Abstract: Objective To observe the contamination control of microorganisms in dental unit waterlines after using the disinfectant agent containing hydrogen peroxide and silver ion. Methods 4 dental units in the department of periodontics were chosen to install disinfection devices and disinfected every three days in six days. before and after the disinfectant,10ml water samples were collected from the operator’s three-in-one air/water syringe, ultrasonic scaler waterlines and water for rinsing the mouth, cultured on R2A ager plates, recorded the Colony-Forming Units, compared them with 500 CFU/ml, analyzed the data with SPSS 19.0.Results Before the application of disinfectant, the bacterial colony reached to 34425CFU/ml from air/water syringe, 42858.33CFU/ml from ultrasonic scalers waterline and 13116.67CFU/ml from rinse water, there is no significant difference of bacterial colony between water samples before disinfecting. After using the disinfectant agent, the sterilization rates were from 92% to 100% and no significant difference was discovered between them. However, on the third morning after disinfecting, the level of bacterial colony has a clear recovery. Conclusion The disinfection effect of disinfectant within hydrogen peroxide and silver ion is significant but the maintenance of microorganisms in dental unit waterlines is not so good.

Key words: dental unit waterline system, disinfectant, hydrogen peroxide, microorganism