“I floss regularly. How could I possibly have a cavity there?”
Michael sat in our Ho Chi Minh City clinic chair, staring at the X-ray showing a dark spot between his molars. He’d come in for a routine checkup, expecting a clean bill of health. The Australian accountant brushed twice daily, flossed most evenings, and avoided sugary drinks. Yet there it was, a cavity in a place his toothbrush never reached.
I’m Dr. Emily Nguyen, Principal Dentist at Picasso Dental Clinic, and I deliver this news several times a week. Interproximal cavities, the technical term for cavities between teeth, are among the most common dental problems I see. Since 2013, treating over 70,000 patients from 65 countries across our Vietnam locations, I’ve learned that most people don’t realize their biggest cavity risk isn’t where they can see.
The space between your teeth accounts for roughly 40% of your tooth surfaces. It’s also the hardest area to clean and the easiest place for decay to hide. Let me explain why these cavities form, how to spot them, and what you can do to prevent them.
Why Cavities Form Between Your Teeth
The space between your teeth creates the perfect environment for decay.
Think about it: when you eat, food particles don’t just sit on the tops of your teeth. Small pieces wedge between teeth, especially in tight contacts. Your saliva can’t easily wash these areas. Your toothbrush bristles can’t fit there. The bacteria that cause cavities love this protected environment.
Here’s what happens: bacteria feed on trapped food particles, particularly carbohydrates and sugars. As they digest this food, they produce acid. This acid sits against your tooth enamel for hours, slowly dissolving the mineral structure. Without intervention, a tiny weak spot becomes a cavity.
The anatomy of tooth contact points makes them vulnerable. Where two teeth touch, a small space exists just below the contact point. This space—called the embrasure—is where interproximal cavities typically start. It’s recessed, protected, and nearly impossible to clean without floss.
I see this daily at our Hanoi clinic. Patients show me their brushing technique, and it’s perfect. But when I ask them to demonstrate flossing, they either skip it entirely or use a sawing motion that doesn’t clean below the contact point. The cavity develops in the exact spot they’re missing.
Your back teeth are especially at risk. Molars have tighter contacts than front teeth. They also do more chewing work, which means more food passes through those spaces. A patient from South Korea recently told me she’d never had cavities in her front teeth but had multiple interproximal cavities in her molars. This pattern is typical.
How Interproximal Cavities Differ From Other Cavities
Not all cavities are created equal. Location changes everything about detection and treatment.
Surface cavities—the kind that form on the chewing surface or outer face of teeth—announce themselves early. You might see a dark spot. You might feel sensitivity. You can often catch them visually during regular brushing.
Interproximal cavities hide. They form on the side surfaces of teeth, in areas you can’t see even when looking in a mirror. By the time you notice symptoms, the cavity has often progressed significantly.
The progression pattern differs too. A chewing surface cavity spreads outward. An interproximal cavity spreads inward toward the nerve and outward toward adjacent teeth. Left untreated, one cavity can threaten two teeth.
I remember a patient from Canada at our Da Nang clinic who ignored mild sensitivity between his teeth for six months. When he finally came in, the cavity had spread so far that both adjacent teeth needed crowns. One cavity became a two-tooth problem because of its location.
Detection requires X-rays. This surprises many patients. During routine exams, I can spot surface cavities with a mirror and explorer. But interproximal cavities? They’re invisible to the naked eye until they break through to a visible surface. Bitewing X-rays—the small films you bite down on during dental visits—are specifically designed to show the spaces between teeth.
This is why I insist on X-rays at appropriate intervals for patients at all our Picasso Dental Clinic locations. Some patients want to skip them to save time or cost. But skipping X-rays means missing interproximal cavities until they cause pain, which means more expensive treatment later.
Signs You Might Have an Interproximal Cavity
Early interproximal cavities are silent. Advanced ones start talking.
The most common first symptom is food packing. You suddenly notice food getting stuck between specific teeth after eating. This happens because the cavity has created a rough surface or small hole where smooth enamel used to be. Patients at our Ho Chi Minh City clinic often mention this symptom weeks before we find the cavity.
Sensitivity to cold, sweet, or acidic foods comes next. The cavity has penetrated through enamel into dentin, which contains nerve endings. You might feel a sharp twinge when drinking cold water or eating ice cream, specifically on one side of one tooth.
Floss shredding or catching is a warning sign. If your floss consistently catches or tears in the same spot, something is wrong. Either you have a rough filling edge, a cavity, or tartar buildup. Any of these need dental attention.
Pain while chewing means the cavity is significant. The pressure of biting forces the tooth surfaces together, compressing the decayed area. This is late-stage. You need treatment soon.
Some patients tell me about a bad taste or smell near specific teeth. Advanced decay produces an odor. If you can taste or smell it, the cavity is large.
A patient from Thailand visited our Da Lat clinic last month with all these symptoms. She’d felt the food packing for three months but assumed it was normal aging. The cavity had reached her tooth nerve, requiring root canal treatment. Earlier detection would have meant a simple filling.
How Dentists Find Interproximal Cavities
Finding what you can’t see requires specific tools and techniques.
Bitewing X-rays are the gold standard. These images show the crowns of upper and lower teeth in the same film, specifically highlighting the spaces between teeth. Cavities appear as dark areas because decay is less dense than healthy enamel. I take bitewing X-rays for my patients every 12-24 months depending on cavity risk.
Visual examination helps with advanced cavities. I use magnification and lighting to look for chalky white spots near the gumline between teeth. These spots indicate demineralization—the earliest stage of cavity formation. Not yet a cavity, but headed that way without intervention.
Dental explorers—the small metal picks dentists use—can detect soft spots in enamel. When I gently probe between teeth, healthy enamel feels hard and smooth. Decaying enamel feels sticky or soft. The explorer tip catches in the compromised area.
New technology is changing detection. Laser cavity detection devices can identify decay without X-rays. These tools measure changes in tooth density. At Picasso Dental Clinic, we use traditional and modern methods together for the most accurate diagnosis.
Digital X-rays have improved interproximal cavity detection dramatically. The images are clearer than old film X-rays, and I can zoom in on suspicious areas. I can also compare images from previous visits to track changes over time. A patient from Singapore recently asked why we took new X-rays when he’d had them done six months before at another clinic. Because cavities develop. What wasn’t there six months ago might be there now.
The frequency of X-rays depends on your cavity risk. Low-risk patients need them every 18-24 months. High-risk patients—those with previous interproximal cavities, poor oral hygiene, or dry mouth—need them every 6-12 months.
Preventing Cavities Between Your Teeth
Prevention is simpler than treatment, though it requires daily commitment.
Flossing is non-negotiable. I tell every patient at our Hanoi clinic: if you do nothing else, floss daily. This single habit prevents most interproximal cavities. But technique matters more than frequency.
Here’s proper flossing technique: Use 18 inches of floss. Wrap most of it around your middle fingers, leaving 1-2 inches to work with. Gently guide the floss between teeth using a back-and-forth motion. Once below the contact point, curve the floss into a C-shape against one tooth. Slide it gently under the gumline. Move the floss up and down several times. Repeat this C-shape process against the adjacent tooth. Use a clean section of floss for each space.
Most patients floss incorrectly. They pop the floss through the contact point, wiggle it once, and pull it out. This cleans the contact point but misses the embrasure space below, where cavities form.
Water flossers work well for some patients. The high-pressure water stream removes food particles and bacteria. They’re especially helpful if you have braces, bridges, or tight teeth where traditional floss won’t fit. But they shouldn’t completely replace string floss. Think of water flossers as supplementary.
Fluoride strengthens enamel, making it more resistant to acid attacks. Use fluoride toothpaste twice daily. Some patients benefit from prescription-strength fluoride toothpaste or fluoride rinses, especially if they’re cavity-prone.
Diet affects interproximal cavity risk significantly. Frequent snacking means constant acid exposure. Sipping sugary or acidic drinks throughout the day bathes your teeth in cavity-causing substances. I recommend eating meals rather than grazing, and drinking water between meals.
A patient from Germany at our Da Nang clinic reduced his interproximal cavities from three per year to zero by making one change: he stopped sipping coffee all morning. He switched to drinking his coffee in 15 minutes, then rinsing with water. His teeth got breaks from acid exposure.
Regular dental cleanings remove tartar from between teeth. Even with perfect home care, some calculus forms. Professional cleanings every six months keep these areas healthy.
Treatment Options for Interproximal Cavities
Treatment depends on cavity size, location, and how far decay has progressed.
Small interproximal cavities need composite fillings. This is straightforward: I remove the decay, clean the area, and fill the space with tooth-colored composite resin. The challenge is access. Getting tools between teeth requires careful technique. Sometimes I need to remove a bit of healthy tooth structure from the adjacent tooth to properly clean out all decay and place the filling.
The filling process takes 30-45 minutes per cavity. I numb the area, isolate the tooth to keep it dry, remove decay with a drill, and layer in the composite material. Each layer is hardened with a special light. The filling is then shaped and polished.
Larger cavities might need inlays or onlays. When decay is extensive, a regular filling won’t hold up to chewing forces. Instead, I prepare the tooth and take an impression. A dental lab creates a custom-fit restoration—usually porcelain—that’s bonded into place. This takes two visits but lasts longer than large fillings.
If decay reaches the tooth nerve, you need root canal treatment. This means removing the infected nerve tissue, cleaning the inner tooth, and sealing it. Then the tooth gets a crown for protection. Root canals get a bad reputation, but modern treatment is relatively comfortable. I’ve performed hundreds at Picasso Dental Clinic locations across Vietnam, and most patients report feeling better immediately after because the infection pain is gone.
Prevention of new cavities during treatment matters. When I find one interproximal cavity, I look carefully for others. They often occur in clusters because the conditions that created one cavity probably exist elsewhere. I work with patients on flossing technique during treatment appointments, not just lecturing about it.
A patient from the United States visited our Ho Chi Minh City clinic with four interproximal cavities. We treated all four over two appointments, but more importantly, I spent time teaching her proper flossing. She returned six months later for a checkup with no new cavities. The technique instruction made the difference.
Questions About Interproximal Cavities I Hear Regularly
“Can you have a cavity between teeth even if you floss?”
Yes. Flossing dramatically reduces risk but doesn’t eliminate it. Some people have very tight tooth contacts where floss can’t effectively clean. Some have natural enamel that’s more susceptible to decay. Some use poor flossing technique despite regular practice. Flossing reduces interproximal cavity risk by about 40%, which is substantial but not perfect.
“Why didn’t my previous dentist find this cavity?”
Cavities take time to develop. What wasn’t visible on X-rays a year ago might be obvious now. Also, cavity detection requires skill and attention. Some dentists are more thorough than others. This is why I recommend staying with one dentist who knows your mouth well and can compare X-rays over time.
“Can interproximal cavities heal on themselves?”
Very early demineralization—before an actual cavity forms—can remineralize with fluoride treatment and improved oral hygiene. But once a cavity exists, it won’t heal. The structure is lost. Treatment is necessary to prevent progression.
“Should I use interdental brushes instead of floss?”
Interdental brushes work well for people with gaps between teeth or around bridgework. For normal tight contacts, traditional floss is more effective. Some patients use both. I’m less concerned about the tool than about daily cleaning of those spaces.
“How much does treatment cost in Vietnam?”
Costs at Picasso Dental Clinic are significantly lower than in Western countries while maintaining international quality standards. A simple interproximal filling runs 800,000-1,500,000 VND depending on size and complexity. This is why we treat so many dental tourists. But prevention costs nothing except time. Floss daily, and you’ll avoid these treatment costs entirely.
Your Interproximal Spaces Deserve Attention
Cavities between teeth are common, preventable, and treatable. The key is understanding that your toothbrush only reaches about 60% of your tooth surfaces. The other 40%—those spaces between teeth—need a different tool.
Having treated over 70,000 patients from 65 nationalities at our clinics in Hanoi, Da Nang, Ho Chi Minh City, and Da Lat since 2013, I’ve seen the pattern repeatedly. Patients who floss daily have dramatically fewer interproximal cavities. Those who skip flossing almost inevitably develop them.
The good news? Starting a flossing habit today prevents problems tomorrow. Even if you’ve never flossed regularly, beginning now makes a difference. Your teeth don’t hold grudges. Give them the care they need, and they’ll respond.
If you’re experiencing symptoms like food packing, sensitivity, or floss shredding between specific teeth, don’t wait. These signs suggest something is wrong. Early detection means simpler treatment. Waiting means more extensive—and expensive—procedures.
Whether you visit us in Hanoi or Ho Chi Minh City, the conversation will include your flossing habits. Not to judge, but because it matters. Those spaces between your teeth are either getting cleaned daily or developing cavities. There’s no middle ground. If you have questions about interproximal cavities, proper flossing technique, or need a checkup with X-rays, I’m here to help. Your teeth will thank you.
About Dr. Emily Nguyen
Dr. Emily Nguyen is the Principal Dentist at Picasso Dental Clinic, where she has served over 70,000 patients from 65 nationalities since 2013. With clinics in Hanoi, Da Nang, Ho Chi Minh City, and Da Lat, Dr. Nguyen specializes in preventive dentistry and restorative care for dental patients throughout Vietnam.
