The hardness of the tooth is essentially being compromised. You’ll notice chalky white spots forming. The enamel is demineralizing because calcium is being lost. Diligent oral hygiene and the minerals that are present in your saliva can help. Eat foods that promote remineralization like cheese & milk
This is where the surface enamel erodes. Once the decay breaks through the surface enamel, it’s likely you will need a dental filling to halt the bacterial progression and restore a protective layer. You may experience some sensitivity/pain at this point or you might not feel anything at all. A composite filling will usually solve the problem.
Tooth decay starts to hurt. This is because the decay has gained access to the nerves. While the decay is going deeper into that tooth it’s also rapidly destroying the softer dentin layer below the enamel. A larger restoration will typically be needed. This will keep the decay from getting to the vital part of the tooth, the pulp
At this stage, you’re going to need a root canal to clean out the bacterial infection. This is because pus is irritating the tissues, making the nerves, blood vessels, and connective tissue in the pulp die. Your dentist may even refer you to a root canal specialist, an endodontist who will clear out the infection that is in the tooth root.
At this stage, the pulp is damaged. Bacteria and decaying pulp remnants cause an infection at the tip of the tooth’s root. Thus, a pus-filled pocket forms. Regular trips to the dentist should catch the abscess in radiographs. You’ll need a root canal in order to try and save the tooth and/or you might need have surgery to open the abscess and drain it. Both typically require antibiotics.