An ultrasonic medical treatment probe has a head with a distal-most circular rim extending along an endless uninterrupted perimeter around a broad recess and formed with a series of serrations or teeth. The rim is thin in comparison to the width of the recess. The serrations or teeth preferably extend continuously along an entire circumference or length of the rim. The probe head is provided along the rim with a plurality of notches or openings communicating with the recess.