Can Composite Bonding Treat Black Triangles Between Teeth?

Black triangles have a way of appearing without announcement. Someone finishes orthodontic treatment pleased with straight teeth, then notices small dark spaces near the gum that were not there before. Others notice them developing slowly over years.

They are properly called open gingival embrasures — spaces beneath the contact point between two teeth that the gum tissue no longer fills. They tend to bother people considerably more than their size suggests, partly because they catch shadow and read as dark against white teeth.

Composite bonding is often an effective answer. The qualification, and it is an important one, is that the gum condition underlying them needs assessing first.

Can these dark spaces be closed?

In many cases yes, at least partially. Composite is added to the adjacent tooth surfaces below the contact point, extending the contact further towards the gum and reducing the open space. For small to moderate black triangles in stable, healthy gums, this can be very effective and is completed in a single visit. Where the papilla has been lost through periodontal disease, complete closure is less predictable, because bonding can only fill from the tooth side — it cannot regenerate lost gum tissue. Treating the space without first stabilising active gum disease would also be the wrong order of operations.

Between any two adjacent teeth there is a small triangular space bounded by the contact point above and the bone below. In health, the gum papilla fills this space completely.

Whether the papilla fills it depends on a well-documented relationship: the distance from the contact point down to the crest of the bone. Where this distance is around five millimetres or less, the papilla fills the space in the large majority of cases. As the distance increases beyond that, the likelihood of complete fill drops sharply.

This single measurement explains most black triangles, and it also explains why the solution usually involves moving the contact point downwards rather than trying to grow gum upwards.

Gum recession. As the gum margin moves apically, the papilla follows. See receding gums.

Periodontal bone loss. The bone crest supporting the papilla is lost, increasing the contact-to-bone distance. This is the most significant cause and needs proper diagnosis — see periodontitis.

After orthodontic treatment. When crowded, overlapped teeth are aligned, the contact point moves and the true shape of the interdental space is revealed. Triangular-shaped incisors are particularly prone to this.

Tooth shape. Teeth that are triangular rather than square in outline have contact points nearer the incisal edge, leaving a wider space below.

Age. Papillae tend to recede gradually over decades.

Aggressive cleaning. Over-vigorous brushing or incorrect interdental technique can contribute to recession.

The principle is simple: add material to the mesial and distal surfaces of the adjacent teeth so that the contact area extends further towards the gum, closing the space from above.

In practice it requires care. Material must be contoured to create a cleanable emergence profile — floss and interdental brushes need to pass without catching, and there must be no overhang at the margin, which would cause chronic gum inflammation. Matrix systems and sectional matrices are used to shape the material below the contact.

Where triangles are large, complete closure may produce teeth that look too wide or squared off. Partial reduction, sometimes combined with slight reshaping, often gives a more natural result than total closure. This is a judgement made case by case.

This deserves emphasis. Black triangles are frequently a visible sign of periodontal bone loss, and treating the appearance while ignoring the cause is poor practice.

Before restorative work, gum condition should be assessed with periodontal charting and, where indicated, radiographs to establish bone levels. Active disease needs gum disease treatment and a period of stability before bonding.

There is also a practical reason: adding material near the gum margin in an inflamed, bleeding field makes good adhesion and accurate contouring considerably harder.

Arrange an assessment if you notice:

• Dark spaces appearing between your teeth near the gum

• Gums that bleed when brushing or cleaning between teeth

• Food packing into spaces between teeth

• Teeth appearing longer than they used to

• Sensitivity at the necks of the teeth

• New spaces following orthodontic treatment

• Existing bonding around the gum that catches floss or feels rough

Assessment establishes whether the space reflects stable anatomy or ongoing disease. That distinction changes the treatment plan entirely.

The NHS provides general guidance on gum care at nhs.uk/live-well/healthy-teeth-and-gums/take-care-of-your-teeth-and-gums/.

Orthodontic movement. Bringing teeth closer together, sometimes combined with interproximal reduction to reshape contact points, can reduce the space without adding material. This works well where teeth are triangular and slightly spaced.

Interproximal reduction alone. Removing small amounts of enamel to flatten and lower the contact point can reduce the triangle.

Porcelain veneers. Where multiple teeth are being restored anyway, porcelain veneers can incorporate the correction, though they require tooth preparation.

Surgical approaches. Papilla regeneration techniques exist but are technically demanding with variable predictability, and they are not routinely offered for aesthetic black triangles.

Doing nothing. A legitimate option where the gums are healthy and the triangles are small. Not every anatomical variation needs treating.

• Clean daily between the teeth — the new contours must be kept plaque-free

• Use interdental brushes sized correctly for the space, or floss where brushes will not fit

• Brush with a soft brush and light pressure; heavy scrubbing contributes to recession

• Use a non-abrasive fluoride toothpaste

• Attend hygiene appointments so margins and gum health are monitored

• Report any bleeding or discomfort around a bonded margin promptly

• Black triangles are open gingival embrasures, not simply gaps

• Papilla fill depends largely on the distance from contact point to bone crest

• Bonding works by extending the contact downwards, not by regenerating gum

• Gum disease must be diagnosed and stabilised before cosmetic treatment

• Complete closure is not always the most natural-looking outcome

• Poorly contoured margins cause gum inflammation

• Orthodontic and interproximal reduction approaches are alternatives worth considering

Composite bonding is a practical and conservative way to reduce black triangles, and for many people the improvement is disproportionate to the amount of material involved. Small dark spaces near the gum draw the eye, and closing them can noticeably change how a smile reads.

What should not be rushed is the assessment beforehand. Black triangles are sometimes purely anatomical and sometimes the visible edge of periodontal bone loss, and those two situations call for very different plans.

If you have noticed dark spaces between your teeth, you are welcome to arrange an appointment at Wimpole Dental, 22 Wimpole St, London W1G 8GQ, or call 020 7183 0692. You can read more about composite bonding on our website.

Dental symptoms and treatment options should always be assessed individually during a clinical examination.

This article is for general educational information only and is not professional dental advice, diagnosis, or a treatment recommendation. Information here is general and cannot replace an in-person assessment by a qualified, GDC-registered dental professional. Symptoms, suitability, fees, timelines, and outcomes vary according to individual clinical circumstances. If you have pain, swelling, or other concerning symptoms, seek prompt professional dental care. Always request a written treatment plan and cost estimate before proceeding with treatment.

Written Date: 20 August 2026

Next Review Date: 20 August 2027