrushing, the weight of the polyamide resin had significantly increased; significant weight losses were observed for conventional heat cure and high impact resins, but none for the CAD/CAM resin. The surface roughness of each group increased significantly owing to the wear caused by toothbrushing. The weight variation and surface roughness were not affected by the hardness. Our results suggested that denture base materials deteriorate after brushing with toothpaste, in which the polyamide resin exhibited lower levels of abrasion.

Surface Characterization, Antimicrobial Activity, and Biocompatibility of Autopolymerizing Acrylic Resins Coated with Reynoutria elliptica Extract

We conducted surface characterization to assess the biocompatibility and investigate the antimicrobial activity against oral pathogens in autopolymerizing acrylic resins, coated with light-curable coating resin, containing various concentrations of Reynoutria elliptica extract (0, 200, 400, and 600 µg/mL). The R. elliptica extract powder was prepared using a freeze-drying technique. Further, a goniometer and microhardness tester were used to determine the water contact angle, and Vickers hardness, respectively; color measurements were performed on the uncoated and coated acrylic resin disks. The polyphenol content of the extracts from the coated acrylic resin disk was analyzed using UV-VIS spectroscopy. The antimicrobial activity of the coated acrylic resin disk against Streptococcus mutans and Candida albicans was observed for 24 and 48 h by measuring the optical density using spectrophotometry. In addition, biocompatibility was confirmed by testing the cell viability according to ISO 10993-5. The water contact angle, Vickers hardness, and color change values of the coated acrylic resin disks were not significantly different from the control. Polyphenol was detected in all experimental groups, with no significant differences between the experimental groups. The experimental groups exhibited significant antimicrobial activity against S. mutans and C. albicans compared to the control group, after 48 h of incubation. The cell viability between the control and experimental groups was not significantly different. The proposed coating resin containing R. elliptica extract is applicable on dental acrylic resins, due to their antimicrobial properties and excellent biocompatibility, with no deterioration of surface characteristics.

Effects of Denture Cleansers on the Flexural Strength of PMMA Denture Base Resin Modified with ZrO2 Nanoparticles

PURPOSE

The additions of zirconium oxide nanoparticles (nano-ZrO₂ ) to denture base materials have produced nanocomposites with satisfactory properties, although there is a lack of research investigating the effects of denture cleansers on these materials. This study aimed to evaluate the effect of denture cleansers on the flexural strength of denture base materials modified with nano-ZrO₂ .

MATERIALS AND METHODS

A total of 270 specimens were fabricated from pure and nano-ZrO₂ reinforced acrylic resins at 2.5% and 5%, resulting in 3 main groups. The groups were further divided into subgroups (n = 10) according to immersion solution (distilled water, Corega, sodium hypochlorite, and Renew) and immersion duration. Flexural strength was measured at baseline (T₀ ) in distilled water and after 180 and 365 days of immersion (T₁ and T₂ ) in denture cleansers. Data were collected and analyzed using repeated measure ANOVA and Bonferroni post hoc tests (α = 0.05).

RESULTS

The flexural strength of the nano-ZrO₂ modified denture base material decreased significantly after immersion in different denture cleansers at different immersion durations in comparison to baseline (T₀ ) (p < 0.001). Sodium hypochlorite showed the highest reduction in flexural strength followed by Corega, while Renew cleansing solution resulted in the least change.

CONCLUSION

Denture cleansers can significantly affect the flexural strength of nano-ZrO₂ modified denture base materials and thus should be used cautiously.

Antifungal effect of tea extracts on Candida albicans

Determining whether tea extracts are effective in removing Candida albicans (C. albicans) from dentures is of interest. This study aimed to investigate the antifungal effect of tea extracts on C. albicans. One green tea (Anji white tea, AGW) and 2 oolong teas (Tie Guan Yin, TGY; Da Hong Pao, DHP) of different concentrations were tested. C. albicans suspensions were inoculated on the plates and the numbers of colony-forming units (CFU) in the culture medium were used to screen for the optimum tea extracts. Polymethyl methacrylate (PMMA) specimens that contained C. albicans biofilms were then treated with the tea extracts and the numbers of CFU were counted. The antifungal activities of the tea extracts were not significantly correlated with their catechin concentrations. Although AGW at 10.0 mg/mL and DHP at 2.5 mg/mL significantly inhibited C. albicans in the culture medium, the extracts failed to exert inhibitory effects against C. albicans biofilms on the PMMA surfaces.

The McGill Denture Satisfaction Questionnaire revisited: Exploratory factor analysis of a binational sample

OBJECTIVES

To examine the McGill Denture Satisfaction Questionnaire (MDSQ) in terms of dimensionality, item reduction and construct validity in a binational sample of complete denture wearers.

MATERIALS AND METHODS

We conducted secondary analyses of baseline data from two studies on implant-retained overdentures: a quasi-experimental study in the United States (n = 145) and a randomised trial in Brazil (n = 120). All participants wore upper/lower dentures and responded at baseline to the MDSQ items concerning their original mandibular dentures. A putative model of the MDSQ items resulted in two question subsets: (a) overall satisfaction, retention/stability, aesthetics, cleaning, speech and comfort, plus general chewing ability; (b) mastication of specific foods. Analyses focused on the internal consistency of each subset and possible item reduction, using Cronbach's alpha (Cα), inter-item correlation and exploratory factor analysis (EFA).

RESULTS

The 1st subset showed high inter-item correlation for most question combinations and no redundancy (r ≤ .8). An item on cleaning had low correlation, but its removal does not increase internal consistency (Cα ≥ .83). Results were similar for both studies, with EFA showing a single significant factor (namely "overall satisfaction, lower denture") able to explain nearly 54% of the variance. The 2nd subset also shows strong internal consistency (Cα ≥ .95) and inter-item correlation, with a single factor representing 65% of the variation.

CONCLUSIONS

This study discloses the reliability and construct validity of the MDSQ for patient-centred evaluation of complete dental prostheses in the edentulous mandible. Findings also support the use of both "overall satisfaction" and "masticatory ability" as summary scores, for improved outcome assessment.

Study on oral hygiene by nanobubbles from high-density nozzle

An experiment was performed on oral bacteria removal using the design variables, which included the three-segment rotor speed of the testing device and three types of stainless steel meshes (with different layers). The overall hygienic results showed an effect of up to 95% bacteria removal, and some combinations had 100% hygienic effect. The study proposed that the use of nanobubble generated by a high-density stainless-steel mesh-manufactured nozzle removes dental bacteria. In addition, the device could also be used for auxiliary oral hygiene to decrease the frequency of future medical visits due to periodontal diseases or to enable the device to assist patients with severe periodontal disease more conveniently for oral hygiene.

Effect of mechanical and chemical cleaning on surface roughness of silicone soft relining material

PURPOSE

This study aims to investigate the effect of mechanical and chemical cleaning on the surface roughness of silicone soft relining materials.

METHODS

We selected silicone soft relining materials with the highest (Soft) and lowest (Supersoft) Shore A hardness. In the abrasion test, specimens were cleaned 50,000 times using a kitchen sponge (Sponge), a soft (Soft brush) or hard (Hard brush) denture brush, or stored in water (No cleaning). In the immersion test, specimens were immersed in either water (Water), neutral peroxide denture cleanser (Neutral), alkaline peroxide denture cleanser (Alkaline), or hypochlorite denture cleanser (Hypochlorite) for 1440 h. Surface roughness of the arithmetic mean height of the surface (Sa) and maximum height (Sz) were measured before and after the tests. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests.

RESULTS

In the abrasion test, significant differences were observed for Sa and Sz with Soft relining materials, but not for No cleaning and Sponge. In the immersion test, significant differences were observed for Sa and Sz with Soft relining materials, but not between Water and Neutral or Water and Alkaline. Significant differences were observed with Supersoft, except between Water and Neutral or Water and Alkaline for Sa and between Water and Neutral for Sz.

CONCLUSIONS

Mechanical cleaning using a sponge did not increase the surface roughness of the material with a high Shore A hardness. Furthermore, neutral peroxide denture cleanser did not increase the roughness of materials with high and low Shore A hardness.