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Occlusion and malocclusion: Angle classes and when to refer

  • Examination

Occlusion is how upper and lower teeth meet. Angle's classes describe the bite by where the upper first molar sits on the lower one.

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See it in 3D: Mandible · Maxillae

What it is

In a normal bite the upper teeth overlap the lower ones slightly in front (overjet and overbite) and the back teeth interlock. Angle's classification uses the first permanent molars. In Class I the mesiobuccal cusp of the upper first molar sits in the buccal groove of the lower first molar; crowding or spacing may still be present. In Class II the lower jaw is behind (retrognathic profile, often with increased overjet). In Class III the lower jaw is ahead (prognathic profile, reverse overjet). Other problems include crossbites, open bites and crowding.

Findings and interpretation

  • Class I: normal molar relation; Class II: lower molar distal; Class III: lower molar mesial.
  • A large overjet raises the risk of incisor trauma in children.
  • Persistent thumb sucking can cause an anterior open bite and a narrow upper arch.
  • Mouth breathing from enlarged adenoids is associated with long-face growth and open bite.
  • Cleft lip and palate cause malocclusion and need multidisciplinary care from birth.

How it is done

  1. Look at the profile: straight, convex (Class II) or concave (Class III).
  2. With the teeth together, look at the relation of the first molars on each side.
  3. Measure the overjet (front-to-back gap between incisors) and overbite (vertical overlap).
  4. Look for crossbites (upper teeth inside the lower), open bite (incisors do not meet) and crowding.
  5. Ask about habits: thumb sucking, dummy use beyond early childhood, mouth breathing, tongue thrust.

Common mistakes

  • A posterior crossbite with a shift of the lower jaw in a child should be treated early, because it can make the jaw grow asymmetrically.
  • Snoring and mouth breathing in a child with malocclusion may be obstructive sleep apnoea: ask and refer.
  • Severe skeletal discrepancies in adults need orthodontics combined with jaw surgery.

Next step / Initial management

  • Large overjet, crossbite with shift, open bite from habits or severe crowding in a child: refer to the dentist or orthodontist for timing of treatment.
  • Snoring, pauses in breathing or mouth breathing: assess for adenotonsillar hypertrophy and sleep apnoea and refer to ENT.
  • Facial asymmetry or skeletal Class III in growing children: refer for orthodontic assessment.

Test yourself

Think of the answer, then tap the question to see it.

What defines Angle Class I occlusion?

The mesiobuccal cusp of the upper first molar sits in the buccal groove of the lower first molar.

Which habit commonly causes an anterior open bite?

Prolonged thumb or dummy sucking.

Why does a large overjet matter in children?

It increases the risk of traumatic injury to the upper incisors.

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See it in 3D2

The structures of Durgical's 3D anatomy where it is found.

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Educational content; it does not replace assessment by a dentist or doctor and is not a clinical instruction. For facial or neck swelling with difficulty swallowing or breathing, a knocked-out tooth or bleeding that will not stop, go to an emergency department at once.

Sources: Orthodontics, Malocclusion (StatPearls Publishing (NCBI Bookshelf), 2023); Anatomy, Occlusal Contact Relations And Mandibular Movements (StatPearls Publishing (NCBI Bookshelf), 2023); Cleft Lip (StatPearls Publishing (NCBI Bookshelf), 2023).

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