1、牙齿的发育萌出 Eruption and Shedding of Teeth,Mixed Dentition: Presence of both dentitions,Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6th edition,牙齿的发生时间,胎龄3周 原始口腔 胎龄6周 牙板(dental lamina) 胎龄7周 20个乳牙牙胚（tooth germ) 胎龄4月 第一恒磨牙 胎龄5、6月 恒切牙、尖牙 出生时 第一前磨牙 78月 第二前磨牙 89月 第二恒磨牙 4岁左右 第三恒磨牙,1. 生长期：特点是牙胚组织
2、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。,牙齿萌出,骨内萌出,临床萌出,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11.5年牙根可以发育完成，而恒牙需要13年才完成。,乳牙早且快，用月来计算： 688（6，812） 12 16（1216） 16 22（1622） 30独一份,恒牙晚且慢，用年来计算：切牙789（78
3、、89） 尖牙113（1113）双尖10 112（1011、1112）磨牙6岁就见面二磨114（1114）1825磨牙全,（二）牙齿萌出顺序,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：AABB 和 ABAB,Source: http:/www.columbia.edu/itc/hs/dental/d9903/lectures/lecture4.pdf,恒牙,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 86 1 2 4 5 3 7 8下：6 1 2 3 4 5 7 8,Essentials of Oral His
4、tology and Embryology. James Avery, 2nd edition,Source: http:/www.columbia.edu/itc/hs/dental/d9903/lectures/lecture4.pdf,Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6th edition,Figure from Ten Cates Oral Histology, Ed., Antonio Nanci, 6th edition,Stages of tooth eruption,Essentials of
5、Oral Histology and Embryology. James Avery, 2nd edition,Essentials of Oral Histology and Embryology. James Avery, 2nd edition,5 months,At birth,1 year,2 years,3.5 years,4.5 years,Shedding of mandibular incisor,Figure Source: Dr. Sandra Meyers,The six/four rule for primary tooth emergence Four teeth
6、emerge for each 6 months of age,6 months: 4 teeth (lower centrals & upper centrals) 12 months: 8 teeth (1. + upper laterals & lower laterals) 18 months: 12 teeth (2. + upper 1st molars & loer 1st molars) 24 months: 16 teeth (3. + upper canines & lower canines) 30 months: 20 teeth (4. + lower 2nd mol
7、ars & upper 2nd molars),Source: http:/www.columbia.edu/itc/hs/dental/d9903/lectures/lecture4.pdf,Summary,By 5 months in utero, all crowns started calcification By 1 year old, all crowns completed formation By 2.5 years, all primary teeth erupted By 4 years old, all primary teeth completed root forma
8、tion,Source: http:/www.columbia.edu/itc/hs/dental/d9903/lectures/lecture4.pdf,The rules of “Fours” for permanent toothdevelopment (3rd molars not included),At birth, four 1st molars have initiated calcification At 4 years of age, all crowns have initiated calcification At 8 years, all crowns are com
9、pleted At 12 years, all crowns emerge At 16 years, all roots are complete,Source: http:/www.columbia.edu/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 o
10、ld: emergence of first permanent tooth,Source: http:/www.columbia.edu/itc/hs/dental/d9903/lectures/lecture4.pdf,Problems of Primary Tooth Eruption,Natal and Neonatal Teeth,Retained Primary teeth,Submerged primary teeth,Hyper or supra eruption,Ankylosis,Source: Color atlas of clinical oral pathology. Neville, Damm and White. 2nd edition,Congenitally Missing Teeth,Cleidocranial Dysplasia,Osteopetrosis Defect in Osteoclasts,thank you!,
