Infection control of exhaust contamination in dental unit suction system

Objectives: Recently the risk of outbreak in emerging infectious disease is increased, and therefore infection control is very important in dental clinical practices. In a dental unit suction system, infection control of waterline has been established, but exhaust contamination is not still clear. So, in this study, a dental unit suction system (Tokyo Giken Co., LTD., TOKYO, TGDUS), which was equipped with a catch water system (CWS) and high efficiency particulate air filters (HEPA), was tested for control of exhaust contamination.

Methods: The test samples were collected from a healthy subject's mouth (n=15) with 50ml of phosphate-buffered salines (PBS) prior to the experiments . The samples contained 2.5±1.5x10⁷ CFU/ml bacteria and some of samples included of oral indigenous virus such as herpes-simplex virus type-7, EB virus or cytomegaro virus (CMV). These test samples were turn into a fine spray by moisture chamber and vacuumed up one hour in a row by TGDUS with or without CWS and HEPA. Dental unit exhaust was collected for one hour by midget impinger glass tube system. A part of samples were tested for bacterial culture and the rest of samples were used for nucleic-acid amplification testing for oral indigenous virus.

Results: In direct exhaust from TGDUS with no CWS and HEPA, there were 5.4±4.0x10³ CFU/ml bacteria, and CMV was detected. Only using the TGDUS with CWS, there were a quiet few level (<10CFU/ml) bacteria in exhaust. And there were no bacteria and oral indigenous virus in the TGDUS with both CWS and HEPA.

Conclusion: These results indicated that CWS was important for control of bacterial contamination in dental unit exhaust and HEPA was very useful for protection of exhaust viral contamination.