**Core Concept**
Pulp polyp, also known as a pulp horn or radicular cyst, is a type of odontogenic cyst that forms as a result of the transformation of the epithelial cells lining the dental pulp. This process is a response to pulpal irritation or necrosis, leading to the formation of a cystic structure.

**Why the Correct Answer is Right**
The formation of pulp polyp is associated with the transformation of the epithelial cells lining the dental pulp into a cystic structure. This transformation is thought to be a result of the inflammatory response to pulpal irritation or necrosis. The epithelial cells, in an attempt to cover the necrotic pulp, proliferate and form a cystic lining, which eventually becomes a pulp polyp.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the correct reason associated with the formation of pulp polyp.
* **Option B:** This option is incorrect because it refers to a different type of dental cyst, not a pulp polyp.
* **Option C:** This option is incorrect because it refers to a non-dental condition, not related to the formation of pulp polyp.

**Clinical Pearl / High-Yield Fact**
It is essential to differentiate pulp polyp from other types of dental cysts, such as periapical cysts, which form in response to chronic pulpal infection. Pulp polyp is typically associated with a more localized response to pulpal irritation.

**Correct Answer:** D.