Why do black triangles form?
They form when the interdental papilla, the gum between the teeth, cannot fill the space all the way. The height of the interdental papilla depends on the point where the teeth touch (the contact point), the height of the alveolar bone beneath it (the bone that supports the teeth), and the shape and alignment of the teeth.
- When the alveolar bone has become lower because of periodontitis
- When the gums have receded with age
- When the teeth are a narrow triangular shape, so the contact point sits high
- When overlapping teeth are straightened by orthodontics and a gap is revealed
- When the gums have receded from scrubbing hard side to side
Can the gums grow back?
Where the bone has become lower, the gum alone does not grow back. That is because the interdental papilla follows the height of the bone. In a well-known study, the rate at which the interdental papilla filled the gap varied greatly with the distance from the contact point to the crest of the bone.
| Distance from contact point to bone crest | Rate at which the papilla filled the gap |
|---|---|
| 5mm or less | Almost all (about 98%) |
| 6mm | About half (about 56%) |
| 7mm or more | About a quarter (about 27%) |
Conversely, there are also cases where swelling from inflammation had been hiding the gap. When gum treatment brings the swelling down, the triangle appears more visible, but this does not mean things got worse; the gap that was always there is now showing.
How are black triangles filled?
Instead of growing the gum, the basic approach is to change the shape of the teeth and move the contact point lower.
| Gap condition | Treatment | Limits |
|---|---|---|
| Small, with bone support | Bring the teeth slightly closer together, or lightly reshape the sides to widen the contact area | There is a limit to how much can be reshaped |
| Narrow, only the shape is the problem | Fill the sides with composite resin | Stains and the margins wear |
| Large, and you also want to change color and shape | Change the side shape with porcelain veneers | Not placed on teeth that stick out forward |
| Inflammation remains | Gum treatment first | We do not fill the gap first |
Even after filling, if periodontitis comes back, a new gap forms. Gaps that appear after orthodontics are covered separately in Why black triangles appear after orthodontics.
Which is better, composite resin or porcelain veneers?
Composite resin suits just filling the gap; porcelain veneers suit changing the gap together with color and contour. Composite resin is finished in one day with almost no shaving, but over time it can stain or its margins can wear so it needs to be reshaped again, and it comes off easily where force concentrates. Porcelain veneers can match the color and contour of several teeth together.
Either way, lowering the contact point requires making the sides of the teeth slightly fuller. If they are filled too much, the teeth look square and wide, and interdental brushes cannot get in, making gum care difficult. So rather than eliminating the gap completely, we decide the shape at the point where the gap is reduced so it is less noticeable.
How we do it at Wonjin Dental
Before filling, I first check the periodontal condition, the alveolar bone, and the alignment. If inflammation remains, we start with gum treatment and fill the gap after the gums are stable. I do not promise to fill a spot where the bone has become lower with gum.
If porcelain veneers are suitable, we consider Brinate, which is placed without shaving the teeth. It can only be placed if the teeth sit inward, and it is not placed on teeth that stick out forward. There is no anesthesia and no temporary tooth.
| Brinate | How it is made | Thickness | Time | Price (per tooth) |
|---|---|---|---|---|
| Basic | Milled by machine | 0.3mm | Same day possible | ₩330,000 |
| Build-up | Layered by hand | 0.1mm | About 1 week | ₩550,000 |
| Platinum | Layered by hand | 0.1mm | About 2 weeks | ₩990,000 |
As of September 2026, VAT included. You can see all prices in Full fee list.
Frequently asked questions
Does using an interdental brush make black triangles bigger?
It is fine if you use a size that fits the gap. Forcing in a brush thicker than the gap can make the gums recede further, so choose a size that slides in gently.
Can it be filled with gum surgery or filler?
There are attempts to rebuild the interdental papilla with surgery or filler, but the results are not consistent, and if the bone is low, the limits are significant. That is why we first look at lowering the contact point by changing the tooth shape.
Does everyone get black triangles with age?
As you age, the gums recede little by little, so they form more easily, but not everyone gets them. Managing gum disease and brushing properly can slow their progress.
