Black Triangles Between Teeth: Causes and How to Fix Them

Editorially reviewed by the Dental.me Editorial Team · Updated July 2026

If you have noticed small dark spaces at the base of your teeth, near the gum line, you are looking at what dentists call black triangles. They are one of the most common cosmetic complaints, and they often appear seemingly overnight, after braces, a deep cleaning, or simply with age. The good news is that black triangles are almost always treatable, but the right fix depends entirely on why they formed in the first place. This guide walks through the causes, whether they are anything to worry about, and the full menu of options for closing them.

What Are Black Triangles?

The technical name is an open gingival embrasure. Between two healthy, touching teeth, a small wedge of gum tissue called the interdental papilla normally rises up to fill the space just below the contact point. When that papilla shrinks, flattens, or fails to fill the space, the gap behind it is left open. Because it sits in shadow, it reads as a dark or black triangle against the brighter enamel.

They show up most often between the two front teeth and the teeth beside them, where they are hardest to hide. The triangle is not a hole through the tooth or a cavity. It is simply empty space that the gum used to occupy, framed on two sides by the teeth and on the bottom by the receded gum.

Why Black Triangles Form

Black triangles are a symptom, not a single disease, and several different causes can produce the same look. Understanding yours is the key to choosing a treatment that lasts.

• Gum recession and lost papilla. The most common cause. Gum disease, aggressive brushing with a hard brush, and normal aging all wear the papilla down. Once that tissue is gone, the space it filled opens up. This overlaps closely with general receding gums, where the gum line drifts lower and exposes more of the tooth.
• Bone loss underneath. The papilla is supported by the bone and gum height between the roots. When periodontal disease destroys that underlying bone, the papilla loses its scaffolding and collapses. This is one of the more stubborn causes because the tissue has nothing to sit on.
• Triangular tooth shape. Some people naturally have teeth that are narrow at the gum and wider at the biting edge. These triangular teeth only touch near the top, leaving a large space below that even a healthy papilla cannot fully close.
• Tooth movement after orthodontics. Very common. Braces and clear aligners straighten the crowns of the teeth, but the papilla does not always migrate to fill the newly opened space, especially in adults. The teeth line up beautifully and a black triangle appears where crowding used to hide it.
• Thin gum tissue. People with a naturally thin gum biotype have less tissue to begin with, so any recession or movement shows up faster and is harder to rebuild.

Are Black Triangles Harmful?

For the most part, black triangles are a cosmetic issue rather than a health emergency. They do not hurt, and they are not a sign that a tooth is dying. That said, they are not purely harmless either. The open space acts as a trap for food and plaque, and it can be harder to clean than a normal contact point. Left uncleaned, that buildup raises the risk of decay along the root surface and of further gum inflammation, which can make the recession worse over time. So while you do not need to panic, black triangles are worth addressing, both for appearance and to keep the area easy to keep clean.

How to Fix Black Triangles

Treatment ranges from a five-minute hygiene change to full cosmetic dentistry. Dentists generally start with the least invasive option that will actually solve your specific cause.

Better cleaning and interdental brushes

If the triangle is small and the gum is inflamed, improving how you clean between the teeth can reduce swelling and, in mild cases, let the papilla plump back slightly. Interdental brushes and gentle flossing keep the space healthy even when they cannot fully close it. This is often step one regardless of what else you do.

Dental bonding

The most common and affordable fix. The dentist adds tooth-colored composite resin to the sides of the adjacent teeth, extending them slightly toward the gum to fill the triangle. It usually takes one visit, requires little or no drilling, and can be reversed or repaired. Bonding is popular precisely because it is fast and gentle on the tooth; you can read more about what shapes the price in our guide to dental bonding cost.

Veneers

For patients who also want to change tooth color or shape, porcelain veneers can be designed to close the triangle while reshaping the whole smile. They cost more and involve some enamel preparation, but they are durable and stain-resistant. If you are weighing this route, it helps to know how long veneers last and how they stack up in our comparison of veneers versus crowns.

Orthodontics and IPR

When the teeth themselves are the problem, an orthodontist may move them closer together or use interproximal reduction (IPR), lightly reshaping the contact points so the teeth touch lower down. Bringing the contact point closer to the gum shrinks the triangle without adding any material. This works best for triangular tooth shapes and post-braces cases.

Gum treatment and tissue options

Rebuilding lost papilla directly is the hardest and least predictable route, because tissue does not regrow easily where the underlying bone is gone. Surgical grafts and regenerative procedures exist and can help selected cases, but results vary. Some patients instead look at gum contouring and related tissue work to improve the surrounding gum line, though contouring reshapes tissue rather than filling the triangle itself.

Hyaluronic acid gel injections

A newer, minimally invasive option. The dentist injects a small amount of hyaluronic acid gel into the papilla to plump it and partially fill the space. It is quick and non-surgical, but the effect is temporary and usually needs repeating, so it suits people wanting a reversible, lower-commitment trial.

Rough Costs and How the Dentist Chooses

Prices vary widely by region and by how many teeth are involved, but as a rough guide bonding tends to be the most affordable per tooth, gel injections sit in a similar low-to-mid range but recur, orthodontics is a larger whole-mouth investment, and veneers are the premium option. Because costs stack per tooth, closing several triangles adds up quickly.

The dentist picks a fix by working backward from the cause. Small triangle with healthy gums and a good tooth shape leans toward bonding. Triangular teeth or a post-braces gap may point to IPR or orthodontics. Widespread recession from gum disease means treating the gum health first, then deciding whether bonding or grafting fits. The severity, your gum biotype, your budget, and whether you want other cosmetic changes all feed into the recommendation.

Prevention, Especially After Braces

You cannot always prevent black triangles, but you can lower the odds. Brush gently with a soft brush, since aggressive scrubbing is a leading cause of recession. Clean between your teeth daily and keep up with professional cleanings to protect the gum and bone that support the papilla. For orthodontic patients, discuss the risk with your provider before treatment; careful planning, IPR where appropriate, and reshaping can reduce the chance a triangle appears once the teeth align. If one does show up after braces, it does not mean anything went wrong, it simply means the gum did not follow the tooth, and it is very treatable. Whatever the cause, a dentist can look at the space, identify why it opened, and match you to the simplest fix that closes it for good.

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