An ultrasonic tool or instrument has a probe shaft with a linear proximal end portion and a linear distal end portion disposed at an angle relative to one another and joined at a bend in the shaft. A coupling is provided at a proximal end of the shaft for connecting the probe to a source of ultrasonic vibrational energy. A head provided at a distal end of the shaft extends eccentrically in a transverse direction to one side of the shaft. The head has an operative tip spaced laterally from the axis and is formed with at least one cutout for reducing mass of the head and concomitantly eccentric mass of the probe. The tool or instrument has at least one interior antinode along the shaft and the bend is located substantially distally of the antinode.
