There are three main reasons why the gap between the front teeth is getting bigger: 1, periodontal disease: more common in adults, with the progress of periodontal disease periodontal tissue is damaged, the position of the teeth gradually drift forward, the incisors produce gaps; 2, bad habits: children or adolescents are more common. Bad habits include biting the lower lip or spitting out the tongue, etc. Although the force caused by this habit is small, but the duration is long enough and the frequency is enough, even a small force will also cause the teeth to shift; 3, bite interference: mainly refers to the bite between the upper and lower incisors is too deep, each bite between the upper and lower incisors will produce a collision, over time, the upper incisors will be the lower incisors forward top, and gradually appear incisors gap.