**Core Concept**
Axial reduction in dental restorations refers to the removal of tooth structure along the axis of the tooth, perpendicular to the occlusal surface. This concept is crucial in prosthodontics, as it affects the retention, stability, and overall success of the restoration.

**Why the Correct Answer is Right**
Axial reduction in a posterior three-quarter crown involves removing tooth structure from the axial walls of the tooth, usually to accommodate the preparation of the crown. This process requires careful consideration of the tooth's anatomy, the extent of the reduction, and the type of restoration being placed. The axial walls of the tooth provide support and retention for the crown, and excessive reduction can compromise the integrity of the tooth.

**Why Each Wrong Option is Incorrect**
**Option A:** Axial reduction is not primarily concerned with the occlusal surface of the tooth.
**Option B:** Axial reduction is not a procedure typically associated with anterior teeth.
**Option C:** Axial reduction is not a term used to describe the process of removing decayed tooth structure.

**Clinical Pearl / High-Yield Fact**
When performing axial reduction for a posterior three-quarter crown, it is essential to maintain the integrity of the axial walls to ensure proper retention and stability of the restoration. This can be achieved by using a series of incremental reductions and carefully evaluating the tooth's anatomy throughout the process.

**Correct Answer:** D.