What Are the Signs of a Dental Cavity You Cannot See?

Why some cavities stay out of sight

A cavity starts when bacteria in plaque turn sugar into acid. The acid slowly dissolves a small area of the tooth. On a front tooth you might see a brown or white spot. But many cavities start where you can't see them, even with a mirror.

Early on, the damage is in the enamel, which has no nerves. That is why a cavity can grow for a long time without hurting. By the time it aches, it has often reached the softer layer underneath.

Where hidden cavities usually start

• Between teeth, where two teeth touch and a toothbrush can't reach
• In the deep grooves on the chewing surfaces of back teeth
• Around the edges of older fillings and crowns, where plaque can collect
• Along the gumline, and on roots that are exposed when gums pull back

Signs that may point to a hidden cavity

None of these signs proves you have a cavity. Each one can have other causes. But if one lasts more than a few days, it's worth having it checked.

• A short, sharp twinge with cold drinks, sweets or sticky food
• Pain when you bite down on one spot, or when you release your bite
• A toothache that comes and goes
• Food that keeps getting stuck between the same two teeth, or floss that shreds in one spot
• A filling or crown that feels rough, cracked or loose, or a new sensitivity around it
• A grey or dark shadow under the enamel, or a spot that looks chalky
• A bad taste or bad breath that doesn't go away with brushing (this has many causes, but decay is one)

How your dentist finds what you can't see

At a checkup, your dentist looks at each tooth, checks the edges of older fillings and dries the teeth to spot early chalky areas. Our intraoral camera can show you a close-up picture of a suspicious spot on a screen, so you see what we see.

X-rays are the main way to find decay between teeth and under fillings. We use digital X-rays. The dose is very low, and your dentist decides how often you need them by looking at your age, past fillings and current cavity risk. Not everyone needs X-rays at every visit.

Can a hidden cavity heal by itself?

Very early decay, before a hole forms, can sometimes be stopped. Fluoride, less frequent sugar and better cleaning between teeth can help that area harden again. Your dentist may choose to watch a small spot and check it again at your next visit.

Once the tooth surface has broken down into a true hole, it will not grow back. A filling then cleans out the decay and seals the tooth. The sooner this is done, the smaller the filling usually is.

What happens if it's left alone

A cavity that keeps growing can reach the nerve in the centre of the tooth. That can cause strong pain or an infection called an abscess. At that point, the tooth may need root canal treatment and a crown, or it may need to come out. Catching decay early usually means simpler treatment and less time in the chair.

Who is more likely to get them

Anyone can get a hidden cavity, even people who brush well. The risk is higher if you snack or sip sweet drinks often, have a dry mouth from medicines, have crowded teeth or many older fillings, or have gums that have pulled back. Children's back teeth are prone to decay in their grooves. Ask your dentist whether sealants, a thin coating painted into those grooves, make sense for your child.

Everyday habits that lower your risk

• Brush twice a day with fluoride toothpaste.
• Clean between your teeth once a day with floss or small brushes.
• Keep sweet foods and drinks to mealtimes instead of grazing.
• Drink tap water between meals.
• Keep up with checkups and cleanings on the schedule your dentist suggests.

Questions