Tooth substance loss resulting from mechanical, sonic and ultrasonic root instrumentation assessed by liquid scintillation.

AIMS: This study investigated the loss of tooth substance (microg) by means of liquid scintillation in combination with profilometric and SEM analyses in order to evaluate the roughness and morphological changes of the root surface before and after instrumentation.
METHOD: 40 polished and irradiated bovine root surfaces were scaled in vitro while covered with 50 ml distilled water using a sonic prototype (Periosonic 1/2), a magnetostrictive ultrasonic (Cavitron with Slimline inserts) scaler and a hand curette. Pressures were applied for the Periosonic, Cavitron and hand curette at 500, 500 and 30 g respectively, for 30-s intervals, up to 120 s. Loss of apatite (microg) was determined from the decays/min (32P) of the water samples using the radiochemical method of liquid scintillation. Replicas were made of the specimens for SEM and profilometric analyses.
RESULTS: The least substance loss was noted significantly (p<0.01) at all time intervals after Slimline, followed by the fine sonic prototype Periosonic 2, then the Periosonic 1 and finally the hand curette. In contrast, profilometric and SEM analyses revealed the smoothest root surfaces after the hand curette, whereas Cavitron produced a less smooth surface.
CONCLUSION: It can be concluded that this method can reveal very precisely small quantities of substance lost and, in combination with SEM analysis and microroughness measurements, be of considerable value in evaluating the aggressiveness and efficacy of periodontal instruments.