




版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
1、The biological basis of the orthodontic Therapy,Law 1In orthodontics, tooth moves through bone and brings the periodontal ligament with it.,The basis of the Periodontal Ligament (PDL),Normal width 0.25 mm or 250 micrometers. Cells, fibers, ground substance.,Cells of PDL,Fibroblasts Osteoblasts, oste
2、oclasts Cell rests of Malassez Mesenchymal stem cells They all proliferate at different stages of tooth movement. You must know what functions each has in tooth movement.,Fibers of the PDL,Collagen and oxytalan Some of them are stretched, torn and ruptured, whereas others are compressed and undergo
3、aseptic necrosis,Ground substance of the PDL,Proteoglycans and other proteins Their contents and expression are altered upon tooth movement Water squeezed in and out during tooth movement,Alveolar Bone,Thin cortical bone and porous (lamina dura) Fluid pumped in and out of the PDL Trabecular bone und
4、erneath Must remodel before teeth can be moved,C:Cell F:Fiber AB: Alveolar bone G:Gingivity CE:,Law 2Tooth cannot move unless bone apposition and resorption take place.,Susan M. Ott Univ of Washington,Law 3There will be no tooth movement unless there is a force.,The basis of Force,The force must hav
5、e the right characteristics such as the magnitude and duration - it must meet certain threshold.,Force Types,Light, continuous forces Never declines to zero. Interrupted forces Declines to zero Intermittent forces Declines to zero,Force Magnitude (Level),In the range of 10 to 200 grams. Varies with
6、the type of tooth movement. Light, continuous forces are currently considered to be most effective in inducing tooth movement. Heavy forces cause damages and fail to move the teeth.,Force Duration,Threshold - 6 hrs per day. No tooth movement if forces are applied less than 6 hrs/d. From 6 to 24 hrs/
7、d, the longer the force is applied, the more the teeth will move.,Law 4Orthodontic tooth movement is not the only type of tooth movement.,Eruption Active Passive Lateral drifts Physiological Due to loss of adjacent teeth Orthodontic tooth movement,Types of Tooth Movement,Types of Tooth Movement,Intr
8、usion Extrusion Tipping Bodily movement Rotation,Mechanisms of Tooth Movement,Piezoelectric theory.,Mechanisms of Tooth Movement,Pressure-tension theory.,The Optimal Force,“High enough to stimulate cellular activity without completely occluding blood vessels in the PDL” (Proffit et al. 2000). Active
9、ly being investigated in a scientific field known as mechanotransduction.,Law 5Orthodontic tooth movement cannot occur unless cells are at work.,Force - fluid flow - cell-level strain Deformation of cell membrane leading to cytoskeletal changes Second messenger pathways Gene upregulation in fibrobla
10、sts, osteoblasts and osteoclasts,Effect of the light force on the PDL,Light, continuous forces Osteoclasts formed Removing lamina dura Tooth movement begins This process is called “FRONTAL RESORPTION,“Frontal resorption” because it occurs between the root and the lamina dura.,Light force leading to
11、frontal resorption,Phase 1 Mechanical compression and tension of the periodontium Phase 2 - Mechanically induced cellular and genetic responses; no tooth movement Phase 3 - Accelerated tooth movement due to frontal bone resorption,Effects of heavy force on the PDL,Heavy, continuous forces Blood supp
12、ly to PDL occluded Aseptic necrosis PDL becomes “hyalinized” “HYALINIZATION” This process is called “UNDERMINING RESORPTION”.,“Undermining resorption” because it occurs on the underside of lamina dura, not between lamina dura and the root.,Law 6Frontal resorption occurs in the PDL, whereas undermini
13、ng resorption occurs underneath the lamina dura.,Heavy force leading to undermining resorption,Phase 1 Mechanical compression and tension of the periodontium Phase 2 - Continuing mechanical compression; little cellular and genetic responses; no tooth movement Phase 3 - Cells recruited from the under
14、mining side of lamina dura, not within the PDL, to induce undermining bone resorption,Tooth movement (mm),Time (Arbitrary Unit),Tooth movement (mm),Time (Arbitrary Unit),Frontal resorption,Undermininging Resorption,Law 7Frontal resorption facilitates orthodontic tooth movement, whereas undermining r
15、esorption impedes orthodontic tooth movement.,Anchorage,Newtons law: for every action, there is reaction. Defined as “resistance to unwanted tooth movement.” The “anchorage value” of any tooth is roughly equivalent to its root surface area. Thus, molars and canines generally have higher anchorage va
16、lues than incisors and bicuspids.,Anchorage types,Reciprocal anchorage. Reinforced anchorage. Stationary anchorage. Cortical anchorage.,Reciprocal anchorage,Both units move roughly equal distance. Exemplified by closing a diastema between two central incisors.,Reinforced anchorage,Unit A has substan
17、tially more anchorage value than Unit B. Thus, Unit A moves little but Unit B moves a lot. Exemplified by retracting anterior teeth to close an extraction space by using posterior teeth as a reinforced anchorage unit.,Unit B,Unit A,Biomechanics of Tooth Movement,Center of Resistance - A point on the
18、 tooth around which the tooth shall move. For most teeth, COR is 2/5 way between the apex and the crest of the alveolar bone. Center of Rotation - The point around which rotation occurs when an object is being moved.,Force and Couple,Force Is applied by orthodontic appliances. Induces tipping, trans
19、lation, intrusion, extrusion and/or rotation. Couple Two forces of opposite directions and with non-overlapping points of application. Translation of teeth occurs in response to appropriate force couples.,Potential Complications of Orthodontic Tooth movement,The pulp Root resorption Alveolar bone he
20、ight,Orthodontic effects on the pulp,Rare if light, continuous forces are applied. Occasional loss of tooth vitality. History of previous trauma Excessive orthodontic forces Moving roots against cortical bone Endodontically treated teeth can be moved like natural teeth, with proper management.,Root
21、resorption,More accurately, resorption of root cementum and dentin. Normal ageing process in many individuals Likely occurring in many cases but not to the degree of clinical significance. Root resorption induced by light orthodontic forces is reversible (by regeneration and repair of cementum and/o
22、r dentin). Can lead to tooth mobility in severe cases.,Generalized Root Resorption,Affects most, if not all, teeth; maxillary incisors more susceptible than other teeth. Could be moderate or severe but commonly in the range of up to 2.5 mm. Etiology largely unknown but predisposing factors include conical roots with pointed apices, distorted tooth form, or a history of trauma.,Localized Root Resorption,Cant always be distinguished from generalized root resorption. Maxillary incisors more susceptible than other teeth. Only in rare cases can the causes, such as heav
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 补偿合同(标准版)
- 西藏自治区财政厅直属事业单位招聘考试真题2025
- 临沧市乡村产业发展集团有限公司招聘考试真题2024
- 2025年度勘察设计注册环保工程师资格考试水污染防治复习题及答案
- 综合解析人教版八年级物理上册第5章透镜及其应用重点解析试卷(含答案详解)
- 2025年万科物业客服试题及答案
- 2025年道路运输企业主要负责人和安全生产管理人员考试(主要负责人)自测试题及答案
- 考点解析人教版八年级上册物理物态变化《熔化和凝固》章节练习试卷(详解版)
- 湖南省益阳市注册环保工程师考试(大气污染防治专业案例)全真模拟题库及答案(2025年)
- 2025年互联网营销师(直播销售员)四级理论考核试题及答案
- T-CFNA 6705-2024 地理标志证明商标 玉林八角 低产林改造技术规程
- 员工离职面谈记录表范本
- 2024建筑消防设施检测技术规范
- 2024年全国“纪检监察”业务相关知识考试题库(附含答案)
- 白芳礼课件教学课件
- 第2课黄河文化网上搜(课件)泰山版信息技术三年级上册
- 《大学课件钻井液》课件
- 资深船长:18天终于把船舶抵达美国加州的注意事项理清了
- 期中试卷(试题)2024-2025学年数学六年级上册北师大版
- 《全面质量管理(习题集)》学习考试题库资料(含答案)
- 新收入准则在电商企业中的应用探析-以阿里巴巴为例
评论
0/150
提交评论