2009 Volume 52 Issue 6 Pages 453-459
The purpose of this basic study using models of intracanal broken instruments was to evaluate the time for removal of broken file pieces depending on the output strength of the ultrasonic device, the lengths or sizes of broken files, and the presence or absence of water coolant. After enlarging the root canals in transparent resin blocks using Peeso reamers at root canal areas and files at apical areas, cut K-files as broken files were pushed into resin blocks, and models of intracanal broken instruments were reproduced. In the experiment on the relation of output strength of the ultrasonic device, the frequencies of 28.8 (strength 1), 29.6, and 30.4kHz were used for removing #30 broken files of 3mm length. In the experiment on the relation of broken piece lengths, the ultrasonic device with strength 1 was used for removing #30 broken files of 3, 5, or 7mm length. In the experiment on the relation of sizes of broken pieces, the ultrasonic device with strength 1 was used for removing #20, 30, or 40 broken files of 3mm length. In the experiment on the relation with or without water coolant, the ultrasonic device with strength 1 was used for removing #30 broken files of 5mm length. All times to remove broken files were compared and discussed. Regarding the output strength of the ultrasonic device, stronger output power was more effective for removing broken files. Regarding the lengths of broken files, longer lengths were more difficult to remove. Regarding the sizes of broken files, bigger pieces were more difficult to remove. Regarding the presence or absence of water coolant, the presence of water coolant was more effective. It was suggested that removal of broken pieces closely depended on the conditions or status, because the times to remove broken files varied reasonably closely with the conditions or status of the ultrasonic device using transparent resin blocks.
