The Index of Orthodontic Treatment Need (IOTN) was developed as a means to objectively measure a person's need for orthodontic treatment.
(1) dental health: 5 grades from none to very great
(2) aesthetics: attractiveness of the patient's labial aspect ranked from 1 (close to normal) to 10
Dental Health Component Grade 1: None
Extremely minor malocclusions including displacements < 1 mm.
Dental Health Component Grade 2: Little
Increased overjet 3.6 - 6.0 mm, with competent lips.
Reverse overjet 0.1 -1.0 mm
Anterior to posterior crossbite with up to 1 mm discrepancy between retruded contact position and intercuspal position.
Displacement of teeth 1.1 - 2.0 mm
Anterior or posterior openbite 1.1 - 2.0 mm
Increased overbite >= 3.5 mm, without gingival contact.
Pre-normal or post-normal occlusions with no other anomalies. Includes up to half a unit discrepancy.
Dental Health Component Grade 3: Moderate
Increased overjet 3.6 - 6.0 mm, with incompetent lips.
Reverse overjet 1.1 - 3.5 mm
Anterior or posterior crossbites with 1.1 - 2.0 mm discrepancy.
Displacement of teeth 2.1 - 4.0 mm
Lateral or anterior crossbite 2.1 - 4.0 mm
Increased and complete overbite without gingival trauma.
Dental Health Component Grade 4: Great
Increased overjet 6.1 - 9.0 mm.
Reversed overjet > 3.5 mm with no masticatory or speech difficulties.
Anterior or posterior crossbites with > 2 mm discrepancy between retruded contact position and intercuspal position.
Severe displacement of teeth, > 4 mm
Extreme lateral or anterior openbites, > 4 mm
Increased and complete overbite with gingival or palatal trauma.
Less extensive hypodontia requiring pre-restorative orthodontic space closure to obviate the need for a prosthesis.
Posterior lingual crossbite with no functional occlusal contact in one or both buccal segments.
Reverse overjet 1.1 - 3.5 mm with recorded masticatory and speech difficulties.
Partially erupted teeth, tipped and impacted against adjacent teeth.
Dental Health Component Grade 5: Very Great
Increased overjet > 9 mm
Extensive hypodontia with restorative implications (more than 1 tooth missing in any quadrant) requiring pre-restorative orthodontics.
Impeded eruptions of teeth (with the exception of the third molars) due to crowding, displacement, the presence of supernumerary teeth, retained deciduous teeth, and any pathological cause.
Reverse overjet > 3.5 mm with reported masticatory and speech difficulties.
Defects of cleft lip and palate.
Submerged deciduous teeth.
A patient's score is based on matching his or her dental appearance with one of a series of 10 photographs showing the labial aspect of different Class I or Class II malocclusions ranked according to their attractiveness.
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