Source: /itc/hs/dental/d9903/lectures/lecture4.pdf
Problems of Primary Tooth Eruption
Natal and Neonatal Teeth
Retained Primary teeth
牙齿的发生时间
• • • • • • • • • 胎龄3周 胎龄6周 胎龄7周 胎龄4月 胎龄5、6月 出生时 7－8月 8－ 9月 4岁左右 原始口腔 牙板(dental lamina) 20个乳牙牙胚（tooth germ) 第一恒磨牙 恒切牙、尖牙 第一前磨牙 第二前磨牙 第二恒磨牙 第三恒磨牙
乳牙早且快，用月来计算： 688ⅠⅡ（6～８，8～12） 12 16Ⅳ（12～16）
16 22Ⅲ（16～22）
30独一份
恒牙晚且慢，用年来计算：
切牙789（7～8、8～9）
尖牙113（11～13）
双尖10 112（10～11、11～12）
磨牙6岁就见面 二磨114（11～14） 18～25磨牙全
1. 生长期：特点是牙胚组织的形成，是组织 学的变化 2. 钙化期：特点是钙盐沉积，基质逐渐变硬， 通过X线片可以看到牙齿钙化的全过程。 Nolla 把 X 线片上的恒牙钙化过程分成 10 个阶 段。
3. 萌出期： 特点是牙齿开始向 面而移动，直到建 立 关系发挥咀嚼功能。牙齿萌出不是发育 结束，正常情况下，牙齿进入口腔时，牙根 仅发育到根长的2/3，所以，牙齿萌出后牙根 继续发育，据临床观察，乳牙根在它萌出后 大约1～1.5年牙根可以发育完成，而恒牙需 要1～3年才完成。 骨内萌出 牙齿萌出 临床萌出
Four teeth emerge for each 6 months of age
1. 6 months: 4 teeth (lower centrals & upper centrals) 2. 12 months: 8 teeth (1. + upper laterals & lower laterals) 3. 18 months: 12 teeth (2. + upper 1st molars & loer 1st molars) 4. 24 months: 16 teeth (3. + upper canines & lower canines) 5. 30 months: 20 teeth (4. + lower 2nd molars & upper 2nd molars)
Source: /itc/hs/dental/d9903/lectures/lecture4.pdf
The rules of “Fours” for permanent tooth development (3rd molars not included)
Source: /itc/hs/dental/d9903/lectures/lecture4.pdf
Rules of “sixes” in dental development
6 weeks old in utero: beginning of dental development 6 months old: emergence of the first primary tooth 6 years old: emergence of first permanent tooth
Source: /itc/hs/dental/d9903/lectures/lecture4.pdf
Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
（二）牙齿萌出顺序
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Stages of tooth eruption
Essentials of Oral Histology and Embryology. James Avery, 2nd edition
Essentials of Oral Histology and Embryology. James Avery, 2nd edition
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À Î Ñ » 1 2 3 4 5 6 7 8 É ò Ï ¢ ±ä Ê ¼ £ ¨ê Ë © £ 7¡ « 8 8¡ « 9 11¡ « 12 10¡ « 11 10¡ « 12 6¡ « 7 12¡ « 13 17¡ « 21 ³ ò Ë Ð 2 3 6 4 5 1 7 8 Ï ò  ¢ ±ä Ê ¼ £ ¨ê Ë © £ 6¡ « 7 7¡ « 8 9¡ « 10 10¡ « 12 11¡ « 12 6¡ « 7 11¡ « 13 17¡ « 21 ³ ò Ë Ð 2 3 4 5 6 1 7 8
Shedding of mandibular incisor
5 months
At birth
1 year
2 years
3.5 years
4.5 years
Figure Source: Dr. Sandra Meyers
The six/four rule for primary tooth emergence
Submerged primary teeth
Hyper or supra eruption
Ankylosis
Source: Color atlas of clinical oral pathology. Neville, Damm and White. 2nd edition
Congenitally Missing Teeth
Source: /itc/hs/dental/d9903/lectures/lecture4.pdf
Summary
1. 2. 3. 4.
By By By By
5 months in utero, all crowns started calcification 1 year old, all crowns completed formation 2.5 years, all primary teeth erupted 4 years old, all primary teeth completed root formation
牙齿的发育萌出 Eruption and Shedding of Teeth
Mixed Dentition: Presence of both dentitions
Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
[乳牙]
顺序 上颌 下颌
1ห้องสมุดไป่ตู้
2 A
3 B
4
5
6 D
7
8 C
9
10 E
A
B
D
C
E
乳牙的萌出－小结
• 时间：6月- 2岁半
个体差异大
• 顺序： A B D C E
差异：A－A－B－B 和 A－B－A－B
Source: /itc/hs/dental/d9903/lectures/lecture4.pdf
At At At At At
birth, four 1st molars have initiated calcification 4 years of age, all crowns have initiated calcification 8 years, all crowns are completed 12 years, all crowns emerge 16 years, all roots are complete
Cleidocranial Dysplasia
Osteopetrosis – Defect in Osteoclasts
[恒牙]
顺序 1 2 3 4 5 6 7 8 9 10 11 12 13 14 上颌 下颌 6 6 1 2 1 2 3 4 4 5 5 3 7 7
恒牙的萌出－小结

时间：6岁－1 2、13岁
个体差异大

顺序：上：6 1 2 4 3 5 7 8
61245378 下：6 1 2 3 4 5 7 8
Essentials of Oral Histology and Embryology. James Avery, 2nd edition