Tooth brushing should be started as soon as the tooth erupts. from your query I assume only front tooth have erupted. So you can either wrap a wet gauze to wipe the tooth or you can use baby tooth brush which is designed to fit on parents finger. remember baby tooth brush is not a toy and should  be used with assistance from an adult. By three years of age when all the milk tooth erupts. A child can be taught how to brush also remember brushing technique varies with age so consult your dentist regarding this

hi hru? u can start brushing whn teeth came out...but at ths age he/she cant brush of their own...gentle soft brushing with soft baby brush s compulsory. parents can guide their kids how to spit and how to brush slowly... minimum parents shd clean and wipe their kids teeth with clean cloth or cotton after every food intake especially milk and milk products....should avoid bottle feeding..