After the formation of permanent dentition, it is normal that the upper and lower jaws should have the following contact relationship.
The distance between the upper and lower incisors must be about 2 mm, that is, the upper incisors are slightly inclined forward, which will not completely fit the lower incisors, but they will not be too far apart. Frontal view, the crown of the upper anterior teeth should not cover more than 2/3 of the lower anterior teeth.
The following occlusal disorders sometimes occur during dentition replacement, but most of them are temporary and can be adjusted freely with growth and development without correction. For example, because the permanent teeth are wider than the deciduous teeth, there will be a temporary slight crowding when the front teeth just erupt. However, this phenomenon can disappear completely with the replacement of posterior teeth and the increase of epiphysis in the future. Another example is: when the maxillary central permanent teeth just erupt, temporary gaps may appear because the tooth germs of adjacent teeth squeeze their roots; As long as there are no factors such as excessive teeth or upper lip lacing, there is no need to panic or correct. However, serious local obstacles in tooth replacement must not be taken lightly. Because this will not only lead to tooth dislocation, uneven dentition, but also make the occlusal relationship between the upper and lower jaws disorder. This will inevitably hinder the health and function of the whole oral and maxillofacial system, affect the smoothness and development of the face, destroy the beauty of the face, and even endanger the whole body.
Second, three common abnormalities when children change their teeth:
1. The deciduous teeth fall off too fast. Because they have not yet reached the age of eruption of permanent teeth, the vacant part will be occupied by the displacement of adjacent teeth and the elongation of corresponding teeth, and permanent teeth will erupt out of position due to lack of space. The earlier the deciduous teeth are missing, the easier the permanent teeth will erupt. According to the statistics of stomatology, children with deciduous teeth (or premature deciduous teeth) for more than 2 years must be dislocated permanent teeth. It is most common in maxillary third permanent teeth, commonly known as "tiger teeth". If it is bilateral, the damage to the appearance will be very obvious, while unilateral dislocation will inevitably lead to asymmetry between the left and right faces, so it is not appropriate to remove the deciduous teeth prematurely.
2. The deciduous teeth stay too long at the age of tooth change, but the delay of deciduous teeth will inevitably hinder the eruption of the permanent teeth below. Even if it barely broke out, it must have been misplaced. Parents should pay special attention to observe whether the deciduous teeth fall off after the child reaches the age of tooth change. In this case, they must go to the hospital to take root X-rays to determine whether there are permanent teeth. If there are permanent teeth, the root development has been more than half, it is necessary to decisively pull out the stranded deciduous teeth. If the X-ray shows that the replacement permanent teeth are congenitally missing, the deciduous teeth should not be hastily removed even if they stay for a long time. As long as the roots of deciduous teeth are intact and their periodontium is healthy, they should be tolerated to continue to exercise their chewing function.
Generally speaking, the eruption age of permanent teeth is roughly as follows: 1 permanent teeth 6 ~ 8 years old; The fourth permanent tooth is 9 ~ 12 years old and the third permanent tooth 1 ~ 14 years old. The fifth permanent tooth 10 ~ 14 years old.
3. The early loss of six-year-old teeth means that the sixth permanent tooth erupts the most among all permanent teeth.