**Apexification**

**Core Concept**
Apexification is a dental procedure used to induce calcification of the root tip (apex) of a tooth with a non-vital pulp, typically after a traumatic injury or pulp necrosis. This process aims to create a calcified barrier at the apex, preventing the tooth from becoming infected or abscessed.

**Why the Correct Answer is Right**
The correct answer involves the use of calcium hydroxide (Ca(OH)2) or a calcium hydroxide-based material, such as MTA (Mineral Trioxide Aggregate), to induce calcification. These materials are placed in the root canal to stimulate the formation of a calcified barrier at the apex. Calcium hydroxide has an alkaline pH, which helps to disinfect the area and stimulate the deposition of calcium ions, leading to calcification. MTA is a biocompatible material that can be used as an alternative to calcium hydroxide.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is not a commonly used material for apexification. While some materials may be used as alternatives, they are not the standard choice for this procedure.
* **Option B:** This option is incorrect because it is not a material that is typically used for apexification. While some materials may be used in dentistry, they are not the correct choice for this specific procedure.
* **Option C:** This option is incorrect because it is not a material that is commonly used for apexification. While some materials may be used in dentistry, they are not the correct choice for this specific procedure.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that apexification is typically performed after a traumatic injury or pulp necrosis, and not as a routine procedure for root canal treatment. The goal of apexification is to create a calcified barrier at the apex, preventing the tooth from becoming infected or abscessed.

**Correct Answer: C. MTA (Mineral Trioxide Aggregate)**