What determines how much gum shows when you smile?
Visible gum most often has four sources, and only one of them lies in the gum itself: the other three are the lip, the height of the teeth and the bone of the upper jaw.
Each of these sources can produce the same picture in the mirror, that is, a lot of gum when smiling. A gummy smile is therefore not a diagnosis but a symptom.
No value of gingival display has been established by measurement as the boundary of an attractive smile. The conventional three-millimetre threshold makes conversation in the surgery easier, but it is sometimes treated as though it were a diagnosis: a patient with a band of three and a half millimetres who is not bothered by it can end up being qualified for correction. What decides is therefore whether the band bothers the patient, not exactly how much it measures.
Four causes, four different pathways
A gummy smile breaks down into four distinct clinical situations and four solutions, and the last column of the table is the most important one, because it contains the commonest reason for disappointment after a procedure.
| Cause | What you see in the mirror | Treatment pathway | Durability of the effect | What this pathway will not change |
|---|---|---|---|---|
| Gum covers part of the crown | Short teeth when smiling, square shape, even gum line, wide pink band | Surgical crown lengthening, often with correction of the bone margin; one procedure | Largely maintained, with slight rebound in the first year | The length or the mobility of the lip |
| Lip too mobile | Large difference between rest and full smile, teeth of normal length | Lip repositioning or an injection of botulinum toxin; one treatment appointment | Toxin has to be repeated; for lip repositioning the data are inconsistent, from a quarter of the effect lost at one year to values that stay stable at three years | The height of the teeth or the dimension of the bone |
| Teeth worn down or not fully erupted | Incisal edges worn, crowns low, the gum looks normal | Restoration of the edges, sometimes with orthodontic treatment; weeks or months | Depends on the durability of the restoration itself | The mobility of the lip or the excess of bone |
| Vertical maxillary excess | Gum visible at the back teeth as well, lower third of the face elongated | Intrusion (moving the teeth deeper into the bone) on miniscrews, or orthognathic surgery; months up to two years | The widest range of correction; after surgery on the upper jaw some patients show partial relapse | The mobility of the lip or gum covering the crown; no other pathway can replace it |
The rows do not exclude one another. In some patients two causes are at work at once, for example a short crown together with a very mobile lip. A single procedure will then take away only part of the visible gum, and that is the commonest reason why a correction falls short of expectations even though it was carried out correctly.
Before you choose a pathway, settle whether you want to change anything at all: a gummy smile is not in itself a disease, and doing nothing is a fully valid option. The answer changes when the exposed gum responds with inflammation, when the incisal edges go on wearing down, or when a skeletal cause affects the bite. Function is then at stake, and not appearance alone.
Whether the band will shrink with age in a young adult enough to justify postponing the decision is not known: there are no data that settle it, and where the procedure is irreversible that lack of knowledge argues for waiting.
The order of procedures can matter as much as their choice, because a restoration placed before the gum is corrected usually has to be redone. More on restoration can be found on the page devoted to veneers and composite bonding.
What can you measure yourself in the mirror?
You will need a millimetre ruler and good light: smile as widely as you can, and hold the smile.
- The band of gum. Measure vertically from the edge of the upper lip to the gum just above a central incisor.
- The height of the central incisor. Measure the tooth from the incisal edge to the gum; in an adult the typical value falls between 9 and 11 mm, in women nearer the lower end.
- Lip movement. Mark the position of the lip edge at rest and at full smile, then subtract one from the other.
- The lips at rest. Without smiling, check whether they meet easily, or part so that the edges of the teeth show.
- Extent. Check whether the gum shows only at the front teeth, or at the back teeth as well.
- Evenness of the line. See whether the gum margin runs level, or drops lower at individual teeth.
How to read your own numbers. A crown clearly below 9 mm with the incisal edges intact points to the first row of the table. Lip movement above 8 mm with a band of 4 mm or more is the second row. Worn incisal edges with a low crown are the third row. Gum visible at the back teeth as well, or lips that part at rest, are the fourth row, and measurement alone is then not enough.
The measurements on this list usually narrow the cause to one or two, but they do not close the diagnosis, because the dimension of the bone cannot be judged in a mirror. A radiograph and an assessment of facial proportions are needed for that. If you cannot take one of the measurements yourself, photograph your smile with a phone at arm's length and show it at the consultation.
Are short teeth a problem of the gum, or of the tooth itself?
Are short teeth a problem of the gum, or of the tooth itself?
If the crown is short, the incisal edge intact and the gum line even, the gum has most likely stopped on its way and is covering part of the tooth that should be showing. Patients usually call this gum overgrowth, although no gum has been added: it simply has not receded as it should have done while the tooth was erupting.
True gingival overgrowth has different causes, more often systemic or drug-induced, and is treated differently. If, on the other hand, the crown is short but the edges are worn and uneven, tooth has been lost, not gum gained. This distinction can usually be made in a mirror, although only examination in the surgery confirms it.
In the first case the treatment is surgical crown lengthening: the procedure uncovers the true dimension of the tooth, and it sometimes requires correction of the bone margin in order to preserve the distance between bone and gum.
The effect is not maintained in full. In a twelve-month follow-up of twenty young women the procedure lengthened the crowns of the upper central incisors by an average of 2.4 mm, but by twelve months the gum had taken back about 0.75 mm of that. The authors judged this rebound clinically insignificant; the patient should nonetheless know about it before the procedure. When a restoration is being planned, these fractions of a millimetre decide whether the margin of a veneer stays hidden. Healing is also affected by the thickness of the tissues, described more fully under gingival phenotype.
In the second case the tooth has to be restored rather than uncovered: veneers or composite bonding restore the height of the crown and leave the gum line alone.
This distinction is sometimes confused in both directions, and then either option costs time and money while the gummy smile stays the same, because the wrong tissue was corrected. The extent of a restoration is covered by a separate article on how many veneers a plan includes.
When does a gummy smile come from the bone?
Usually when gum shows not only above the central incisors but at the back teeth too, and the lower part of the face appears elongated.
Increased height of the anterior alveolar segment together with a deep bite can be treated by orthodontic intrusion of the incisors on miniscrews. In a randomised trial of such intrusion, root shortening occurred in both of the compared variants, but without a control group that underwent no intrusion the whole of that change cannot be attributed to the treatment itself. Where the vertical excess of the upper jaw is genuinely skeletal, the standard route is combined orthodontic and surgical treatment with surgical repositioning of the upper jaw. In the retrospective study cited here, surgery gave a greater improvement in attractiveness ratings than botulinum toxin.
How long does the effect of each pathway last?
It depends on the pathway.
The durability column in the table sets them side by side. The depth of the data behind each of them is different. Publications on procedures on the gum and on the lip usually stop at one year of follow-up, and single ones reach three years; orthognathic surgery was followed for up to five years, but in publications from three decades ago. How these procedures look after a decade is at present essentially not known.
The effect of botulinum toxin lasts the shortest time. Gingival display fell from about 4.9 mm to 1.9 mm within two weeks in the group given the agent into the levator labii superioris alaeque nasi muscle. At six months the measurement had not yet returned to the baseline value; both figures come from a trial with random allocation to groups. The procedure has to be repeated, and that is its main limitation.
For lip repositioning the data are inconsistent, and this is the least certain point in the whole subject. One pooling of studies shows an effect that diminishes with time: about 2.9 mm at three months, 2.7 mm at six months and 2.1 mm at one year, which amounts to roughly a quarter of the effect lost.
For lip repositioning the data are inconsistent, and this is the least certain point in the whole subject. One pooling of studies shows an effect that diminishes with time: about 2.9 mm at three months, 2.7 mm at six months and 2.1 mm at one year, which amounts to roughly a quarter of the effect lost.
The difference comes from which publications were included and from exactly how the procedure was carried out, because the technique has several variants, and for an individual patient durability depends on which variant the operator performs. It is worth hearing both series of figures and asking at the consultation which variant the operator uses, and what his or her own one-year observations after it are.
Skeletal correction is the most demanding of the four, and its durability has not been compared directly with the other pathways.
Consult your case with an expert and get your treatment plan
Frequently asked questions
Can a gummy smile be improved without surgery?
Sometimes. If the cause is an excessively mobile lip, an injection of botulinum toxin reduces gingival display without an incision. If the cause is gum covering the crown, or an excess of bone, non-surgical methods do not solve the problem and only postpone the decision. Whether to change anything at all is for you to decide. What to do it with is decided by the cause, and the cause cannot be chosen.
Will the gum grow back after a gum line correction?
Partly. After the procedure the gum margin moves towards the incisal edge and takes back about 0.75 mm of the length gained. That is what came out of a twelve-month follow-up after surgical crown lengthening in twenty young women, and the authors judged the change clinically insignificant. The risk of greater rebound rises when the procedure was carried out without correction of the bone margin and the patient's tissues are thick.
How long does healing take after surgical crown lengthening?
The soft tissue closes within ten days to a fortnight, but the gum margin goes on moving for months, and in the study with twelve-month follow-up it was still changing position up to the twelfth month. That second window sets the timing of the prosthetic restoration, which is usually planned several months later. Fixing the margin of the crown earlier risks it becoming exposed. The healing schedule is described in surgical crown lengthening.
What does the gum look like in the first two weeks after the procedure?
For the first few days it can be swollen and paler than usual, and sutures or a dressing change its shape. Brushing of the operated area is restricted at that stage and is replaced by a rinse prescribed by the dentist. Redness that gradually subsides is expected. Increasing pain, purulent discharge or fever call for contact with the practice the same day.
Will veneers solve the problem of short teeth?
It depends on why the teeth are short. With worn teeth, veneers restore the height of the crown and improve the proportions. Where gum is covering part of the crown, a veneer extends the tooth towards the lip, so it does not reduce the band of gum, and it can make it stand out even more. The order is then reversed: the gum first, the restoration afterwards.
Does botulinum toxin used on the lip give a lasting effect?
No. The effect is reversible and has to be repeated, although in the trial the measurement at six months had not yet returned to the starting point. For this reason the injection is sometimes treated as a trial before a decision on surgery, because it lets the change be seen before it becomes irreversible.
The procedure is matched to the cause, not to the appearance
Measuring in the mirror narrows the list, and the consultation closes it. A radiograph settles the matter when bone is involved. You can start with an aesthetic dentist or a periodontist (a dentist who treats gum disease), and where a skeletal cause is suspected an orthodontist is needed. The greatest risk is not a failed procedure, but a procedure performed well on a wrongly identified cause. The gummy smile then comes back unchanged, and the patient has been through a period of healing that changed nothing.
Read more:
- Periodontics
- Veneers and Composite Bonding in Warsaw
- Surgical crown lengthening — when is it necessary and how is it performed
- How many teeth do veneers go on — why rarely on eight
- Smile design step by step:
- Gingival phenotype — thin or thick? Why it matters for treatment
Content and liability disclaimer
This article is informational and educational in nature and does not constitute medical advice, a diagnosis or a therapeutic recommendation — it does not replace a consultation with a specialist. If you are experiencing symptoms, have doubts or are facing a decision about treatment, consult a dentist. The methods described and the data cited are general in nature. The results of scientific studies relate to populations, not to an individual patient. The course and outcome of therapy depend on the individual clinical situation and may vary between patients. No information contained in this article constitutes a guarantee of result. The content has been prepared with due care, based on publicly available medical knowledge and the scientific publications indicated in the Sources section. We do not advise taking or refraining from any health-related action solely on the basis of the content of this article, without prior consultation with a doctor.
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