Apical root strain as a function of post extension into a composite resin core

This study tested the hypothesis that there is no difference in the amount of strain measured in the root of an extracted tooth at the apical end of a prefabricated post, whether a composite resin core completely covers the head of the post or the post is exposed at the occlusal surface of the core. Twenty extracted teeth were measured (1) after endodontic treatment (baseline), (2) after a composite resin core was fabricated over a prefabricated post, and (3) after a cast crown was cemented. The teeth were randomly divided into two groups after baseline testing. In group 1, the post was buried within the core, and in group 2, the head of the post was exposed on the occlusal surface of the core. Analysis of results indicated a statistically significant decrease in strain from the baseline to the crown when 1 mm of composite resin covered the head of the post. However, based on the small strain values measured, the difference may not be clinically significant.