Some observations on the breakage of ultrasonic files driven piezoelectrically.
The incidence of breakage of Piezon-Master ultrasonic K files were evaluated. Three groups of unused files were subjected to three treatments, namely; free vibration in air without irrigation, free vibration in root canal while minimizing contact with the wall of canal in the presence of irrigation and light filing in root canal with free flow of irrigation. Cavitation produced by files in contact and free of contact with a glass surface was examined in order to observe the relationship between cavitation defects and breakage. In addition, the fractured and unfractured files were examined under a scanning electron microscope for the presence of cavitation pits. The results indicated that more files broke in air. In water, a higher incidence of breakage occurred when files were allowed to freely vibrate while no breakage occurred when the files were used in filing. All files generated cavitation which resulted in pitting of their surfaces. However, it was considered unlikely that the pits contributed to fracture. Fatigue cracks which could be the result of the manufacturing process were observed at some of the corners of the cross sections of the fractured files and could be the main contributory factor to fracture.
Brittle and ductile torsional failures of endodontic instruments.
Abstract A wide variety of brands and sizes of endodontic files and reamers all displayed decreased revolutions to failure when placed in counterclockwise torsion. This suggests that endodontic practitioners should be cautioned to exercise great care when "backing off" an inadvertently lodged instrument during the cleansing and shaping of the root canal. Moreover, the results indicate that future dental specifications should include tests of counterclockwise mechanical properties.
Endosonic endodontics: the ultrasonic synergistic system.
A biotechnological approach using ultrasound has led to the development of a method of root canal therapy in which effective debridement, shaping, irrigation and disinfection of the root canal are easily and quickly completed. This is achieved by a handpiece and a file both energized by ultrasound. A flow-through component enables an irrigation solution to pass along the file into the canal system. The ultrasonically energized file activates the irrigant facilitating solvent, cleansing and disinfecting actions within the root canal system. The energized file is able to debride the canal wall with great facility in an extremely rapid and simple fashion. Progress in metallurgical bonding has enabled a diamond coated file to be developed which gives efficient and rapid preparation of the root canal. Use of this combination of ultrasound, flow-through irrigation and diamond-coated files enables the dentist to perform endodontic treatment expeditiously while adhering to biologic principles.