Lip Analysis

We study the patient’s lips and how they relate to the area around them when making the orthodontics study, comparing them to their whole face, their tongue and their teeth. This enables us to make a diagnosis of the patient’s dental situation and plan their treatment.

Lip thickness

As previously discussed in the article on Facial Analysis, lip thickness helps us to decide which treatment to apply.

Thick lips

This means weak muscles and, therefore, that the teeth can be moved forward easily. It will also be easier to keep them in place after treatment.


Thin Lips

This means strong muscles which will try to stop the teeth from moving forwards. If we move the teeth forwards during treatment, we will later have to use fixed (fitted to the inside of the teeth) or removable transparent retainers for quite some time.


Relationship of the lips with the immediately surrounding area

Relationship with the chin

This is the sub-labial or mento-labial fold. In other words, the fold immediately beneath the lower lip.

  • This fold is known as ‘deep’ when the top and bottom lips don’t meet, i.e. when the top lip juts out, leaving a space between the top and bottom lips.

The same occurs in the event of a skeletal deep bite, i.e. when the bottom third of the face is shorter due to the fact that the space between the base of the nose and the chin is shorter with respect to the rest of the face.

  • It is known as ‘small’ or flat, in the case of a long face.

Relationship with the nose

This is the naso-labial angle, i.e. the angle between the upper lip and the base of the nose.

If the angle is small, less than 90 degrees, the upper teeth may have an exaggerated forward tilt or proclination which is pushing the top lip upwards.

In the event of having decided to straighten teeth which are strongly proclined, crowded or crossed, we may find that the treatment is pushing them too far forwards and upwards, making the roots come away from the upper jawbone. This means that we must extract one or more teeth to make place for the others when aligned.

Relationship between the lips and the teeth

Don’t forget that your lips are surrounded by circular muscles known as orbicularis oris. It is these muscles, together with your lips, which model the position of your teeth.

Prior to orthodontics, your teeth occupy a specific position due to a certain neuro-muscular balance.

That’s why, on changing their position during treatment, we must take care not to excessively force the initial position of the teeth in relation to the cheeks and tongue; this is because of the risk that the teeth will return to their initial position after treatment, particularly if the necessary retainers are not used.

These retainers normally take the shape of a fixed wire on the inside of the lower teeth, invisible to the eye, or transparent retainers acting as a plastic sheath which is only worn when sleeping.

On analysing the relationship between the lips and the teeth, we will concentrate on the following aspects:

Gummy smile

When smiling broadly, or forcing a smile, the patient should reveal all of their superior central incisors, including some 2mm of gum.

When too much of the gum above the upper teeth is revealed, something we find more commonly in women, we call it a ‘gummy smile.’

Decades ago it was considered attractive to show a lot of gum. Today it is not so popular. One example is the beautiful Spanish model and actress Inés Sastre: when smiling in natural photographs for magazines, she reveals a great deal of gum. However, when advertising cosmetics, the image is photoshopped and shows her with splendid long, white teeth, and hardly any gum.

As well as showing a lot of gum, the problem is that these smiles clearly reveal the area where the root joins the tooth, and in smokers or former periodontitis sufferers the gum recedes, leaving pockets, or black spaces visible between the teeth.

Similarly, in the event of the gum receding due to gingivitis or poor hygiene in people with veneers or crowns, the contrast of the dark root above the veneer becomes visible.

Patients with a gummy smile must ensure that their teeth are in as perfect condition as possible, given that any defects are clearly visible.


In the event of patients with a slight gummy smile, the recommendation is to do nothing, since, with age, the upper lip sags to reveal less gum and dental root.

Orthodontics to correct a gummy smile should start at 9 years of age, although the smile will also improve if treatment is started in adolescence.

Whatever the case, sometimes corrective surgery is also required. In adults, a gummy smile can only be improved by means of maxillary surgery.

Upper lip with respect to the incisal edge

Coming back to the maxillary central incisors, the dentist will observe how much tooth is visible on speaking naturally, from the lower edge of the lip to the lower or normal incisal edge. Here the norm is to show 2-4mm of tooth.

Visibility of the upper tooth is synonymous with youth, given that, with age, our faces start drooping to show very little or none of the upper teeth, so that what we see when talking are the bottom teeth.

People with a gummy smile start looking better as they get older, since they reveal less gum, while continuing to show more upper tooth than people of their age, giving them a younger appearance.

The amount of upper tooth shown is important, particularly when carrying out full dental rehabilitation, whether with removable dentures or implants.

Labial tonicity

To establish the patient’s lip strength, the dentist holds their upper or lower lip with their index finger and thumb.

Strong lips are thin and indicate that if, when proceeding with the treatment, we have to bring the teeth forward a great deal, it will be difficult to maintain the result, meaning that it may be advisable to extract one or more teeth to make space so that the teeth do not have to be brought so far forward.

If the lips are weak, and in this case generally thick, we can bring the teeth forward a fair bit, obtaining a stable result.

Lip closure

We study the way the lips behave while at rest and with the teeth closed. In this case, the lips must meet and close against one another. Open lips, which don’t cover the teeth or close the mouth, are known as incompetent.

This labial incompetence may be due to:

Dental causes:

  • Too much of an overjet; i.e. the upper front teeth are overly prominent with respect to the lower teeth, leaving an anteroposterior space when using all of the teeth to bite.
  • Too much of a dental protrusion. This means that the teeth are too far forward with respect to the maxillary bone, and to the face in general.

Facial causes:

  • Very long face, with a highly pronounced open or large angle between the upper and lower jawbones.
  • Short upper lip.

Functional causes:

  • The patient has a labial or lingual habit, i.e. they frequently, and particularly when swallowing, stick their lip or tongue between their front teeth, preventing their lips from meeting properly when their mouth is closed. This is known as an anterior open bite. The problem may also be the result of either sucking their thumb or excessively using their dummies in children aged 6 and over.
  • Breathing through the mouth, as a result of having adenoids or obstructed nasal cavities. Here the patient’s mouth stays open, even at night.The tongue remains in the lower position, without leaning against the palate, causing the latter to narrow.

Once we have studied the lips, we will do the same with the tongue.

Lingual analysis

We check to establish whether or not the patient has anomalous lingual positions causing the bones to develop inappropriately and the teeth to move into the wrong position.

The tongue is made up of a very powerful group of constantly moving muscles due to the fact that we swallow constantly, day and night. This makes it very strong from birth, gradually giving shape to the upper jawbone and the palate, the lower jaw and the teeth themselves.


Let’s look at two cases where the tongue has an influence on the diagnosis and on the orthodontics treatment.

Lingual habit

In normal circumstances, when swallowing, the lip, cheek and tongue muscles contract to send saliva or food down into the throat, enabling us to swallow.

The front of the mouth must be closed, because otherwise food or saliva would spill out of it. The teeth therefore normally close while swallowing, coming into contact with one another.

If for reasons related to the bones or teeth, the top and bottom front teeth do not come into contact with one another, the patient will use their tongue to close the area. This is called a lingual habit.

Lingual habit, which tends to occur in children, means that their permanent front teeth do not grow in properly, leaving a space between them.

A check is made to see if they have this habit by asking the patient to swallow water with their lips separated and studying their teeth as they do so. On swallowing, we can see whether or not the patient pushes their tongue between their teeth.

We must establish whether the initial culprit is the tongue, or if another problem has caused the teeth to separate, meaning that the tongue simply fills the space in order to be able to swallow. For in For instance, in patients who suck their thumb, their permanent front teeth don’t grow in properly and don’t therefore meet when swallowing. In such cases, they use their tongue to close the area, meaning that the dental malposition persists even when the patient stops sucking their thumb.

Lingual ankyloglossia


This is when the tongue has limited ability to move.

In normal conditions, patients can stick their tongue out more than 2mm beyond the lower lip. Also, with their mouth open, they can touch their palate with the tip of their tongue.

This movement is impossible in the case of lingual ankyloglossia, a condition which tends to occur when the lingual frenulum is short and prevents the tongue from moving properly upwards, or forwards, so that the tongue always stays in its lower position, making the jaw wider. Given that in these cases the tongue never touches the palate and therefore fails to shape it, patients with this problem will always have a narrow palate.

Sometimes it is the cause of skeletal class III. In these cases the lingual frenulum must be snipped to free the tongue to prevent it from sitting constantly in the lower position.

Observing the lips and tongue is part of the orthodontics study. In addition to observing the actual patient, the dentist also studies X-rays, photographs and plaster models.