Key points
- Early decay often has no symptoms, which is why check-ups matter
- Early stages can be reversed with fluoride
- A cavity needs a filling; decay at the nerve needs a root canal
- Less sugar, fluoride toothpaste and cleaning between teeth prevent it
Signs of tooth decay
Decay may not cause any symptoms at first. As it gets worse, the NHS lists:
- A hole in the tooth (a cavity)
- Toothache
- Sharp pain with hot, cold or sweet food and drink
- White, brown or black spots on the tooth
How decay progresses, and how each stage is treated
Decay starts when bacteria in plaque turn sugar into acid that gradually breaks down the tooth surface. What a dentist does depends on how far it has gone:
- Early decay: fluoride varnish or mouthwash can reverse it
- A cavity: a filling, usually in one visit
- Decay reaching the pulp (the nerve): root canal treatment
- Severe damage: the tooth may need to be removed
This is why a regular check-up is so valuable: small decay found early often needs only fluoride or a small filling.
How to prevent tooth decay
The NHS recommends:
- Brush at least twice a day with fluoride toothpaste, and spit rather than rinse
- Clean between your teeth every day with floss or interdental brushes
- Cut down on sugary food and drink, and choose sugar-free medicines where possible
- Don't smoke, and keep up regular dental check-ups
When to see a dentist
See a dentist if you have
- Toothache, or sharp pain when eating or drinking
- Painful, swollen or bleeding gums
- A routine check-up if you haven't had one in 2 years (1 year for under-18s)
How Dental Plus can help
At Dental Plus, small decay found at a check-up can usually be fixed with a single filling. Deeper decay is treated by Dr Ahmad Mahmood, whose MDS covers restorative dentistry and root canals. See our fillings guide.
Common questions
Can tooth decay be reversed?
In its earliest stage, yes, with fluoride treatment from a dentist. Once there is a hole, the tooth needs a filling.
How do I know if I have a cavity?
Often you don't at first. A check-up, with an X-ray where needed, finds decay between the teeth while it is still small.
Does tooth decay always hurt?
No. Early decay is usually painless. Pain often means it has got deeper, closer to the nerve.
How long does a filling last?
Usually 10 to 20 years, depending on the material and how well the tooth is looked after.
Sources
Checked on 16 October 2026. This guide is general information, not a diagnosis. If you are worried, see a dentist.