What happens when a permanent tooth comes in behind a baby tooth? Shark teeth is a term used to describe the situation when a child's permanent teeth start to grow in before she loses her baby teeth. If a baby tooth is in the way, the permanent tooth simply sprouts up behind it. This gives the child two rows of teeth at once When a permanent tooth grows directly underneath the baby tooth, it then reabsorbs the roots of the baby tooth, which then cause it to become loose and ultimately fall out. ... This occurrence causes the permanent tooth to grow in behind the baby tooth giving it that shark tooth appearance.