Endodontology
Shaping ability and safety of five different rotary nickel-titanium instruments compared with stainless steel hand instrumentation in simulated curved root canals

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Objective

To compare the shaping ability and safety of engine-driven FlexMaster, GT Rotary, ProFile, ProTaper, and RaCe rotary instrumentation and Hedström hand instrumentation in simulated root canals.

Study design

One hundred fifty simulated colored root canals with a curvature of 20 degrees and a radius of 10 mm were randomly distributed among 6 groups of 25 specimens each. After preparation to apical size 30 the area of remaining color on the canal wall indicating unprepared areas was measured in mm2 using image analyzer software.

Results

Specimens treated with RaCe left least areas of remaining color compared to all other groups (P < .001), followed by ProTaper. Preparation with ProFile left behind the highest amount of unprepared areas. The ProFile group revealed significantly more remaining color than ProTaper, GT Rotary, and FlexMaster (P < .05). Four FlexMaster files separated.

Conclusion

RaCe rotary files were safe and more effective compared to the other instruments.

Section snippets

Specimens

One hundred fifty transparent resin simulated root canal blocks (Endo-Trainer; Frasaco, Tettnang, Germany) were randomly distributed among 6 groups of 25 canals each. The walls of the simulated canals were colored red. The material for coloration is the manufacturer's secret. Preliminary tests of the present study did not show any influence of sodium hypochlorite and lubricant on the removal of color. The simulated canals had a length of 18 mm, a curvature of 20 degrees determined by the

Unprepared areas

In most of the canals remaining color was observed apically and/or in the outer aspect of the curve (Fig. 1). Specimens with fractured files were not considered for comparison of unprepared areas, preparation time, and loss of working length.

Imaged in both directions canals enlarged with RaCe showed least areas of remaining color compared to all other groups (P < .001), followed by ProTaper. Preparations with ProFile showed the highest means of unprepared canal walls. The ProFile group showed

Discussion

In recent years computerized tomography studies have been performed for analyzing canal shapes after preparation of extracted human root canals with different instruments.25, 26 However, preparation of simulated resin root canals is a widely used and simple technique to evaluate the shaping ability of endodontic instruments, in particular with regard to newly developed instruments.2, 4, 14, 15, 16, 17, 18

In contrast to time-consuming computerized tomography studies using extracted human teeth,

Conclusion

Under the conditions of the present study the design with the alternating cutting edges of RaCe rotary files revealed less unprepared areas and minor loss of working distance compared to the other instruments. Hedström files, ProTaper, and RaCe showed the lowest preparation times. GT Rotary, ProFile, ProTaper, RaCe, and Hedström files seemed to be very safe. Only the FlexMaster group showed file fractures during preparation of resin blocks. Hedström and ProTaper files seemed to have a higher

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