Abstract: A handpiece (3a, 3b) includes an ultrasonic vibrator (21A) driven by an ultrasonic oscillator (40A) for vibration at an ultrasonic frequency in the range of 20 to 100 kHz, a low-frequency vibrator (21B) driven by a low-frequency oscillator (40B) for vibration at a low frequency, and a contact blade (10) connected to both the vibrators. Only the ultrasonic vibrator (21A) is driven for vibration and the contact blade (1) is brought into contact with an affected part for the mechanical anesthetization of the affected part. When the low-frequency vibrator (21B) is driven together with the ultrasonic vibrator (21A), low-frequency vibrations effective in separating the affected part, such as an affected tooth, are applied to the affected part in the mechanically anesthetized condition. The ultrasonic vibration of the ultrasonic vibrator (21A) does not stop and hence an operation, such as a tooth-extracting operation, is not interrupted even if the operator exerts large force on the contact blade (10).

Abstract: A dental tool is provided for extracting a tooth which is secured to an alveolar bone through a pericementum. The tool includes an elongate, flat and thin blade operatively connected to an acoustic transducer which produces ultrasonic vibrational energy. The blade has a thickness on the order of about 0.2 to 0.5 mm which is substantially less than the thickness of the pericementum to enable the blade to and cut through the pericementum located between the tooth and the alveolar bone along the profile of the tooth under excitation by the acoustic transducer. The blade transmits ultrasonic oscillation to the tooth so as to insensitize the pain transmitting system of the tooth. The pericementum is effectively cut with a reduced average cutting resistance while the insensitization is maintained.

Abstract: A vibrational cutting system for a tooth is disclosed which comprises a combination of a cutting tool adapted to rotate at a high speed and having a tip which is effective to cut a tooth, and an apparatus for exciting the tooth. The apparatus excites the tooth to vibrate at a frequency which is greater than the natural frequency of the tooth. The cutting tool is operated under either condition (1) that the feed rate of the cutting tool is less than the maximum vibrational speed of the tooth, as viewed in the feed direction, or condition (2) that the depth of cut into the tooth is less than the amplitude of vibration of the tooth as excited by the apparatus.