Fixing a cavity between teeth requires a specialized version of a standard filling, one where the dentist has to rebuild the side wall of the tooth rather than simply patching a hole on top. The procedure typically takes 30 to 60 minutes under local anesthesia, and while the core concept is the same as any filling (remove decay, fill the space), the tight quarters between teeth add extra steps that make the process more involved.
Why Between-Teeth Cavities Are Different
A cavity between two teeth, called an interproximal cavity, forms in the contact zone where your teeth press together. This area is hard to clean with a toothbrush alone, which is why flossing matters so much for prevention. It’s also hard for your dentist to see, which means these cavities often go undetected until they’ve moved past the outer enamel and reached the softer layer underneath called dentin. At that point, you may start noticing sensitivity to sweets, cold drinks, or discomfort when chewing.
Bitewing X-rays remain the primary tool for catching these cavities. They’re the ones where you bite down on a small tab while the X-ray captures both upper and lower teeth at once. Bitewing images are significantly better at detecting early-stage decay between teeth than other types of dental X-rays. Some newer optical tools exist, including devices that shine near-infrared light through the tooth to reveal decay, but none are reliable enough yet at catching cavities still in the enamel stage. For decay that has reached dentin, transillumination agrees closely with bitewing X-rays, but for early enamel cavities, the agreement drops dramatically.
The Standard Filling Procedure
Once the dentist confirms the cavity’s location and depth on the X-ray, the repair follows a predictable sequence. After numbing the area with local anesthetic, the dentist uses a small drill to access the decay. This is where between-teeth cavities get tricky: to reach decay hiding between two teeth, the dentist has to cut in from the chewing surface and work down toward the side of the tooth. Traditional preparation requires removing a meaningful amount of healthy tooth structure just to get access to the decayed area, because the drill can only approach in a straight line.
Once the decay is fully removed, the dentist needs to reconstruct the missing side wall of the tooth. For a cavity on top of a tooth, you’re just filling a bowl-shaped hole. For a cavity between teeth, you’re essentially rebuilding a wall that no longer exists, and that wall has to make proper contact with the neighboring tooth. Too loose and food will pack in. Too tight and your bite will feel off.
How the Wall Gets Rebuilt
This is where a tool called a matrix band comes in. The dentist slides a thin metal strip between the teeth to act as a temporary mold for the missing wall. The band wraps around the tooth and is held in place by a retainer (the most common type is called a Tofflemire). A small wedge gets pushed in at the gum line to seal the bottom edge and prevent filling material from oozing out. Some dentists use a sectional matrix system instead, which consists of three components: a curved metal band, a ring that holds it snug, and a wedge. Sectional systems are designed to create tighter, more natural contact between the teeth.
With the matrix in place, the dentist applies the filling material in layers. For composite (tooth-colored) fillings, each layer is hardened with a blue curing light before the next layer goes on. Once the space is filled and the matrix band is removed, the dentist shapes and polishes the new surface, then checks your bite to make sure the filling isn’t sitting too high.
Filling Materials and How Long They Last
Most between-teeth fillings today are composite resin, a tooth-colored material that bonds directly to the tooth. Silver amalgam fillings are still used in some practices, though they’ve become far less common for visible teeth.
How long either material lasts depends heavily on the size of the cavity, where it is in your mouth, and how well it’s maintained. In clinical studies conducted under controlled conditions, composite fillings in two-surface cavities show median survival times of about 9 to 19 years. Amalgam fillings in similar cavities tend to last somewhat longer, with median survival times ranging from about 11 to 23 years in controlled studies. In everyday dental practice, though, both materials fail sooner. Surveys of private dental offices report median lifespans of 6 to 15 years for amalgam and 4 to 8 years for composite. One large review found that after 10 years, 72% of amalgam fillings were still functional compared to 56% of composite fillings.
The trade-off is mostly cosmetic versus durability. Composite matches your tooth color and bonds chemically to the enamel, which can help preserve remaining tooth structure. Amalgam is stronger under heavy chewing forces but is silver-colored and doesn’t bond to the tooth.
A Less Invasive Option for Early Cavities
If the cavity is caught very early, before it has moved past the enamel into dentin, a treatment called resin infiltration can sometimes skip drilling entirely. The dentist applies a special low-viscosity resin that soaks into the porous, demineralized enamel and seals it from the inside. The resin fills the tiny channels that bacteria have created and hardens the weakened area. Lab studies show that treated enamel is significantly harder than untreated decayed enamel, with the resin completely blocking the damaged enamel structure.
This approach only works for the earliest stages of decay, typically when the damage is limited to the first or second visible changes in the enamel surface and hasn’t created an actual hole. Once the cavity has progressed into dentin or formed a visible break in the tooth, a traditional filling is necessary.
A Newer Drilling Approach
For cavities that do need drilling, some dentists offer a technique called tunnel preparation as an alternative to the traditional approach. Instead of cutting through the top ridge of the tooth to access the decay on the side, the dentist drills a small tunnel from the chewing surface at an angle to reach the cavity while leaving the ridge of the tooth intact. The idea is to preserve more healthy tooth structure, and it can make it easier to maintain a tight contact point between the teeth.
The downsides are real, though. It’s a technically demanding procedure, and the dentist has limited visibility while working through a small tunnel. There’s a higher risk of missing some decay or fracturing the thin ridge of enamel that was preserved. For these reasons, tunnel preparations remain less common than the standard approach.
What Recovery Feels Like
After the numbness wears off (usually one to three hours), some sensitivity is normal. You may notice discomfort with hot, cold, or sweet foods, or a twinge when chewing. In one clinical study, 15% of patients reported sensitivity two days after getting a filling, but that dropped to 4% by one week and zero by 30 days. Even in cases where sensitivity lingers, it generally resolves within 90 days.
If you feel a sharp pain when you bite down, especially when your teeth first come together, the filling is likely sitting slightly too high. This is a simple fix: your dentist can adjust it in a few minutes. A different kind of pain, one that occurs during chewing rather than initial contact, can happen when the filling material shrinks microscopically as it hardens, creating tiny gaps between the filling and the tooth. Fluid moves through these gaps during chewing and irritates the nerve. This type of sensitivity also tends to fade as the tooth adjusts, but deeper and larger fillings are more likely to cause it.
Preventing the Next One
Between-teeth cavities are largely a flossing problem. Your toothbrush physically cannot reach the contact surfaces where these cavities form. Data from a national health survey found that adults who cleaned between their teeth four to seven days per week had 33% lower odds of untreated decay compared to those who didn’t clean between their teeth at all. For middle-aged adults, the reduction was even larger at 40%. Interdental brushes, floss, and water flossers all access this zone. The key is frequency: the protective benefit shows up at four or more days per week, not occasional use.