What is the maximum width of the bur that should be used for a post?

Using a bur that is no wider than one-third the diameter of the root is optimal for several reasons. The primary goal when preparing a post site is to ensure adequate retention while minimizing the risk of damaging the remaining tooth structure. A bur width that is too large can compromise the integrity of the root, potentially leading to fracture or weakening of the tooth.

By limiting the bur to one-third of the root's diameter, sufficient space is created for the post while maintaining a solid foundation of tooth structure around it. This balance is critical for the long-term success of the post-retained restoration. Furthermore, using this size helps to avoid unnecessary removal of dentinal tissue, ensuring that the root canal system remains intact and healthy.

Ultimately, choosing a bur width in this manner promotes both the stability of the post and the overall health of the tooth, making it the preferred standard in dental practice.