A cavity between teeth, called an interproximal cavity, can only be permanently fixed by a dentist. If the decay has broken through the enamel surface, no amount of brushing or home care will reverse it. However, if the cavity is caught early enough, before a visible hole forms, non-invasive treatments can stop it from progressing and even help the enamel repair itself.
Understanding which stage your cavity is in determines what “fixing” it actually looks like, ranging from a simple fluoride treatment to a filling or crown.
Why Cavities Between Teeth Are Harder to Spot
Cavities on the biting surface of a tooth are relatively easy to see. Interproximal cavities hide in the tight contact point between two teeth, where your dentist can’t see them during a visual exam alone. That’s why bitewing X-rays are the standard tool for catching them. These images show the space between your back teeth clearly, and dentists typically take them once a year or every other year depending on your risk level. Panoramic X-rays, the wide images that capture your whole jaw, are significantly less accurate for detecting decay between teeth.
Because these cavities are hidden, they’re often further along by the time they’re found. You might not feel anything until the decay reaches deeper layers of the tooth, which is why routine X-rays matter more than waiting for pain.
When a Cavity Can Be Reversed Without Drilling
Not every cavity needs a filling. If the decay is still in its earliest stage, limited to the outer half of the enamel with no visible hole or defect in the tooth surface, it can sometimes be arrested or reversed. At this stage, the enamel has lost minerals but hasn’t collapsed structurally. Your dentist might describe it as a “white spot” or “incipient lesion.”
The American Dental Association recommends several non-invasive options for these early lesions. The most effective include 38% silver diamine fluoride (SDF), professional fluoride varnish, and prescription-strength fluoride toothpaste (five times stronger than what you’d buy at a drugstore). These treatments work by driving minerals back into weakened enamel and creating a chemical environment that slows or stops bacterial acid production.
Silver diamine fluoride is particularly interesting for cavities between teeth. Because the space is so tight, a dentist can apply SDF using woven floss threaded between the teeth to deliver the solution directly to the decay. In one study of 185 interproximal cavities, 84% showed no further progression after 12 months of SDF treatment. The tradeoff: SDF permanently stains decayed enamel black, which matters more on front teeth than back ones.
Once an early enamel lesion progresses and forms an actual cavity, a hole in the tooth surface, it can no longer heal naturally. That’s the dividing line between “watch and treat conservatively” and “this needs a filling.”
How Dentists Fill a Cavity Between Teeth
The standard fix for an interproximal cavity that has broken through the enamel is a composite resin filling, a tooth-colored material that bonds directly to your tooth. The process is more involved than filling a cavity on the top of a tooth because your dentist has to rebuild the side wall of the tooth while keeping it separate from the neighboring tooth.
Here’s what the procedure typically involves. After numbing the area, your dentist drills out the decayed portion of the tooth, accessing it from the top and working down into the space between the teeth. They then place a thin metal band (called a matrix) around the tooth to act as a temporary wall, giving the filling material something to press against so it forms the correct shape. A small ring or wedge holds this band tightly against the neighboring tooth to prevent the filling material from bonding the two teeth together.
The filling is placed in layers, with each layer hardened using a curing light before the next one goes on. Once built up, the dentist carves and polishes the filling to restore the natural contour of the tooth, including the contact point where it touches the adjacent tooth. Getting this contact point right is critical. Too loose and food will pack between the teeth constantly. Too tight and flossing becomes difficult.
A composite filling for a single tooth averages around $191, with a typical range of $100 to $400. Cavities between teeth often involve two surfaces of the tooth, which can push the cost toward the higher end of that range. Dental insurance usually covers a significant portion of filling costs.
When a Filling Isn’t Enough
If the decay is extensive and has undermined a large portion of the tooth structure, a standard filling may not hold up. In these cases, your dentist might recommend an inlay (a lab-made piece that fits into the tooth like a puzzle piece) or a crown, which covers the entire visible portion of the tooth. Crowns are typically reserved for situations where so much tooth has been lost to decay that a filling would leave the remaining walls too thin and prone to fracture. They can be made from porcelain, ceramic, metal alloys, or combinations of these materials.
If the cavity has gone untreated long enough to reach the pulp, the living tissue inside the tooth containing nerves and blood vessels, the situation changes significantly. At this stage, called pulpitis, you’ll likely notice sensitivity to hot, cold, or sweet foods that lingers for more than a few seconds after the stimulus is removed. If the pulp damage is too advanced to recover, you’ll need a root canal to remove the infected tissue before the tooth can be restored with a crown. Left completely untreated, the pulp tissue dies, which can lead to an abscess and potential tooth loss.
Preventing New Cavities Between Teeth
The space between teeth is vulnerable because toothbrush bristles can’t reach it. Cleaning between teeth daily is the single most important thing you can do to prevent interproximal cavities. Both floss and interdental brushes (the small bristled picks that slide between teeth) are effective options. Interdental brushes are often easier to use correctly, especially for people with wider gaps between teeth or dental work like bridges.
Fluoride toothpaste strengthens enamel against acid attacks. If your dentist has identified you as cavity-prone, they may prescribe a high-concentration fluoride toothpaste or recommend professional fluoride varnish applications at your regular visits. Limiting sugary snacks and acidic drinks between meals also reduces the number of acid attacks your enamel faces throughout the day.
The most important factor, though, is catching problems early through regular dental visits and X-rays. An interproximal cavity found while it’s still in the enamel is a simple, inexpensive fix. The same cavity found six months or a year later, after it’s reached the inner layer of the tooth, can mean the difference between a $200 filling and a $1,500 root canal and crown.