Comparative effects on acrylic resin properties of short- and long-term immersion in alkaline peroxide solution.

PURPOSE: To evaluate the color stability (ΔE), surface roughness (ΔRa), and flexural strength of denture base acrylic resin after short (20 minutes) and long-term (8 hours) immersions simulating a period of 5 years of use. METHODS: 120 disk-shaped (16 mm x 4 mm) and 120 rectangular (65 mm x 10 mm x 3.3 mm) specimens were prepared (Lucitone 550) and distributed into three groups (n=20): distilled water (Control); Corega Tabs (CT) and Polident (Po), for immersions of 20 minutes and 8 hours. ΔE were determined by a colorimeter, ΔRa by a profilometer and the flexural strength by a universal testing machine. Data were evaluated by two-way ANOVA followed by Tukey's test and Bonferroni correction (α= 0.05). RESULTS: Short-term immersions for 20 minutes resulted in significant differences in ΔE, as CT values (1.46 ± 1.41) were higher than Po (0.55 ± 0.25) and Control (0.47 ± 0.21). Specimens immersed for 8 hours showed more extensive alterations overall than the control (ΔE [Po: 7.27 ± 0.53; CT: 5.58 ± 0.49; Control: 1.26 ± 0.23]; 916;Ra [Po: 0.16 ± 0.08; CT: 0.12 ± 0.11; Control: 0.07 ± 0.06]; flexural strength [Po: 42.99 ± 9.34; CT: 63.96 ± 12.98; Control: 64.59 ± 12.87]). The tested alkaline peroxide-based solutions promoted significant alteration on acrylic resin properties after overnight immersion. Therefore, short-term immersions seem to be more suitable for daily denture hygiene. CLINICAL SIGNIFICANCE: Alkaline peroxides were able to alter color stability, surface roughness and flexural strength of acrylic resin after overnight immersions, in a 5-year-simulated period of use.

Effect of toothbrushes and denture brushes on heat-polymerized acrylic resins.

It is important to choose an appropriate brush for denture cleaning to prevent damage to the surface properties of prosthetic devices. The purpose of this study was to evaluate the abrasiveness of toothbrushes and denture brushes on boiled and microwave-processed acrylic resins. Specimens of 4 resin brands were prepared (n = 30). Five brands of brushes (n = 6) were used in a toothbrushing machine, first for 17,800 strokes and then for an additional 35,600 strokes (total of 53,400), at a load of 200 g. An analytical balance and a profilometer were used to assess the weight and surface roughness, respectively, before and after 17,800 and 53,400 strokes. Analysis of variance and Tukey tests were used for data analysis (α = 0.05). Weight loss increased with time, while surface roughness remained the same. There were no statistically significant differences among toothbrushes and denture brushes in the resulting weight loss (17,800 strokes, 1.83 mg; 53,400 strokes, 3.78 mg) or surface roughness (17,800 or 53,400 strokes, 0.14 µm). The weight loss values after 53,400 brush strokes indicated that Clássico (2.28 mg) and VIPI Wave (2.75 mg) presented significantly greater abrasion resistance than Lucitone 550 (3.36 mg) and Onda-Cryl (2.85 mg) (P < 0.05). The type of brush and the polymerization method did not influence resin wear after brushing.

Strategies for Preventing and Treating Oral Mucosal Infections Associated with Removable Dentures: A Scoping Review.

Oral infections occur due to contact between biofilm rich in Candida albicans formed on the inner surface of complete dentures and the mucosa. This study investigated historical advances in the prevention and treatment of oral mucosal infection and identified gaps in the literature. Bibliographic research was conducted, looking at PubMed, Embase, Web of Science, and Scopus, where 935 articles were found. After removing duplicates and excluding articles by reading the title and abstract, 131 articles were selected for full reading and 104 articles were included. Another 38 articles were added from the gray literature. This review followed the PRISMA-ScR guidelines. The historical period described ranges from 1969 to 2023, in which, during the 21st century, in vitro and in vivo studies became more common and, from 2010 to 2023, the number of randomized controlled trials increased. Among the various approaches tested are the incorporation of antimicrobial products into prosthetic materials, the improvement of oral and denture hygiene protocols, the development of synthetic and natural products for the chemical control of microorganisms, and intervention with local or systemic antimicrobial agents. Studies report good results with brushing combined with sodium hypochlorite, and new disinfectant solutions and products incorporated into prosthetic materials are promising.

Effects of Different Forms of Denture Adhesives on Biofilm Formation, Adhesive Strength and Hygiene of Complete Dentures.

PURPOSE: To evaluate the effect of different forms of denture adhesives on the formation of biofilm and on adhesive strength, as well as the effectiveness of hygiene protocols for their removal. MATERIALS AND METHODS: Samples of the heat-cured polymethyl methacrylate denture base resin were made and divided into four groups: control (no adhesive), ultra Corega cream, Corega strip adhesive, and ultra Corega powder (GlaxoSmithKline). Biofilm formation was evaluated by counting colony-forming units and fluorescence microscopy. To evaluate the effectiveness of the hygiene protocols, the samples were divided into five subgroups: brushing with distilled water; brushing with Protex soap; brushing with Colgate toothpaste; immersion in Corega Tabs; and immersion in Corega Tabs followed by brushing with the solution itself. The remaining adhesive was quantified with ImageJ software. The adhesive strength was tested at different time intervals after application. After verifying the data distribution using Shapiro-Wilk test, parametric or nonparametric analysis was applied (α = .05). RESULTS: Candida albicans formed more biofilm in strip (P = .007) and powder (P = .001), Pseudomonas aeruginosa in cream (P < .001) and powder (P < .001), and Staphylococcus aureus in strip (P < .001). All forms of the adhesives promoted higher biofilm formation when compared to control (P = .003). Brushing with Colgate and Protex was most effective for removing the adhesives (P < .05). Independently, Powder had the highest adhesive strength (P < .05). Only Strip showed a change in adhesive strength, with higher values after 3 hours of application (P = .004). CONCLUSION: Daily treatments with mechanical cleaning of the prosthesis are important for removing the adhesives, since the presence of this material can favor biofilm accumulation. The adhesive strength may vary depending on the commercial type, but all forms can be effective in retaining prostheses for a satisfactory period of time.

Evaluation of three indices for biofilm accumulation on complete dentures.

OBJECTIVES: The objective of this study was to evaluate the accuracy and reproducibility of three complete denture biofilm indices (Prosthesis Hygiene Index; Jeganathan et al. Index; Budtz-Jørgensen Index) by means of a computerised comparison method. BACKGROUND: Clinical studies into denture hygiene have employed a large number of biofilm indices among their outcome variables. However, the knowledge about the validity of these indices is still scarce. MATERIALS AND METHODS: Sixty-two complete denture wearers were selected. The internal surfaces of the upper complete dentures were stained (5% erythrosine) and photographed. The slides were projected on paper, and the biofilm indices were applied over the photos by means of a scoring method. For the computerised method, the areas (total and biofilm-covered) were measured by dedicated software (Image Tool). In addition, to compare the results of the computerised method and Prosthetic Hygiene Index, a new scoring scale (including four and five graded) was introduced. For the Jeganathan et al. and Budtz-Jørgensen indices, the original scales were used. Values for each index were compared with the computerised method by the Friedman test. Their reproducibility was measured by means of weighed kappa. Significance for both tests was set at 0.05. RESULTS: The indices tested provided similar mean measures but they tended to overestimate biofilm coverage when compared with the computerised method (p < 0.001). Agreement between the Prosthesis Hygiene Index and the computerised method was not significant, regardless of the scale used. Jeghanathan et al. Index showed weak agreement, and consistent results were found for Budtz-Jorgensen Index (kappa = 0.19 and 0.39 respectively). CONCLUSION: Assessment of accuracy for the biofilm indices showed instrument bias that was similar among the tested methods. Weak inter-instrument reproducibility was found for the indices, except for the Budtz-Jørgensen Index. This should be the method of choice for clinical studies when more sophisticated approaches are not possible.

Use of the DNA Checkerboard hybridization method for detection and quantitation of Candida species in oral microbiota.

The DNA Checkerboard method enables the simultaneous identification of distinct microorganisms in a large number of samples and employs up to 45 whole genomic DNA probes to gram-negative and gram-positive bacterial species present in subgingival biofilms. Collectively, they account for 55%-60% of the bacteria in subgingival biofilms. In this study, we present the DNA Checkerboard hybridization as an alternative method for the detection and quantitation of Candida species in oral cavities. Our results reveal that DNA Checkerboard is sensitive enough and constitutes a powerful and appropriate method for detecting and quantifying Candida species found in the oral cavity.

In vitro and clinical evaluation of specific dentifrices for complete denture hygiene.

OBJECTIVES: To study the physical properties of two experimental dentifrices for complete denture hygiene, their effect on denture biofilm removal and antimicrobial properties by means of a clinical trial. MATERIALS AND METHODS: The experimental dentifrices comprised two compositions. One was based on the addition of 1% chloramine T (D1) and the other on the presence of 0.01% fluorosurfactant (D2). Measurements of density, pH, consistency, rheological features and abrasiveness were conducted. Sixty complete denture wearers were randomly assigned to three groups and were instructed to brush their dentures with a specific toothbrush: (1) Water (control); (2) D1; or (3) D2. Each method was used for 21 days. Denture biofilm was disclosed by a 1% neutral red solution and quantified by means of digital photos taken from the internal surface. Microbiological assessment was conducted to quantify Candida sp. and mutans streptococci. Data were evaluated by one-way anova and Tukey HSD, or Kruskal-Wallis (alpha = 0.05). RESULTS: Both dentifrices decreased biofilm coverage when compared with the control group. D1 was the most efficacious treatment to reduce mutans streptococci, whereas D2 showed an intermediate outcome (ANOVA, p < 0.040). No treatment influenced Candida albicans or non-albicans species (Kruskal-Wallis, p = 0.163 and 0.746, respectively). CONCLUSION: It can be concluded that brushing complete dentures with the experimental dentifrices tested could be effective for the removal of denture biofilm.

Effect of denture cleansers on physical properties of heat-polymerized acrylic resin.

PURPOSE: This study aimed to measure the color change, surface roughness and flexural strength of heat-polymerized acrylic resin after its immersion in denture cleansers, simulating a 180-day use. METHODS: Thirty disk-shaped (15mm x 4mm) and 30 rectangular samples (65mm x 10mm x 3.3mm) were prepared from heat-polymerized acrylic resin and immersed in Corega Tabs, Bony Plus, and distilled water. Color measurements (DeltaE) were determined by a portable colorimeter. A surface analyzer was used to measure the roughness before and after immersion (DeltaRa). The flexural strength (S) was measured using a 3-point bending test. The DeltaE values were submitted to statistical analysis by the Kruskal-Wallis test, followed by Dunn's Multiple Comparisons test. The DeltaRa and S values were submitted to statistical analysis by ANOVA, followed by a Student-Newman-Keuls test (alpha=.05). RESULTS: The color changes were significantly higher for the Corega Tabs than for the control group. The mean DeltaE values quantified by the National Bureau of Standards (NBS) were classified as Trace (0.0-0.5). The Bony Plus group had significantly higher surface roughness than the other groups. Corega Tabs and Bony Plus groups presented lower flexural strength than the control group. CONCLUSIONS: Although the color changes after the immersion in denture cleansers were clinically insignificant, the Corega Tabs group showed higher color differences. The Bony Plus group showed significantly increased surface roughness. Both effervescent tablets Corega Tabs and Bony Plus significantly diminished the flexural strength of the acrylic resin.