As we all know, there are two sets of teeth in a person’s life. The baby’s milk teeth begin to erupt 6 to 8 months after birth, and 20 teeth erupt one after another until the age of about 2.5 years. From 6 to 7 years old to 12 to 13 years old, the milk teeth are gradually lost and replaced by permanent teeth. 2.5 years old to about 6 years old is called the milk tooth row. From the age of 6, the child starts to change teeth, and there are both unlossed milk teeth and newly erupted permanent teeth in the mouth, and generally by the age of 12, all milk teeth in the child’s mouth are lost and the eruption of permanent teeth is completed, and this period is called mixed dentition. From this time on, the teeth in the mouth will be with us for the rest of our lives, even if they are lost due to disease or accidental damage, there will be no more tooth replacement. Teeth are not only an organ for direct chewing function, but also have a close relationship with pronunciation, speech and keeping the harmony and beauty of the face. Therefore, it is very important to protect our teeth. Most of the bad oral habits occur during childhood, when children do the same action repeatedly, consciously or unconsciously, for a relatively fixed interval of time and continue. If not corrected in time, it will cause a variety of malocclusions such as upper and lower teeth misalignment. More noteworthy is that a bad oral habits, sometimes often secondary to a second bad habits, such as finger sucking can cause inadequate contact with the front teeth, and inadequate contact with the front teeth will be secondary to the habit of spitting out the tongue. 1, finger-sucking habits Most children have finger-sucking habits. Finger-sucking habits of children before the age of 2 or 3 can be regarded as a normal physiological activity, and this habit usually gradually decreases and disappears on its own after the age of 4 to 6. Continuing after this age is a bad habit and can lead to significant malocclusion. If the thumb is placed between the erupting upper and lower front teeth during thumb sucking, the normal eruption of the front teeth will be prevented and the front teeth will be rounded and open. At the same time, when sucking the finger, the buccal muscle contracts, the dental arch narrows, the upper front teeth protrude, and the lips open. 2, licking habits Children often lick the loose milk teeth or the first permanent teeth during the period of tooth replacement, thus forming tongue or licking habits. Usually, children who have the habit of tongue licking often stick the tip of their tongue between the upper and lower front teeth, so that the permanent teeth cannot erupt to their normal position, forming a local pike shaped open dentition. If the children often lick the lower front teeth or loose milk teeth during the period of tooth replacement, forming the habit of licking teeth, it is easy to promote the lower front teeth to the labial side of the tilt, the emergence of gaps, and even the formation of anti-lip bite bad habits of biting the lower lip, which increases the pressure on the lingual side of the upper front teeth and the labial side of the lower front teeth, can cause the upper front teeth to the lip tilt and interdental gaps; impede the lower dental arch and jaw forward development, and pressure on the lower front teeth to the lingual side of the tilt shift is Crowded state, facial performance for open lips and teeth, the upper lip is short and thick, the upper front teeth protrusion and jaw retraction, etc.; and biting the upper lip habit is easy to form the lower jaw protrusion, anterior teeth anticlinal (envelope) and other deformities. 3, the habit of biting things Most see biting pencils and chewing nails, but also see biting fingers, cuffs, handkerchiefs, being corner, etc.. Bite objects fixed in a part of the dental arch, can form a small open dentition in that place. 4, lateral chewing Under normal circumstances, people alternately use both sides of the teeth to chew food. Lateral chewing is common when there is deep caries of molar teeth on one side or early loss of milk molar teeth, which affects the normal chewing of that side of the teeth. Children are willing to use the healthy side to chew food and form the habit of chewing on one side. The lower jaw often moves to the chewing side, and the dental arch rotates to the chewing side, causing the lower front teeth to shift in the midline, and the left and right sides of the face develop asymmetrically. At the same time, the teeth on the disused side are not chewing and the self-cleaning effect is obviously weakened, so the surface of teeth on the disused side will accumulate a lot of soft scale of food and bacteria will grow here, thus causing tooth decay. 5.Breathing with mouth Normally, we are breathing with nose, but if there is tonsil hypertrophy, turbinate hypertrophy, nasal septum curvature, rhinitis and other diseases, it often causes partial obstruction of nasal cavity. Open-mouth breathing habits can cause narrowing of the upper dental arch, high arch of the palatal cover, anterior protrusion of the maxillary teeth or crowding unevenly, and even lead to open lips and teeth, gum hypertrophy and hyperplasia, gum bleeding. 6, adults to help chew and feed children In the mouth, there are many viruses and bacteria, even brushing, can not remove them completely. Some adults have poor oral hygiene and suffer from various oral diseases, these disease-causing microorganisms are present in the oral cavity even more. When young children eat food that has been chewed by adults, these disease-causing microorganisms will be brought into their bodies, which, together with the low immune function of children, may cause the occurrence of diseases such as vomiting, hepatitis and tuberculosis, causing serious harm to young children. Chewing training can stimulate the development of the jawbone and dental arch of the face and keep the relationship between the jawbone and dental arch normal, thus facilitating the eruption of teeth, which is also an important condition that can keep the permanent teeth in normal alignment later. Therefore, as children grow older, the gingival mucosa gradually becomes hard, especially after the milk incisors appear, we should provide children with semi-solid or solid food without fail, and let them chew with their gums or teeth, so that the chewing function can be trained. Exercising children’s chewing function helps children’s digestion and absorption. Investigation shows that rural children’s teeth are generally neater than urban children’s teeth, digestive function is generally stronger than urban children, because rural babies eat more coarse food, more opportunities to chew on their own, digestive capacity is also strengthened. 7.You don’t need to brush your teeth when you are young, and brush them when you grow up Children all like to eat sweets, and breastfeeding is also dominated by sweets, and the carbohydrate or sugar content in sweets is very high, which can easily produce acid in the mouth under the action of lactobacillus, erode tooth enamel and make teeth decay. Therefore, it is important to pay attention to children’s oral hygiene habits from childhood. After eating, especially after eating sweets and sweet drinks, make sure to rinse your mouth, brush your teeth at night before going to bed, and stop eating before going to bed. If you have the habit of eating extra meals before bedtime, you should rinse your mouth and brush your teeth in time after eating. At the same time, pay attention to the changes in children’s mouth, do regular oral examination, ask the doctor to carefully check children’s teeth for decay or misgrowth, so that timely treatment or correction can be carried out. 3 years old or younger should be brought to the dentist for examination every three months or so, so that problems can be detected early.