First use your finger to brush it. Take a glass of water, add a pinch of salt and boil. cool it and use in washing baby's mouth. if all teeth or front set of teeth has emerged then you can take baby brush with soft bristles ( check it should not be hard orelse will affect the gums) and brush with plain water or Colgate tooth pwder. After 2 years you can use paste. Ask your doctor. they will recommend you the right paste. I am using Colgate junior.