A Comparion Between Slow-Speed Handpiece And Ultrasonic Instrument On Posterior Teeth In Root-End Preparation

Objective: (l)To compare the difference between ultrasonic instruments and traditional slow-speed handpiece in retropreparation(2)to evaluate the ultrasonic instruments effecting on canal isthmus (3)to evaluate the feasibility, advantages and disadvantages of ultrasonic instruments on posterior teeth in root-end preparation.Methods: In Part 1, 27 maxillary second bicuspid teeth with two canals and an isthmus, mature root apices were randomized to 3 groups equally. The root-end preparations were made respectively using ultrasonic diamond tip Berutti and NiTi tip RE2 ,ultrasonic #40K file and slow-speed handpiece with NO.2 round bur. In Part 2, 32 mesial roots of the mandibular first molars with two canals, mature root apices, and periodontal tissue were randomized to 2 groups equally. The root-end preparations were made respectively using ultrasonic diamond tip Berutti and NiTi tip RE2 and slow-speed handpiece with NO.2 round bur. Observed and photographed by Image processing and analysis system and Scanning electron microscope impression technique. The cutting volume, the number and type of the micro-cracks, the quality of cavity margin, the debris and smear layer in the cavities were compared between the two techniques respectively in Part 1 and Part 2.Results: The cutting volume ,the number of micro-crack ,the debris and smear layer in the cavities of the slow-speed handpiece were significantly more than the ultrasonic instruments(P<0.05); The type of micro-cracks has no significant difference between the two techniques (P>0.05).In Part 1, the quality of cavity margin of the slow-speed handpiece group was significantly inferior to the ultrasonic #40K file group(P=0.039); there was no significant difference between the two ultrasonic groups(P=0.637);there was no significant difference between the ultrasonic Diamond tip Berutti and NiTi tip RE2 group and the slow-speed handpiece group(P=0.136).However, the quality of cavity margin of the slow-speed handpiece group was significantly inferior to the ultrasonic Diamond tip Berutti and NiTi tip RE2 group(P=0.029)in Part 2.Conclusion: Ultrasonic instrument is feasible in the retropreparation on posterior teeth with isthmus.