1, most of the friends who need orthodontic treatment have crowded teeth alignment, crowded teeth are not easy to clean, the teeth are not effectively cleaned for a long time will lead to alveolar bone resorption. So wait until the adult correction, it is likely that the alveolar bone has been absorbed to varying degrees, this is very, very common in the orthodontic treatment of adults. So for crowded teeth, the sooner orthodontics the better. 2, clinical work, due to dental protrusion to correct a large proportion of friends; these friends have varying degrees of underdevelopment of the lower jaw, correction during adolescence is more appropriate, because at this time is not fully developed, there is a certain growth potential, when the correction is not only better, and the effect is more stable, not easy to relapse. 3, during the adolescence, because the development has not been completely set, this correction is not only shorter, and the effect is stable, relatively easy to relapse.