Results : with the loss of the alveolar height , the maximum equivalent stress and the principle stress of the upper central incisor periodontium increased 結(jié)果:隨著牙槽骨高度的降低,上中切牙牙周膜最大等效應(yīng)力和主應(yīng)力逐漸增大。
Methods : spiral ct ( sct ) scanning technology , digital image transfer and transcription were used to obtain the initial 3 - d data of the upper central incisor 方法:采用螺旋ct掃描、數(shù)字影像傳輸與轉(zhuǎn)錄方法,獲得中切牙三維形態(tài)的原始數(shù)據(jù)。
As early as 4 months , the first primary , or baby teeth , to erupt through the gums are the lower central incisors , followed closely by the upper central incisors 最早在4個月的時候,首先萌出的是下頜第一乳切牙,緊接著萌出的是上頜中切牙。
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歲左右,開始于第一恒磨牙以及下頜第一中切牙。這個過程一直持續(xù)到將近21歲。