What can someone do when one of there cavities starts to spread further and further?

He/she don't need to use medicine for that first. First he/she need to use hot water for that. If he/she use hot water it can be remove. He/she can also use salt with that. It is the first way to remove that. If the cavities not goes even then he/she can use Sensodyne toothpaste. It is a toothpaste that can remove headlong. If that is not go even then he/she need to goes to the dentist.