**Core Concept**
The buccinator muscle is a thin, quadrilateral muscle of facial expression that forms the anterior part of the lateral wall of the oral cavity. It plays a crucial role in mastication, swallowing, and speech. Several important structures pierce through this muscle to maintain the normal function of the oral cavity.

**Why the Correct Answer is Right**
To determine which structure does not pierce the buccinator muscle, let's first identify the structures that do. The buccal branches of the mandibular nerve (V3), the buccal artery, and the buccal vein pierce the buccinator muscle. These structures are essential for the innervation and blood supply of the buccal mucosa. Additionally, the parotid duct also pierces the buccinator muscle to open into the oral cavity.

**Why Each Wrong Option is Incorrect**
**Option A:** The buccal branches of the mandibular nerve (V3) pierce the buccinator muscle, so this option is incorrect.
**Option B:** The buccal artery and vein also pierce the buccinator muscle, making this option incorrect.
**Option C:** The parotid duct pierces the buccinator muscle, so this option is incorrect as well.

**Clinical Pearl / High-Yield Fact**
To remember the structures that pierce the buccinator muscle, recall the mnemonic "Buccal Branches, Artery, Vein, and Duct" (BBADV).

**Correct Answer:** D.