How to tell if your baby is teething or he is sick of another reason? Cutting teeth isn't one of those milestones a baby reaches all at the same time. To turn from the stage of gummy grin to the stage of mouthful of teeth is something that take three years to complete in our toddlers. He will get through some painful moments that differ from baby to another. Anyway, you have to consult your pediatrician first for advice though to help alleviate your baby's pain.