Effect Of Various Methods For Cleaning Candida Biofilm Formed On Three Prosthesis Materials In Vitro

Objective: To evaluate the effect of different denture hygiene methods againstCandida biofilm formed on three oral commonly used prosthesis materials.Methods: Prepare40specimens (1.3*20*10mm) for each of the followingmaterials: Co-Cr alloy, Ni-Cr alloy and heat-polymerized acrylic resin. All specimenshave been made with one rough surface for simulate the intaglio surfaces of a completedenture; and one smooth surface. For Co-Cr alloy and Ni-Cr alloy, all specimens havebeen polished by sandblasting, coarse grinding, fine grinding and overallelectropolishing. For heat-polymerized acrylic resin, all specimens have been polishedby wet/dry sandpapers (up to1000-grit), rubber polishing wheel and cloth polishingwheel. Alloy type of specimens have been sterilized by autoclaving; specimens ofheat-polymerized acrylic resin were using ultraviolet irradiation for disinfection, thenthey have been used for culturing of Candida albicans biofilms. By different cleaningmethods, they are divided into4groups:①Control(stroke-physiological salinesolution);②Mechanical(brushing by toothbrush);③Chemical(medicamentsimmersion);④A combination of chemical and mechanical treatments(brushing withtoothbrush followed by medicaments immersion). By different materials, each groupcan be divided again into3subgroups:①heat-polymerized acrylic resin group;②Ni-Cr alloy group;③Co-Cr alloy group. After the cleaning, the specimens have beenimmersed in liquid medium for residual biofilms re-growth, then estimate by colonyforming unit enumeration. The dates obtained were analyzed with the two-wayANOVA and multiple comparison (α=0.05) by the SPSS17.0.Results: When the samples are diluted to10-2, their bacterial count from high tolow are ordered as: Aa group (8.50±0.43)；Ac group (3.89±0.54)；Ab group (3.87±0.39)；Ba group (2.45±0.19)；Bb group (1.36±0.25)；Bc group (0.53±0.26).The results of Two-way ANOVA shows that factors of materials (p=0.000) and treatmentprocesses (p=0.000) are significantly influence the bacterial count, and those two factorsare interacting with each others (p=0.000). With different treatment processes, materialsand mixed combination, the results are significantly different (P<0.05). Furthermorecomparisons between chemical and combined treatment processes, when the samples atoriginal dilution, their bacterial count from high to low are ordered as: Ca group(3.25±3.61);Da group (2.95±2.57);Cb group (2.80±2.74);Db group (1.95±1.14);Ccgroup (0.15±0.34);Dc group (minimum down to0).The results of Two-way ANOVAshows that factors of materials (p=0.000) is significantly influence the bacterial count,but the treatment processes (p=0.445) has less affect on bacterial count, and those twofactors are not interacting with each others (p=0.867). With different materials, theresults are significantly different (P<0.05).Conclusion: Within the limitations of this in vitro study, the followingconclusions were drawn:1. All three types of treatment processes can result a certain cleaning effect, andthe chemical treatment group and the combined treatment group show the best results.2. After the treatment for Co-Cr alloy, Ni-Cr alloy and heat-polymerized acrylicresin, biofilms on the Co-Cr alloy were the easiest one that can be removed, and theheat-polymerized acrylic resin was the hardest one to be cleaned.