Upper lip covers teeth when smiling

You’d be forgiven for thinking that counting the different types of smiles would be straightforward. It’s anything but.

In the mid-19th century, French neurologist Guillaume Duchenne wanted to distinguish real smiles from fake. Interested in the response of nerves and muscles to stimulation, he applied electricity to particular parts of faces to see the results.

He divided smiles into two groups: those that involved the crinkling of the eyes—sincere smiles—and those that used only the muscles around the mouth—insincere smiles.

AP Photo

Today, the full smile that uses the muscles around the mouth and eyes is known as a “Duchenne smile,” and the fake one is the “Pan Am smile,” named after the kind of smile you might greet someone with if it’s part of your job to be friendly.

In 1974, Leonard Rubin described three basic types of smile, based on his study of 100 people:

• The “Mona Lisa,” where the corners of the mouth go up and outwards and the upper teeth are exposed. The dominant muscle action is from the zygomaticus major. About two-thirds of people studied smile this way.

• The “canine” smile, where the canine teeth are exposed. The dominant muscle action is from the levator labii superioris. 31% of people smile like this.

• The “full-dentured,” where the lips are pulled back strongly, showing both upper and lower rows of teeth. All muscles are equally dominant. Just 2% of people were found to smile this way.

Cosmetic surgeons, who have to be meticulous in identifying the smiles that their patients are paying good money to try to achieve, call these three types commissure, cuspid, and complex, respectively.

Phuong Nguyen, a Philadelphia plastic and reconstructive surgeon, attempts to clarify the matter using celebrities. The “Mona Lisa,” he says, is the Angelina Jolie. The Tom Cruise smile is a “canine smile,” and a Julia Roberts is the “full-dentured” smile. This is a subjective matter—other doctors place Jolie in the second or third categories.

AP Photo/Francois Mori

Smiling is not a realm given over to easy description. Contemplate the ideal smile as recounted by one clinician in the Journal of Clinical Orthodontics:

An optimal smile is characterized by an upper lip that reaches the gingival margins, with an upward or straight curvature between the philtrum and commissures; an upper incisal line coincident with the border of the lower lip; minimal or no lateral negative space; a commissural line and occlusal frontal plane parallel to the pupillary line; and harmoniously integrated dental and gingival components.

The total number of different types of smile is frequently debated. A recent BBC article gave the total as 19.

Arguably the most important researcher into smiles over the past 30 years has been Paul Ekman at the University of California. His 1978 Facial Action Coding System, written with Wallace V Friesen, seeks to create an atlas of nearly all possible human expressions. Ekman says, in his book Telling Lies, that their technique for measuring the face can distinguish over 50 different smiles.

Confused? You’re not the only one. Perhaps the best approach is to just grin and bear it.

This article originally appeared on Mosaic. This article is part of Quartz Ideas, our home for bold arguments and big thinkers.

Are you unhappy with the way your smile looks? Does this keep you from smiling more? Do your teeth look too small for the rest of your mouth? If so, then you may have what is known as a gingival smile line. A gingival smile line is the dental term used to describe the exposure of the upper gum tissue when smiling naturally. It is also sometimes called gummy smile, high lip line, and full denture smile. 

Aesthetically speaking, cosmetic dentists generally consider an ideal smile to be one where the upper lip covers both the upper gum line, as well as the top portion of the front upper teeth. However, some cosmetic dentists note that minimal gum exposure can still produce an aesthetically pleasing look so long as the gum tissue is evenly contoured. These types of smiles are known as low smile lines, while a gingival smile is known as a high smile line. 

There are many different factors that can determine whether you have a low or high smile line. These can include some or all of the following: your facial muscles, size and shape of your teeth, gum tissue, and the size and shape of your lips. Therefore, when it comes to treating a gingival smile line, the primary cause will first need to be identified and addressed to ensure the best treatment results. 

In fact, some causes of gingival smile lines are also symptoms of underlying dental conditions. For example, if developmental problems with the upper jaw is the cause, then orthodontic treatment may be required to reposition the jaw and prevent bite problems down the line. Another possible cause can be a hyperactive upper lip muscle, which can be treated by relaxing the muscle. 

Other cases of gingival smile lines may not have an underlying cause and may simply be considered a cosmetic issue. Nevertheless, there are still cosmetic dental procedures available to treat a high smile line. The most common procedures for correcting a gummy smile are crown lengthening and gingivectomy procedures. Crown lengthening works to expose more of the tooth’s crown by removing excess gum tissue, while a gingivectomy removes and reshapes excess gum tissue. 

These two procedures may also be performed in coordination with other restorative dental treatments. This is often because having a high smile line can negatively affect the appearance of certain restorations. For example, if you need to have a dental crown placed, your cosmetic dentist may recommend a crown lengthening procedure as well to make the final result look more natural. Depending on the type of restorative treatment, as well as the extent of your gingival smile line, your dentist may present you with different options. 

Overall, having a gingival smile line simply means that you show more upper gum tissue when you smile. For most people with gingival smile lines, the concern is mainly cosmetic, however it can be a symptom of another dental issue for some. Regardless, a high smile line can be easily treated cosmetically or through addressing papertyper its cause. 

Dr. Roman Fedorciw has been in private practice in Cromwell since 1991. He is a member of the Academy of General Dentistry, American Academy of Cosmetic Dentistry and the American Dental Association. He is also a member of the Connecticut Dental Association and Middlesex County Dental Association. Dr. Fedorciw has been acknowledged by his peers as one of the “Top Dentists” in Hartford County by Hartford Magazine and in the state of Connecticut by Connecticut Magazine.

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