Treatment
Tooth decay: causes, signs, treatment and prevention
A white or brown spot on a tooth, a small hole where food gets stuck, pain with sweet things: tooth decay is one of the most common diseases in the world, in children as well as adults. The good news: in the early stages, it progresses slowly and can be stopped or treated simply if it is found early. This guide explains, in simple words, how a cavity forms, how it is treated and how to prevent it, based on Cochrane reviews and the main published studies. It is here to inform you; it does not replace an examination.
How does a cavity form?
Tooth decay is a disease of the hard tissues of the tooth. It comes from an imbalance, over time, between the bacteria in dental plaque and the sugars we eat: the bacteria turn sugars into acids, which gradually dissolve the surface of the tooth (Walsh et al., 2019, PubMed).
So it is not only the amount of sugar that matters, but also how often you have it: every sugary drink or sweet between meals exposes your teeth to a new acid attack.
The stages of tooth decay and its signs
- The white spot: the enamel loses minerals and a dull white spot appears. There is no pain, and the decay can still be stopped with fluoride and better cleaning.
- Enamel decay: the spot turns brown or black, and a small hole starts. Usually there is no pain.
- Dentine decay: the decay reaches the layer under the enamel and progresses faster: sensitivity to sweet things or cold, food getting stuck.
- Nerve involvement: strong pain that lasts, wakes you up at night, and can lead to an infection or an abscess: see a dentist without delay.
A cavity between two teeth often cannot be seen in the mirror: regular check-ups, and an X-ray if needed, find it before it gets bigger.
Treating a cavity according to its stage
| Stage | Usual treatment |
|---|---|
| White spot without a hole | Fluoride, better brushing and diet, monitoring |
| Hole in the enamel or dentine | Remove the decayed part and place a filling |
| Large cavity that has weakened the tooth | Large filling or crown, depending on the case |
| Decay that has reached the nerve | Root canal treatment and then rebuilding the tooth, or extraction if the tooth cannot be saved |
The earlier the decay is found, the simpler, quicker and less costly the treatment.
Tooth decay in children
Baby teeth are thinner than permanent teeth: decay moves faster in them. A common myth is that they "will fall out anyway": a decayed baby tooth hurts, can become infected, and holds the space for the permanent tooth that will come after it.
What works in children? Cochrane reviews conclude that fluorides applied to the teeth (toothpaste, gel and varnish applied by the dentist) are effective in children and teenagers, as are fissure sealants on permanent molars (Smaïl-Faugeron et al., 2014, PubMed); a recent meta-analysis confirms that topical fluorides work in children and teenagers (Shao et al., 2026, PubMed).
In young children, the strength and the amount of toothpaste are chosen according to age, because swallowing a lot of fluoride can stain teeth that are still forming (Walsh et al., 2019, PubMed): ask your dentist for the right amount for your child's age, and supervise their brushing.
Preventing tooth decay
- Brush your teeth twice a day with a fluoride toothpaste: the Cochrane review confirms that fluoride toothpaste reduces decay compared with toothpaste without fluoride, in children, teenagers and adults (Walsh et al., 2019, PubMed).
- Spit out the toothpaste without rinsing too much with water after brushing, to keep the fluoride on your teeth.
- Cut down on how often you have sugar between meals: fizzy drinks, sweetened juices, sweets, sweet tea throughout the day.
- Clean between your teeth every day.
- Have regular check-ups, at a frequency that fits your risk of decay.
- For children: ask for fluoride varnish and fissure sealants on the permanent molars.
Frequently asked questions
Can I treat a cavity at home?
An early white spot can be stopped with fluoride and good cleaning; a hole, however, does not close up on its own and must be treated with a filling at the dentist.
Why do I get cavities even though I brush my teeth?
Brushing may not reach well enough in some places, especially between the teeth and at the back of the molars, or you may have sugar too often during the day; and the risk of decay varies from one person to another.
Does treating a cavity hurt?
Treatment is most often done under local anaesthetic if needed, so it is usually not painful; slight sensitivity may last a few days afterwards.
Should cavities in baby teeth be treated?
Yes: a decayed baby tooth can hurt and become infected, and it holds the space for the permanent tooth; the dentist chooses the treatment that suits the child's age and the state of the tooth.
Which toothpaste is best against tooth decay?
A fluoride toothpaste, at a strength and in an amount suited to age; ask your dentist for advice for yourself and your children.