**Core Concept**
Apexification is a technique used in endodontics to induce a calcific barrier in a tooth with an open apex, allowing for the completion of root development and subsequent obturation. This procedure is essential in maintaining the structural integrity and vitality of the tooth.

**Why the Correct Answer is Right**
Apexification is indicated in cases of permanent teeth with wide open apexes, particularly in young patients with non-vital teeth. The goal of apexification is to create a calcified barrier within the canal, which will eventually allow for the completion of root development and the obturation of the canal. This is achieved by using a medicated intracanal dressing, such as calcium hydroxide or a calcium hydroxide-based paste, to induce a calcific barrier.

**Why Each Wrong Option is Incorrect**
**Option A:** Apexification is not the treatment of choice for teeth with narrow or calcified canals, as it may not be effective in inducing a calcific barrier in these cases.
**Option B:** Apexification is not typically used in cases of teeth with significant periodontal involvement, as the procedure is focused on the endodontic aspect of the tooth.
**Option C:** Apexification is not the same as apexogenesis, which is a technique used to promote the continued development of the root apex in immature teeth.

**Clinical Pearl / High-Yield Fact**
Apexification is a time-consuming procedure, often requiring multiple visits and a period of several months to induce a calcific barrier. It is essential for dentists and endodontists to carefully evaluate the prognosis of the tooth and determine the most suitable treatment option.

**Correct Answer: C.**