Statement of Problem: Ultrasonic Scaling is one of the main sources of producing infected aerosols in dentistry. These aerosols are able to spread pathogens such as microorganisms associated with tuberculosis, conjunctivitis, influenza and other respiratory diseases, herpetic and other skin diseases, ADIS and hepatitis B.
Purpose: The aim of this study was to investigate the clinical effectiveness of an aerosol- reduction device attaching to ultrasonic scaler handpiece.
Materials and Methods: In this experimental study 18 patients participated. Randomly, mandibular and maxillary quadrants of one side, in each subject, were scaled using an ultrasonic scaler with aerosol-reduction device for 5 minutes. After 30 minutes, another quadrant was scaled by ultrasonic scaler without aerosol- reduction device. In order to determine the effectiveness of aerosol- reduction device, blood agar plates attached to the surgical mask of the operator, 30 cm far from the patient's mouth, were incubated in 37°c for three days and the colonies were counted. Median, Interquartile eange and Wilcoxon test, at the 0.05 level of significance, were used to analyze the data.
Results: The median and interquartile range for the number of colony forming units (CFUS) without aerosol- reduction device was 17.5 (8, 24), while the median for the number of CFUS when using aerosol-reduction device was 0 (0, 1), indicating significant statistical difference (PO.001)

Conclusion: The aerosol- reduction device significantly reduces the amount of aerosols produced during ultrasonic scaling.