**Question:** Lingual plate is indicated in all, except

A. Mandibular ankylosis
B. Mandibular hypoplasia
C. Maxillary hypoplasia
D. Open bite

**Correct Answer:** D. Open bite

**Core Concept:** Lingual plates are dental appliances used in orthodontic treatment to correct various malocclusions, particularly those involving the mandible. They are made of stainless steel and are bonded to the lingual surface of the teeth, exerting pressure and guiding tooth movement.

**Why the Correct Answer is Right:** Lingual plates are primarily indicated in cases involving mandibular malformations or deviations (e.g., mandibular ankylosis, hypoplasia). In these situations, the lingual plate helps to correct the mandibular ankylosis or hypoplasia by exerting pressure and guiding tooth movement.

**Why Each Wrong Option is Incorrect:**

A. Mandibular ankylosis: Ankylosis is a condition in which the tooth root fuses with the alveolar bone, preventing further tooth movement. In such cases, lingual plates would not be effective, as they are designed to work with normal tooth movement.

B. Mandibular hypoplasia: Hypoplasia refers to the underdevelopment of the mandible (jaw bone). Lingual plates can be used to treat mandibular hypoplasia, as they exert pressure and guide tooth movement, helping to correct the malocclusion.

C. Maxillary hypoplasia: Hypoplasia refers to the underdevelopment of maxilla (upper jaw bone) and is not the reason for using lingual plates. Therefore, this option is incorrect.

D. Open bite: An open bite refers to a malocclusion characterized by an excessive vertical dimension of occlusion, where the front teeth do not overlap when the jaws close. Lingual plates are not indicated in cases of open bite, as they are designed for correcting mandibular malocclusions, not maxillary or vertical malocclusions like open bite.

**Clinical Pearl:** In cases of mandibular malformations or deviations, orthodontic treatment options like lingual plates, lingual orthodontics, or surgical procedures should be considered, rather than lingual plates. Each option may be used for different malocclusions, ensuring appropriate treatment selection for each case is crucial for successful outcomes.