biomechanics

1、 正畸牙移动的生物机制Be the most kind and happy princess in my own realm-hh Biomechanics in orthodontics 王钟华王钟华 1.1.为什么能移动？为什么能移动？ 2.2.对周围组织影响？对周围组织影响？ 3.3.牙齿移动的规律？牙齿移动的规律？ 4.4.临床中的生物学现象？临床中的生物学现象？1 .Why the teeh can move ？2.What are the effects of force to the Periodontal Ligament and Bone ?3.The regular pat

2、tern of teeth movement?4.Biological phenomena connected with clinical practice?contents 正畸治疗的一个首要基础： 当有足够的力(拉力压力)持续的作用在一颗健康的牙齿上时，它周围的骨组织会发生相应的改建 The orthodontic treatment is based on the simple premise that whenever pressure is applied to a healthy tooth for a sufficient long duration of time, its s

3、urrounding bone remodels. The main theories on tooth movement biomechanics 当前流行的正畸矫治的生物学机制 Sandstedt(1904) （第一个通过动物实验研究）（第一个通过动物实验研究）It It is observed that when the appliance with the is observed that when the appliance with the contious ligh t force of duration applied on contious ligh t force of d

4、uration applied on dog ,the bone on the pression side of the dog ,the bone on the pression side of the alveolar fossa resonpts,however,the tension alveolar fossa resonpts,however,the tension side start to deposite. When applied with side start to deposite. When applied with contiuos heavy force ,the

5、re is no resonption contiuos heavy force ,there is no resonption on the pression side .For a short time ,the on the pression side .For a short time ,the bone start an activaty called underming bone start an activaty called underming resorption,after that ,the tooth moveresorption,after that ,the too

6、th move. . 给狗戴上矫治器，发现牙齿在给狗戴上矫治器，发现牙齿在缓和持续力缓和持续力作用下，作用下，牙槽窝压力侧发生骨吸收，牵引侧新骨形成。牙槽窝压力侧发生骨吸收，牵引侧新骨形成。 在在持续强力持续强力作用下，压力侧牙周膜组织由于过度受作用下，压力侧牙周膜组织由于过度受压，牙槽窝内壁反而没有骨质吸收。短时间内会发压，牙槽窝内壁反而没有骨质吸收。短时间内会发生骨内吸收；继而挖掘性吸收，最后导致牙齿移动。生骨内吸收；继而挖掘性吸收，最后导致牙齿移动。 1 PRESSURE TENSION THEORY Schwartz proposed the pressure tension theo

7、ry in1932. This is the simplest and the most widely accepted theory.骨压迫学说是最容易理解，也是最被广泛接受的 1. According to this theory:Whenever a tooth is subjected to an orthodontic force, it results in areas of pressure and tension. 一但牙齿受到正畸力时，会相应在牙齿的两侧产生压力和张力区 2.The alveolar bone is resorbed whenever the root, fo

8、r a certain length of time, causes compression of the periodon tal ligament, i.e. the pressure side. 当根侧牙周膜受到足够长时间的压力时，会在压迫侧产生牙槽骨的吸收。 3. New alveolar bone is deposited whenever there is a stretching force acting on the periodental ligament fibers, i.e. the tension side 。而在牙周纤维膜受到牵拉一侧即拉力区，会有新骨沉积。 2.B

9、LOOD FLOW THEORY I FLUID Bien (1966)has been credited for proposing the fluid dynamic or the blood flow theory.液体动力学，或者血液流动理论 According to this theory: Tooth movement occurs as a result of alterations in fluid dynamics in the periodontal ligament. 牙周膜中的液体流动,导致了牙齿的移动 牙周的内部环境： 1.Periodontal space is a

10、 confined space and the passage of fluid in and out of this space is limited. 牙周组织中的间隙是个固定大小的、有液体流动的空间.2.The contents of the periodontal ligament create a unique hydrodynamic condition resembling a hydraulic（水压力） mechanism.牙周膜中的物质 可以创造了一个独特的、类似于水压力 的流动的条件. 3. When a force of short duration is applie

11、d to a tooth, the fluid in the periodontal space escapes through tiny vascular channels. 当短时间的持续的力量施加在牙齿上时,其牙周间隙中的液体通过小的管道流出. 牙齿受力后组织改变： 1.When an orthodontic force is applied, it results in compression of the periodontal ligament on the pressure side. The blood vessels in this region also get compr

12、essed and this results in their stenosis(狭窄）.当 牙齿受到正畸的力量时,压力侧的牙周膜受到挤压,其中的血管会相应的变的狭窄. The blood vessels beyond the stenosis balloon up, resulting in the formation of aneurysms.而在狭窄点以外的血管就会有 相对多的血流通过,进而形成了动脉瘤样结构 The formation of aneurysms causes the blood gases to escape into the interstitial fluid th

13、ereby creating a favorable environmentfor resorption.当动脉瘤样结构形成时,其内部的有氧气物质流会被挤入其他血流中,这样,就形成了氧浓度降低，骨吸收的有利的条件2.When the force is removed, the fluid is replenished （补充）by diffusion from capillary walls and recirculation of the interstitial(空隙的） fluid. 当牙齿受到的力消失时,狭窄的血管中会由毛细血管网和再循环而来的由空隙中血流 补充.充足 的血液流动和氧浓

14、度，使得骨可以再次生成。 3.A force of greater magnitude and duration causes the interstitial fluid in the periodontal ligament space to get squeezed out and move towards the apex and cervical margins. This results in the slowing down of the tooth movement and is called the squeeze film effect 当持续的施加于牙齿的力量很大时,就会

15、导致牙周膜中的空间受到很大的挤压力,其中的液体就会向根两端走，而大部分流入牙齿的根尖和牙颈部,不会流进入牙周其他管道,不能形成上述的效应，这样就会使牙齿移动的速度降低.force compression of PDlocclusion of blood vesselsformation of aneutysmsact as spring between tooth and alveolar bone, help in replenishing the squeeze film补充受挤压血管的血流alternation in the chemical envioment decreased ox

16、ygen concentration in compressee areas血氧浓度降低blood gasses escape into local environmentfavorable environment for bone resorption3. BONE BENDING/PIEZOELECTRIC/BIOELECTRIC THEORY Piezoelectricity is a phenomenon observed in many crystalline material （骨压电效应是从存在于骨内胶原成份晶状样物质中骨压电效应是从存在于骨内胶原成份晶状样物质中观察到观察到的的

17、）. The deformation of the crystal structure produces a flow of electric current as electrons are displaced from one part of the crystal lattice to another.（当骨产生（当骨产生扭转形扭转形变变时，不对称的晶体变形可以产生时，不对称的晶体变形可以产生电荷电荷，当这种电荷在晶体层，当这种电荷在晶体层中运动时，会在其中产生电流效应）中运动时，会在其中产生电流效应） When the force is applied on a tooth, the

18、adjacent alveolar bone bends. the osteoclast (破骨细胞) cells start to active. 当牙齿受到正畸力量是,临近的牙槽骨受压或者受拉力而变形 Areas of concavity are associated with negative charge and cause bone deposition. Areas of convexity are associated with positive charge and cause bone resorption 张力侧形成的凹面区域中带负电荷，成骨细胞活动，而压力侧形成的凸面区域

19、中产生了正电荷，破骨细胞活动，牙槽骨外板也有类似的特点。4.the elasty of the bone 4.the elasty of the bone 骨弹性学说骨弹性学说 Kingsley WalkhoffKingsley Walkhoff： Without experiments ,he belives that the Without experiments ,he belives that the character of elasty character of elasty compressionan and compressionan and tenderness of bon

20、e lead to tooth movement.tenderness of bone lead to tooth movement. 在没有实验根据条件下认为：正畸牙移动是因在没有实验根据条件下认为：正畸牙移动是因为骨小梁有可压缩性、弹性和柔性。为骨小梁有可压缩性、弹性和柔性。5.the transformation of the bone 5.the transformation of the bone 骨转化学说骨转化学说 Oppenhein(1930)（狒狒和狗作实验进行正牙实验）狒狒和狗作实验进行正牙实验） when the right force is applied on the

21、 tooth ,both on the pression and tension sides,the alveolar bone s compact bone is dismished then the spongy bone and the trabcular bone appears After that there is osteoblast on the tension side,osteoclasts on the pression side . 牙齿在接受正常矫治力时，无论是压力侧还是张力侧，牙槽嵴牙齿在接受正常矫治力时，无论是压力侧还是张力侧，牙槽嵴致密骨板均消失，致密骨板均消失

22、， 以海绵骨代替，而后又出现横行排列的骨小梁，以海绵骨代替，而后又出现横行排列的骨小梁， 压力侧向牙端有破骨细胞，背牙端有成骨细胞，张力侧向牙端压力侧向牙端有破骨细胞，背牙端有成骨细胞，张力侧向牙端有成骨细胞，背牙端有破骨细胞出现。这二种作用使骨发生整有成骨细胞，背牙端有破骨细胞出现。这二种作用使骨发生整体改建，形成现代骨转化学说。体改建，形成现代骨转化学说。 6. 6.m me echanics and chemistry chanics and chemistry 机械机械化学学说化学学说JustusJustusLuft(1970)Luft(1970)：the mechanics chan

23、ge the the mechanics change the hyduoxyapatite s soluvility ,then osteoclasts hyduoxyapatite s soluvility ,then osteoclasts activate.activate.机械应力变化能改变羟基磷灰石晶状体溶解度，引机械应力变化能改变羟基磷灰石晶状体溶解度，引起破骨细胞作用。起破骨细胞作用。 Davidovitch ShanfeldDavidovitch Shanfeld：with the mechnics the with the mechnics the alveolar bon

24、e produce special bio-chemistry alveolar bone produce special bio-chemistry change,the cyclic adenosine monophosphate induce the change,the cyclic adenosine monophosphate induce the bone absorp and deposite.bone absorp and deposite.牙槽骨在机械应力作用下特有的牙槽骨在机械应力作用下特有的生物化学变化，环磷酸腺苷活性作用，促使骨形成和吸收。生物化学变化，环磷酸腺苷活性

25、作用，促使骨形成和吸收。 机械刺激机械刺激电位改变电位改变生物活性物质生物活性物质组织改建组织改建 These theories are neither incompatible nor mutually exclusive.既不互相排斥，也不是互相有矛盾的 From a contemporary perspective,i t appears that both mechanisms may play a part in the biologic control of tooth movement各种机制可能在牙齿移动的生物机制中都起到了一种作用。The biologic The biolo

26、gic basis 牙齿移动的牙齿移动的生物学基础生物学基础 the regenerativeness of the the regenerativeness of the alveolar bonealveolar bone： ( (颌骨可塑性颌骨可塑性) ) the dentoaleolar bone active the dentoaleolar bone active quikly with the resorption and quikly with the resorption and absorption absorption . .颌骨和牙槽骨生长发育最颌骨和牙槽骨生长发育最活

27、跃，它们改建主要是增生和吸收的质活跃，它们改建主要是增生和吸收的质和量相互平衡和量相互平衡。the resistance of the cementumthe resistance of the cementum ( (牙骨质的抗压性牙骨质的抗压性) )： with the orthodontic force ,due to with the orthodontic force ,due to the resistance of the cementum ,there the resistance of the cementum ,there is no resorption in the d

28、ento is no resorption in the dento cenmentumcenmentum. . 在正畸力作用下，牙骨质没有多少吸收变在正畸力作用下，牙骨质没有多少吸收变化，主要是其外表的类牙骨质具有抗压性。化，主要是其外表的类牙骨质具有抗压性。the stability of the periontal ligament 牙周膜内环境稳定：牙周膜内环境稳定： with the force applied ,the PDl cells absorpe and compose constantly. 受外力作用，牙周膜细胞能根据功能和正畸需受外力作用，牙周膜细胞能根据功能和正畸需

29、要；具有不断发生吸收要；具有不断发生吸收 和合成功能。和合成功能。 the most important pinciple for teeth movement is complete PDL，if not ,like ankylosis, the teeth cant move . 牙齿移动的首要条件是完整的牙周膜，如果没有牙周膜，牙根与牙槽骨直接接触，发生骨性粘连，则不能移动。 for the implant,the way the bone connect with it just like ankylosis,there is no exisiting PDl,so the teeth

30、 cant move.that s why we take it as anchorage,but it still need light force 种植体修复中，骨融合是唯一的愈合方式，这种方式类似于骨粘连，应力缓冲的能力有限，没有牙周膜，没有动度，所以不能接受正畸移动，这也是其可以选为增强支抗的原因，但因其缓冲能力有限，仍然需要用轻柔的力量The reaction of the tissue组织反应组织反应1 1the absorption and resorption of the alveoar bonethe absorption and resorption of the alv

31、eoar bone 齿槽骨改建齿槽骨改建 with the proper force: the osteoblasts on the inner tension side and the outside of the pressure side active correspondingly ,then the bone deposite, the ostelclasts on the opposite sides appear,then the orignal bone start to absorp. 适当作用力大小情况下：适当作用力大小情况下： 张力侧的内侧面和压力侧外侧面，均有成骨细胞活

32、动，新骨张力侧的内侧面和压力侧外侧面，均有成骨细胞活动，新骨沉淀。沉淀。 张力侧的外侧面，压力侧内侧面，破骨细胞活跃，原有骨质张力侧的外侧面，压力侧内侧面，破骨细胞活跃，原有骨质被吸收。被吸收。 the osseous lamella of the dentoalvelar bone the osseous lamella of the dentoalvelar bone disapear,then the trabecula appear and arrange disapear,then the trabecula appear and arrange as the force direc

33、tion. as the force direction. 齿槽骨致密骨板消失，产生齿槽骨致密骨板消失，产生横行排列的骨小梁，方向与受力方向一致。横行排列的骨小梁，方向与受力方向一致。 on the one side ,the osteoblsats make the bone on the one side ,the osteoblsats make the bone to deposite ,on the other side ,the osteoclsats to deposite ,on the other side ,the osteoclsats make it absorb. i

34、t is called transition bone and make it absorb. it is called transition bone and the new bone form after half to one year.the new bone form after half to one year. 改建齿槽骨内新骨小梁横向排列，称之为改建齿槽骨内新骨小梁横向排列，称之为“过渡性骨过渡性骨”。新骨小梁一端破骨细胞活跃，骨质吸收；另一端牙齿成新骨小梁一端破骨细胞活跃，骨质吸收；另一端牙齿成骨细胞活动，骨质沉淀。牙齿停止移动后，过渡性骨需骨细胞活动，骨质沉淀。牙齿停止移动

35、后，过渡性骨需要要0.5-10.5-1年左右转变成正常牙槽骨组织。年左右转变成正常牙槽骨组织。 direct bone resportiondirect bone resportion( (直接骨吸收直接骨吸收) )：the the absorption happen on the surfaceabsorption happen on the surface如果压力区牙槽如果压力区牙槽骨面吸收是在骨表面直接发生，称之为骨面吸收是在骨表面直接发生，称之为直接骨吸收直接骨吸收； underming bone resportion (underming bone resportion (间接骨吸收

36、间接骨吸收) )：with with much more heavy force ,the absorption happen much more heavy force ,the absorption happen further than the surface further than the surface 作用力过大时，骨吸收作用力过大时，骨吸收有时不在牙槽骨内面直接吸收，而在稍远处发生骨吸有时不在牙槽骨内面直接吸收，而在稍远处发生骨吸收，这种吸收为收，这种吸收为间接骨吸收间接骨吸收或或“潜行性骨吸收潜行性骨吸收”（或（或“挖掘性骨吸收挖掘性骨吸收”）。 “ “潜行性骨吸收潜行性骨吸

37、收”使牙齿移使牙齿移动变缓，被矫治牙产生松动、疼痛。动变缓，被矫治牙产生松动、疼痛。2.the resportion and deposition of the PDL 牙周膜反应牙周膜反应 with the orthodontic force ,one with the orthodontic force ,one sides PDL under pressure ,but on the sides PDL under pressure ,but on the other side ,under tension ,then it other side ,under tension ,then

38、 it start to metabolize.start to metabolize.牙齿受到矫治力的牙齿受到矫治力的作用后，一部分牙周膜受牵引，另一部分作用后，一部分牙周膜受牵引，另一部分牙周膜受压迫。牙周膜将产生代谢变化牙周膜受压迫。牙周膜将产生代谢变化 tension zone 张力侧：张力侧：not only are existing fibers in the pdf entrpped passively by adwancing front to form Shappeys fibers,but new are also secreted simultaneously by fi

39、broblasts migrating from the bone 牙周纤维牵拉伸长，间隙增宽，牙周纤维牵拉伸长，间隙增宽，胶原纤维和基质胶原纤维和基质增增生，生，成纤维细胞成纤维细胞增殖，增殖，成骨细成骨细胞胞分化活跃。当外力降低或分化活跃。当外力降低或消失，牙周纤维再排列和附着，继而恢复正常牙周膜宽度。消失，牙周纤维再排列和附着，继而恢复正常牙周膜宽度。 pressure side压力侧：压力侧：the fibers become more narrow and the blood blows more slowl then collagen fiber and substrate van

40、ish,the change above induce osteoclasts牙周膜受压迫而宽度变窄，血牙周膜受压迫而宽度变窄，血管受压，血流减缓，细胞分化，胶原纤维和基质降解，破管受压，血流减缓，细胞分化，胶原纤维和基质降解，破骨细胞活跃。骨细胞活跃。3.牙骨质组织反应牙骨质组织反应 It is reasonably that when the tooth It is reasonably that when the tooth move ,the cementum inevitably absorb.but move ,the cementum inevitably absorb.but

41、depending on the resistance of the depending on the resistance of the cenmentum, the absorption ocurres only cenmentum, the absorption ocurres only in the small zone ligtly ,then the in the small zone ligtly ,then the secondary cenmentum repair it quikly. secondary cenmentum repair it quikly. 临床上希望使

42、齿槽骨吸收，牙齿移动迅速，不造成牙骨质吸收。临床上希望使齿槽骨吸收，牙齿移动迅速，不造成牙骨质吸收。实际上牙骨质不可避免实际上牙骨质不可避免轻度吸收轻度吸收。由于类牙骨质抗压性质，决。由于类牙骨质抗压性质，决定吸收程度较轻，范围小。成牙骨质细胞形成牙骨质，吸收后定吸收程度较轻，范围小。成牙骨质细胞形成牙骨质，吸收后的陷窝很快由的陷窝很快由新生牙骨质进行修复。新生牙骨质进行修复。the primary and secondary cementum 4.牙髓组织反应牙髓组织反应the reaction of the pulpwith the proper force ,the apex is un

43、der light pressure,the pulp with the proper force ,the apex is under light pressure,the pulp is on congestion and the activity may become lower.After the is on congestion and the activity may become lower.After the movement ,the pulp is normal movement ,the pulp is normal with more heavy force ,the

44、pulp may cecrosis with darker with more heavy force ,the pulp may cecrosis with darker colour,but after the RCT ,the tooth can move as usual.colour,but after the RCT ,the tooth can move as usual.1.1.当矫治力值在理想范围之内，根尖部轻度受压，牙髓组织轻度充血，牙当矫治力值在理想范围之内，根尖部轻度受压，牙髓组织轻度充血，牙髓活性可能稍微下降，牙齿停止移动后又恢复正常。髓活性可能稍微下降，牙齿停止移动

45、后又恢复正常。 2 2当矫治力力值过大，则会导致牙髓炎性反应。如果根尖血管阻塞，则可当矫治力力值过大，则会导致牙髓炎性反应。如果根尖血管阻塞，则可能发生牙髓炎，牙髓变性，甚至坏死，牙冠颜色发生（暗红色）改变。能发生牙髓炎，牙髓变性，甚至坏死，牙冠颜色发生（暗红色）改变。3 3死髓牙如果进行治疗后，根尖周组织正常，也可以进行正畸移动（根管死髓牙如果进行治疗后，根尖周组织正常，也可以进行正畸移动（根管治疗后）治疗后） for the teeth after RCT,the demand list as follows: no clinic symptoms ,normal X-rays,at le

46、ast 6 ms obseration for teeth after trauma,light force ,x-rays every 6 m 对于根管治疗后的牙齿移动有以下要求：无临床症状、X线检查满意、外伤 或根尖治疗后至少观察6个月，无异常时可正畸移动，但是应使用轻柔的力量，每6个月X线检查5.the effect on the root and apex 正畸对牙根及根尖组织影响正畸对牙根及根尖组织影响 For the root and apex ,the reaction happen on the For the root and apex ,the reaction happe

47、n on the surface,just as the absorption of cementum.surface,just as the absorption of cementum. 牙根对正畸力的组织反应主要是牙根表面吸收和根尖吸收。牙根对正畸力的组织反应主要是牙根表面吸收和根尖吸收。牙根表面吸收的组织反应同上述牙骨质吸收相同。牙根表面吸收的组织反应同上述牙骨质吸收相同。 The aborption happen on the root is connected with the force applied. Most of the teeth s root would absorb

48、 ,but it is difficult to see on the X-rays 牙根轻微吸收时，吸收发生在根尖，与矫治力大牙根轻微吸收时，吸收发生在根尖，与矫治力大小相关。小相关。 大部分牙移动时均会发生，一般在牙骨质表面，大部分牙移动时均会发生，一般在牙骨质表面，呈浅在性，牙科呈浅在性，牙科X X片上较难发现。片上较难发现。 0 0级：级：complete root complete root 牙根不存牙根不存在可以识别的吸收，根尖完整。在可以识别的吸收，根尖完整。 1 1级：级：only the apex surfaceonly the apex surface牙根尖表面不均匀规则，

49、开始显示牙根尖表面不均匀规则，开始显示处吸收征候，仅仅限于根尖表面。处吸收征候，仅仅限于根尖表面。 2 2级：级：blunt on the rootblunt on the root牙根牙根呈钝状轻度吸收。呈钝状轻度吸收。级：级：obvios blunt obvios blunt 牙根钝状牙根钝状吸收明显，约占牙根长度吸收明显，约占牙根长度1/3-1/51/3-1/5。级：级：serious absportionserious absportion牙根牙根严重吸收，吸收约占牙根长度严重吸收，吸收约占牙根长度1/31/3以上。以上。the absorption of the apex 根尖吸收的

50、两种情况根尖吸收的两种情况 1 1the going-on absorption the going-on absorption 进行性吸收进行性吸收, ,most most happen in the apex,it can be seen from x-happen in the apex,it can be seen from x-raysrays大部分发生在根尖，呈进行性。可在大部分发生在根尖，呈进行性。可在X X片上观片上观察到。察到。 2 2specific absorptionspecific absorption 特发性吸收特发性吸收：depending on the pers

51、onality,but the force depending on the personality,but the force can accelerate it ,the ratio between femal can accelerate it ,the ratio between femal and mal is 3.7:1 and mal is 3.7:1 与个体敏感性相关，与矫治力与个体敏感性相关，与矫治力无关无关. . 在所有牙齿上可以不同程度的发生，但矫治力会在所有牙齿上可以不同程度的发生，但矫治力会加重其吸收速度与程度。女性与男性牙根吸收比加重其吸收速度与程度。女性与男性牙根

52、吸收比率约为率约为3.7:13.7:1，但与男女激素水平无关。，但与男女激素水平无关。 the absorption of the apex is inevitable the absorption of the apex is inevitable all kinds of movement can lead to all kinds of movement can lead to resorption,especially for incisorss intrusionresorption,especially for incisorss intrusion so the proper f

53、orce should be continous and so the proper force should be continous and light ,trying to decrease the absorptionlight ,trying to decrease the absorption 牙根吸收（变短、钝）是正畸治疗的牙根吸收（变短、钝）是正畸治疗的必然后果必然后果，它它的发生不可预测；的发生不可预测； 任何类型的牙齿移动都可以引起牙根吸收，而任何类型的牙齿移动都可以引起牙根吸收，而切牙压切牙压低低时牙根吸收最严重。时牙根吸收最严重。 正畸治疗应该使用正畸治疗应该使用间歇力

54、、轻力间歇力、轻力，尽可能减少牙根吸尽可能减少牙根吸收的程度。收的程度。 切牙过度倾斜移动，冠根反向移动，根尖突破骨皮质6. effect in the TMD正畸对颞下颌关节及下颌骨影响正畸对颞下颌关节及下颌骨影响 when the condyle process move forwards ,the posterior of the glenoid fossa hyperplasia,the anterior absorb,the posterior ascending ramus hyperplasia while the anterior absorb when the condyle

55、 process move backwards ,do as the opposite 适度矫治力作用下适度矫治力作用下 如果使下颌髁突前移，关节凹后壁增生，前壁吸收，如果使下颌髁突前移，关节凹后壁增生，前壁吸收，下颌升支后缘增生，升支前缘及内角吸收。下颌升支后缘增生，升支前缘及内角吸收。 如果使下颌髁突后移，反应与上述相反如果使下颌髁突后移，反应与上述相反7.腭中缝的变化 the centre joint of palate 青春期前腭中缝无完全的骨缝联合，其间由结缔组织相连。组织切片中，腭中缝是一条不规则的分界线，由左右骨缝交错向对方而形成。其间是一条潜在的裂隙，被结缔组织充填。 Befo

56、re adolescence ,the centre joint ist filled up with complete bone ,but syndesm in the latent space between the two interlck palate. 快速腭开展中，随着扩弓进行，期间的 潜在裂缝逐渐扩大，骨质增生发生在每侧骨质顶端，成骨细胞在此聚集，形成类骨质，同时，血管数目增多，纤维细胞数目增多，活跃的组织增生状态。随着类骨质的钙化，腭中缝逐渐形成骨性连接。 With the RPE, the latent space expand ,the bone deposite in b

57、oth sides ,the number of the osteoblasts 、fiber cells and blood vessels increase while,after the bone calcification ,the bone joint get formed.8.面部肌肉的变化 The facial muscles 正畸矫治过程中，由于硬组织形状和位置的改变，口颌及面颊部肌肉等软组织也相应发生改变，以取得新的平衡。如改变下颌的位置，肌电检查到下颌向前时翼外肌电活动增强。这是功能性矫治器治疗的基础。 When the bone position change ,the

58、muscles follow with it to make new balance.This is the basis for functional treatment. 用神经肌肉机制矫治早期畸形，在儿童时期易建立反射通路，机体很快适应。另外，牙齿颌骨到达新的 位置后，肌肉的动力平衡后，才会得到稳定的治疗效果。如上颌前突、开合等矫治结束后还要肌肉训练。 The adolescence can adapt to the functional bone and musle position change quikly,only with the new musle balance ,can t

59、he position be firm enough .For the case,after the treatment of the openbite and m.x protursion ,muscle training is necessary.9.the effect of milk teeth movement on the 9.the effect of milk teeth movement on the permanent teethpermanent teeth 乳牙移动对恒牙胚的影响乳牙移动对恒牙胚的影响the permanent teeth reside in the l

60、ingual side of the milk,the premolar on the root branching when the milk teeth root,the permanent move together with the milk ,but too much heavy force make it move tipply,the permanent move to the opposite way 恒切牙位于乳牙舌侧，前磨牙位于根分叉处恒切牙位于乳牙舌侧，前磨牙位于根分叉处乳牙根未吸收情况下，恒牙随乳牙一起移动。乳牙根未吸收情况下，恒牙随乳牙一起移动。 正畸力过大、乳牙呈倾