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Effect of retrograde cavity preparations on root apexes.

Ultrasonic cavity preparations in endodontic surgery has become a popular procedure with several advantages noted: Smaller cavities, deeper and cleaner preparations, less removal of surrounding bone needed for instrumentation and less removal of root apex dentin. Concern has been raised that lines of infraction have appeared in some instances when the ultrasonic instruments have been used. We wished to examine the result of cavity preparations in root apexes using five different methods: high and slow speed handpieces, sonic instruments, and ultrasonic instruments at two power settings, medium and high levels, respectively. The results showed that all the methods produced some infractions; the high power ultrasonics produced the most infractions while the lowest numbers were associated with the slow speed handpiece and ultrasonic instruments at the medium power setting.