You do need to actively clean your infant’s gums, even if a tooth hasn’t erupted. At first there will be some squirming, but then they will get used to it. Use a soft baby toothbrush or a soft washcloth to gently clean their mouth.
When the first tooth erupts it’s time to use an infant toothbrush and a fluoride toothpaste twice daily. This is the way to start a lifetime ritual of good oral hygiene.