A Comparative Study of the Efficiency of FlexMaster ® NiTi Rotary and K-Flexofile ® Stainless Steel Hand Instruments

The aims of this study were to compare the effectiveness of FlexMaster® nickeltitanium rotary and K-Flexofile® hand instruments with regard to straightening of curved root canals and preparation time, and to evaluate the morphological aspects of instrumented root canal walls in extracted human teeth. A total of 60 root canals in molar teeth, with curvatures ranging between 0 and 35°, were divided into three groups of 20 root canals each, based on the degree of curvature. Half of each group was prepared using FlexMaster® instruments by a crown-down preparation technique and the other half using K-Flexofile® by a conventional technique. After each instrumentation, the root canals were flushed with 3 ml of 5.25% sodium hypochlorite and 3% hydrogen peroxide, alternatively, and 1 ml of 14% EDTA. Using radiographs taken before and after root canal preparation, the angles of root canal curvature of all specimens were determined. The preparation time was also recorded. All roots were bisected longitudinally and the canal walls were examined by scanning electron microscopy for morphological aspects. The use of FlexMaster® instruments resulted in significantly less straightening of root canal curvatures and a shorter preparation time compared to K-Flexofiles® (p <0.01) . They resulted in less debris, but left a thicker smear layer at the apical third of root canal than the K-Flexofile®. These results showed that rapid preparation of curved root canals with minimal canal straightening was possible using FlexMaster® instruments, and the use of FlexMaster® resulted in less debris, but a thicker smear layer than that of K-Flexofile®.