Permanent teeth begin appearing around age 6 , starting with the first molars and lower central incisors . this process continues until approximately age 21 恒牙萌出于6岁左右，开始于第一恒磨牙以及下颌第一中切牙。这个过程一直持续到将近21岁。
With increase of soil hardn ess , digging duration in incisors significantly increased , but dried soil mass d ug out by the zokors in each bout reduced 随着土壤硬度的增加，高原鼢鼠挖掘的时间及每次挖掘时持续的时间明显增加，而每次的掘土量显著减少。
I put his face labeled as color , head labeled as shock , labeled as polyphonic ears , nose labeled as monoblock , incisors labeled as clamshell , a word he used daogu % 我把他的脸打成彩屏的，脑袋打成震动的，耳朵打成和弦的，鼻子打成直板的，门牙打成翻盖的，总之把他捣鼓成二手的！
So what does a beaver without teeth eat ? " since she does n ' t have her incisors , we ' ve been feeding her salad greens , applesauce and vegetable - based baby foods , " finch said by e - mail wednesday 芬奇对此表示： “自从贝莉的门牙没有了之后，我们就一直在喂它绿叶蔬菜，苹果酱和蔬菜成分的婴儿食品。
The first group is the 6 incisors , the next group is the four premolars on the bottom and top of each side , and the final group is the three top molars and two molars on the bottom of each side 第一组是6颗门齿,第二组是每边的底部和顶端上的四个小臼齿，最后的一组是两边顶端三颗臼齿和底部的二颗臼齿。
The permanent incisor will assume normal position and it is not necessary to extract the mobile primary incisor if there is enough room for the permanent incisor . delayed eruption of permanent teeth 一般来说，乳齿会因为牙根收缩而变得松动，跟着自然脱落，这是正常现象，不会影响恒齿的生长，所以不一定要拔掉松动的乳齿。
Ru1ls : the root surface with high root caries prevalence rate are labial surfaces of incisor and canine , mandibular premolar and molar , lingual surfaces of mandibular incisor and canine and maxillary molar , distal surface of premolar and mesial surface of molar 结果：根面龋易感性高的根面为前牙、下领前磨牙、磨牙的唇（颊）面、下前牙与上领磨牙的舌面、前磨牙的远中面、磨牙的近中面。
These are 1 ) the case of an inversely impacted permanent maxillary incisor secondary to a supernumerary tooth , and 2 ) the case of severe root dilacerations of a horizontally impacted incisor with midline deviation , severe space deficiency and congenital absence of bilateral mandibular lateral incisors 第二个病例是一位十一岁六个月的女孩，他的左上颚正中门牙因为牙根大角度弯曲，造成水平阻生，同时合并有空间丧失，中线不正，严重空间不足及双侧下颚侧门牙先天缺牙等问题。
Result : the midfacial complex was displaced anteriorly , forward growth of mandible was restricted ; the mandible exhibited a downward and backward rotation ; an significant increase was showed on the lower facial height ; the class incisor relationship was corrected by anterior displacement of the upper incisors and posterior displacement of the lower incisors 结果：上颌向前移位改良生长量，下颌的向前生长受到抑制；下颌以髁突为中心向下、后旋转，使下颌空间位置发生变化；下颌的顺时针旋转将造成面下1 3长度增大；上、下颌前牙发生牙性代偿的掩饰作用。
