In the process of growth and development, due to a variety of reasons such as teeth misalignment, upper and lower dental arch relationship misalignment, maxillary and mandibular position or size abnormalities and teeth and jaws and facial and cranial relationship is not coordinated and other deformities, referred to as malocclusion. This disease, together with caries and periodontal disease, is listed as one of the three major diseases of the oral cavity by the World Health Organization, and the incidence rate of this disease in China is about 49%. The harm of malocclusion 1, affecting the jawbone and facial soft tissue development. If the lower front teeth bite on the outside of the upper front teeth, that is, the front teeth anti-collision is not treated in time, the lower jaw dental arch will limit the upper jaw dental arch, the forward development of the jaw bone, and the power of the upper jaw forward development in turn promote the lower jaw excessive forward development, resulting in a vicious circle, the result of the deformity is even more serious, manifested as a sunken middle of the face, the lower jaw protruding chin, looks like a “moon child “The result is more serious deformity. 2, affect oral health. Arrangement of crowded teeth because it is not easy to self-cleaning, brushing is not easy to brush thoroughly clean, and therefore good caries, gingivitis and periodontitis. 3, affect oral function. Serious upper and lower dental arch occlusal disharmony teeth can not properly bite, cut and chew food, thus increasing the digestive burden of the gastrointestinal tract, may cause gastrointestinal dysfunction, affecting the digestion of food and nutrient absorption, which affects the health of the body; when the posterior teeth have bitten and the front teeth can not bite on the front teeth are known as the anterior teeth open, at this time, the front teeth can not cut the food, some of the utterance of the pronunciation of the unclear; some teeth are misaligned and disorders of the bite relationship, which may cause temporal Some teeth misalignment and occlusal relationship disorders may cause temporomandibular joint dysfunction, affecting the functional movement of the jaw. 4.It affects the beauty of face. If not corrected in time, the malocclusion will affect the beauty of the face and cause pressure on the patient’s mind and spirit. The best age of various types of malocclusion 1, in the period of milk teeth (3 ~ 5 years old) and replacement teeth (6 ~ 11 years old), general malocclusion such as individual teeth misalignment does not require immediate correction, should continue to observe and correct the bad habits of the oral cavity, because in this period, the teeth and jaws are in the period of adjustment, along with the correction of bad habits, the malocclusion can be partially corrected on its own. At this time of rapid growth and development, inappropriate orthodontic treatment will affect the development. 2, for the serious impede growth and development of the malocclusion, then need to be timely correction. The anterior teeth will hinder the development of the maxilla and affect the appearance of the face. If the child can cooperate, the effect of correction at the age of 4-8 years will be more ideal. ② Severe mandibular retraction or underdevelopment should be carried out during the peak growth period (usually around 12 years old for boys and 10 years old for girls) to promote the growth of the mandible and reduce the difficulty of continuing orthodontic treatment in the future. 3.Most of the malocclusions will be corrected until the permanent teeth stage, around 14 years old. Because at this time, the roots of permanent teeth gradually develop and the occlusal relationship between upper and lower teeth is also adjusted, the type of malocclusion can be clearly diagnosed and corresponding orthodontic methods can be taken, and it is easy to maintain stable results after the orthodontic treatment is completed. Theoretically speaking, the best age for children to be corrected for malocclusion is at the peak of children’s growth and development. Boys at 12 to 14 years old, girls at 11 to 13 years old. However, the growth and development of each child is individual and cannot be generalized. The correct method is to estimate the growth spurt through certain tests, such as wrist X-ray, continuous height measurement, understanding the first menstruation of women, and paying attention to children’s shoes, socks, clothes and hats. Orthodontic treatment during this period is short and effective. If this period is missed, but the child is still in adolescence, although it is slightly more difficult, the orthodontic effect is also better. If after the age of 18, the growth and development is basically completed, the orthodontic effect is not as good as in childhood and adolescence. However, for serious bony malocclusion, orthodontic treatment cannot be completed by orthodontics alone, but must wait until adulthood after the age of 18 to be treated with surgery. Prevention of malocclusion Malocclusion is a developmental deformity with a complex etiology, generally caused by genetic and environmental factors. According to the survey statistics, 60%-70% of malocclusion is caused by acquired environmental factors, so it can be prevented. 1, from the eugenics to solve the malocclusion caused by heredity. Attention to maternal nutritional health care and prevention of maternal diseases are prerequisites for normal fetal development. When the fetus is born, trauma during labor should be prevented. 2. Pay attention to the feeding of infants and young children. It is very important to feed infants and young children reasonably and adopt correct feeding posture. Advocating breastfeeding, artificial feeding, it is best to use the nipple similar to the mother’s nipple, the opening of the nipple should not be too large, the diameter of 1-2 millimeters is appropriate. Children can chew food, should eat some slightly hard and easy to digest food to exercise the chewing muscles, to promote the development of chewing organs. 3, pay attention to the physical and mental health of young children, strengthen nutrition and pay attention to oral hygiene. Timely detection and treatment of systemic diseases, such as rickets, dyspepsia, endocrine disorders and chronic inflammation of nasopharynx, early filling caries. 4, correct the bad habits of infants and young children. The first is to remove the cause of bad habits, the occurrence of a short period of time, the duration of the bad habits, after the parents to guide the reminder and patience to persuade, it is not difficult to correct. If necessary, the use of a variety of bad habits broken device, to help children overcome bad habits. Warm tips: 1, orthodontic treatment course is longer, but also regular follow-up, so patients should be fully prepared, can not rush, should also avoid halfway. 2, patients wearing orthodontic appliances, there will be mild pain, soreness and other uncomfortable feeling, the orthodontic appliances are not adapted to, this is a normal phenomenon, it takes a period of time to adapt to the process. 3, orthodontic treatment during the period of time can’t eat too hard, too sticky food, front teeth Can not directly bite hard food, in order to prevent damage to the orthodontic appliances. 4, orthodontic treatment of teeth and periodontal tissues of the disease-resistant ability has been reduced, poor oral hygiene will lead to teeth and periodontal caries, gingivitis and so on more easily than usual, so we must insist on morning and evening and after meals, carefully brushing teeth. Especially for fixed orthodontic appliances, every time you brush your teeth, you must clean them thoroughly; movable orthodontic appliances should be brushed and cleaned every day, otherwise there will be odor for a long time. 5, children are in the period of growth and development, and orthodontic appliances limit the intake of some food, so the orthodontic treatment period should be increased appropriately.