Ledges are result of careless instrumentation
caused by:
1] large instruments out of sequence and
2] insertion of instruments short of working length or
3]use of inflexible instruments in a curved root canal
4]poor design access cavity prevent direct access to apical third of root canal
The access curvature in the coronal part of canal may prevent negotiation of an instruments through the apical curvature in a fine, tortuous canal and may result in ledge formation
ledges and...
