How do nickel-titanium rotary systems compare to stainless steel hand files in terms of canal preparation safety and efficiency?

• A. NiTi files are more flexible, maintain canal curvature and centering, generally faster with less transportation; stainless steel is stiffer and more prone to ledges and perforations in curved canals.
• B. NiTi files are less flexible and cause more ledges than stainless steel.
• C. NiTi files are slower and more prone to breakage.
• D. NiTi files cannot be used in curved canals.

Answer: (A)