A comparison of the dentine-removing characteristics of two endosonic units.

The purpose of this study was to compare the dentine-removing characteristics of size 25 K-files activated by the Cavi-Endo and Piezon-Endo units. The influence of power-setting, direction of file oscillation, interfacial force and operator-assisted movement were studied. Filing was performed on flat surfaces of dentine and impressions of the instrumented surfaces revealed characteristic patterns of dentine removal corresponding to the area of contact with the file which was quantified using a Reflex microscope. Differences in dentine removal as affected by the power output of the two systems were only apparent when the maximum power-setting on the Cavi-Endo was compared with the maximum recommended for root canal preparation on the Piezon-Endo. The Cavi-Endo removed significantly more dentine than the Piezon-Endo. When operator-assisted movement of the file was superimposed, both systems removed significantly more dentine than without assisted filing, However, the Piezon-Endo now removed significantly more dentine than the Cavi-Endo. This difference was more apparent when the file oscillated perpendicular to the dentine surface, compared with oscillation parallel to the substrate. An increase in the interfacial force from 30 g to 60 g resulted in a greater reduction in dentine removal by the Cavi-Endo compared with the Piezon-Endo. Thus, at a 30 g interfacial force there were insignificant differences between the endosonic units but at 60 g, the Piezon-Endo removed significantly more dentine than the Cavi-Endo. The dentine-removing characteristics of the two endosonic units tested are very different under certain conditions. These findings may have important clinical implications.