| Objective: To evaluate the capacity of five denture cleansers which are commonly used at home on reducing the Candida albicans biofilms activity and biomass. To provide references for choosing the operative denture cleanser.Methods: C. albicans strain SC5314 biofilms were formed on polystyrene, flat-bottomed, 96-well microtiter plates for 24 h. To confirm that the mature biofilms have been formed under the conditions of this experiment, crystal violet staining method was used. The biofilms were immersed in Polident, Victoria-C, Protefix, 0.2% chlorhexidine gluconate and Y-Kelin denture cleansers. Positive (immersed in sterile distilled water) and negative (no biofilm) controls were included. Each denture cleanser was further divided into 2 subgroups, either immersed for the time indicated by the manufacturers or for 12 h (overnight). The activity of the biofilms was then quantified using a formazan salt-based XTT reduction assay, and the biomass using a crystal violet assay.Results: In terms of reducing the biofilms activity, after the recommended time of immersion, reduction rate of the five denture cleansers were (%):( 80.2±3.6), (23.4±3.3), (81.3±1.0), (65.5±1.8), (66.6±3.5). Polident and Protefix were the highest (P <0.001), while Victoria-C was the lowest (P <0.001). After overnight immersion, except that the reduction rate of 0.2% chlorhexidine gluconate lowered, others increased (P <0.05), higher than 80%, especially Polident (88.8±4.4) %. In terms of reducing the biofilms biomass, after the recommended time of immersion, reduction rate of the five denture cleansers were (%):(38.2±10.2), (8.7±6.2), (22.0±2.6), (34.2±3.9), (24.7±8.0). Polident and 0.2% chlorhexidine gluconate were the highest (P <0.05), while Victoria-C was the lowest (P <0.01). After overnight immersion, the reduction rate of former three denture cleansers increased (P <0.05), especially Polident (56.8±4.8) %.Conclusion: Among the five denture cleansers, Polident exhibited the best effect on reducing the C. albicans biofilms activity and biomass. However, residual biofilm retention with a few living cells was still observed. Denture cleansers can improve their effects after overnight immersion except 0.2% chlorhexidine gluconate.PartⅡInfluence of denture cleansers on physical and mechanical properties of heat-curing denture base resinObjective: To evaluate the color stability, surface roughness and flexural strength of heat-curing denture base resin after its immersion in five denture cleansers which are commonly used at home, simulating a 180-day use.Methods: Thirty rectangular samples (64 mm×10.0 mm×3.3 mm) were prepared from heat-curing denture base resin according to ISO 1567-1999.They were immersed in Polident, Victoria-C, Protefix, 0.2% chlorhexidine gluconate, Y-Kelin denture cleansers and distilled water. The immersion time was indicated by the manufacturers. The procedure of immersion was repeated 180 times over a period of 6 days, simulating 180 days of cleansing by the patient. Color changes (ΔE) were determined by a colorimeter. After immersion, a surface profiler was used to measure the roughness. The flexural strength was measured using a 3-point bending test in a universal testing machine. Results: The color changes were significantly higher for the 0.2% chlorhexidine gluconate and Y-Kelin denture cleansers than the negative control group (P were 0.001, 0.005). TheΔE values quantified by the NBS (National Bureau of Standards) were classified as Slight in all groups (0.5-1.5). When comparing the surface roughness and flexural strength, no statistical significance was found among the different immersion procedures (P were 0.512, 0.969).Conclusion: It was concluded that immersion in 0.2% chlorhexidine gluconate and Y-Kelin denture cleansers influenced the color stability of heat-curing denture base resin, simulating a 180-day use, but were clinically acceptable. The two denture cleansers had no influence on surface roughness and flexural strength. Polident, Victoria-C, Protefix did not influence the color stability, surface roughness and flexural strength.
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