2Gazi University, Faculty of Dentistry, Department of Oral Microbiology, Ankara, Turkey
3Baskent University, Faculty of Dentistry, Department of Oral and Maxillofacial Surgery, Ankara, Turkey
Keywords: Hydrogen peroxide colloidal-Ag; Dental unit wastewater; Biofilm
The high-speed dental instruments that are used during dental treatments produce bioaerosols composed of particles varying in size. Some particles evaporate forming droplet nuclei < 5μm in diameter that remain airborne for many hours [10]. This DUW contamination poses risks for immune compromised individuals [1]. In addition, chronic endotoxin inhalation represents an occupational respiratory hazard to dental professionals [11]. Furthermore, water line and hand piece anti-retraction valves can transport the pathogens from asymptomatic patients and cause cross-infection [12].
In addition to these concerns the issue of microbiological and chemical compounds in wastewater has become a major problem in terms of both human health and the environment. This situation led to the launch of studies for the examination of compounds in dental unit wastewater. To date, many techniques and antimicrobial agents were used to eliminate biofilm from the inner surface of DUWLs [13-15]. These techniques include the use of waterline flushing, independent water reservoir systems, distilled water, ultraviolet light, ultrasonic, drying of DUWLs, inline micropore filtration and periodic or continuous chemical disinfection [2,18-20].
The present study was investigated the ability of minimize biofilm formation of two different application method of hydrogen peroxide-based disinfectant in waterlines and wastewaters of dental units.
Group 1: For the first group (n = 10) dental units were modified to facilitate the addition of a disinfectant to the water used in the DUWLs by fitting an externally mounted purge system (Dose up, Ultrasan Elektronik Ltd. Şti. Ankara, Turkey). Using this system, the municipal water supply could be bypassed and the system used to add a disinfectant automatically and continuously to the DUWLs throughout patient treatment sessions. For this study continuous application of 5% hydrogen peroxide Colloidal- Ag (5% Huwa-San Dent-6, Roam chemie, Belgium) was preferred and were applied to the DUWLs.
Group 2: For the second treatment group (n = 10) 5% hydrogen peroxide Colloidal-Ag was applied manually to the water bottles of the dental units.
Group 3: 10 of the units served as controls and no disinfectant applied and only distilled water is used in bottles.
The presence of staphylococci was identified by culturing samples on mannitol salt agar for discrimination of S. aureus and they were also investigated by conventional microbiological test method and identified by API Staph system (BioMèrieux, France). The presence of Streptococci w was identified by morphologically and serologically by grouping specifies of them.
The presence of gram negative bacteria w was evaluated by using Citrate, Indole and urea media. Pseudomonadaceae were identified by culturing samples on Cetrimide agar media and using Triple sugar iron media and oxidase test. Besides, colonies which are supposed to be Pseudomonas aeruginosa were underwent biochemical identification test using API 20 NE system (BioMèrieux, France).
The presence of Candida strains were evaluated by culturing them on Sabouraud Dextrose Agar dimorphically and were identified as yeast-like fungi by their morphological properties and by using germ tube assay they were defined as C. albicans and C. non albicans. Legionella spp. was evaluated by culturing the samples on Legionella selective medium.
The mean differences among groups within each measurement time were evaluated by One-Way ANOVA. When the p value from One-Way ANOVA are statistically significant post hoc Tukey HSD test was used to identify which group differ from others. According to the Bonferroni Correction, p < 0.005 was considered statistically significant. The mean differences among measurement times within each group were analyzed by Repeated Measurement of ANOVA, Wilks' Lambda test. According to the Bonferroni Correction, p < 0.01 was considered statistically significant. Logarithmic transformation was done for number of microorganism within each statistical analysis. For all possible multiple comparisons, the Bonferroni Correction was applied for controlling Type I error.
Ten weeks of logarithmic mean of microorganism calculated for the whole groups (Figure 1). There was no significant difference between the treatment groups' DUWLs and had counts of less than 200 CFU/ mL A statistically significant difference in median TVCs reduction was found between the treatment and control groups' DUWLs for all weeks (p < 0.01). However, there was no significant difference between Group 1 and control group's waste waters. Biofilm formation was more evident in the control group's both DUWLs and waste waters.
Biofilms have a big role in certain infectious diseases and importance in a variety of device-related infections so it is important to understand biofilm processes, effective control strategies to resulting improvement in patient management [7]. In a series of trials, treating of DUWLs with sodium hypochlorite,
Sample groups |
Gram positive bacteria |
Gram negative bacteria |
Fungal agents |
|
Group 1 |
Waterlines samples |
Coagulase-Negative Staphylococci [CNS] Streptococci spp.
|
- |
- |
Waste water samples |
Staphylococcus aureus Streptococci spp. Viridans streptococci |
Pseudomonas aeruginosa, Escherichia coli, Klebsiella sp. Enterobacter spp. Citrobacter spp.
|
Candida albicans, Candida non albicans |
|
Group 2 |
Waterlines samples |
Coagulase negative staphylococci [ CNS], Methicillin- Sensitive S. aureus [MSSA]
|
- |
- |
Waste water samples |
Coagulase-Negative Staphylococci [CNS], Methicillin sensitive S. aureus [MSSA], Streptococci spp. Viridans streptococci
|
Pseudomonas aeruginosa, Escherichia coli, Klebsiella spp. Enterobacter spp. |
Candida albicans, Candida non albicans |
In fact, in most countries, no distinction is usually made between the dental unit wastewaters and urban effluent, and this can cause potentially hazardous loads which are generally discharged directly into the public sewage network. Identifying environmental reservoirs of Methicillin-sensitive Staphylococcus aureus (MSSA), as well as Methicillin-resistant Staphylococcus aureus (MRSA) in the community, might be critical for controlling the spread of community–acquired staphylococcal infections [25]. Dental unit waterlines are known as reservoirs since they are frequently contaminated by pathogenic and opportunistic microorganisms and [26], the contamination of dental unit waterlines by MSSA strains is also important as MRSA strains because they are accepted as being a causative agent for the community- acquired infections and recently, the incidence of these types of infection are getting very much higher. In the present study, we have demonstrated MSSA strains in the waste water samples. Attention should be paid to the occurrence of MSSA since it is a probable way of contamination for people who are in contact with reclaimed wastewater. Previous studies investigated the effect of detergents, organic compounds, disinfectants and several metals for the hospital environment [27,28]. However, there scarcity of data on the topic of dental unit wastes waters' microbiological compounds and counts. One of the aims of this study was to investigate the effect of hydrogen peroxide Colloidal-Ag on dental unit waste waters. According to the results of this study; the tested dose of hydrogen peroxide Colloidal-Ag was ineffective to reduce TVC for the dental units' waste waters. There are still areas that require further work in terms of controlling the microbial loading of dental unit waste waters such as engineering systems that can apply more efficient doses of disinfectants for the dental unit wastewater.
2. The system of automatic adjusting is effective as manual application of the material for improving the dental unit waterlines.
3. None of these systems has not proved enough antibacterial effect for dental unit wastewaters that has become a major problem in terms of both human health and the environment.
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