IOTN Classification — ORE Part 1 MCQ
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Correct answer: A — Grade 4 (treatment need)
The correct answer is A, Grade 4. In the IOTN Dental Health Component, an increased overjet of more than 6 mm up to and including 9 mm is classified as Grade 4a. A 7 mm overjet therefore falls directly within Grade 4. Grade 3 is not correct because its relevant overjet criterion extends only to 6 mm and additionally specifies incompetent lips. Grade 5 requires an overjet greater than 9 mm, so 7 mm does not qualify. Grades 1 and 2 represent no or little treatment need and are incompatible with this degree of increased overjet. The question concerns the DHC measurement category alone; no Aesthetic Component score is required to assign this grade.
Reference: Oxford University Hospitals NHS Foundation Trust. Orthodontics referrals: IOTN Grade 4—"Increased overjet greater than 6 mm but less than or equal to 9 mm"; Grade 5—greater than 9 mm. Current page accessed July 2026. https://www.ouh.nhs.uk/services/referrals/specialist-surgery/orthodontics/