Preparation of curved canals using a combined hand-filing, ultrasonic technique

Because of the difficulties involved in endodontic preparation of curved canals, many techniques have been suggested using mechanical means to improve final results. Ultrasonics have been used in dentistry for many years as adjuncts for cleaning instruments and as aids in scaling during periodontal treatment. Recent reports on their use in canal preparation have indicated that cleaner canals were obtained. This has led to attempts at using this instrument in curved canals. In this study, preparation with ultrasonics alone in canals of extracted human teeth with curvatures of 30 degrees or greater led to severe straightening, zipping, and strip perforations. The use of ultrasonics more coronally, with hand filing at the apex, avoids these problems. This article presents a step-by-step technique for a combination of hand filing with ultrasonics preparation.