The Effect of a Continuous Mechanical Polishing Protocol on Surface Roughness, Biofilm Adhesion, and Color Stability of Acrylic Resin Artificial Teeth.

PURPOSE: Acrylic resin properties are susceptible to change over the duration of use, thereby decreasing prosthesis longevity. To make the material less susceptible to the action of external agents such as stain-causing liquids and cleaning solutions, polishing procedures are recommended. A specific mechanical polishing procedure performed regularly was evaluated regarding the biofilm adhesion, surface roughness (Ra), color stability (ΔE), and mass changes in acrylic resin artificial teeth. MATERIALS AND METHODS: Sixty artificial teeth divided into two groups (n = 30) were immersed in distilled water (WT) and coffee (CF). These groups were then subdivided (n = 10) according to the type of polishing procedure administered: no polishing, biweekly polishing (once every 2 weeks) (pol 1), or monthly polishing (once a month) (pol 2), using aluminum oxide paste and a felt polishing wheel attached to an electric motor at a speed of 3000 rpm. Properties were evaluated at baseline and after 4, 8, 12, and 24 months of simulated immersion. At the end, the adhesion of Candida albicans and Streptococcus mutans multispecies biofilm in all groups was assessed. RESULTS: The CF group showed an increased Ra and weight, and a significantly greater ΔE compared to the WT group. The polishing procedure reduced Ra and minimized the stains caused by coffee, without losing mass, with the biweekly regime more effective than the monthly regime. Also, polishing reduced the adhesion of biofilm in the CF groups, again with the biweekly regime the most effective. CONCLUSIONS: When performed regularly, the mechanical polishing procedure tested reduces the changes in artificial teeth subjected to immersion in coffee, with the biweekly frequency most effective regarding the properties evaluated.

Genomic identification of microbial species adhering to maxillofacial prostheses and susceptibility to different hygiene protocols.

This study investigated the microbial colonization of maxillofacial prostheses and support tissues using the Checkerboard DNA-DNA hybridization method, and the efficacy of 0.12% chlorhexidine gluconate, 10% Ricinus communis solutions, or brushing, on colony forming unit (CFU) reduction in monospecies biofilms (Candida glabrata, Staphylococcus aureus, Streptococcus mutans, Escherichia coli, Enterococcus faecalis, and Pseudomonas aeruginosa) formed on two silicones (MDX 4-4210 and Bio-Skin). Biofilm was harvested from 43 maxillofacial prosthesis wearers for detection of 38 species of microorganisms. The CFU counts of the six above mentioned species were recorded after using the hygiene protocols. All 38 investigated species were identified in prostheses and tissues, with a higher prevalence in the prostheses. 0.12% chlorhexidine gluconate immersion showed the greatest antimicrobial effectiveness, followed by mechanical brushing protocols. MDX 4-4210 silicone produced lower CFU counts than Bio-Skin.

Antimicrobial action and long-term effect of overnight denture cleansers.

PURPOSE: To evaluate two denture cleansers for overnight soaking (0.5% sodium hypochlorite and peroxide alkaline) regarding efficacy against Candida spp. biofilms (randomized clinical trial) and their effects on the physical properties of a denture base acrylic resin simulating a period of 5 years of use (laboratory study). The Candida spp. were identified and their resistance to main antifungal agents was evaluated. METHODS: 32 complete denture wearers were instructed to brush their dentures three times a day and to soak them (≥8 hours) in: control - water (C); alkaline peroxide (AP); or 0.5% sodium hypochlorite (SH). According to a randomized sequence, each solution was used for three alternate periods of 7 days. The antimicrobial action was performed by counting the colony forming units (CFU) of Candida spp. For collection of the biofilm, each upper complete denture was placed in a Petri dish, the internal surface was brushed (Tek brush) with saline solution for 2 minutes and the suspension was transferred to a test tube. After dilutions (10 0 to 10-3), aliquots of 50 µL were seeded inside Petri dishes containing Candida Chromagar. After incubation, the colonies were counted and the values of CFU/mL calculated. Data were transformed in log10 (CFU +1) and analyzed by the Friedman test (α= 0.05) followed by Wilcoxon and Bonferroni tests (α= 0.05). Each of the different species identified perfunctorily has been confirmed through the identification of yeasts kit. The resistance to antifungal agents (amphotericin B, nystatin, flucytosine, econazole, ketoconazole, miconazole and fluconazole) was also evaluated. Adverse effects were estimated on heat-polymerized resin specimens, simulating a 5-year period of overnight use. Acrylic resin specimens were randomly distributed into three groups: C: Control (distilled water); AP: alkaline peroxide; and SH: 0.5% sodium hypochlorite. Color change, surface roughness and flexural strength were evaluated at baseline and after immersion procedures. Data were compared by Kruskall-Wallis followed by Dunn's test (color change and surface roughness) and one-way ANOVA (flexural strength) (α= 0.05). RESULTS: There was a reduction of Candida spp. counts after using both solutions (AP and SH). The Candida spp. most often isolated was C. albicans, followed by the C. glabrata. Only 24.7% of isolate strains were resistant to at least one of the tested antifungals, highlighting azole compounds. Immersion in AP [ 5.73 (5.45-5.91)] caused significantly higher color change, with lower ΔE values for C [1.12 (1.15-1.37) ] followed by SH [3.70 (3.51-3.98) ]. The NBS values were classified as "slight" for C (1.12) group and " considerable" for AP (5.27) and SH (3.40). No solution altered surface roughness significantly. Flexural strength (in MPa) was significantly lower for C (64.59), AP (63.96 ± 12.98) and SH (62.84 ± 8.62) when compared to a group without any immersion (109.12 ± 8.37). CLINICAL SIGNIFICANCE: Both solutions tested presented antimicrobial action against Candida spp. and may be useful for denture biofilm control, but should be used with caution as an overnight immersion solution since they may damage denture bases in the long-term. Candida was most frequently isolated at baseline and after using the products. Only 24.7% of isolate strains were resistant to at least one of the tested antifungals, especially with azole compounds.

Antimicrobial efficacy of complete denture cleansers.

PURPOSE: To evaluate the in vitro antimicrobial efficacy of alkaline peroxides against microbial biofilms on acrylic resin surfaces. METHODS: Denture base acrylic resin (Lucitone 550; n= 360) circular specimens (15 x 3 mm) were obtained from a circular metal matrix and sterilized with microwave irradiation (650 W, 6 minutes). The specimens were then contaminated with suspensions [106 colony-forming units (CFU)/mL] of Candida albicans (Ca), Candida glabrata (Cg), Staphylococcus aureus (Sa), Streptococcus mutans (Sm), Bacillus subtilis (Bs), Enterococcus faecalis (Ef), Escherichia coli (Ec), and Pseudomonas aeruginosa (Pa). After contamination, the specimens were incubated at 37 degrees C for 48 hours and then placed in a stainless steel basket, which was immersed in a beaker with one of the following solutions prepared and used according to the manufacturers' instructions (n= 10 per group): Group PC (positive control), phosphate-buffered saline (PBS) solution; Group MI, NitrAdine, Medical Interporous; Group EF, Efferdent Plus; Group CT, Corega Tabs; and Group NC (negative control; n= 5), no contamination and immersed in PBS. After incubation (37 degrees C, 24 hours), the number of colonies with characteristic morphology was counted, and CFU/mL values were calculated. The data were processed following the transformation into the formula log" (CFU + 1) and statistically analyzed by the Kruskal-Wallis and Dunn's tests (alpha = 0.05). RESULTS: There were significant differences between the groups for the evaluated microorganisms with a significant reduction in the CFU/mL. MI was effective for Ca, Cg, Sa, Sm, Ef, Ec and Pa; EF was effective for Cg, Sm, Ef, Ec and Pa; and CT was effective for Sa, Bs and Ec, when compared with the PC group.