Tooth Decay and Cavities
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The most important thing about tooth decay is that it does not hurt until it is well advanced. By the time a tooth aches, the decay has usually been developing for a long time and the options have narrowed.
Decay is a chemical process before it is a hole. Bacteria in plaque feed on sugars and release acid; the acid dissolves mineral out of the enamel. Saliva then works to replace that mineral over the following hours. Each is a normal, repeating cycle, and the tooth is fine as long as the two roughly balance.
What tips the balance is not usually how much sugar, but how often. Each exposure starts another acid attack, and frequent snacking or sipping never lets the repair phase catch up. Once enough mineral has been lost the surface collapses into a cavity, and at that point it cannot heal itself — enamel has no living cells to rebuild it.
How It Progresses
Understanding the stages explains why the timing of treatment changes so much about it.
Early demineralisation
A chalky white mark, no hole and no pain. At this stage it can often be arrested and partly remineralised without drilling — the one stage where that is possible.
Enamel cavity
The surface has broken. Still frequently painless, because enamel has no nerve supply. Usually a straightforward filling.
Into dentine
Now it can spread faster, and sensitivity to cold or sweet often begins. A larger filling, and sometimes a crown or onlay.
Reaching the pulp
The nerve becomes inflamed or infected. This is where genuine toothache, lingering pain and night pain arrive, and where root canal treatment or extraction become the realistic options.
Signs Worth Noticing
Early decay is usually silent, which is exactly why check-ups find things you have not felt. Later, it may show as:
Sensitivity to cold, hot or sweet in one particular tooth.
A visible hole, or a white, brown or black mark on the surface.
Food consistently packing into the same spot.
A rough edge you keep finding with your tongue.
Discomfort on biting.
Toothache, pain that lingers, or pain that wakes you — which suggests the nerve is involved and should not be left.
Facial swelling, which needs to be seen promptly. Call us rather than waiting for a routine appointment.
How Decay Is Diagnosed
Some decay is visible on examination, and some genuinely is not. The surfaces between teeth are hidden from view, and decay there can be well established before anything shows.
Bitewing X-rays exist for that reason, and are how decay between teeth is usually found. Where the nerve may be involved, further assessment — including testing how the tooth responds to cold and an X-ray of the root — helps establish whether the pulp is likely to recover or not. That distinction determines whether a filling is enough.
Common Treatment Approaches
What is appropriate depends on how far it has gone, which is why the same word covers very different treatments.
Fluoride and monitoring
for early demineralisation that has not yet cavitated.
A filling
for cavities confined to enamel and dentine. See general dentistry.
A crown or onlay
where too much tooth structure has been lost for a filling to be reliable. See restorative dentistry.
Root canal treatment
where the pulp is irreversibly inflamed or infected, followed by a restoration to protect what remains.
Extraction
where the tooth cannot be restored predictably — usually with a conversation about replacing it afterwards.
Fissure sealants
to protect the deep grooves of children's back teeth before decay starts. See kids dentistry.
Reducing the Risk
Cut how often sugar is eaten rather than only how much. Three sweet things with meals does less damage than the same three spread across the day.
Brush twice daily with fluoride toothpaste. Spit after brushing rather than rinsing, so the fluoride stays on the teeth.
Clean between the teeth daily — between-teeth surfaces are where decay is most often missed.
Be aware of sipping. A sweet or fizzy drink nursed over an hour is a longer acid attack than the same drink finished quickly.
Water between meals is the safest thing to drink for teeth.
Keep check-ups, so decay is found while a small filling is still the answer.
Ask about sealants for children's permanent back teeth as they come through.
Tooth Decay Questions, Answered
Related Treatments and Conditions
Check-ups & Fillings
Examination, X-rays and fillings before decay reaches the nerve.
Root Canal Treatment
Where decay has reached the nerve inside the tooth.
Tooth Sensitivity
One of the earliest symptoms decay produces.
This page is general information, not a diagnosis. What is causing your symptoms can only be established by examining you. If something in your mouth has changed, please arrange an appointment rather than self-treating.
Written by Dental Leaf Clinical Team. Last updated 2026-08-18.
Found a Hole, or Overdue a Check-up?
Decay found early is usually a small filling. Found late it is a much bigger conversation. Book an examination and we will tell you exactly what we can see.
