Cavities: How They Start, and Whether One Can Heal

A question I hear almost every week, usually right after I mention a small spot on an X-ray: can we just watch it? Or, asked the other way around, can a cavity heal on its own? The honest answer is that it depends entirely on how far along it is. There is a real window early on when decay can be stopped and sometimes reversed, and there is a point past which it cannot be. Most people have never been told that window exists, so here is what is actually happening inside a tooth, and where the line falls.

Decay is a losing streak, not a single event

Your mouth is in a tug-of-war all day. Bacteria living in plaque feed on sugars and starches and produce acid. That acid pulls calcium and phosphate out of the enamel surface. Then saliva, helped along by fluoride, puts minerals back. Both directions happen several times a day, every day.

A cavity is what you get when the losing side wins for long enough. It is not one soda or one night of skipped flossing. It is months of the balance tipping the wrong way in one particular spot.

The early stage can often be turned around

Before there is a hole, decay shows up as a chalky white or slightly dull patch on the enamel, called a white spot lesion. The mineral content is down, but the surface is still intact, and intact enamel can take minerals back up.

That is the stage where watching a spot is a real plan rather than putting things off. What tips it in your favor is unglamorous: fluoride toothpaste twice a day, cleaning between the teeth, keeping sweets and acidic drinks to mealtimes instead of spread across the day, and sometimes a higher-strength fluoride or a varnish applied in the office. It works over months rather than days, and it needs rechecking to know whether it is working at all.

Once the surface caves in, it does not grow back

Enamel is not like bone. It has no blood supply and no living cells inside it, so it cannot rebuild itself across a broken surface. Once decay has gone through and the surface has collapsed, bacteria are sitting inside the tooth, in a space no toothbrush reaches. From there it only goes one direction.

So a filling is not us giving up on prevention. It is clearing out the part that is gone and sealing the tooth so the rest can be defended. Waiting at that stage does not keep the repair small either, since decay that reaches the nerve turns a filling into a root canal or an extraction.

Frequency matters more than amount

Each time sugar or acid reaches your teeth, the acid attack carries on for a while afterward. A can of soda sipped over two hours is harder on enamel than the same can finished in ten minutes, and steady grazing is harder than a larger dessert eaten in one sitting. If you change one thing, make it the number of separate exposures rather than the size of them.

What raises your risk

• Dry mouth. Saliva is your main defense, and plenty of common medications reduce it, including some for blood pressure, allergies, depression, and overactive bladder.

• Teeth that are simply hard to clean: deep grooves in molars, crowding, tight contacts.

• Existing fillings and crowns, since new decay tends to start at the edges of older work.

• Receded gums, which expose root surfaces that are softer than enamel.

• Skipping cleaning between the teeth, which is where most adult cavities begin.

• A history of cavities, which is the best single predictor of the next one.

It usually does not hurt until later

Enamel has no nerves in it. A cavity can be well established before you feel anything, and by the time there is real pain it has often gotten close to the pulp. So the absence of pain is not evidence that nothing is there. That is most of the reason for regular exams and X-rays, to find these while the options are still the small ones.

Worth being seen sooner

• A visible hole or dark spot, or a rough edge you can feel with your tongue

• Food catching in the same place every time you eat

• Sensitivity to cold or sweet that lingers after the trigger is gone

• An ache when you bite down on one particular tooth

• A filling that feels loose or broken, or has come out

Pain that wakes you at night, or swelling in the gum or face, should be looked at promptly rather than at the next convenient appointment.

Two questions worth asking

If you are told you have a cavity, ask how deep it is and whether it is one that can be monitored or one that needs treating now. A small lesion in enamel and a cavity into dentin are different situations, and you are entitled to know which one you have. If it can be watched, ask what to change in the meantime and when it will be rechecked.

This post is general information rather than a diagnosis, and what is right for your teeth depends on an exam and X-rays of your own. If any of it sounds like your situation, or there is a spot someone mentioned a while back that you have been meaning to deal with, we are glad to take a look.

Hashimi Dental, 3701 Market St. Suite E, Riverside, CA 92501