Malocclusion Classification

Prepared and reviewed by the PrepElephant Academic Review Team

First published 2 Oct 2026 · Spot an error?

On this page

Direct answer
What you must remember
Classifying one child three ways
Where students lose the easy marks
Frequently asked questions
Related topics

Direct answer

Edward Angle keyed his 1899 classification to the mesiodistal relation of the first permanent molars: Class I neutrocclusion, where the mesiobuccal cusp of the upper first molar occludes in the mesiobuccal groove of the lower; Class II distocclusion, where the lower molar sits distal, in division 1 with proclined upper incisors and increased overjet or division 2 with retroclined upper centrals and deep bite; and Class III mesiocclusion, where the lower molar sits mesial. Subdivision marks a unilateral discrepancy named by the affected side. Because molars can mislead, the British Standards classification grades the incisor relationship instead, Simon related the arches to three facial planes, and modern practice adds aetiology.

What you must remember

Angle (1899): Class I neutrocclusion; Class II distocclusion with divisions 1 and 2; Class III mesiocclusion; subdivision = unilateral, named by the side in discrepancy.
Class II division 2: retroclined upper central incisors, deep overbite, and characteristically normal or reduced overjet — the trap for anyone who equates Class II with big overjet.
British Standards incisor classification: Class I — lower incisor tip touches or lies directly below the upper incisor cingulum; Class II — posterior to it (division 1 proclined uppers, division 2 retroclined uppers); Class III — lower incisor edge anterior to the upper with reversed overjet.
Dewey's modification subdivides Class I into five types (crowded anteriors, proclined incisors, lingually placed incisors in crossbite, posterior crossbite, mesially drifted molars) and Class III into three.
Simon's gnathostatic classification relates arches to three anthropometric planes — Frankfort horizontal, orbital and midsagittal — giving protraction/retraction, attraction/abstraction and contraction/distraction respectively; his law of the canine puts the orbital plane distal to the maxillary canine.
Ackerman and Proffit's five characteristics — alignment, transverse, anteroposterior, vertical, profile — escape Angle's single plane.
Aetiology divides into general (heredity, congenital defects such as clefts, environment, nutrition, endocrine) and local factors — premature loss of deciduous teeth the most significant local cause, then prolonged retention, anomalies of number, size and form, caries and oral habits.
Prevalence data vary with index and population; in most surveys Class I predominates, Class II is the next most common, and Class III the least.

Classifying one child three ways

A 13-year-old presents after early loss of both upper deciduous second molars: the maxillary first permanent molars have drifted mesially into the leeway space and sit full-cusp Class II, the upper incisors are proclined with 8 mm of overjet, and a persistent thumb habit is evident. By Angle this is Class II division 1 bilaterally — and partly acquired, not inherited. By the British Standards incisor classification, also Class II division 1; the two can disagree — a skeletal Class III may carry a Class I molar relation through dentoalveolar compensation, with only the incisor relation exposing the truth. Aetiologically, the local factors lead: premature loss with mesial drift of the maxillary molars, the retained habit, crowding of the erupting second premolars, over a mild hereditary Class II tendency. Each classification earns its place: Angle communicates the molar story, the incisor classification communicates severity, aetiology decides the treatment plan — space regaining, habit control and interception now, because the cause is environmental and therefore correctable.

Where students lose the easy marks

The classic error is calling the incisor relation "Class II by Angle" — Angle's classes are molar-based, and if the question names incisors the answer belongs to the British Standards system. Second, subdivision: named by the side showing the Class II or Class III deviation — "Class II subdivision right" means the right side is Class II. Third, Class II division 2 does not require increased overjet — retroclined upper centrals with a deep overbite define it — and candidates who expect a big overjet miss the diagnosis at the chair and in the MCQ. Fourth, Simon's six terms get scrambled unless each pair is pinned to its plane: protraction/retraction to orbital, attraction/abstraction to Frankfort, contraction/distraction to midsagittal. Finally, the commonest local cause of malocclusion is premature loss of deciduous teeth — not thumbsucking, however tempting.

Frequently asked questions

What is the criterion of Angle's classification and its three classes?

The anteroposterior relation of the mandibular to the maxillary first permanent molar: Class I neutrocclusion, Class II distocclusion, Class III mesiocclusion.

How does Class II division 2 differ from division 1?

Division 2 has retroclined upper central incisors with a deep overbite and typically normal or reduced overjet, whereas division 1 has proclined upper incisors with increased overjet.

What does "subdivision" mean in Angle's system?

A unilateral discrepancy — the molar relation differs on the two sides, and the class is named for the side in deviation.

Which planes and terms does Simon's classification use?

Three anthropometric planes — Frankfort horizontal, orbital and midsagittal — with protraction/retraction, attraction/abstraction and contraction/distraction respectively.

Which local factor is the most significant cause of malocclusion?

Premature loss of deciduous teeth, through mesial drift of permanent molars, space loss and crowding of successors.