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Biology of Tooth Movement

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Introduction to Orthodontics
Fifth Year

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Biology of Tooth Movement

  1. 1. 16th Lecture Biology of Tooth Movement-II April 28, 2012 Dr. Ahmed Basyouni 1
  2. 2. • • • • April 28, 2012 Clinical consideration of the periodontium: Periodontal Ligament: Mechanisms of Orthodontic tooth movement: Tissue Reaction To Tooth Movement: Physiologic Tooth Movement: a) Resorptive bone wall b) Depository bone wall Dr. Ahmed Basyouni 2
  3. 3. Orthodontic Tooth Movement (OTM): a) Dentoalveolar tissue reaction: i. Pressure side: ii. Tension side: b) Hyalinization April 28, 2012 Dr. Ahmed Basyouni 3
  4. 4. Factors Influencing Orthodontic Tooth Movement April 28, 2012 Dr. Ahmed Basyouni 4
  5. 5. Factors Influencing Orthodontic Tooth Movement Tissue changes associated with OTM are affected by: A) Characteristics of supporting bone: i. Cancellous ii. Compact iii. Recent extraction space B) Physiologic activity: Hormonal balance, age, health & general condition of the patient. C) Force application: Type, Amount, direction. April 28, 2012 Dr. Ahmed Basyouni 5
  6. 6. Factors Influencing Orthodontic Tooth Movement A) Character of bone: i. Cancellous OTM within cancellous bone offer a large surface area for cellular activity, allowing faster tooth movement. ii. Compact In cortical bone surface area for cellular reactions is vastly reduced, so tooth movement is more difficult and much slower, with high risk of creating over compression and hyalinization. Practically, tooth should be kept in center of the alveolar process, rather than being allowed to move against compact cortical bone. April 28, 2012 Dr. Ahmed Basyouni 6
  7. 7. Factors Influencing Orthodontic Tooth Movement A) Character of bone: iii. Recent extraction space contain tissue undergoing reconstruction which is rich in cells and vascular supply. Such area is ideally suitable for tooth movement, so treatment should start as soon as possible following an extraction. April 28, 2012 Dr. Ahmed Basyouni 7
  8. 8. Factors Influencing Orthodontic Tooth Movement B) Physiologic activity: Tissue reaction and turnover varies from one patient to another and is dependent on numbers of variables such as: 1. Hormonal balance 2. Patient age 3. Health & general condition of the patient April 28, 2012 Dr. Ahmed Basyouni 8
  9. 9. Factors Influencing Orthodontic Tooth Movement B) Physiologic activity: 4. Histologic picture of PDL of a growing young patient 5. Histologic picture of PDL of adult patient 6. Patient receives medication (e.g. steroids, or non-steroids) as tissue changes & cellular reactions will be influenced. April 28, 2012 Dr. Ahmed Basyouni 9
  10. 10. Factors Influencing Orthodontic Tooth Movement C) Force application: Force type, magnitude, direction and duration are affecting OTM. i. Types of applied force: Intermittent: It is associated with removable appliances. Dissipating: It is a continuous force but demonstrates a decreasing amount of force within a short period of time (e.g. elastic bands). Continuous: It is achieved by fixed orthodontic appliance with application of coil springs. April 28, 2012 Dr. Ahmed Basyouni 10
  11. 11. Factors Influencing Orthodontic Tooth Movement C) Force application: ii. Amount of applied force: Ideal force should not exceed capillary blood pressure and result in optimum rate of tooth movement of about 1mm/month. “Optimum force is high enough to stimulate cellular activity without completely occluding blood vessels in the PDL” (Proffit et al. 2000). April 28, 2012 Dr. Ahmed Basyouni 11
  12. 12. Factors Influencing Orthodontic Tooth Movement C) Force application: April 28, 2012 Dr. Ahmed Basyouni 12
  13. 13. Factors Influencing Orthodontic Tooth Movement C) Force application: iii. Direction of force: Force direction results in different types of tooth movements: 1. Tipping movement: This is the simplest and most readily carried out. Center of rotation is assumed to lie near center of the root, but actual location depends on dimensions of roots, condition of supporting tissues and point of force application. April 28, 2012 Dr. Ahmed Basyouni 13
  14. 14. Factors Influencing Orthodontic Tooth Movement C) Force application: iii. Direction of force: 2. Rotational movement: Rotation requires application of force couple. Center of rotation lies along long axis of the tooth. There is greater tendency for relapse so, overcorrection is a must. April 28, 2012 Dr. Ahmed Basyouni 14
  15. 15. Factors Influencing Orthodontic Tooth Movement C) Force application: iii. Direction of force: 3. Bodily movement: means complete transmission of a tooth to a new position, all parts of the tooth moving an equal distance. Center of rotation is at infinity. This type requires a greater force than simple tipping movement. Only, it can be carried out with fixed orthodontic appliances. April 28, 2012 Dr. Ahmed Basyouni 15
  16. 16. Factors Influencing Orthodontic Tooth Movement C) Force application: iii. Direction of force 4. Torque movement: It is commonly applied to root torque when movement of the root is desired with little movement of the crown. In this sense it is opposite of the tipping. It is usually achieved by applying couple to the crown of the tooth, same time mechanically restricting crown movement in opposite direction. April 28, 2012 Dr. Ahmed Basyouni 16
  17. 17. Factors Influencing Orthodontic Tooth Movement C) Force application: iii. Direction of force 5. Vertical movement: It is essentially bodily movement but considered separate because they are easier to produce, they involve: a) Extrusion: of the tooth from its socket which can be achieved without much resorption of bone. b) Intrusion: of the tooth involves resorption of bone, particularly around apex of the tooth. April 28, 2012 Dr. Ahmed Basyouni 17
  18. 18. April 28, 2012 Dr. Ahmed Basyouni 18
  19. 19. Factors Influencing Orthodontic Tooth Movement C) Force application: iii. Direction of force • Center of Resistance --- A point on the tooth around which the tooth shall move. For most teeth, COR is ½ way between the apex and the crest of the alveolar bone. April 28, 2012 Dr. Ahmed Basyouni 19
  20. 20. Limitation to Tooth Movements A) B) C) D) E) Size and form of basal bone of the jaw. Adverse forces on the tooth. Intensity of applied force. Age. Individual variations April 28, 2012 Dr. Ahmed Basyouni 20
  21. 21. Limitation to Tooth Movements A) Size and form of basal bone of the jaw: Tooth apex must remain on the basal bone. Therefore, severe discrepancies in skeletal form, size or relationship can not be completely overcomed by tooth movement alone. The cooperation between Orthodontist and Maxillofacial surgeon is helpful in treatment of skeletal defects. April 28, 2012 Dr. Ahmed Basyouni 21
  22. 22. Limitation to Tooth Movements B) Adverse forces on the tooth: Adverse forces on the tooth are usually brought about by oral musculature. It is possible to overcome the forces of oral muscles during orthodontic treatment, but it would be difficult to retain teeth in their final position thereafter. Therefore, if tooth position at end of treatment is to be stable, the muscular forces acting on the teeth must hold teeth in balance in their final position. April 28, 2012 Dr. Ahmed Basyouni 22
  23. 23. Limitation to Tooth Movements C) Intensity of applied force: Both light and heavy forces will result in orthodontic tooth movement. However, if light forces are used, minimizing hyalinization of the periodontal ligament, rate of tooth movement will be greater. April 28, 2012 Dr. Ahmed Basyouni 23
  24. 24. Limitation to Tooth Movements D) Age: In adults, periodontal ligament is much less cellular than in children. Also, alveolar bone in children is less dense than in older patient. In general, tooth movement in adults will be slower. April 28, 2012 Dr. Ahmed Basyouni 24
  25. 25. Limitation to Tooth Movements E) Individual variations: Depend on density of alveolar bone. In some individuals, alveolar bone is loose and cancellous with large marrow spaces. Whereas, in others it is dense lamellated bone with few marrow spaces. Tooth movement will be much slower in the latter. April 28, 2012 Dr. Ahmed Basyouni 25
  26. 26. Potential Complications of Orthodontic Tooth movement: • The pulp • Root resorption • Alveolar bone height April 28, 2012 Dr. Ahmed Basyouni 26
  27. 27. Potential Complications of Orthodontic Tooth movement: 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. April 28, 2012 Dr. Ahmed Basyouni 27
  28. 28. Potential Complications of Orthodontic Tooth movement: Root Resorption Concurrent with OTM Roots of permanent teeth are very resistant to resorption because it is protected by a barrier of unmineralized hard tissue (cementoid) which is resorbed only with great difficulty. April 28, 2012 Dr. Ahmed Basyouni 28
  29. 29. Potential Complications of Orthodontic Tooth movement: Explanation: Teeth are permanent depositories of mineral salts with continuous apposition, While, bony system is a mineral reservoir for whole organism, with physiologic resorption and apposition going on all time. April 28, 2012 Dr. Ahmed Basyouni 29
  30. 30. Potential Complications of Orthodontic Tooth movement: Root Resorption Concurrent with OTM Development of root resorption seems to be interrelationship between: 1. Temporary damage of the root surface barrier (cementoid). 2. General resistance against resorption and remodeling of the alveolar bone. April 28, 2012 Dr. Ahmed Basyouni 30
  31. 31. Potential Complications of Orthodontic Tooth movement: Root Resorption Concurrent with OTM Root resorption ceases if orthodontic forces is interrupted or stopped. Repair will take place cause new deposits of pre-cementum on the root surface, thus establishing a new barrier. Rest periods without force application should be included in treatment of patient with high tendency for root resorption April 28, 2012 Dr. Ahmed Basyouni 31
  32. 32. Orthodontic tooth movement remains one of the most successful procedures with predictable outcome in medicine and dentistry. April 28, 2012 Dr. Ahmed Basyouni 32
  33. 33. Summary • Factors Influencing Orthodontic Tooth Movement: A) Characteristics of supporting bone: B) Physiologic activity: C) Force application: i. Types of applied force: ii. Amount of applied force: iii. Direction of force: 1. Tipping movement: 2. Rotational movement: 3. Bodily movement: 4. Torque movement: 5. Vertical movement: April 28, 2012 Dr. Ahmed Basyouni 33
  34. 34. Summary Limitation to Tooth Movements A) Size and form of basal bone of the jaw. B) Adverse forces on the tooth. C) Intensity of applied force. D) Age. E) Individual variations April 28, 2012 Dr. Ahmed Basyouni 34
  35. 35. Summary Potential Complications of Orthodontic Tooth movement: • • • The pulp Root resorption Alveolar bone height April 28, 2012 Dr. Ahmed Basyouni 35
  36. 36. Buccal Canine Retractor April 28, 2012 Dr. Ahmed Basyouni 36
  37. 37. Buccal Canine Retractor • Used for buccally erupted canine. • To Retract the canine palatally and distally. April 28, 2012 Dr. Ahmed Basyouni 37
  38. 38. Coil high enough, not interfering with muscle attachment, just distal to Canine long axis April 28, 2012 Dr. Ahmed Basyouni 38
  39. 39. April 28, 2012 Dr. Ahmed Basyouni 39

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