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1 J Dent Hyg Sci Vol. 15, No. 5, 2015, pp RESEARCH ARTICLE 치과용유니트수관물빼기 (Flushing) 가세균오염도감소에미치는영향 윤혜영ㆍ이시영 강릉원주대학교치과대학구강미생물학교실, 구강과학연구소 Effects of Flushing in Dental Unit Waterlines on the Bacterial Contamination Level Hye Young Yoon and Si Young Lee Department of Oral Microbiology, College of Dentistry, Research Institute of Oral Science, Gangneung-Wonju National University, Gangneung 25457, Korea A wide variety of methods have been used to control Dental Unit Waterline (DUWL) contamination. Among the methods, flushing is mainly used because it is simple and easy to use. Generally, flushing of DUWL for 20 or 30 sec before using high speed handpieces or scalers is recommended. However, the appropriateness of flushing time was not investigated thoroughly. The purpose of this study was to check the effective time of flushing for decreasing bacterial contamination. Seven dental unit chairs were randomly selected in student clinical simulation laboratory for this experiment. DUWLs were continuously flushed and water samples were collected at an interval of 30 seconds for 15 minutes. From five dental unit chairs, water samples were collected every 10 seconds for 1 minute. Bacterial levels in water samples were examined by the culture method on R2A plates. After 10 second flushing of DUWLs, the number of bacteria significantly reduced and decreased continuously up to 40 seconds. However, even after the water was flushed for 15 minutes, the bacterial contamination level was not reduced below recommended bacteria level, 200 CFU/ml. In addition to flushing, the periodic chemical disinfection is required to control the DUWL water to the recommended level. Key Words: Biofilm, Decontamination, Flushing, Water microbiology, Water quality 서론 치과용유니트 (dental chair unit, DCU) 에서배출되는물은치과진료중에주로사용되지만여러연구를통해 DCU 에서배출되는물이높은수준으로세균에오염되어있는것으로밝혀졌다 1-7). 오염된 DCU 물로인해감염된사례가국내에서아직보고된것은없지만, 과거영국이나미국에서감염사례가보고되었고 8,9), 오염된 DCU 물에서 Pseudomonas species, Legionella species, 비결핵성 Mycobacterium species와같은기회감염성병원균이검출되고있어 1,2,10-14) DCU 물을통한감염의잠재적인위험성이항상존재한다. DCU의물은환자구강에직접접촉되고치료중발생하는에어로졸에치과종사자들이항상노출되어있기때문에, DCU 물은음용수와같은수준으로깨끗하게유지되어야한다. 이를위해, 미국질병관리본부에서는치과치료에사용하는물의세균수준을음용수와같은기준인 500 colony forming unit (CFU)/ml 이하로유지해야하며수술시에는멸균수가공급되는독립적장치를사용할것을강조하고있다 10). 또한, 미국치과의사협회는 DCU 물내세균의수준을 200 CFU/ml 이하로유지하도록권고하고있다 15). Received: September 1, 2015, Revised: October 4, 2015, Accepted: October 4, 2015 ISSN (Print) / ISSN (Online) Correspondence to: Si Young Lee Department of Oral Microbiology, College of Dentistry, Research Institute of Oral Science, Gangneung-Wonju National University, Gangneung 25457, Korea. Tel: , Fax: , siyoung@gwnu.ac.kr Copyright 2015 by the Korean Society of Dental Hygiene Science This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

2 J Dent Hyg Sci Vol. 15, No. 5, 2015 DCU의물을권장수준으로유지하기위해현재까지다양한방법들이사용되어왔다. 치과용유니트수계 (dental unit water system, DUWS) 내에필터를설치하는방법, 독립적인저수통을사용하는방법, 사용전치과용유니트수관물빼기방법, 화학소독제로주기적소독을하는방법등이있으며지금까지도다양한방법들이개발중에있다. 이중치과에서환자진료를위해 DCU를사용하기전치과용유니트수관 (dental unit waterline, DUWL) 의물을미리배출시키는수관물빼기방법이가장사용이쉽고간단하여, 환자진료전후에 20 30초동안물을미리배출시킬것을미국질병관리본부와미국치과의사협회에서는권장하고있다 10,15). 수관물빼기의효과를확인한다양한연구들이있지만, 수관물빼기의권장시간인 20 30초에대한과학적근거가명확하지않으며이보다더짧은시간혹은긴시간의수관물빼기효과에대한연구는부족한실정이다 16-20). 따라서, 본연구의목적은수관물빼기권장시간인 초의적절성을확인하고권장시간보다더짧거나긴시간의수관물빼기를수행한후세균오염감소의효과를확인하는것에있다. 연구대상및방법 1. 시료수집강릉원주대학교치과대학학생실습시뮬레이션실내중앙급수체계를통해도시용수를사용하고있는치과용유니트를대상으로수행하였다. 7개치과용유니트의초음파치석제거기에서 15분동안수관물빼기를진행하면서 30초간격으로배출되는물을수집하였다. 추가적으로 5개의치과용유니트에서는 1분동안물을배출시키면서 10초간격으로물을수집하였다. 15분동안진행한실험에서는각치과용유니트당 30초간격으로총 31개의물시료를수집하였고, 1분동안진행한실험에서는 10초간격으로총 7개의 Fig. 1. The number of bacteria (log CFU/ml) after flushing of dental unit waterlines. Value of the bar represents the mean value of the water samples collected every 30 secondsin flushing for total 15 minutes. Line value represents a standard of the American Dental Association (200 CFU/ml). The error bars indicate standard deviations of the mean. 660

3 윤혜영ㆍ이시영 : 치과용유니트수관물빼기 (Flushing) 가세균오염도감소에미치는영향 Fig. 1. Continued. 물시료를수집하였다. 수집한물시료에는잔류염소를중화시키기위해 10% sodium thiosulfate (Yakuri Pure Chemicals Co., Ltd, Kyoto, Japan) 를수집된시료양의 0.1% 를넣어주었다 21). 그후시료는즉시실험실로옮겨졌다. 2. 종속영양세균수확인종속영양세균수는배지배양법으로확인하였다. 수집한물시료를 phosphate-buffered saline (PBS, ph 7.4) 용액에 1:10, 1:100으로희석하였고희석물의 50 l를 R2A agar 배지 (Becton, Dickinson and Company, Sparks, NV, USA) 에각각 2장씩 spiral plater (IUL, S.A., Barcelona, Spain) 를사용하여도말하였다. 도말한 R2A배지를 24 o C에서 7일동안배양후세균집락을 colony counter (IUL) 로계수하였다 결과 Fig. 1과 Fig. 2는수관물빼기를시행한시간에따른 CFU/ml의수치를보여준다. 0초에서 10초사이배출되는 물은 0초물시료로표시하였고, 10초에서 20초사이배출되는물은 10초물시료로표시하였다. 치과용유니트에서최대 15분동안물을배출시킨경우 (Fig. 1), 7개중 5개치과용유니트의세균수가 200 CFU/ml 이하로감소되지않았다. 수관물빼기후 3번과 5번치과용유니트에서 200 CFU/ml 이하로세균수가감소하였는데, 3번치과용유니트에서는 9분 30초동안수관물빼기를했을때처음으로 200 CFU/ml 이하로감소했으며 5번치과용유니트에서는 6분에처음으로 200 CFU/ml 이하로감소했다. 추가적으로 5개의치과용유니트에서 1분동안 10초간격으로배출되는물을수집하여세균수를확인하였을때, 10초동안수관물빼기를한후세균수가상당히감소하였고그후 40초까지세균수가점점감소하였다 (Fig. 2). 30초간격으로 15분동안수관물빼기를진행하였을때, 1분부터 2분 30초까지는 85% 88% 의세균감소율을보여주었다. 3분이상수관물빼기를진행했을때세균수감소율은평균최소 90% 에서최대 94% 로나타났다 (Fig. 1). 10초간격으로 1분동안수관물빼기를한실험에서는, 10초동안수관물빼기를한 661

4 J Dent Hyg Sci Vol. 15, No. 5, 2015 후세균수감소율은평균 63% 였고 20초동안수관물빼기를한후세균수감소율은평균 84% 였다 (Fig. 2). 1, 3, 5번치과용유니트에서는 15분동안수관물빼기를시행하였고최대 99% 의감소율을보여주었다 (Fig. 1). 실험에사용된치과용유니트에서수관물빼기를수행하기전평균오염수준은 244,725 CFU/ml로최대 502,400 CFU/ml, 최소 43,720 CFU/ml로나타났다. 고찰 연구에사용된치과용유니트의초기오염수준은평균이 244,725 CFU/ml로미국의치과에서사용중인치과용유니트의세균오염수준인 350,130 CFU/ml 22) 과미국치과대학병원내치과용유니트의세균오염수준인 140,000 CFU/ml 23) 과비슷한수준이었다. 치과용유니트에서최대 Fig. 2. The number of bacteria (CFU/ml) after flushing of dental unit waterlines. Value of the upper line represents the mean value of the water samples collected every 10 seconds in flushing for 1 minute. The bottom line value represents a standard of the American Dental Association (200 CFU/ml). The error bars indicate standard deviations of the mean. 662

5 윤혜영ㆍ이시영 : 치과용유니트수관물빼기 (Flushing) 가세균오염도감소에미치는영향 15분동안수관물빼기를시행하였을때, 세균오염수준이미국치과의사협회에서권장하는수준인 200 CFU/ml 이하로감소되지않았다. 15분동안수관물빼기를시행한후세균의오염수준이 0까지감소된결과를보여준 Whitehouse 등 19) 의연구와약 4분동안수관물빼기를시행한후 200 CFU/ml 이하로세균수의감소를보여준 Scheid 등 16) 의연구결과와상반된결과이다. 우리실험과이들의실험결과사이에차이가나는이유로각연구마다시료수집과정이나 DUWL에사용되는물의특성등여러차이점이있겠지만, 사용한배지가다른것이가장큰원인이라고생각된다. 수관물빼기의효과를확인한이전연구들은대부분 nutrient agar, plate count agar, blood agar 배지를사용하였고, 본연구에서는 R2A agar 배지를사용하였다. R2A 배지는저영양배지로낮은배양온도와긴배양기간을필요로한다 24,25). 영양이풍부한배지와비교하여, R2A 배지가물처리과정중스트레스받고염소에내성을가지는세균의회복을향상시키기때문에, R2A 배지사용시가장많은세균을얻을수있다고보고되었다 26). 또한치과용유니트물속세균을배양하기위한다양한방법중 R2A agar 배지에물시료를도말하여배양하는방법이추천되고있다 24,27,28). 실험에사용된치과용유니트중 200 CFU/ml 이하로세균수준이감소한경우가 2개의치과용유니트에서나타났으며, 200 CFU/ml 이하로감소시킨가장짧은시간은 6분이었다. 7개의치과용유니트중 1개의치과용유니트에서만 6분수관물빼기가권장수준이하로오염도를떨어트리는데효과적으로나타났으나 6분이후의시간까지세균수를 200 CFU/ml 이하로유지하지는못했으며, 6분은실제로치과에서물을배출시키기에는매우긴시간이기때문에이시간을가장효율적인시간으로일반화시켜권장하기어려울것이다. 40초이상의시간동안물을배출시켰을때큰폭의감소없이비슷한수준으로세균수가유지되었다. 물을배출시키는시간을증가시켜도세균수가비슷하게유지되는것은수관내부표면에존재하는바이오필름 (biofilm) 때문인것으로보인다. 수관내부표면에부착하고있는바이오필름이지속적인세균공급원으로작용하기때문에물의흐름과함께계속적으로바이오필름을구성하고있는일부세균들이방출되어세균의수가크게감소되지못한것으로생각된다. 또한한치과용유니트에서는 (Fig. 1, Unit chair #5) 8분까지는세균수가감소하다가그이후에는오히려증가하는양상을보여주었다. 이는수관물빼기를긴시간동안진행하는것이바이오필름을구성하는세균을다량떨어트려오히려물속에세균수를증가시켰을것으로추측된다. 수관물빼기는수관오염의근원지인바이오필름을 제거하지못하기때문에치과용유니트의물을관리하는가장보편적인방법으로사용되기는한계가있다고판단된다. 하지만짧게 10초동안수관물빼기를시행했을때세균수를그전보다 62.5% 감소시켰기때문에환자진료전, 간단하고쉽게세균수를감소시키는방법이될수있을것으로생각된다. DCU 물의오염수준을권장수준이하로유지시키기위해서는수관물빼기외에화학소독제로수관을주기적으로청소하는것이반드시필요할것이다. 본실험에사용된치과용유니트의오염수준은최대 502,400 CFU/ml에서최소 43,720 CFU/ml로높았으며, 낮은오염수준의치과용유니트에서수관물빼기를시행했을시효과는본실험에서확인하지못했다. 또한, 본실험에서사용된치과용유니트모두학생실습을위해 20년동안동일하게사용된치과용유니트로, 사용기간이다른치과용유니트에서수관물빼기의효과를확인하지못했다. 따라서다양한사용기간을가진치과에서사용중인치과용유니트를대상으로수관물빼기의효과를확인하고추가적으로환자진료전과후에 10초동안수관물빼기를시행하는것의효과를확인하기위한실험이필요할것이다. 그리고휴일이후나진료전아침시간또는점심시간에오랜시간동안시행하는수관물빼기의효과와진료사이사이에 10 초동안수관물빼기를하는것의효과를비교하는실험이추가적으로진행될필요가있다. 수관물빼기가미국치과의사협회의권장수준으로치과용유니트물의오염수준을감소시키지못하지만, 수관물빼기를하는것은시행하기전보다수관내세균수를상당히감소시키므로진료전, 후에수관물빼기가시행되어야하며, 20 30초동안수관물빼기를하는것을권장하고있지만, 10 20초동안시행하는것또한세균수를충분히감소시키므로효과적이라고할수있다. 요약 DCU의물을관리하는다양한방법들중치과용유니트를사용하기전수관물빼기방법이가장사용이쉽고간단하기때문에, 미국질병관리본부와미국치과의사협회에서환자진료전후에 20 30초동안물을미리배출시킬것을권장하고있다. 하지만, 수관물빼기의권장시간인 초와관련한과학적근거가명확하지않고, 20 30초이외의시간동안수관물빼기효과를확인한연구가부족한실정이다. 본연구의목적은권장시간인 20 30초뿐만아니라이보다더짧거나긴시간동안치과용유니트수관물빼기를수행한후각시간별오염세균수의감소정도를조사하 663

6 J Dent Hyg Sci Vol. 15, No. 5, 2015 여 20 30초권장시간의적절성을확인하고더효과적인수관물빼기시간이있는지를조사하는것이다. 물시료수집은치과대학학생실습시뮬레이션실내치과용유니트를대상으로수행하였다. 7개치과용유니트의초음파치석제거기에서 15분동안수관물빼기를진행하면서 30초간격으로배출되는물을수집하였다. 추가적으로 5개의치과용유니트에서는 1분동안물을배출시키면서 10초간격으로물을수집하였다. 물시료내오염세균수는 R2A agar 배지에수집된물을도말한후배양하여확인하였다. 7개의치과용유니트에서최대 15분동안물을배출시켰을때치과용유니트의오염수준이 200 CFU/ml 이하로감소되지않았다. 추가적으로 5개의치과용유니트에서 1분동안 10초간격으로배출되는물을수집하여세균수를확인하였을때 10초동안수관물빼기를한후세균수감소율은평균 63% 였고, 20초동안수관물빼기를한후세균수감소율은평균 84% 였다. 본실험의결론은다음과같다 : 첫째, 수관물빼기의권장시간인 20 30초뿐만아니라최대 15분동안수관물빼기를시행하는것은권장수준 ( 200 CFU/ml) 으로세균오염도를감소시킬수없었다. 둘째, 수관물빼기의권장시간인 20 30초보다짧게 10초동안수관물빼기를하는것도세균수감소에효과가있었다. 셋째, 치과용유니트내물의세균오염수준을권장수준으로유지시키기위해서는수관물빼기와함께주기적으로화학소독제로치과용유니트수관을소독하는것이필요하다. References 1. Walker JT, Bradshaw DJ, Finney M et al.: Microbiological evaluation of dental unit water systems in general dental practice in europe. Eur J Oral Sci 112: , Williams JF, Johnston AM, Johnson B, Huntington MK, Mackenzie CD: Microbial contamination of dental unit waterlines: Prevalence, intensity and microbiological characteristics. J Am Dent Assoc 124: 59-65, Lee BM, Kim CW, Kim YS: A study on the microbial contamination of dental unit and ultrasonic scaler. J Korean Acad Prosthodont 36: 64-80, Walker JT, Bradshaw DJ, Bennett AM, Fulford MR, Martin MV, Marsh PD: Microbial biofilm formation and contamination of dental-unit water systems in general dental practice. Appl Environ Microbiol 66: , Barbeau J, Tanguay R, Faucher E, et al.: Multiparametric analysis of waterline contamination in dental units. Appl Environ Microbiol 62: , Uzel A, Cogulu D, Oncag O: Microbiological evaluation and antibiotic susceptibility of dental unit water systems in general dental practice. Int J Dent Hyg 6: 43-47, Yoon HY, Lee SY: Bacterial contamination of dental unit water systems in a student clinical simulation laboratory of college of dentistry. J Dent Hyg Sci 2: , Martin MV: The significance of the bacterial contamination of dental unit water systems. Br Dent J 163: , Atlas RM, Williams JF, Huntington MK: Legionella contamination of dental-unit waters. Appl Environ Microbiol 61: , Kohn WG, Harte JA, Malvitz DM et al.: Guidelines for infection control in dental health care settings J Am Dent Assoc 135: 33-47, Schulze-Robbecke R, Feldmann C, Fischeder R, Janning B, Exner M, Wahl G: Dental units: An environmental study of sources of potentially pathogenic mycobacteria. Tuber Lung Dis 76: , Porteous NB, Redding SW, Jorgensen JH: Isolation of non-tuberculosis mycobacteria in treated dental unit waterlines. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 98: 40-44, Ma'ayeh SY, Al-Hiyasat AS, Hindiyeh MY, Khader YS: Legionella pneumophila contamination of a dental unit water line system in a dental teaching centre. Int J Dent Hyg 6: 48-55, Al-Hiyasat AS, Ma'ayeh SY, Hindiyeh MY, Khader YS: The presence of Pseudomonas aeruginosa in the dental unit waterline systems of teaching clinics. Int J Dent Hyg 5: 36-44, Shearer BG: Biofilm and the dental office. J Am Dent Assoc 127: , Scheid RC, Kim CK, Bright JS, Whitely MS, Rosen S: Reduction of microbes in handpieces by flushing before use. J Am Dent Assoc 105: , Williams HN, Baer ML, Kelley JI: Contribution of biofilm bacteria to the contamination of the dental unit water supply. J Am Dent Assoc 126: , Mayo JA, Oertling KM, Andrieu SC: Bacterial biofilm: A source of contamination in dental air-water syringes. Clin Prev Dent 12: 13-20, Whitehouse RL, Peters E, Lizotte J, Lilge C: Influence of 664

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untitled J Dent Hyg Sci Vol. 15, No. 2, 2015, pp.232-237 http://dx.doi.org/10.17135/jdhs.2015.15.2.232 RESEARCH ARTICLE 치과대학임상시뮬레이션실습실치과용유니트수계의세균오염도조사 윤혜영ㆍ이시영 강릉원주대학교치과대학구강미생물학교실및구강과학연구소 Bacterial Contamination