Intraoral photographs show a Class I molar relationship together with crowding, rotations and an irregular anterior segment. How is this best described?

Correct answer: A. Class I malocclusion

• A. CORRECT. CLASS I MALOCCLUSION. Angle's classification describes the ANTEROPOSTERIOR molar relationship only. A Class I molar relationship with crowding, rotations, spacing, crossbite or an anterior irregularity is a Class I MALOCCLUSION — the commonest malocclusion of all, and the group Dewey subdivided into types I to V.
• B. 'Class I occlusion' (normal occlusion) means a Class I molar relationship with the teeth also in correct alignment on a normal line of occlusion — no crowding, no rotations. That is not what these photographs show.
• C. A Class II relationship would place the mesiobuccal cusp of the maxillary first molar mesial to the mandibular molar's buccal groove — not present here.
• D. 'Class II occlusion' is not a recognised term; a Class II relationship is by definition a malocclusion.

Note: The distinction is examined repeatedly and is easy to lose marks on: OCCLUSION means correct relationship AND correct alignment; MALOCCLUSION means anything deviating from that, even when the molar relationship itself is Class I.