INTRODUCTION:Microorganisms are ubiquitous species which are present as nonpathogenic organisms in the environment. Under the influence of external environmental and host factors, these non pathogenic micro organisms have a tendency to become pathogenic causing infection and other diseases. Hence, in order to prevent the conversion of non pathogens into its pathogenic form, strict sterilization and disinfection protocols should be followed. Sterilization and disinfection are procedures which are carried out in order to kill or inactivate these microbial species, thus preventing contamination, spread of nosocomial infections and cross infection. Sterilization by definition is a process by which an article, surface or a medium is freed of all living microrganism either in their spore or vegetative forms (1). Disinfection is defined as a process of destruction or removal of all pathogenic micro organism for a particular site, it does not kill the microbe but inhabits its growth. (1). In today’s practice, infection control and prevention of cross infection is more emphasized as it can be hazardous to both the dental personnel as well as to patients visiting the dental clinic (2). This is a major concern in cases of immunodeficient patients as they are more prone to infectious diseases due to their poor immune responses (3). In dental clinics, it is mandatory to disinfect the dental unit, instruments used for treatment and other laboratory instruments, and dental materials in order to prevent cross contamination and infection transmission. But how does this microbialtransmission happen? The answer to this question is that transmission can happens through various methods, it can happens from patient to the clinician, from the clinician to the patient, from one patient to another visiting the dental clinic or from the dental office to the surrounding community and environment (4).The usual sources of infection in a dental clinic are blood, saliva, droplet contamination, aerosols, instruments, equipments, and other materials that are used on a daily basis for treatment and other purposes in the working environment (3,5,6). When a clinician performs any treatment, he does contact various surfaces of the dental unit which in turns transmits microbes from the clinician onto these surfaces. These are basically designated as the surface contact areas in a dental clinic and these are the highest source of microbial colonization usually colonized by species such as bacillus, enterococcus, staphylococcus aureusetc. Though the microbes colonized are non pathogens but due to environmental and other changes occurring in the surrounding these pathogens become more virulent and hence causesvarious infectious diseases. When disinfection of these surfaces to prevent microbial colonizationare not done routinely to the required amount, there is an increased risk of infection transmission. The surface contact areas on a dental unit are the handles of the light in the dental chair, the airotor, surfaces of air water syringes, the dental seat provided for the patient to be seated, instrument trays, water lines, suction tips, etc (7). Cross infection is basically the transfer of infectious agents from patient to health care provider or vice versa. The dental clinic has a wide zone of microbial contaminants especially on the surface contact areas, transmitting many infectious diseases, forming a chain of transmission from the patient to the clinician, the assistant, family members, etc. the transmission of microbes can occur through direct contact, indirect contact or inhalation of infectious aerosols (8). Asepsis and disinfection can help reduce the amount of contaminants and can help control infection(9,10,11).Disinfection is the destruction of pathogenic microorganisms using physical or chemical agents. It kills most but not all visible microbes (12). It is a two step process involving initial scrubbing of the surface to be disinfected and cleaning followed by wetting the surface with a disinfectant and allowing it to dry as long as mentioned by the manufacturer (13). The following are the properties of a disinfectant, Broad spectrum of activity, Acts rapidly, non corrosive, Environment friendly, Is free of volatile organic compounds, Nontoxic , High-level disinfection(14,15).Gigasept which contains succindialdehyde and dimethoxytetrahydrofuran are used for disinfection of plastic and rubber materials eg: dental chair (14,15).Disinfection of the dental clinic on an everyday basis or after every procedure is a difficult task,but has to be carried out to ensure prevention of infections as discussed earlier. disinfection on an everyday basis does not provide an aseptic environment throughout the day, and hence disinfection of at least surface contact areas in dental clinics should be done between appointments. We all know that the most erogenous zones in a dental clinic where high microbial load can be detected are the light handles, instrument trays, air-water syringe, and the dental chair itself. Hence regular disinfection should be carried out. A wide variety of chemical agents have been used over the years for disinfection purposes. These generally include alcohols like ethyl alcohol and isopropyl alcohol, aldehydes like formaldehyde and gultaraldehyde, phenols, halogens, gases like ethylene oxide and formaldehyde gas etc. fumigation of the dental clinic should also be done regularly, once in 2 weeks in order to ensure that the aerosol contaminants are eliminated from the surrounding environment, thereby providing an aseptic environment to work. The present study was done to evaluate the microbial count and also determine the predominant microbial species present in order to create awareness as to how important it is to follow a strict disinfection protocols in dental clinics such that spread of infections and degree of contamination can be prevented.This study aims to evaluate the microbial count and the predominant species on air-water syringes in a dental clinic. MATERIALS AND METHODS:The following methodology was followed to carry out this study.1. sample collection2. determination of number of colonies formed3. slide preparation4. gram’s staining and microscopic evaluation5. tabulation and statisticsSample collection:A total of 20 samples were collected from air-water syringes of dental chairs at Saveetha Dental College and hospitals, Saveetha institute of Medical and technical sciences, Chennai. laboratorypreparation of agar plates was done. The samples were then collected from air water syringes during inter appointments (between two patients). Swab tips were used to collect the samples,which were rubbed 2 to 3 times at the site of sample collection i.e. the swab was rubbed on the surface of the air water syringes. The swab was then reinserted into the tube such that there is no contamination from the external environment and the tubes were labeled. This same procedure was followed each time the sample was collected.Microbiological analysis of samples:20 Petri plates of nutrient agar were prepared. The swab tip onto which the sample was collected, were rubbed over the surface of nutrient agar to inoculate the sample. The plates were then incubated for 24hrs in an incubator at 34degree celcius.Data collection:After incubation of the plates for 24 hours, the petri plates were retrived from the incubator and the number of colonies formed in each plate was noted. The colony count was done manually and the values were noted in terms of colony forming units respectively. The form and they type of colonies formed in nutrient agar was also noted.Determination of type of species:A Single colony was up for preparation of smear using platinum loop and was smeared over aclean, grease free slide. Heat fixation was done to ensure that the smear isn’t lost during staining procedure. Hence 20 slides were prepared using bacterial colonies from all 20 pates. Gram staining was the chosen method of staining to study the type of bacteria present. it is a method of differentiating gram positive and gram negative bacteria, also helps to analyse the form andarrangement pattern of the bacteria . gram staining procedure is done in the following way. theheat fixed smear was first subjected to methyl violet for 1 minute, and then washed under running tap water. It was then subjected to Gram’s iodine for 1 minute and then washed under running tap water. For 2-3 seconds, the smear was subjected to acetone and then washed under running tap water. Dilute carbol fuschin was then added for 1 minute and then washed under running tap water. These slides were allowed to dry and then focused under 100X oil immersion microscope to visualize and determine the type of species present in the given sample. The results were tabulated, with the number of colonies formed in each plate. The predominant species was determined by microscopic evaluation of the complete slide and noted.RESULTS:SAMPLECOLONY COUNT (CFU)PREDOMINANT SPECIES114Bacillus25Bacillus31Bacillus430Enterococcus57Enterococcus627Enterococcus79Gram +VE cocci in cluster, Staphylococcus albus89Micrococcus 913Micrococcus 1010Micrococcus 1137Micrococcus 12110Micrococcus 13260Micrococcus 1414Micrococcus1567Micrococcus 16478Micrococcus, Enterococcus1725Micrococcus, Staphylococcus albus1880Staphylococcus albus1950Staphylococcus albus2013Staphylococcus citrusTOTAL COLONY COUNT 1259 AVERAGE62.95 PREDOMINANT SPECIESCOLONY COUNT (CFU)PERCENTAGE(%)bacillus 201.5Enterococcus30324Gram +VE cocci in cluster50.39Micrococcus 77161.2Staphylococcus albus16012.7 1Bacillus2Enterococcus3Gram +ve cocci in clusters4Micrococcus5Staphylococcus albus In the present study, an average of 63 colony units were formed after 24 hr incubation of the sample. On microscopic evaluation, the species detected were micrococcus, enterococcus, staphylococcus albus, gram +ve cocci in clusters and bacillus. Out of these, the most predominant species detected was micrococcus. It accounts for 61.2% of colonies formed. This was followed by the presence of 24% of enterococcus species, 12.5% of staphylococcus albusspecies, 1.5% of bacillus species and 0.8% of gram +ve bacteria in clusters.DISCUSSION:Dental operatory surfaces and equipment can become contaminated with patients’ blood and other oral fluids through contact with dental healthcare personnel’s (DHCP) gloved hands; spray and splash created by dental instruments such as handpieces, air/water syringes, and ultrasonic scalers; and through contact with contaminated instruments placed on various surfaces. Hence disinfection to prevent cross infection should be done routinely (16).The number of viable bacteria detected on each sampling occasion during inter appointmentalvisits range from 10 to 478 colony forming units of bacteria with an average of 62.9 CFU. A total of 1259 colonies were isolated from the surfaces of air water syringes. This is in conjunction to the fact that the samples were collected when the clinic was in use i.e. in between appointments so as to relatively emphasize on the need for disinfection of surface contact areas of the dental clinic due to increased microbial load. The risk of cross infection, infections and transmission of diseases is increased with increased colonization of bacteria, hence it is important to follow routine disinfection protocol in order to prevent disease transmission and also provide holistic dental treatment. in a study conducted by Nihal et.al, an average of 200 bacterial colony units were formed in samples collected from air water syringes (17). An evaluation of the colonies formed after incubation of samples for 24 hrs was done, which showed predominance of non pathogenic organisms. These non pathogens are present as commensal bacteria in the oral cavity and also in the skin, but can become pathogenic under environmental and host immune factors resulting in infectious diseases. These include, micrococcus, bacillus, enterococcus, staphylococcus species. Though these species are not pathogenic it is important to follow disinfection protocol.E.H. Spaulding, a pioneer in healthcare disinfection and sterilization, identified three classifications of disinfectants, based on the product’s ability to kill certain organisms (18). High-level disinfectants are capable of killing all microorganisms, including resistant bacterialspores. High-level disinfectants, such as glutaraldehyde and hydrogen peroxide-based products, are not appropriate for use on environmental surfaces and dental equipment; these products are intended for immersion disinfection or sterilization of heat-sensitive instruments (19).Intermediate-level disinfectants are not necessarily capable of killing spores, but will inactivate Mycobacterium tuberculosis var. bovis, which is considerably more difficult to kill than vegetative bacteria. These intermediate-level disinfectants will also kill fungi and all types of viruses (19).Low-level disinfectants will not reliably inactivate spores, mycobacteria, all fungi, and all viruses (19). Some disinfectants have active ingredients that at one concentration will be categorized as intermediate-level and at a different concentration will be classified as low-level. Careful review of the manufacturer’s label of a product will provide the necessary information to select among the three classifications of disinfectants and the proper dilution and use of the product. DISINFECTION PROCEDURE:Simply applying a disinfectant to a clinical contact surface will not reliably decontaminate the surface. A number of factors influence the effectiveness of the disinfectant and the disinfecting process. The number and location of the microorganisms is significant, because there is a relationship between the total number of organisms and the time needed for complete destruction. Cleaning surfaces before applying disinfectant solution will reduce the total microbial contamination, reducing the amount of time needed for germicides to work. In addition, clumped cells are more difficult to inactivate, and the physical activity of cleaning a surface helps disrupt potential clusters or clumps of debris containing microbes (20).Other factors that can influence the effectiveness of disinfectants include dilution, temperature, pH, relative humidity, and water hardness. Organic debris, such as blood, tissue, or lubricant material, can interfere with the efficacy of disinfectants either by chemical reaction between the material and the germicide or by the organic material’s acting as a physical barrier that protects microorganisms (21).The time needed for disinfectants to kill the organisms listed on the label is provided by the manufacturer, and clinician or assistant performing disinfection procedures should ensure that the surfaces remain wet for the time indicated to ensure complete disinfection. Do not include the time needed to pre clean the surface in the disinfection time. Disinfectants may be delivered as either a spray or a wipe to clinical contact surfaces. In either case, the procedure is the same. The surfaces should be sprayed, then wiped, or they should be wiped with disinfectant-soaked towels, to remove debris. After the cleaning step, the surface should be sprayed again, or wiped with disinfectant towels and allowed to remain wet for the time indicated on the product label. A fresh wipe should be used for each of the cleaning and disinfecting steps. There is some indication that the improper use of wipes (ie, the use of one wipe on multiple surfaces) may result in the cross-contamination of surfaces in the patient environment (22). Another alternative is the use of barriers that are impervious to fluids. When using barriers, change them between each patient and carefully place and remove them in a manner that does not cause contamination of the protected surface or the DHCP’s hands. Used barriers should only be handled while wearing gloves (23).The most commonly used disinfectants in dental offices are glutaraldehyde, glutaraldehyde with phenol, hydrogen peroxide, hydrogen peroxide with per acetic acid, OPA (ortho-phthalalhyde), alcohols (ethanol, isopropyl alcohol), quaternary ammonium chloride oxidizers, formaldehyde and phenolics. CONCLUSION:The management of clinical contact surfaces remains an important aspect of an infection control program for all oral healthcare settings. Understanding the proper use and selection of disinfectants and barriers helps ensure a safe patient environment.