الفهرس 
AIM OF THE STUDYOnly 14 pages are availabe for public view
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Abstract
The contamination of dental unit water lines (DUWLs) with microorganisms is documented by a preponderance of scientific evidence. Most of these microorganisms are aquatic bacteria suspended in the incoming water, which colonize the walls of the DUWs and form a biofilm. The initial adhesion of these bacteria is promoted by water stagnation during periods of inactivity of the dental unit, because of the characteristics of the tubes and the presence of minerals such as; calcium carbonate deposited on water‐bearing surfaces. During periods when the unit is in use, small particles of the biofilm may break off because of the water flow and heavily contaminate the water.Different authors have shown that this system is extensively colonized by microorganisms with at least 40 different species including: S. aureus, Pseudomonasspp. andEnterobacteria.
The presence of bacteria within the tubing is conducive to the formation of biofilm that becomes the primary reservoir for continuous contamination of the system. Although data on healthcare-associated infections in dentistry are under-reported in the literature, a small number of case-reports directly linked to contaminate DUWLs are described.
The general objective of present study was to evaluate the efficacy of two different disinfectant agents on the quality of water in dental unit waterlines (DUWLs). The specific objective was to determine the physiochemical and microbiological quality of water from dental units and to evaluate the efficacy of different disinfection protocols with regard to the microbiological quality of water from dental units.
The sampling unit was the DCU. The DCUs were in the dental clinic at the Medical Research Institute, Alexandria University.
Water samples were obtained from; the municipal water lines as well as the DCUs under study. Two DCUs went through a disinfection protocol while one DCU was used as a control. The bacterial load was assessed in all obtained water samples. In addition, the physiochemical characteristics of the water samples were examined.
Two types of disinfectants were used in the present study; 10% hydrogen peroxide with two concentrations (1:100, 1:10) and biosanitizer A with two concentrations (1:100, 1:50). The disinfection protocol was carried out for six successive weeks for each concentration.
• 10% hydrogen peroxide (diluted at 1:100, 1:10) was used in UA for 12 weeks; six weeks for each dilution.
• BiosanitizerA (diluted at 1:100, 1:50) was used in UB for 12 weeks; six weeks for each dilution.
• UC was used as control and with no disinfection regimen during the whole period of the study.
The disinfectants were applied to the water bottle attached to the DCU on the last day of the week after finishing the work of that day. The disinfectants were allowed to remain in situ for the whole weekend.
Water samples were collected from high-speed hand pieces. Generally, 100 ml water samples were collected aseptically in sterile containers with sodium thiosulfate at the beginning of the first day of the week. Another water samples were collected on the last day of the week. All water samples were transferred to the laboratory and examined for THPC as well as E. coli,P. aeruginosa and S. aureus
Before the start of the disinfection protocol, all examined water samples showed THPC exceeding the ADA and CDC guidelines, together with the detection of
P. aeruginosa and S. aureus in all samples taken at baseline. Yet, complete absence of
E. coli was recorded in all tested water samples.
Phase One study took a period of 6 weeks; where hydrogen peroxide 10% was used in UA with a concentration of 1:100.Biosanitizer A was used in UB with a concentration of 1:100. The third dental care unit UC was used as a control with no application of disinfectants.
It was noticed that the water samples collected from UA showed a decreased mean value of THPC, S. aureus and P. aeruginosa than those recorded from the baseline water samples. It decreased from 3.5×106 CFU/ml to 5×103 CFU/ml (p=0.020), 1.6×104 CFU/ml to 0.35×102 CFU/ml (p=0.015) and 1.6×104 CFU/ml to 0.35×102 CFU/ml (p=0.015) respectively.
Whereas in case of UB, the mean count of THPC decreased from 4.6×105 CFU/ml to 0.76×102 CFU/ml (p=0.015), the mean count of S. aureus dropped from 7.6×103 CFU/ml to 0.0 CFU/ml (p=0.005) and finally the mean count of P. aeruginosa was decreased from 7.6×103 CFU/ml to 0.0 CFU/ml (p=0.005).
The results revealed that using biosanitiser A with a concentration of 1:100 was more effective than using 10% hydrogen peroxide with a concentration of 1:100 in reduction of all tested microorganisms.
The disinfection protocol adopted in UA resulted in a decrease in the minimum value of THPC to 2.8x102 CFU/ml in the fourth week and was not detected in the sixth week. On the other hand S. aureusand P. aeruginosa were not detected in the third week.
As for the use of biosanitizerA used in UB it was noticed that the value of THPC decreased to the level that met the ADA and CDC guidelines starting from the second week. In addition, the value of S. aureusand P. aeruginosafailed to be detected starting from week one.
The period of disinfection of Phase Two study was 6 weeks; where hydrogen peroxide 10% was used in UA with a concentration of 1:10biosanitizerA was used in UB with a concentration of 1:50. The third dental care unit UC was used as a control with no application of disinfectants.
Water samples collected from UA,showed a decrease in the mean count of THPC,
S. aureus and P. aeruginosa in the first day of the week than those recorded in the base line. The decrease recorded in THPC wasfrom 3.5x106 CFU/ml to 4x102 CFU/ml (p=0.020), the mean value of S. aureus decreased from 1.7 x104 CFU/ml to 0.5x102 CFU/ml (p=0.015) and in case of P. aeruginosa the decrease was observed to be from 1.7x104 CFU/ml to 0.33x102 CFU/ml (p=0.014). Meanwhile, in UB showed a significant decreased mean count of THPC, S. aureus and P. aeruginosa than those recorded from the baseline water samples. It decreased from 4.6×105 CFU/ml to 0.3×102 CFU/ml (p=0.014), 7.6×103 CFU/mlto 0.00 CFU/ml (p=0.005) and 7.6×103 CFU/ml to 0.00 CFU/ml (p=0.005) respectively.
In the present study four physiochemical parameters were studied (turbidity, pH, total solids and residual chlorine).
Results obtained from the present study revealed that the water samples collected from the DUWLs showed a minimum pH was 6.70 and a maximum of 7.65. The levels of residual chlorine obtained from the two DCUs in the present study ranged from 0.33-0.56 ppm, these results were complying with those obtained in other studies.
The study concluded that a regular disinfection protocol should be adopted to get the quality of water delivered by DUWLs to the standards of drinking water quality.
The present study recommended that the outlet water from the DUWLs should be subject to a disinfection protocol to eliminate microbial contamination and routine monitoring to guarantee an acceptable quality of water used in dental treatment.