Background. Ni-Ti instruments present different characteristics and principles of canal preparation. The aim of this study is the comparison of shaping on endobloc between two types of endodontic rotary instruments, Mtwo and FlexMaster (FM). Methods and materials. Twenty endo training-bloc were divided into two groups of 10, the first one shaped with the single length technique (Mtwo), the other one with the FM (crown-down technique). Pictures of specimens were acquired by using a stereomicroscope before and after shaping; in all the images was calculated the enlargement of canal walls from median line (Image ProPlus and Autocad) at 18 levels (6 in each canalar third). Data were analyzed by independent-samples T test. Results. A not homogeneous shaping was produced by FM; they induced a major transportation of external side in proximity of the canal curve, but a minor canal enlargement. Statistically significant differences were found between the groups at each level except the first apical one (p<0,005-0,001). Conclusions. Although both techniques demonstrated a good shaping in respect of the original canal anatomy and with a minimal lateral transportation, Mtwo instruments seem to have a simpler and faster using with a minor tendency to the simulated canal screwing.
