Abstract: An ultrasonic instrument having biological, medical, dental and periodontal applications, the instrument producing a jet of oxygen which may be projected toward diseased tissue or any other site in need of cleansing and oxygenation. The instrument includes a hand-held ultrasonic transducer having a nozzle attached thereto, the transducer being energized by a high-frequency generator. The nozzle is coupled by a flexible tube to a tank of pressurized oxygen, the stream of oxygen passing through the vibrating nozzle being ultrasonically activated thereby to produce a highly reactive jet which may be directed toward the site being treated.