| [Background and Objective]Disinfection of impressions, gypum cast and denture metal has been one of the main focuses for cross-infection control in dental hospital. Dental impressions and casts are possibly contaminated with microorganisms from Oral cavity of patients; during the procedure of taking impressions and casting. Simple rinsing of impressions can only remove approximately 90% of the microorganisms. The accomplished dentures should be disinfected before use. In addition, in order to meet the requirement of keeping their dimensional accuracy and surface quality, impressions cast and denturecan't be disinfected with many classical disinfection methods such as microwave, gluteraldehyde, autoclave, etc.Electrolyzed oxidizing water(EOW) has be used recently as a strong disinfectant which was invented by Japanese. Its disinfection mechanism: EOW has a pH ofapproximately 2.5, and oxidation-reduction potential (ORP) of 1150mV, and a chlorine concentration ranging from 40 to 90 ppm.Its disinfection capability is due to its low pH and high ORP, and relative concentrations of aqueous molecular chlorine, chlorine, hypochlorous acid (HOCl), and hypochlorite ion (OCl~-), which can change the environment and the membrane potential of microorganisms. Therefore, it is a safe, efficient disinfectant for less environmental impact. However,immersion in aqueous disinfectant is inevitably to change the dimensional accuracy of hydrocolloid impressions. Therefore, it can't be directly used as disinfectant for dental impressions.The purpose of present study is to find how to use EOW as a disinfectant for dental impressions and metal. We try to nebulize electrolyzed oxidizing water and spray it onto the impressions and metal in order that the injure of impressions,gypsum and metal will be reduced to the lowest incidence and we can make full use of the disinfection ability of EOW.[Materials and methods]The experiment was constituted of three parts:1. Observation of disinfection efficacy of ultrasonically nebulized electrolyzed oxidizing water(UNEOW). We selected Staphylococcus aureus,hemolyticus Streptococcus,Bacillus subtilis var. niger as indicators which were subjected to different disinfection procedures: control (0 min), disinfected with ultrasonically nebulized electrolyzed oxidizing water(UNEOW)for 15min, 30min, and 45min. We compared the killing rate between control group andexperiment groups to investigate and evaluate its bactericidal efficacy.2. The effect of corrosion on denture metal of UNEOW. Pure titanium was polished and subjected into different groups. After disinfection, samples were washed with demineralized water for three times and dried in oven overnight. The surface images of samples were examined with SEM after gold-sputtering.3. The influence of UNEOW on dimensional accuracy of impression .The dimensional changes of samples were measured and calculated by using caliper of high accurate. The data was changed into percentage deviation and compared among different groups. Results were analyzed with one-way analysis of variance (ANOVA). Significant differences between treatments were evaluated using SPSS 11.5 statistical package and established at a significance level of P=0.05.[Resultes]1. Compared to control group, the killing rate of UNEOW in groups of 15min, 30min, 45min respectively showed as follow: Staphylococcus aureus 92.15%, 100%, 100%; hemolyticus Streptococcus 94.2%, 100%, 100%; Bacillus subtilis var. niger 87.77%, 97.55%, 99.99%.2. The images on titanium showed clear polished strips without apparent corrosion dent. There was no apparent corrosion effect of UNEOW on pure titanium.3. There were no significant differences in dimensional accuracy of alginate and silica rubber impression between control group and UNEOW treated groups ofdifferent time point.[Conclusions]Through above research, we achieved following conclusions: Following conclusion could be obtained by this research:1. UNEOW has no significant effect on alginate impressions and dental mental of titanium in dimensional accuracy and surface quality in 45min.2. UNEOW can effectively reduce and kill the microorganisms between 30-45min.3. UNEOW can be used as a novel disinfection procedure for cross-infection control of dental hospital. |
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