Post design and its impact on the root and crown.

To optimize the longevity of an overlying restoration, it is important to follow proper engineering principles. These include the requirement of either an internal or external ferrule. When sufficient tooth structure does not exist to support an internal ferrule, it becomes necessary to use a porcelain-fused-to-metal restoration. The posts supporting these restorations should have low insertional stresses, high retentive values, and an even distribution of functional stresses. In the author's opinion, the split-shanked design of the Flexi-Post and Flexi-Flange is the only design that can deliver this essential combination. The purpose of a post is to help restore or reinforce the coronal structure of a tooth to further increase the retention and stability of an artificial crown. Removing tooth structure to place a post does not increase the root's resistance to vertical or horizontal fracture.