Stage 1: White spot (loss of enamel minerals)
The first sign of decay is usually an opaque white spot on the enamel. At this stage the tooth surface still looks intact and there is no cavity. With fluoride, good hygiene and less sugar, this stage can be stopped and even improve.
In the ICDAS system these early enamel changes are recorded with codes 1 and 2.
Stage 2: Enamel breakdown
If acid attacks continue, the enamel breaks down and microcavities form. Sometimes a dark shadow is visible beneath the enamel, showing that the decay has come close to the dentin. In ICDAS this is usually described with codes 3 and 4.
Stage 3: Dentin involvement and cavity formation
Dentin is softer than enamel and decay progresses faster in it. At this stage the cavity becomes obvious and sensitivity to cold and sweets may appear. Restorative treatment (a filling) is usually needed. ICDAS codes 5 and 6 refer to obvious and extensive cavities.
Stage 4: Nerve involvement
If decay reaches the pulp (the tooth's nerve), severe pain, inflammation or infection may follow. At this stage treatments such as root canal treatment or, in severe cases, extraction are considered. Facial swelling or fever needs an urgent visit.
Why does early detection matter?
- The early stages are often painless and can't be seen without an examination.
- Treating the early stages is simpler, cheaper and more conservative.
- Regular follow-up shows whether a lesion is active or has stopped.