1. INTRODUCTION:

Dental unit waterlines (DUWLs) called of this name because a dental unit is furnished with a system of thin plastic tube delivering water to the different hand pieces, the water may circulate in an open system where its source is a municipal water supply or in a closed system where it is taken from a container belonging to a unit.Szymanska,Wirthlinetal^1,2 The contamination of DUWLs is an emerging concern in dentistry since the proportion of elderly and immune- compromised patients seeking dental care is increasing, bacteria exist in nature almost exclusively as biofilm and are associated with up to 65% of human bacterial infection so the dental examples of biofilms include: on teeth, as sub gingival and supragingival plaque and on the lumen wall of dental unit water lines.Sprattetal^lWalkeraetal.

Barbot, etalColemanetal³^,4,5,6 Aerosols and droplets produced by dental instruments connected to DUWLs during dental care may contain microorganisms that can be opportunistic pathogens for patients and dentists, microbial proliferation inside DUWLs inevitable and is principally associated with biofilm formation, maximum biofilms are heterogeneous with regard to species and morphology and are embedded in a slime layer of extracellular polymeric substances, the composition of this matrix is not fully known but fundamentally comprises polysaccharides, proteins, water, lipids, RNA and DNA also biofilm development formation a universal strategy used by microbial cells to optimize the probility of survival and proliferation. Bennettetal Shepherdetal, Panagakosetal^7,8,9 Direct sources of DUWLs bacterial contamination are municipal water piped into dental unit and suck-back of patient’s saliva into the line due to lack of preventive valves or an indirect source of contamination forming within the waterlines also bacterial contaminants can also originate from DUWLs where it can exit in the form of an aerosol spray, these aerosols are capable of spreading contaminants throughout the dental surgery attempts to determine the contaminants in aerosols have focused on the bacterial contaminantsAl Maghlouthetal^,. Rautemaaetal, Smith, etal^10,11,12.There are many physical methods that can improve themicrobiological quality of DUWLs output water, the using ofdisinfectant is the most efficacious by ensuring decontamination.The efficacy of disinfection depends on the number of microorganisms present on items to be disinfected and biocidal action of the disinfectant or disinfection processScarlett,Rutala, and Weber,.^13,14Alcohol is intermediate level disinfectants refers to two water-soluble chemicals: ethyl alcohol and isopropyl alcohol, its rapidly bactericidal rather than bacteriostatic against vegetative forms of bacteria (Gr+ and Gr -), it is not effective against bacterial spores and have limited effectiveness against non-enveloped viruses, their cidal activity drops sharply when diluted below 50% concentration and the optimum bactericidal concentration is in the range of 60-90% solutions in water (volume /volume),the antimicrobial activity of C₂H₆O can be attributed to their ability to denature proteins also higher concentrations are less effective as the action of denaturing proteins is inhibited without the presence of waterGamage,Martínez,^15,16Hydrogen peroxide is high level disinfectants can be used to disinfect environmental surfaces and germicidal effectiveness, and potential uses for stabilized hydrogen peroxide in the hospital setting. Stabilized C₂H₂ are effective against a broad range of pathogens including both enveloped and nonenveloped viruses, vegetative bacteria, fungi and bacterial sporesRutala,. and Weber, Samahaetall^17,18.

2. MATERIAL AND METHODS:

2.1. Dental Units

This study involved one hundred and twenty samples of water from 5 dental chairs, 5 ml of water sample was collected into sterile plane tube, water sample was collected from four different sites: water reservoir (bottle), air -water syringe, turbine, tube of turbine. These water samples were taken from each part of each dental chair in three times (before treatment by disinfectants, after treatment by disinfectants and after using the patient's dental chair).The bacteriological study including cultural properties, microscopic examination and biochemical tests was done according to.Macfaddin¹⁹Statistical analysis used in this study includes calculation of mean ± SD and T- test.

2.2. Sterilization of DUWLs:

The method of cleaning and sterilizing the dental chairs as follows: Clean all parts of the external dental chair and the inner cavity of the water reservoir (bottle) with water and liquid detergents and sodium hypochlorite (NaCIO) also mix the detergent and NaCIO with water pumping across the network water chair dental to turbine and air -water syringe for 5 minutes then is wash in water fully, thereafter the disinfectants are used. Alcohol was used with a concentration of 96% and a quantity for each bottle and pumped it continuously for 5 minutes during the water network of the dental chairs to the turbine and the air-water syringe after this step, the remaining alcohol was discharged from the bottle and washed in sterile distilled water according toDon,²⁰ also the bottle is filled with this sterilized water again and continue pumping this water in DUWLs network until it is sure to remove all alcohol from the internal walls of the network and Hydrogen Peroxide the same steps alcohol in sterilization dental chairs but 1% of it was added to a liter of sterilized waterWalkeretal.²¹

3. RESULTS:

Study concerning DUWLs have primarily focused on bacterial colonization. Table (1) shows the distribution of microbial contamination values where (2887) clinical sample consisting of (846) sample from bottle, (753) sample from turbine, (720) sample from air-water syringe and (568) sample from tube on turbine which subjected for culturing on bacterial culture media that showed the bottle contain the highest contamination from the other parts of DUWLs

The study included collection of water sample which collected from four different sites: water reservoir, air -water syringe, turbine and tube of turbine, these water samples were taken from each part of each dental chair in three times (before treatment by disinfectants, after treatment by disinfectants and after using the patient's dental chair). Results obtained from C₂H₆O in table (2) and table (3) show non-significant difference was observed in sterilization were from compared before treatment in C₂H₆O with after treatment and after used by patient.

Table (2): Show the compares between the control and after treatment in DUWLs sterilized by C2H6O

Side of collection	Before treatment Mean±SD	After treatment Mean±SD	P.value
Bottle	15.80 ± 2.61	15.20 ± 3.19	0.6508
Turbine	14.40 ± 2.75	13.60 ± 3.59	0.5828
Air-water syringe	13.60 ± 3.62	13.20 ± 3.91	0.8151
Tube of turbine	10.60 ± 4.71	10.40 ± 4.69	0.9252

Table (3): Show the comparison between the control and after used by patients DUWLssterilized by C2H6O

Side of collection	Before treatment Mean±SD	After use by patient Mean±SD	P.value
Bottle	15.80 ± 2.61	16.60 ± 2.54	0.4962
Turbine	14.40 ± 2.75	15.10 ± 2.80	0.5797
Air-water syringe	13.60 ± 3.62	14.60 ± 3.50	0.5379
Tube of turbine	10.60 ± 4.71	11.20 ± 4.91	0.4835

While observed in table (4) and table (5) significant difference appear clearly when comparing the bacterial contamination before treatment with H₂O₂, after treatment and after used by patient.Immediately seen afterusingH₂O₂ the output water from the disinfected dental chair units showed a high reduction in bacterial density.

Table (4):Shows the comparison between the control and after treatment in DUWLs sterilized by H2O2

Side of collection	Before treatment Mean±SD	After treatment Mean±SD	P.value
Bottle	17.30 ± 2.75	8.30 ± 3.30	0.0000
Turbine	15.90 ± 3.21	6.90 ± 3.21	0.0000
Air-water syringe	15.10 ± 2.84	6.10 ± 2.99	0.0000
Tube of turbine	12.70 ± 3.68	4.50 ± 2.27	0.0000

Table (5): Shows the comparison between the control and used by patients inDUWLs sterilized by C2H6O

Side of collection	Before treatment Mean±SD	After use by patient Mean±SD	P.value
Bottle	17.30 ± 2.75	11.40 ± 3.30	0.0004
Turbine	15.90 ± 3.21	9.40 ± 3.65	0.0005
Air-water syringe	15.10 ± 2.84	9.40 ± 2.71	0.0002
Tube of turbine	12.70 ± 3.68	7.40 ± 2.50	0.0004

4. DISCUSSION:

The present study shows that the contamination of water in dental unit reservoirs with aerobic and facultative anaerobic bacteria is commonplace and the most numerous water bacteria colonizing in dental unit reservoirs are Gram-negative rods, Gram-positive cocci these results were parallel withBennettetal^,Donlan ,Harrel, andMolinar^22,23,24 that elucidate those bacteria characteristic of physiological flora of the human skin and mucosa and present in the environment of a dental surgery, probably entered the unit water reservoir during work.Our study shows thatdetermination of concentration and composition of microflora in the water unit is the basis for evaluation of DUWLs microbial contamination , Łuczaketal,²⁵they were stated that total isolated from gram positive were the bacteria of Streptococcusspp., Staphylococcus spp. and Lactobacillusspp., which form the physiological flora of the oral cavity, when it present in DUWLs probably because of sucking back fluids from patients’ oral cavities, and subsequent multiplication in the unit reservoirs, this may be a potential source of cross infections. Previous study done by.Szymańska,²⁶ showed high levels of microbial load, mainly Gram negative aerobic mesophilic heterotrophic bacterial species are in DUWLs, although most of them are harmless in aquatic bacteria, some of them are opportunistic pathogens such as Pseudomonasspp, Legionellaspp, Klebsiellaspp. andE. coli, also who was found that high contamination of water by gram negative bacteria due to when this bacteria after having passed through DUWLs flows from hand pieces during treatment and forms aerosol and splatter.Regarding the level of bacterial contamination of water, found at the examined dental units during restorative treatment sessions was high and the results of the present study are not fully comparable between C₂H₆O and H₂O₂. Alcohol has little effect on bacteria when compared with hydrogen peroxide. These results similar withAteş.; and Turgay²⁷, whom stated that alcohol has non inhibitory effect against the bacteria, while H₂O₂ was more effective compared to alcohol on reducing bacterial contamination. Also in agreement with .Pareeketal²⁸ they were showed high concentration of water borne organisms causes multiple public health problems. Contamination of water lines could be inhibited by using some disinfectants. removal of these substances from water delivered into patient’s mouth may reduce the potential for post treatment inflammatory.

5. CONCLUSION:

We concluded that dental unit water lines can transmit infection to and from the patient,whereas highest contamination rate of dental unit chair was found in the bottle. H₂O₂ disinfectant was more effective than C₂H₆O.

6. ACKNOWLEDGEMENTS:

We are extremely thankful to the Collage of Dentistry, Babylon University for providing all the needed facilities, which are essential for successful completion of thiswork.

7. REFERENCES:

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Received on 04.11.2017 Modified on 07.12.2017

Research J. Pharm. and Tech 2018; 11(2):604-607.

DOI: 10.5958/0974-360X.2018.00111.7

Collection Sites	Number of contaminated samples
Collection Sites	Bottle	Turbine	Air-water syringe	Tube of turbine	Total of samples
Before treat	331	303	287	233	1154
After treat	235	205	193	149	782
After use by patient	280	245	240	186	951
Total	846	753	720	568	2887