Final answer:
The Nanda or CIA is an orthodontic appliance used for the intrusive movement of teeth to correct overbites and gummy smiles without excessive force.
Step-by-step explanation:
The Nanda or CIA (Connecticut Intrusion Archwire) is primarily used for intrusive movements of teeth in orthodontic treatments. It's a specialized orthodontic archwire that applies light, continuous forces to intrude the incisors. This technique is significant in cases where an overbite needs to be corrected or there is excessive display of the gums (gummy smile). The archwire, designed by Dr. Ravindra Nanda, is known for its efficiency in intruding anterior teeth without the need for excessive force, which can reduce the risk of root resorption and other adverse effects.