Table 1: IOTN treatment grades.

Grade 5 (Extreme/Need treatment)
5•i Impeded eruption of teeth (except for third molars) due to crowding, displacement, the presence of supernumerary teeth, retained deciduous teeth and any pathological cause.
5•h Extensive hypodontia with restorative implications (more than 1 tooth missing in any quadrant) requiring pre-restorative orthodontics.
5•a Increased overjet greater than 9 mm.
5•m Reverse overjet greater than 3.5 mm with reported masticatory and speech difficulties.
5•p Defects of cleft lip and palate and other craniofacial anomalies.
5•s Submerged deciduous teeth.
Grade 4 (Severe/Need treatment)
4•h Less extensive hypodontia requiring pre-restorative orthodontics or orthodontic space closure to obviate the need for a prosthesis.
4•a Increased overjet greater than 6 mm, but less than or equal to 9 mm.
4•b Reverse overjet greater than 3.5 mm with no masticatory or speech difficulties.
4•m Reverse overjet greater than 1 mm but less than 3.5 mm with recorded masticatory and speech difficulties.
4•c Anterior or posterior crossbites with greater than 2 mm discrepancy between retruded contact position and intercuspal position.
4•l Posterior lingual crossbite with no functional occlusal contact in one or both buccal segments.
4•d Severe contact point displacements greater than 4 mm.
4•e Extreme lateral or anterior open bites greater than 4 mm.
4•f Increased and complete overbite with gingival or palatal trauma.
4•t Partially erupted teeth, tipped and impacted against adjacent teeth.
4•x Presence of supernumerary teeth.
Grade 3 (Moderate/Borderline need)
3•a Increased overjet greater than 3.5 mm, but less than or equal to 6 mm with incompetent lips.
3•b Reverse overjet greater than 1 mm, but less than or equal to 3.5 mm.
3•c Anterior or posterior crossbites with greater than 1 mm, but less than or equal to 2 mm discrepancy between retruded contact position and intercuspal position.
3•d Contact point displacements greater than 2 mm, but less than or equal to 4 mm.
3•e Lateral or anterior open bite greater than 2 mm, but less than or equal to 4 mm.
3•f Deep overbite complete on gingival or palatal tissues, but no trauma.
Grade 2 (Mild/Little Need)
2•a Increased overjet greater than 3.5 mm, but less than or equal to 6 mm with competent lips.
2•b Reverse overjet greater than 0 mm but less than or equal to 1 mm.
2•c Anterior or posterior crossbite with less than or equal to 1 mm discrepancy between retruded contact position and intercuspal position.
2•d Contact point displacements greater than 1 mm but less than or equal to 2 mm.
2•e Anterior or posterior open bite greater than 1 mm but less than or equal to 2 mm.
2•f Increased overbite greater than or equal to 3.5 mm without gingival contact.
2•g Pre- or post-normal occlusions with no other anomalies (includes up to half a unit discrepancy).
Grade 1 (No Need)
1• Extremely minor malocclusions including contact point displacements less than 1 mm.

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