Why can cavities develop between teeth?

You brush every day, and your dentist still finds a cavity between two teeth. It can feel unfair, but a toothbrush can’t fully clean the spaces between teeth. Plaque can settle there, and the acids it produces can damage enamel in spots you can’t see or feel. That’s why decay between teeth often turns up during an exam or on an X-ray before it causes any discomfort. 

What you will learn in this article: 

• Why plaque can remain on the surfaces between neighboring teeth 

• How sugar exposure, saliva and fluoride affect cavity risk 

• Why an examination and dental X-rays may reveal hidden decay 

• How early enamel damage differs from a cavity that needs repair 

Ready to have your teeth checked? Schedule an appointment with an Aspen Dental provider to discuss any concerns and your cavity risk. 

What are cavities between teeth? 

Cavities between teeth develop on the surfaces facing neighboring teeth. Only the location is different; the decay process is the same one that affects other tooth surfaces. 

A cavity is a hole caused by tooth decay. Decay can begin before that hole forms, when acids damage enamel, the hard outer covering of a tooth.¹ This distinction matters because early damage and a physically broken-down surface may need different care. “Between teeth” also does not necessarily mean both teeth have cavities. 

Why does plaque cause decay between teeth? 

Plaque is a sticky film containing bacteria. When those bacteria use sugars from food and drinks, they produce acids. Because plaque clings to the tooth, the acids stay in contact with the enamel and can gradually damage it.¹ The same process can occur on the closely facing surfaces of neighboring teeth. 

Frequent sugary snacks or drinks give bacteria repeated opportunities to produce acid. Saliva helps replace minerals in enamel, and fluoride supports that repair process. Too little saliva, sometimes related to medications or health conditions, and inadequate fluoride exposure can increase cavity risk.²

Several factors can work together. A useful conversation with your dentist considers your daily routine, dry mouth symptoms and past cavities rather than assuming there is one explanation. 

Can cavities form between teeth even if you brush? 

Yes. The American Dental Association notes that even a good toothbrush can’t fully clean the spaces between teeth.³ Cleaning between them daily helps remove plaque and food a toothbrush misses. Floss, interdental brushes and water flossers are among the available options.³ 

If cleaning a particular area is difficult, ask your dentist or hygienist which tool suits that space. Describe the problem: Teeth that feel tightly packed, dental work that gets in the way or discomfort when you clean. 

Good habits reduce risk, but they are not a guarantee that you will never develop decay.

Why are cavities between teeth hard to spot? 

The sides of contacting teeth are partly hidden from view. Looking in a mirror cannot reliably tell you whether those surfaces are healthy. Dental X-rays can reveal decay that is not yet visible during an examination.⁴

Early decay usually has no symptoms. As it progresses, it may cause toothache or sensitivity to sweets, heat or cold.² Feeling comfortable does not rule out a problem, and sensitivity alone does not establish how deep the decay is. 

Keep your regular dental visits even when nothing hurts. If a dentist identifies a suspicious area, ask them to show you where it is and explain what the finding means. 

How do dentists check for cavities between teeth? 

Your dentist examines your teeth and asks about symptoms and previous dental treatment. When imaging is needed, bitewing X-rays show the visible parts of the upper and lower teeth together and help reveal decay between teeth.⁴ 

Ask why an X-ray is recommended and whether recent images are available for review. Dental X-rays involve very low radiation, and no one should receive more than necessary.⁴ 

Can early decay between teeth be reversed? 

Early decay may be stopped or reversed before a hole forms. Fluoride and minerals from saliva can help repair weakened enamel. Once a cavity has formed, that lost tooth structure does not grow back. A filling is a common treatment, while more extensive damage may require additional care.²

If your dentist recommends monitoring an early area, ask what the prevention plan includes and when it should be checked again. Monitoring should come with a clear plan, not leave you wondering whether anything has changed. 

When should you contact a dentist? 

Contact your dentist about persistent tooth pain or new sensitivity rather than waiting for a routine visit. Mention when it happens and how long it lasts. Cavity symptoms can overlap with other dental problems, so an examination is needed to identify the cause. 

Report facial swelling or fever promptly, particularly with tooth pain. These can occur with a dental infection.² Let the office know about these symptoms when you call so they can advise you about urgent assessment. 

Schedule an examination with your local dental provider to check a concerning area and discuss what care makes sense. 

Why can cavities develop between teeth? FAQs 

Can decay develop beside an existing filling? 

Yes. A filling repairs a damaged area, but the surrounding tooth can still decay. As fillings age, cracks or gaps at their edges can collect bacteria and contribute to new decay.¹ Tell your dentist if an older filling feels different or repeatedly traps food. 

Does floss catching mean I have a cavity? 

Not by itself. Floss catching is not enough to diagnose a cavity. If it repeatedly catches or shreds in the same spot, describe that to your dentist and ask them to examine the area. Avoid using the floss as a test to decide whether you need treatment. 

Can a water flosser replace string floss? 

It can for some people, depending on your spaces and dental work. A water flosser is one option for cleaning between teeth, particularly when other tools are difficult to use.³ Ask your dentist which device suits you. The goal is effective daily cleaning with a tool you can use comfortably and consistently. 

Sources 

¹ American Dental Association, MouthHealthy: “Cavities.” https://www.mouthhealthy.org/all-topics-a-z/cavities
² National Library of Medicine, MedlinePlus: “Tooth Decay.” https://medlineplus.gov/toothdecay.html 
³ American Dental Association, MouthHealthy: “Flossing.” https://www.mouthhealthy.org/all-topics-a-z/flossing 
⁴ National Library of Medicine, MedlinePlus: “Dental x-rays.” https://medlineplus.gov/ency/article/003801.htm