Gap retainers are worn because of premature loss of milk teeth, in order to prevent the position of permanent teeth from being occupied by other teeth, gap retainers are worn to preserve the gap between the eruption of permanent teeth. Because of the young age of wearing the retainer, the child is not able to maintain good oral hygiene, and a large amount of plaque will gather at the position of the retainer causing inflammation of the gums and decay of the adjacent teeth, which are the hazards of the retainer. The gap retainer is not firmly bonded to other teeth, because the other baby teeth are relatively small and poorly bonded, which can easily lead to a series of discomforts caused by the child swallowing into the stomach, and even some children will inhale the gap retainer into the trachea, which is very dangerous.