Perforations: Etiology

Accidental perforations from the pulp chamber into the periodontium (e.g. furcation area) occur more frequently in obliterated teeth when an attempt is being made to locate the pulp chamber and/or root canals. Also, an artificial crown may result in confusion regarding the true orientation of the root, thus increasing the risk of perforation.
During preparation, strip perforations of curved canals may occur following excessive cleaning and shaping or the inappropriate use of rigid instruments.
Zip perforations at the apex (usually in curved canals) are usually caused by the improper use of instruments with actively cutting tips. However, even flexible instruments with modified tips may cause apical perforations when used incorrectly.