Changes in S. mutans/total bacteria depending on types of braces. (A) Levels of S. mutans/total bacteria in different braces at each time-point. Changes of S. mutans/total bacteria in patients stratified into (B) the conventional braces group and (C) self-ligating braces group from T1 to T4. A significant difference existed regarding bracket types (P<0.05). *P<0.05. Time-points: T1, Prior to bonding; T2, 3 months after bonding; T3, 6 months after bonding; and T4, 18 months after bonding. S. mutans, Streptococcus mutans; S/T, ratio of S. mutans/total bacteria.