Abstract: Objective To observe the effect of mouth rinse before ultrasonic scaling on microorganism concentration in air of dental clinics.Methods Patients were divided into listerine^® mouth rinse group,chlorhexidine mouth rinse group,water mouth rinse group,and non mouth rinse group.Air samples were collected from dental clinics after ultrasonic scaling with sedimentation and cultured in blood agar plates for 48h.Then,the number of bacterial colonies formed on the plates was counted.Results The organism concentration was statistically lower in listerine^® mouth rinse group and chlorhexidine mouth rinse group than in water mouth rinse group and non mouth rinse group before ultrasonic scaling（P＜0.05）.However,no statistical difference was found in organism concentration between water mouth rinse group and non mouth rinse group and between listerine^® mouth rinse group and chlorhexidine mouth rinse group before ultrasonic scaling（P＞0.05）.Conclusion Mouth rinse using gargles before ultrasonic scaling can reduce the organism concentration in air of dental clinics.