Dental hard tissue cutting characteristics of an ultrasonic drill

Ultrasonic instruments are used in clinical dentistry to perform a variety of tasks. Several designs of instrument are commercially available, which operate at ultrasonic frequencies of 20–42kHz. They may be used for various purposes such as removal of hard deposits from tooth surfaces, cleansing root canals, and more recently preparation of cavities in tooth tissue during surgical procedures. The aim of this study was to investigate the clinical effectiveness of a working ultrasonic instrument designed for surgical use (Neosonic, Amadent Corp, Cherry Hill, N.J. U.S.A.). The instrument is supplied with stainless steel cutting tips that facilitate cavity preparation in hard tooth tissue. Three designs of tip, designated CT1-3 were chosen for this study. The tips were calibrated by measuring their oscillation displacement amplitudes in air, using light microscopy over increasing power settings. Extracted teeth were sectioned and polished to produce a smooth dentine surface. The instrument was applied to the dentine surfaces for 1 minute across the same power range at a load of approximately 20g which was representative of clinical loading. The prepared specimens were scanned with a Form Talysurf and the depth of the resulting grooves measured (n=6 for each power setting). Results showed that for all tip designs an increase in power setting resulted in increased displacement amplitude and cutting ability. This increase was linear, with minimal cutting occurring at lower power settings.