What is the required post diameter in relation to the width of the tooth structure?

The correct answer reflects the guideline in restorative dentistry regarding the relationship between the post diameter and the width of the remaining tooth structure. Specifically, a post diameter that is one-third the width of the tooth structure provides a balance between retention and preservation of tooth material.

A post that is too large (relative to the width of the tooth structure) may compromise the remaining tooth, leading to fracturing. Conversely, a post that is too small may lack adequate retention, thus failing to support the restoration effectively. Therefore, designing a post with a diameter that is one-third the width of the remaining tooth structure optimally maintains structural integrity while ensuring sufficient retention for the restoration. This balance is crucial for the longevity and function of the dental restoration.

Other options suggest either too little or too much material in relation to the remaining tooth structure, which can lead to potential complications in clinical practice.