Your Teeth Cannot Heal Themselves
Unlike your skin or bones, teeth are unable to repair decay once it happens. Because they lack regenerative cells, once acid eats through your enamel, the damage is permanent and requires external intervention.
Teeth are unique structures that do not possess the stem cells necessary to regrow lost tissue or fix structural holes. While your body constantly heals most other injuries, a cavity is a scar that never fades on its own. Scientists are currently researching stem cell treatments to potentially reverse this process in the future. For now, modern dentistry remains limited to patching damage rather than true healing.
Source: Tooth decay