Teeth difficult to treat endodontically include teeth with dilacerated or calcified canals. Due to difficult canal morphology, treatment may result in under-filling, root perforation, or inadvertent instrument fracture within the canal. Although under-filling or a fractured instrument in the root canal may not be a problem in vital teeth, it may lead to problems in necrotic teeth or those with an apical lesion.Regardless, retreatment interventions are often fraught with mishaps, namely, root perforations. Although such complications may occur in all types of teeth and during the various stages of endodontic treatment, they are more common in teeth with anomalous root canal anatomy, narrow canals, abnormally-positioned teeth, and teeth with root curvatures. Perforations may also occur during removal of guttapercha for preparation of post space, root canal cleaning and shaping, or while attempting to bypass fractured instruments in the root canal system. Procedural errors
impede proper treatment of the tooth, compromising the prognosis, especially in teeth with necrotic pulps or periradicular lesions. While some teeth with fractured files or perforations may be treated orthograde from within the canal, a perforated tooth with a curved root which cannot be negotiated and is associated with an apical lesion often requires both orthograde and retrograde treatment. Sometimes, teeth with perforations or fractured files are considered hopeless and are needlessly extracted by the dentist, whereas many of these teeth can be successfully treated.
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