Class III malocclusion
Class III malocclusion is the bite class with the lower jaw or lower teeth, or both, set ahead of the upper jaw or teeth, as the American Association of Orthodontists’ glossary defines it; underbite is the everyday name for it.
The AAO’s Class III entry, and Class II beside it
In the Glossary of Orthodontic Terms of the American Association of Orthodontists (AAO), Class III malocclusion is “A malocclusion where the lower teeth and/or jaw is positioned ahead relative to the upper teeth and/or jaw.”
The glossary’s Class II entry describes the reverse case, with the lower teeth or jaw positioned back, so the two classes are opposite ways for the lower teeth and jaw to sit out of line with the upper.
Mesio-occlusion: Class III in the AAPD guideline
Mesio-occlusion is the clinical name Class III carries in the American Academy of Pediatric Dentistry (AAPD) guideline on managing the developing dentition and occlusion: “Class III malocclusion (mesio-occlusion) involves a mesial relationship of the mandible to the maxilla or mandibular teeth to maxillary teeth.”
On causes, the AAPD says the relationship “may result from dental factors (malposition of the teeth in the arches), skeletal factors (asymmetry, mandibular prognathism, and/or maxillary retrognathism), anterior functional shift of the mandible, or a combination of these factors.” In plainer words: teeth out of position, a lower jaw set forward, an upper jaw set back or an uneven jaw, a forward functional shift of the lower jaw, or a mix. An orthodontist tells these apart by examining the teeth and jaws.
Underbite: the plain word, and how the AAO links it to Class III
Underbite names the same bite in everyday speech, and the AAO glossary’s own Underbite entry makes the link in its last sentence: “The lower front teeth or jaw sit ahead of the upper front teeth or jaw. Also known as a Class III malocclusion.” Crossbite is a different word; asked whether a crossbite is the same as an underbite, the AAO’s crossbite page answers no.
The answer page on what an underbite is and how it is treated goes into its causes and treatment, and crossbite and the other bite words sit in the glossary’s list of bite problems.
Sources
- American Association of Orthodontists, Orthodontic Glossary: Braces & Dental Terms Defined
- American Academy of Pediatric Dentistry, Management of the Developing Dentition and Occlusion in Pediatric Dentistry
- American Association of Orthodontists, What Is A Crossbite?
Class III or underbite: bring the question to a consultation
Use either name, Class III or underbite, in a consultation request from the band below.
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