الفهرس 
TitleOnly 14 pages are availabe for public view
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Abstract
The specific structure of dental units favors the presence of biofilm and microbial
contamination of the dental unit waterlines (DUWL) water. The ability of bacteria to
colonize surfaces and to form biofilm in water supply tubes, including DUWL, is a
common phenomenon, which has been well documented, just as with difficulties in biofilm
removal and prevention of its regrowth. Microorganisms from contaminated DUWL are
transmitted with aerosol and splatter, generated by working unit handpieces. Most of the
microorganisms isolated from DUWL are of low pathogenicity. Nevertheless, the public
health significance of many of the microorganisms found in DUWL is unknown.
According to current knowledge, it is not the mere presence of bacteria that is important in
DUWL contamination monitoring, but their number, the presence of potential pathogens
The aim of the present workis to compare the effects of flushing procedures and
treatment with chlorhexidine as two means of disinfection on the bacteriological quality of
dental unit water lines.
A total of 52 water samples were collected over a period of 3 weeks, these samples
included 4 baseline samples that were obtained at the start of the study. All samples were
collected on the morning before the beginning of the working day.
In addition a control water sample directly from the tap water from the participated
dental clinic was processed along with the study samples.
1. The results of the tap water sample denotes that its microbiologic parameter met the
water quality regulation for potable water when tested at 37⁰c (<10 cfu/ml) and at
22⁰(<100 cfu/ml)
2. Initially before application of the two DUWLs decontamination methods (treatment
with 0.12% CHX and flushing for 1min and 2 min), we found that the mean TVC of
the 4 pretreatment samples of the 4 dental units(A,BC&D) on nutrient agar at (22⁰c,
37⁰c) were about 1*104 .
3. After treatment with 0.12 %CHX,Unit A and unit B watersamples showed
statistically significant decrease in their TVC over the 3 weeks study period.TVC
reduced from 1*104 to (0-350 cfu/ml).All the 4 samples showed compliance with the
CDC DUWLs guidelines (≤500 cfu/ml).
4. After application of flushing procedures 1 min and 2 min, Unit C and unit Dwater
samples showed statistically significant decrease in their TVC among the 3 weeks
study period. TVC was reduced from 1*104to 2*103 but this decrease in the microbial
load did not meet the CDC guidelines (≤500cfu/ml. All samples showed no
compliance with the CDC guidelines (≤500cfu/ml).
5. Gram positive microorganisms were isolated from the 4 Pretreatment (baseline)
water samples (A-D). Bacteriologic identification of the isolates reveals
Staphylococcus aureus, Staphylococcus epidermidis, Bacillus, micrococci and
candida spp. Also, Gram negative bacilli was isolated from 3 out of 4 Pretreatment
(baseline) water samples from units (B, C&D). Bacteriologic identification of the
isolates reveals pseudomonas stutzerii (160-100 cfu/ml).
Summary & Conclusion
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6. Treatment of DUWL A&Bwith 0.12% CHX : A significant reduction in the gram positive
microbial count from1x 104 to ≤500cfu/ml and in the count of gram negative organisms as no
gram-ve bacilli was isolated from the 2 DUWLs over the 3 weeks study period.
7. Treatment of DUWL C&D with 1 and 2min flushing procedures respectively, a
significant reduction in the gram positive microbial count.Although there was a
significant reduction. Yet the bacterial count is still above the CDC guidelines (>500
cfu/ml). No gram-vebacilli was isolated from the 2DUWLs over the 3 weeks study
period except at the 3rd week from unit D (100cfu/ml).
8. By comparing the effect of both the 1 min and 2 min flushing procedures on the mean of
TVC of 2 DUWLs(C and D), the results reveals that there was no significant difference
between the use of 1 min and 2 mins’ flushing procedures on the mean value (cfu/ml) of the
12 samples taken over the 3 weeks study period. (p>0.05). The same results were also
observed when the blood and the macconkey agar plates were examined. p= (0.839, 0.317)
9. By comparing the effect of the 2 decontamination methods chlorhexidine and 1 min
flushing procedure used in DUWLs (A+ B&C) on the mean TVC reduction and on
the bacterial growth on both blood and macconkey agar over the 3 weeks study
period , there was a statistical significance difference (p ≤ 0.05) between the effects of
the 2 used methods.
10. By comparing the effect of the 2 decontamination methods chlorhexidine and 2 min
flushing procedure used in DUWLs (A+ B&D) on TVC reduction and on the bacterial
growth on both blood and macconkey agar over the 3 weeks study period, there was a
statistical significance difference (p ≤ 0.05) between the 2 used methods.
11. The four DUWL water samples taken in the extra 4th week showed fluctuation in the TVC
denoting incompliance of the staff with the daily decontaminating procedures protocol.