PubMed1986
Once the individual components of the Richmond crown were isolated from the post-core-crown complex, each was subjected to scrutiny. Consensus declared that the core portion should resemble the ideal preparation for a vital tooth. Current techniques allow the dentist to create an "ideal" preparation to accommodate clinical conditions such as occlusion and esthetics. Post construction evaluation can be divided into two categories: retention and stress distribution. Research has demonstrated that threaded posts screwed into tapped post holes were the most retentive, followed by cylindrical posts, and the tapered posts were the least retentive. In photoelastic stress distribution studies, cylindrical posts showed the most favorable patterns, with screw posts demonstrating the least desirable configurations. There is no exclusive technique that satisfies all criteria for success. Compromise is common and the method with more advantages and fewer disadvantages is chosen. Stress distribution is of greater importance than retention because a post can be recemented if dislodged from a tooth. However, if the root fractures, the tooth is commonly lost. Cementation of posts has received limited attention. Some posts with vents are commercially available, but there is little evidence that this effectively decreases hydrostatic pressures during cementation. An important consideration is the choice of materials. Traditionally, pulpless teeth were restored with cast gold posts covered with either complete gold crowns or gold crowns with acrylic resin veneers. These materials had a similar modulus of elasticity and coefficient of thermal expansion.(ABSTRACT TRUNCATED AT 250 WORDS)