Black Triangles Between Teeth: Closing Them with Composite

Black triangles have three broad causes: lost gum between the teeth, gum recession and bone loss, or the shape and position of the teeth. A 2024 review notes that one person can have several causes at once, so each case needs individual assessment.

Telling the causes apart matters because composite changes only the teeth; where gum disease lies behind the space, the gums need attention first. Our page on receding gums and their causes covers recession itself.

How does the distance from contact point to bone matter?

A 1992 study of 288 sites in 30 patients found the gum present almost every time the contact point was within 5 mm of the bone crest. At 6 mm it was present 56% of the time, and from 7 mm, 27% of the time or less.

A 2003 study of 200 upper front sites in 45 Taiwanese adults, measured on X-rays, found the gum present at 51% of sites at 6 mm and 23% at 7 mm or more, calling the measurement a useful guide for clinical evaluation. A 2006 study of 80 patients examined after gum disease treatment suggests root spacing matters too. These figures describe groups of sites and cannot predict whether gum will fill any one space.

Composite can narrow or close a black triangle by building out the sides of the teeth near the gum, so they meet lower down.

It does not regrow the gum: a 2024 review says restorative work masks a black triangle by lengthening the contact, without rebuilding lost gum. The British Society of Periodontology and Implant Dentistry says gum disease must be treated before anything is done to replace or mask receded gums; once gums are healthy, it says, white fillings can disguise the gaps.

What do trials of composite closure show?

The evidence is small and short-term, and a 2014 UK review notes a lack of long-term studies. A 2023 trial in Cairo treated 26 adults aged 35 to 50 with good oral hygiene, no gum disease, no uncontrolled grinding and the two milder grades of gum loss between upper front teeth, comparing two composite techniques. Contact points, tooth form, speech and food trapping were rated successful in every case over 12 months, though tooth form was rated as deviating from normal but acceptable in 6 of 13 cases in one group and 2 of 13 in the other.

Gum scores worsened over the year: at 12 months, plaque and gum bleeding at a level the trial rated acceptable were recorded in 6 of 13 cases in one group, with one further failure, and 9 of 13 in the other. By 6 months most cases in both groups showed staining at the edges, mostly minor and removable, and by 12 months 7 of 13 cases in one group and 4 of 13 in the other had moderate staining. Each group of 13 had one failure by 12 months. The authors say results depend on the operator's skill.

A 2026 trial in China randomised 71 people to composite placed with a dedicated matrix system, conventional layered composite, or no treatment, followed for 6 months. Gum recession progressed in all three groups. Bleeding sites fell with the matrix system but rose from 21.7% to 26.1% with layering, where 8% of restorations failed against none (not statistically significant).

Deepcar Dental Care's current fee list does not name black triangle closure, and it does not say whether any of its lines covers it.

Show a new or growing black triangle to a dentist. The British Society of Periodontology and Implant Dentistry says receding gums and gaps between teeth may be a sign of active disease or a consequence of treatment for gum disease.

NHS gum disease guidance says to see a dentist if:

• your gums bleed when you brush your teeth or eat hard foods
• your gums are painful and swollen
• you have bad breath
• your child has sore, bleeding gums

If you or your child has gum disease and other symptoms, such as very sore and swollen gums, teeth becoming loose or falling out, ulcers or red patches in your mouth, or a lump in your mouth or on your lip, the NHS says to ask for an urgent dentist appointment. With no dentist, or no emergency appointment available, call 111.