人的一生中均有乳、恒两副牙齿,而乳牙在口腔内使用时间不长,自6～12周岁先后被恒牙所替换,在这期间的儿童少年口腔内,既有乳牙,又有新萌牙出的恒牙,故称为混(?)牙期。若由於某些原因(遗传、营养不良、龋病、乳牙滞留和不良习惯等)使恒牙萌出过程中受到障碍,造成牙齿排列不齐、上下颌牙齿不正常接触和颌骨发育畸形。主要表现有牙齿 People have milk in life, constant two teeth, and deciduous teeth in the oral use of time is not long, from 6 to 12 years of age has been replaced by permanent teeth, in this period of childhood children's teeth, both deciduous teeth, there are New adorable permanent teeth, it is called mixed (?) Period. If for some reason (genetic, malnutrition, dental caries, deciduous teeth retention and bad habits, etc.) to the process of eruption of permanent teeth are obstructed, resulting in missing teeth, upper and lower jaw teeth are not normal contact and jaw deformity. The main performance of teeth