The factors that cause malocclusion are generally divided into two main categories, one is genetic factors and the other is environmental factors. The following gives you some of the factors that can lead to malocclusion can be noted and prevented as early as possible. A, oral bad habits 1, thumb sucking, thumb sucking habits occur at the age of 2-3 years is normal, often stop at the age of 4-5 years, if continue and continue for a long time, it will cause some disorders of the teeth. 2, lip biting habits, repeatedly biting the upper lip or lower lip for a long time, will also appear different misaligned jaw. 3, tongue spitting habit, children in the process of tooth replacement spit out the tongue, or lick the eruption of new teeth. This and bite hard objects (pencil), hand on the cheek, sleep always put the arm under the face, these are bad habits, should be found early and give correction. These are bad habits that should be detected and corrected as early as possible. Second, the function of abnormal mouth breathing, normal breathing is to use the nose to breathe, but due to some nasal diseases will be replaced by the mouth, which will cause dental abnormalities, because the mouth can not close the lips when breathing, there will be dry mouth and gingivitis. Therefore, parents need to pay attention early and solve the nasal problems as soon as possible so as not to seriously cause breathing disorders and snoring. The eruption of milk teeth is usually at 7-8 months, and the eruption is complete at about 2-3 years old. 1. The most common thing when the incisors are just erupted is that the two incisors are slanted to both sides and there is a gap in the middle, then there is no need to be anxious, when the lateral incisors grow out, the gap can be closed naturally, which is a normal phenomenon, but if all four incisors grow out and there is a gap in the middle, then it is necessary to draw parents’ attention. 2, some children, the milk teeth did not fall out, permanent teeth in another row squeezed out, this time need to be timely extraction of milk teeth, permanent teeth may grow to the normal position. The most common is the lower front teeth. 3, “big teeth”, the new incisors look very large, parents do not need to worry about this, because the child is slowly growing up, but the teeth grow out of the size is certain, and will not grow with the age of growth. 4, from childhood to develop good oral hygiene habits, because decay is also one of the causes of tooth misalignment. Here, I wish you all have a healthy and beautiful set of teeth.