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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Index for orthodontic treatment needs is/are:
assistant
The correct answer is  SCAN index is the synonym for Index for Orthodontic Treatment Needs (IOTN). IOTN index was developed by BROOK and SHAW to link dentofacial variation to perceive esthetic impairment.
Key Concept:
The other Orthodontic treatment need indices are:

Handicapping Labio-lingual Deviation Index (HLD) (Draker)
Dental Aesthetic Index (DAI) (Cons et al)
Index of Complexity, Outcome and Need (ICON) (Daniels & Richmond)