The SAF is actually very safe to use, and has an extremely low chance for separation. Despite its fragile appearance, the lattice-like structure provides the SAF more strength than instruments with a solid central core. The SAF works in vertical vibration and does not rotate inside the root canal, in contrary to rotaries, that bind with the canal walls, rotate and tend to break when they encounter increased strain.
As other instruments made of Nickel-Titanium, the SAF is very flexible, but is bound to break eventually. However, its operation in vertical vibration and not rotation, as well as its lattice-like structure, prevent it from screwing into the walls of the canal as rotary instruments do when they break. This means that a broken SAF fragment can easily be removed or bypassed, without unnecessarily sacrificing sound dentin.
Farmakis (Int Endod J, 2013) showed that deformation of the SAF occurs mainly as detachment of one of the arches or struts at the connection point on one of the longitudinal beams of the file, and that in no case did the metal fragment block the canal. When such a strut starts to separate, the initiation of separation can be seen before it separated, and the dentist can stop using the file.
Solomonov (J Conserv Dent, 2015) showed that the chance for file separation of the SAF inside the canal during clinical use is 0.6%, and that the separated part can almost always be easily retrieved, to a level that non-retrievable separation only occurred in 0.1% of the cases. Even when the separated fragment remains inside the canal and cannot be retrieved, the separation always occurs in an environment with copious amounts of sodium hypochlorite, the fragment is very thin, and no excessive removal of sound dentin is required to bypass it.