Shaping ability of NiTi rotary versus stainless steel hand instruments in simulated curved canals.

OBJECTIVES The purpose of this in-vitro study was to compare shaping ability of NiTi rotary Mtwo and FlexMaster with stainless steel hand K-Flexofile in simulated curved root canals. STUDY DESIGN Forty-five simulated canals in resin blocks were prepared with Mtwo, FlexMaster and stainless steel hand K-Flexofile (15 blocks in each group). Using pre- and post- instrumentation images, straightening of the canal curvature was determined with a computer image analysis program. Material removal was measured at 5 measuring points, beginning 1 mm from the apex. Changes of working length (WL) were also recorded. The data were analyzed statistically using paired T-test and one way ANOVA. RESULTS The mean material removal from the inner canal wall was different from the outer canal wall at all measuring points for each system (p<0.0001) except for FlexMaster at WL-9 (p=0.123) and K-Flexofile at WL-5 (p=0.093). The mean ratio of material removal (inner/outer) at all measuring points was different for all systems except for FlexMaster and Mtwo at 3, 5 mm (p=0.984, p=0.242), and K-Flexofile and rotary systems at 1, 3 mm from the apex (p=0.565, p=0.218) (p=0.794, p=0.693). A mean loss of working length of 0.02 mm for Mtwo and 0.01 mm for FlexMaster and K-Flexofile was measured although the difference was not significant. CONCLUSIONS In the apical points of the curvature (1, 3 mm), there was no significant difference between three systems. At point 5mm from the apex, K-Flexofile remained better centered, while in the coronal points (7, 9 mm) NiTi rotary systems achieved better canal geometry.