Key points in brief
- Black triangles between teeth form when the gum does not reach the point where the teeth touch. The most common reasons are bone loss between the teeth, the shape or position of the teeth, or age.
- The shape of the teeth is changed with bonding, which means building up tooth-coloured material, and their position is corrected with orthodontic treatment. The interdental papilla, that is, the gum between the teeth, can be partly rebuilt with a gum procedure.
- If your gums bleed or are inflamed, they need to be treated first. Closing the space next to a diseased gum may make cleaning harder and keep the inflammation going.
- A small triangle with healthy gums can often be closed with bonding. A large one, especially after bone loss, usually needs a combination of methods, and the aim is to make the triangle smaller.
- If the triangle does not show when you smile naturally and your gums are healthy, cleaning it well is often enough. Once a triangle has been closed, the space needs daily cleaning with floss or an interdental brush chosen for you at the practice.
Where black triangles between teeth come from
A black triangle appears when the interdental papilla - the triangular piece of gum between two teeth - does not reach the point where the teeth touch. Black triangles between teeth, also called gaps at the gum line, therefore mean that the papilla is partly or entirely missing. They are not a hole in the tooth.
The papilla rests on the bone that lies between the roots of neighbouring teeth. The point where two teeth touch is called the contact point. The further this point lies from the bone, the harder it is for the papilla to reach it. Between the upper front teeth, the papilla almost always fills the space if the distance from the contact point to the bone is about 4 mm. At a distance of 7 mm or more, it rarely does.
The four most common causes are:
- bone loss between the teeth after periodontitis, an inflammation of the tissues that hold the tooth in place: the gum, the bone and the fibres that attach the root to the bone
- the shape of the teeth: teeth that are wide at the biting edge and narrow at the gum touch far from the gum
- a change in the position of the teeth
- age, because the papilla may gradually recede as we get older
When teeth are crowded, they overlap and hide the space at the gum. Once orthodontic treatment lines them up, this space becomes visible, especially if the teeth are triangular in shape or their roots tilt away from each other.
In adults with healthy gums who were treated with clear aligners and had no teeth removed, a triangle appeared between the lower central incisors, the two middle front teeth, in roughly 4 people in 10. Between the upper central incisors, it appeared in 1 person in 4. It seems likely that this happens more often when teeth are removed as part of treatment. A triangle after orthodontic treatment can be made smaller by adjusting the position of the teeth or with bonding, if the gums are healthy. It may also be accompanied by bone loss between the teeth.
After gum treatment, a triangle may become visible because the previously swollen gum shrinks. This is a result of healing and does not mean that the treatment has failed.
If the gum recedes from the front surface of the tooth and exposes its neck, that is gum recession. If the teeth do not touch at all, it is more likely a diastema, a gap between the teeth. Closing a diastema is planned differently, because there is no contact point that could be moved.
What you can check before your visit
Pay attention to whether:
- there is one triangle or several, and whether it involves the upper or the lower teeth
- it appeared after orthodontic treatment or after gum treatment
- your gums bleed when you brush or floss
- food gets trapped in the space or it gets in the way when you speak
- the triangle shows when you smile naturally
Also take a photo of your smile from the front in daylight, and use it to check whether the papilla reaches almost to the contact point. In a few months, the photo will let you compare whether the triangle is getting bigger. A phone photo cannot, however, show how far the contact point lies from the bone.
Bonding, gum treatment or a combination of methods
Black triangles between teeth are closed with different methods depending on the cause, but if the gums are diseased, the inflammation is treated first.
| Cause | What can be done | Limitation |
|---|---|---|
| Triangular teeth, healthy gums, small triangle | Bonding: widening the teeth near the gum, usually without grinding the tooth | With a larger triangle, the teeth may look wide and square |
| Bone loss between the teeth after periodontitis | Gum treatment first, then bonding or a gum procedure | After bone loss, the papilla usually does not fully return |
| Teeth that have shifted or tilted apart, for example after orthodontic treatment | Correcting the position of the teeth with orthodontic treatment, sometimes with gentle reshaping of the enamel on the sides of the teeth, then bonding if needed | It cannot be predicted in advance whether orthodontic treatment alone will be enough |
| Papilla only slightly receded, bone at a good level, you do not want your teeth widened | Gum procedure: a graft of tissue from the palate or hyaluronic acid injections | The effect is usually partial. After injections it may fade, and how much the acid itself helps is uncertain |
If the triangle does not show when you smile naturally and your gums are healthy, cleaning it well is often enough. Closing it makes sense when the triangle bothers you, traps food or makes speaking harder.
Bonding means applying composite to the tooth, a tooth-coloured material that hardens under a lamp. For a black triangle, the dentist uses it to widen the side walls of the teeth just next to the gum. The contact point then moves towards the gum and the space becomes smaller.
Bonding means applying composite to the tooth, a tooth-coloured material that hardens under a lamp. For a black triangle, the dentist uses it to widen the side walls of the teeth just next to the gum. The contact point then moves towards the gum and the space becomes smaller.
Bonding often does not need a local anaesthetic. At the end of the procedure, the dentist polishes the edges of the composite and checks whether the space can be cleaned. The composite can later be adjusted or removed without much loss of enamel, because the tooth underneath has usually not been ground down.
When methods are combined, the order matters. The gums are treated or the position of the teeth is corrected first. After a few months, once the gums are healthy, the dentist assesses how much is left to close, and bonding comes last. The composite is usually applied in layers, as with composite veneers and bonding of the whole front surface of the tooth. If the teeth also need a change of colour or shape, veneers come into consideration, and they may close the triangle as part of broader treatment.
What the dentist checks before treatment
First of all, the dentist checks whether the gums and the bone around the teeth are healthy. Using a thin probe, they measure the pockets - the narrow gaps between the gum and the tooth - and look at whether the gum bleeds when it is gently examined. If the pockets are deeper than they should be or the gum bleeds, the inflammation is treated first, and only then is closing the triangle planned.
An X-ray shows the level of bone between the teeth and the position of the roots. On that basis, the dentist assesses how far the contact point lies from the bone and whether the papilla has a chance of filling the space once the contact point has been moved.
The size of the triangle itself also matters. In a small triangle, the papilla reaches almost to the contact point and only a narrow gap is left. In a large one, the papilla ends far from the contact point, sometimes at the level of the necks of the teeth. Whether bonding alone will be enough depends on this.
The dentist also looks at the shape of the teeth and at gum thickness. Gum thickness alone does not decide whether the papilla will fill the space. It does, however, matter when a gum procedure is being planned. The dentist will also ask whether you smoke. Smoking makes it harder for the gums to heal, so it may change the plan for gum procedures.
How the shape of the composite affects cleaning and the look of your teeth
Composite that closes a triangle has to blend into the tooth smoothly, with no step and no excess under the gum. If a step or excess is left, plaque builds up next to it and the neighbouring gum easily becomes inflamed.
In people with healthy gums, composite closing a small triangle gave a good result over the first year. Over time, however, more plaque built up around the composite than at the start. That is why the result also depends on daily cleaning and on visits to the hygienist, who checks whether plaque is building up there.
When the space is open, cleaning relies mainly on interdental brushes matched to its width. A brush that is too large can injure the gum, so the size and the way to use it are best chosen with the hygienist. Once a triangle has been closed, the space is narrower, so a smaller brush or floss is usually needed. Do not force a toothpick or other hard tools into the space, because the pressure may push the papilla further down.
The shape of the composite shows most on the upper central incisors. There the dentist plans it in the same way as for central incisor bonding.
What you can expect after treatment
The interdental papilla is rebuilt either with a graft of tissue from the palate or with hyaluronic acid injections. Most is known about the graft, in which the dentist places a small piece of tissue from the palate under the papilla. After this procedure, the triangle filled in, on average, by roughly half within a year. Injections may make the triangle smaller. After more than 3 months, however, they did not work clearly better than injections without the active substance. So it is not yet known how much the acid itself helps. Several injections are usually needed.
Bonding on its own is generally a single visit. Gum treatment usually takes a few weeks, and bonding is planned only after the gums have been reassessed, typically after a few months. Orthodontic treatment most often lasts from a few months to more than a year. How many years the composite will last is hard to say today, which is why its edge is examined at every check-up.
Where to start if a black triangle bothers you
Start with a visit at which the dentist examines your gums and takes an X-ray. If there is inflammation, it needs to be treated first, and closing the triangle is discussed after a reassessment. When choosing a method, ask whether the space can be cleaned with an interdental brush or floss after treatment. If a closed space cannot be cleaned, plaque collects there and the gum becomes inflamed.
Consult your case with an expert and get your treatment plan
Frequently asked questions
Will the interdental papilla grow back on its own?
Loss of the interdental papilla caused by bone loss between the teeth usually does not reverse on its own. The papilla rests on bone, and bone lost through periodontitis does not come back by itself. If the bone is at a good level and the triangle comes from the shape or position of the teeth, the papilla may partly fill the space once the contact point has been moved closer to the gum.
Does bonding always close a black triangle?
Bonding does not always close a black triangle completely. It works well for a small triangle with healthy gums, because the teeth only need to be widened slightly. With a large triangle, so much composite would have to be added that the teeth would look too wide. In that case the dentist usually combines bonding with gum treatment, orthodontic treatment or a gum procedure, and the aim is to make the triangle smaller.
Is the result of a gum procedure long-lasting?
It is not yet known exactly how well the result holds up over many years. Most is known about the graft of tissue from the palate. After hyaluronic acid injections, it is hard to predict how long the effect will last. How long it lasts also depends on daily cleaning and on whether the gums stay healthy.
Can just one triangle be treated?
Yes, if only one bothers you and the other spaces are filled by the papilla. With a triangle between the upper central incisors, the dentist usually widens both teeth, because widening only one can easily upset the symmetry of the smile. A trial application of composite before the procedure makes the decision easier, because it lets you compare in the mirror how treating one tooth and treating both would look.
How should I clean the space after a triangle has been closed?
Clean the space every day with an interdental brush or floss, depending on how much room is left. The brush should go in without resistance. If you have to force it, it is too large and can injure the gum. When the space has closed completely, floss is usually enough. The size and the cleaning method are best chosen with the hygienist at the first check-up.
What does the gum look like in the first week after a black triangle is closed?
After bonding alone there is no wound on the gum, although for a few days the gum may be slightly tender when you clean it. After a gum procedure, the area can be swollen and sore for a few days, and if tissue was taken from the palate, the palate hurts as well. If the swelling increases after the third day, the bleeding does not stop, or you develop a fever or notice pus, contact the practice the same day.
Can the space reappear a year after the triangle has been closed?
Yes, the space can reappear. The papilla may continue to recede with age, and with poor cleaning, plaque keeps the inflammation going and the gum recedes. The composite may also chip or stain at its edge. That is why regular check-ups are needed after black triangles between teeth have been closed, so that the dentist can adjust the shape of the composite in good time.
Read more:
- Veneers and Composite Bonding in Warsaw
- Gum recession — why the gum recedes and when surgical treatment is needed
- Gingival phenotype — thin or thick? Why it matters for treatment
- Central incisor bonding — what does the procedure on the front teeth look like?
- Veneers or crowns — when to choose which restoration
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.
Sources
Source 1
Links https://doi.org/10.1111/jerd.13480 │ https://pubmed.ncbi.nlm.nih.gov/40296347/
Description Vandeweghe C, Agossa K, Sabri H, Wang HL, Colard T. „Evaluating Radiographic Measurements for Detecting Interdental Papilla: A Pilot Study.” Journal of Esthetic and Restorative Dentistry. 2025;37(8):2002-2010.
Source 2
Links https://doi.org/10.1186/s40510-022-00452-1 │ https://pubmed.ncbi.nlm.nih.gov/36617584/
Description Zhang Y, Wang X, Wang J, Gao J, Liu X, Jin Z, Ma Y. „IPR treatment and attachments design in clear aligner therapy and risk of open gingival embrasures in adults.” Progress in Orthodontics. 2023;24(1):1.
Source 3
Links https://doi.org/10.1002/jper.11373 │ https://pubmed.ncbi.nlm.nih.gov/40627751/
Description Zhang Y, Li X, Wang X, Lei X, Gao J, Zhang X, Ma Y, Jin Z. „Clear aligners and open gingival embrasures: Retrospective study of epidemiology and risk factors.” Journal of Periodontology. 2026;97(3):373-386.
Source 4
Links https://doi.org/10.1186/s12903-021-01400-x │ https://pubmed.ncbi.nlm.nih.gov/33485351/
Description Belák Š, Žižka R, Starosta M, Zapletalová J, Šedý J, Štefanatný M. „The influence of gingival phenotype on the morphology of the maxillary central papilla.” BMC Oral Health. 2021;21(1):43.
Source 5
Links https://doi.org/10.1186/s12903-023-03102-y │ https://pubmed.ncbi.nlm.nih.gov/37330484/
Description Hussien AOT, Ibrahim SH, Essa MES, Hafez RM. „Restoring black triangle with bioclear matrix versus conventional celluloid matrix method: a randomized clinical trial.” BMC Oral Health. 2023;23(1):402.
Source 6
Links https://doi.org/10.1111/jopr.13912 │ https://pubmed.ncbi.nlm.nih.gov/39073711/
Description Ladia O, Ntovas P, Gogolas N, Sarafianou A, Blatz M, Tarnow D. „Impact of long contact areas for the management of varying levels of interdental papilla loss on the perception of smile esthetics between dentists and laypersons in asymmetric and symmetric situations.” Journal of Prosthodontics. 2025;34(5):478-489.
Source 7
Links https://doi.org/10.1007/s00784-023-05409-0 │ https://pubmed.ncbi.nlm.nih.gov/38231354/
Description Patel M, Guni A, Nibali L, Garcia-Sanchez R. „Interdental papilla reconstruction: a systematic review.” Clinical Oral Investigations. 2024;28(1):101.
Source 8
Links https://doi.org/10.1007/s00784-023-05486-1 │ https://pubmed.ncbi.nlm.nih.gov/38206354/
Description Barakat SO, Tawfik OK, El Kholy S, ElNahass H. „Evaluation of advanced platelet-rich fibrin compared to subepithelial connective tissue graft in the surgical management of interdental papilla recession: a randomized controlled trial.” Clinical Oral Investigations. 2024;28(1):87.
Source 9
Links https://doi.org/10.1111/jcpe.13290 │ https://pubmed.ncbi.nlm.nih.gov/32383274/
Description Sanz M, Herrera D, Kebschull M, Chapple I, Jepsen S, Berglundh T, Sculean A, Tonetti MS; EFP Workshop Participants and Methodological Consultants. „Treatment of stage I-III periodontitis-The EFP S3 level clinical practice guideline.” Journal of Clinical Periodontology. 2020;47(Suppl 22):4-60.