We do our best to prevent any decay or damage to the teeth but once the decay has started it’s hard to get it reversed.
The best approach would be regular brushing and flossing but if the decay has started then we should take care of it before it gets worse.
To restore the tooth we excavate the decay and fill it up with tooth colored material that blends with the tooth and doesn’t come off.
Still brushing , flossing is essential as restoration doesn’t give immunity to the tooth.
Decay can restart at another site .
If we ignore the decay and it goes on getting deeper into the tooth, it may extend from enamel through dentin to the pulp( blood vessels and nerves in the tooth).
Then we can’t do filling ( restoration).
Then we have 2 options:
We can extract (pull) the tooth or
Make it non vital (dead) by cutting its blood supply and nerves(Root canal treatment). Then put a cap (crown) on the tooth to make it look and function like a normal healthy tooth.