Canal preparation with Hero 642 rotary Ni-Ti instruments compared with stainless steel hand K-file assessed using computed tomography

Abstract

Aim To compare ex vivo root canal preparation with conventional stainless steel K-files and Hero 642 rotary Ni-Ti instruments. Methodology Mesiobuccal canals of 20 maxillary first molars (with angles of curvature between 25 degrees and 35 degrees) were used. After preparation with Hero 642 rotary instruments and stainless steel K-files, the amount of transportation that occurred was assessed using computed tomography. The teeth were scanned by computed tomography before instrumentation. One millimetre thick slices were prepared from the apical end point to the pulp chamber. The first two sections were 3 mm from the apical end of the root (apical level) and 3 mm below the orifice (coronal level). A further section (mid-root level) was recorded, dividing the distance between the sections of apical and coronal levels into two equal lengths. Ten teeth were instrumented using Hero 642 rotary instruments and another 10 teeth were instrumented using stainless steel K-files. Following the completion of the instrumentation, the teeth were again scanned and compared with the cross-sectional images taken prior to canal preparation. Amount of transportation and centreing ability was assessed. Student's t-test was used for statistical analysis. Results Less transportation occurred with Hero 642 rotary instruments than stainless steel K-files at the mid-root and coronal levels (mid-root: P < 0.05 and coronal: P < 0.001). Hero 642 rotary instruments had better centreing ability than K-files at all three levels (apical: P < 0.05, mid-root: P < 0.05 and coronal: P < 0.001). Conclusions Hero 642 rotary instruments transported canals less, especially at the middle and coronal thirds of the root canals than stainless steel K-files. Hero 642 instruments had better centreing ability.