Gummy Smile: Causes and Treatment Options

The main causes of a gummy smile fall into four groups: the gum, the teeth, the upper lip and the upper jaw.

• The gum: in altered passive eruption, gum overlaps more of the enamel than usual, a 2011 review explains. Sometimes the gum has overgrown, which is worth showing to a dentist.
• The teeth: upper front teeth that have come down further than usual, known as over-eruption.
• The upper lip: a hypermobile upper lip, which rises further than usual on smiling, or, some reviews add, a short upper lip.
• The jaw: vertical maxillary excess, a skeletal cause in which the upper jaw has grown more than usual in height.

In a 2024 study of 123 healthy, non-smoking adults with all their upper front teeth and 4 mm or more of gum showing, at a Saudi university, altered passive eruption was the commonest cause (73.2%, alone or with others), and 55.3% had more than one.

A 2020 review says the cause of a gummy smile must be accurately diagnosed for treatment to be appropriate. In a 2024 study of 123 adults, the examiners' checks included:

• how much gum showed above an upper front tooth at a full smile;
• upper lip length at rest, and how far the lip rose to a full smile, with more than 8 mm counted as hypermobile;
• the front teeth's width against their length, and the bone level on X-rays, for altered passive eruption;
• facial proportions, confirmed on a side-view X-ray of the skull, for vertical maxillary excess.

A 2016 review adds that every cause should be identified, even though not all may be resolved by treatment; otherwise treatment may not follow an adequate order, which may lead to unexpected and unacceptable results.