| 摘要 |
<p>A tooth de-scaling instrument is rotated at over 100,000 (pref. about 120,000) r.p.m. in a dentist's hand tool. The de-scaler has a conical end (pref. 15 deg. cone) with four to eight (pref. six) smooth sides. Behind this is preferably a concavity which allows the instrument to reach down beyond a tooth crown. At these speeds of rotation, the de-scaler's pref. slightly rounded corners contact the tooth with ultra-sonic frequency, and quickly remove the scale. Simultaneously a stream of water is also directed at the tooth.</p> |
