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J Conserv Dent. 2011 Jul;14(3):264-8. doi: 10.4103/0972-0707.85809.

Change of working length in curved molar root canals after preparation with different rotary nickel-titanium instruments.

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Department of Conservative Dentistry and Endodontics, Swami Devi Dyal Dental College and Hospital, Panchkula, India.



The purpose of this study was to investigate change of working length in curved molar root canals after preparation with Profile, ProTaper and K3 Rotary Nickel-Titanium (Ni-Ti) instruments.


One hundred and eighty maxillary and mandibular molars were divided into group I having root curvature angle <300 and group II having root curvature angle >300 comprising 90 teeth in each group based on Schneider's method. Group II and I were further divided into sub group A, B and C having 30 teeth each based on type of instrument used. Profiles, ProTaper and K3 Rotary Ni-Ti files were used to prepare mesial and buccal roots of molars. Radiography platform was made to allow technique for constant object to film distance and object to sensor distance. Conventional access opening was prepared in each tooth. Preoperative and postoperative working length was measured to an accuracy of 0.1 of mm on Dexis 3.0 direct digital radiograph's onscreen measurement device.


Mean loss of working length varied from 0.28 to 0.92 mm. Highest working length loss was seen in ProTaper followed by K3 files and Profiles, which is statistically significant.


Angle of curvature; Ni-Ti; direct digital radiography; loss of working length; rotary instruments

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