Levator labii superioris and the gummy smile
- Muscle
- Highlighted area
Quick facts
- Origin
- Infraorbital margin of the maxilla, just above the infraorbital foramen.
- Insertion
- Muscles and skin of the upper lip, between the levator labii superioris alaeque nasi and the zygomaticus minor.
- Action
- Lifts the upper lip and deepens the upper part of the nasolabial fold.
- Innervation
- Zygomatic and buccal branches of the facial nerve.
- Relevance in facial harmonization
- One of the elevators involved in gummy smile of muscular cause.
The levator labii superioris is a muscle of facial expression that arises just below the rim of the orbit and runs down to the upper lip. When it contracts, it lifts the lip and shows the upper teeth. It is one of the muscles that set the height of the lip in the smile and, when very active, contributes to gummy smile, in which a wide band of gum shows when smiling.
Where is it and how is it built?
The muscle is broad and flat. It arises from the infraorbital margin of the maxilla, just above the infraorbital foramen, and covers the foramen, through which the infraorbital artery and nerve exit. Its fibers run down and converge on the upper lip, where they blend with the orbicularis oris.
Together with two neighbors, it forms the upper lip elevator group:
| Muscle | Origin | Main action |
|---|---|---|
| Levator labii superioris alaeque nasi | Frontal process of the maxilla, beside the nose | Lifts the lip and flares the nostril |
| Levator labii superioris | Infraorbital margin of the maxilla | Lifts the upper lip |
| Zygomaticus minor | Zygomatic bone | Lifts the lip and moves it outward |
More lateral, the zygomaticus major pulls the mouth corner up and outward. Deeper, the levator anguli oris arises from the canine fossa, below the infraorbital foramen.
Why does it matter in facial harmonization?
The levator labii superioris is involved in two frequent topics in the office:
- Gummy smile: when the elevators are hyperactive, the lip rises more than usual and exposes more gum. Botulinum toxin can reduce this elevation temporarily. See botulinum toxin for gummy smile.
- Nasolabial fold: contraction of the elevators deepens the upper part of the smile lines and is part of the dynamic component of the fold.
Before thinking about toxin, the causes of gummy smile need to be separated. Vertical maxillary excess, a short lip, short dental crowns, altered passive eruption and excess gum each have their own diagnosis and treatment, often dental or surgical. Toxin acts only on the muscular component.
How does it show up in the assessment?
- Measure gum exposure in a broad smile, from the front, and record it in a photo or video.
- Compare the sides: a gummy smile can be asymmetric, more evident at the front or at the back teeth.
- Assess the length of the upper lip at rest and the exposure of the incisors.
- Check the proportion between tooth and gum, and refer for dental assessment when there is a dental or bony component.
For the lip itself, see the lips area.
Also called: levator labii superioris, upper lip elevator, infraorbital head of the old quadratus labii superioris.
Frequently asked questions
Which muscles cause a gummy smile?
In a gummy smile of muscular cause, the main muscles involved are the levator labii superioris, the levator labii superioris alaeque nasi and the zygomaticus minor. But a gummy smile can also have a bony, dental or gingival cause.
Does botulinum toxin fix any gummy smile?
No. It acts only on the muscular component, reducing lip elevation, and the effect is temporary. Vertical maxillary excess, short crowns or excess gum call for other approaches, after diagnosis.