Study of the Progressive Changes in Canal Shape After Using Different Instruments by Hand in Simulated S-Shaped Canals

All four instruments straightened the S-shaped canals, except the combination of PHU (S1, Sx, and S2) and NiTi K-files, which created a continuous funnel shape. There was a significant difference in the amount of material removed between S2 and F1 of the PHU system (p < 0.05), and the finishing files of PHU created the same transportation as the stainless steel instruments with the same tip size (p > 0.05).