Index for orthodontic treatment needs is/are:
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)
SCAN index
ICON index
DAI index
All of the above