The document describes the Index of Orthodontic Treatment Need (IOTN), which is used to assess the severity of malocclusion or misalignment of teeth. It assigns severity levels from 1 to 5 for various dental traits, with 1 indicating little or no need for treatment and 5 indicating the most extreme need for treatment. Traits assessed include overjet, overbite, crossbite, displacement of teeth, missing teeth, impeded eruption, and cleft lip or palate. Each level provides guidelines on the parameters that define the severity of the trait.

1. IOTN
Dental Health
1
(No
need)
2
(Mild/ Little need)
3
(Moderate/
Borderline need)
4
(Severe/ need treatment)
5
(Extreme/ need
treatment)
Overjet 3.5-6 mm +
competent lips
3.5-6 mm +
incompetent lips
6-9 mm > 9 mm
Reverse Overjet 0-1 mm 1-3.5 mm >3.5 mm + no masticatory
& speech difficulties
1-3.5 mm + masticatory &
speech difficulties
>3.5 mm +
masticatory &
speech difficulties
Crossbite Ant/post X-bite + <
1 mm discrepancy
Ant/post X-bite +
1-2mm
discrepancy
Ant/post X-bite + > 2mm
discrepancy
Post lingual X-bite no
contact 1/both segment
Displacement < 1 mm 1-2 mm 2-4 mm > 4 mm
Overbite ≥ 3.5 mm, , no
gingival contact
Complete, no
gingival trauma
Complete + Gingival
trauma
Lat/Ant openbite 1-2 mm 2- 4 mm > 4 mm
Missing teeth Less extensive hypodontia
1/quadrant
Extensive
hypodontia
>1/quadrant
Impeded eruption/
Impacted tooth
Partially
impacted/erupted tooth
Impeded eruption
(except 3
rd
molar)
Supernumery
tooth
Supernumery tooth
present
Cleft Cleft lip and palate