The prosthodontic use of endodontically treated teeth: theory and biomechanics of post preparation.

It is impossible to state that any given system is better than another system for any and all situations. In all systems it is advisable to leave at least 3 to 5 mm of root canal filling to preserve the integrity of the apical seal. From a retentive standpoint, the parallel-sided posts have a greater retention than the tapering-sided posts but, because they are placed within a tapering root, they require more finesse on placement. In all teeth the length of the post is important since it is directly proportional to the amount of support offered by the post and its resistance to root fracture.