BIOLOGY OF TOOTH MOVEMENTS
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Biology of tooth movements and Tissue reaction to various forces in periodontium , sutures ,TMJ , retention & relapse . Deleterious effects of orthodontic forces , Drugs affecting & accelerated tooth movements.
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BIOLOGY OF TOOTH MOVEMENTS
- 1. BIOLOGY OF TOOTH MOVEMENTS Presented by Ashok kumar A 1st year PG
- 2. CONTENTS ⢠Introduction ⢠Historical Perspective ⢠Tooth & Supporting Tooth Structure ⢠Tissue Response To Normal Forces ⢠Physiologic Response To Sustained Pressure Against A Tooth ⢠Orthodontic Versus Orthopedic Force ⢠Theories Of Tooth Movement ⢠Phases Of Tooth Movement ⢠Pathways Of Tooth Movement ⢠Local Biological Mediators Of Orthodontic Tooth Movement ⢠Tissue Reactions With Varied Force Application ⢠Deleterious Effects Of Orthodontic Force ⢠Tissue Response In Sutures , TMJ , Retention And Relapse ⢠Conclusion ⢠References
- 3. Introduction Basics of Tooth movements 1.Physiologic tooth migration 2.Pathologic tooth migration 3.Orthodontic tooth movement Orthodontics, current principles and techniques by Graber & Vanarsdall -5th edition
- 4. Carl Sandstedt, 1860â1904 The father of biology of orthodontic tooth movement. Chappin Harris-1839 The Dental Art Kaare Reitan Albert KetchamOppenheim-1911 1--Below threshold stimulus; 2--Most favorable-about 20 g/cm2 of root surface, 3--Medium strength, which stops the PDL blood flow 4--Very high forces, capable of crushing the tissues ,irreversible. Schwarz (1932) HISTORY *Biologic mechanism of tooth movement by Krishnan 2nd edition
- 5. Components 1.Fibers 2.Cellular components 3.Tissue fluids Tooth & supporting tooth structure
- 6. ⢠Teeth & periodontal structures are subjected to forces (Intermittent heavy force ) up to 1-2 kg (soft foods) to as much as 50 kg (more resistant object) during mastication . ⢠Force is transmitted to the alveloar bone which bends in response with generation of piezoeelectric currents . ⢠It acts as a important stimulus to skeletal regeneration & repair resulting in adaptation of bony architecture to fuctional demands TISSUE RESPONSE TO NORMAL FORCES Contemporary Orthodontics â WILLIAM R. PROFIT 5 th EDITION
- 7. Resting pressure from lips, check and tongue against the teeth FORCE (PRESSURE) PDL- Adaptive Prolonged force Remodeling of adjacent bone Short duration Contemporary Orthodontics â WILLIAM R. PROFIT 5 th EDITION
- 8. Physiologic Response to Sustained Pressure Against a Tooth LIGHT FORCE HEAVY FORCE
- 9. Orthodontic Versus Orthopedic Force Orthodontic force âforce applied to teeth for the purpose of effecting tooth movement, generally having a magnitude lower than an orthopedic force,â Orthopedic force âforce of higher magnitude in relation to an orthodontic force, when delivered via teeth for 12 to 16 hours a day, is supposed to produce a skeletal effect on the maxillofacial complex. Glossary of orthodontic terms. Berlin: Quintessence; 2000. Remodeling & adaptive changes in paradental tissues - amounts of force - 20 to 150 g / tooth. Higher magnitudes of mechanical forces-more than 300 g in attempts to modify the form of craniofacial bones
- 10. STAGES OF TOOTH MOVEMENT According to Burstone (1962), Orthodontics, current principles and techniques by Graber & Vanarsdall -5th edition
- 11. Frontal resorption Light continuous forces Compression of blood vessels & PDL Prostaglandins are released Synthesis of cAMP activation of Ca Metabolic activity Activation of osteoclast Frontal resoption
- 12. Contemporary Orthodontics â WILLIAM R. PROFIT 5 th EDITION Hyalinization Sterile necrosis of PDL
- 13. Undermining resorptionElimination of hyalinized tissue ⢠Invasion of cells and blood vessels from the periphery of the compressed zone by which necrotic tissue is removed. ⢠The invading cells penetrate the hyalinized tissue and eliminate unwanted fibrous tissue by enzymatic action and phagocytosis.
- 14. Stages of bone formation: 1. Osteoid 2. Bundle bone 3. Lamellated bone Bone resorption processes occur 1.Decalcification 2. Degradation of matrix 3. Transport of soluble products to the extracellular fluid Bone deposition Bone resorption Orthodontics, current principles and techniques by Graber & Vanarsdall -5th edition
- 15. Theories Of Tooth Movement 1) Mechanochemical Hypothesis â Justus & Luft 1970 Physical stress to bone Changes the solubility of hydroxyapatite crystals Remodeling of bone 2) BIOELECTRIC THEORY Application of orthodontic forces Alveolar bone flexes & bends Generate electric potential Alter metabolism of bone Piezoelectricity Streaming potential Bioelectric potential
- 16. Piezoelectricity ⢠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. I) Quick decay rate II) Reverse piezoelectricity 1. Collagen 2. Hydroxyapatite 3. Collagen hydroxyapatite interface 4. The mucopolysaccharide of the ground substance. Fukada & Yasuda 1957 Contemporary Orthodontics â WILLIAM R. PROFIT 5 th EDITION
- 17. Davidovitch â In hydrated tissues ,streaming potential predominate as the interstitial fluid moves. Bioelectric potentialStreaming potential The tissue, cellular, and molecular regulation of orthodontic tooth movement: 100 years after Carl Sandstedt . Murray C. Meikle EJO 2006
- 18. Blood flow theory/fluid dynamic theory Bien (1966) Force of greater magnitude and duration Interstitial fluid in the PDL space to get squeezed out and move towards the apex and cervical margins Slowing down of the tooth movement âSqueeze filmâ effect.
- 19. Pressure-tension theory Sandstedt (1904), Oppenheim (1911), and Schwarz (1932) The hypothesis explains that Pressure side- the PDL disorganization and diminution of fiber production, cell replication decreases due to vascular constriction. Tension side- stimulation produced by stretching of PDL fiber bundles results in an increase in cell replication . Compressed PDL Stretched PDL
- 20. Local Biological Mediators of Orthodontic Tooth Movement
- 23. PATHWAYS OF TOOTH MOVEMENT Mostafa et al (1983) described integrated model showing 2 pathways of tooth movement ď Pathway I- More physiologic response - Associated with normal bone growth and remodeling ď Pathway II- Alternative pathway -Classic inflammatory response after force application ď Recent model based -Stress in any form- compressive, tensile, shear, will evoke many reactions in the cell, leading to development of Strain *Vinod Krishnan and Davidovitch. Cellular, molecular & tissue level reactions to othodontic force. AJODO 2006
- 25. Contemporary Orthodontics â WILLIAM R. PROFIT 5 th EDITION â˘Continuous-force maintained at some appreciable fraction of the original from one patient visit to the next ⢠Interrupted-force levels decline to zero between activations â˘Intermittent-force levels decline abruptly to zero intermittently, when the orthodontic appliance is removed by the patient Tissue Reactions With Varied Force Application
- 28. Optimum Force value: 35 to 60g FORCE DISTRIBUTION TIPPING BODILY MOVEMENT Optimum Force value: 70 to 120g Contemporary Orthodontics â WILLIAM R. PROFIT 5 th EDITION
- 29. TORQUING ROTATION Force value: 50 to 100g Force value: 35 to 60g Orthodontics, current principles and techniques by Graber & Vanarsdall -5th edition
- 30. Orthodontics, current principles and techniques by Graber & Vanarsdall -5th edition INTRUSIONEXTRUSION Force value: 35 to 60g. Force value: 10 to 20g.
- 31. PROMOTER DRUGS SUPPRESSOR DRUGS ď Prostaglandins ď corticosteroids ď Para thyroid hormone ď NSAIDS ď Vitamin D ď Calcitonin ď L-arginine ď Estrogens ď Bisphosphonates ď Anti cancer drugs ď Fluorides
- 32. Different method of accelerated tooth movement
- 33. Deleterious effects of orthodontic forces ⢠Mobility ⢠Pain ⢠Effects on Pulp ⢠Effects on root Generalized resorption â moderate , severe Localised resorption ⢠Effect on treatment height of alveolar bone
- 34. Mobility ⢠Radiographically, it can be observed that the PDL space widens. ⢠Heavier force - greater the amount of undermining resorption expected - greater the mobility. ⢠If a tooth becomes extremely mobile during orthodontic treatment, all forces should be discontinued until the mobility decreases to moderate levels Effects on the pulp ⢠Modest and transient inflammatory response within the pulp, with no long- term significance ⢠Abrupt movement of the root apex could severe the blood vessels as they enter. ⢠According to some studies, endodontically treated teeth are slightly more prone to root resorption during orthodontics. Contemporary Orthodontics â WILLIAM R. PROFIT 5 th EDITION
- 35. Effect on alveolar bone height ⢠Excessive loss of crestal bone height is almost never seen as a complication of orthodontic tooth movement ⢠Almost never exceeds 1 mm, greatest changes at extraction sites Pain related to orthodontic treatment Force application No pain felt immediately After few hours,pain & tenderness starts Last for 2-4 days Then disappear until next reactivation
- 36. Effects on root Moderate generalized resorption Severe generalized resorption â Rare â Hypothyroidism Treatment containdicated Contemporary Orthodontics â WILLIAM R. PROFIT 5 th EDITION
- 37. Localized resorption Maxillary incisors âThickness of labial cortical plate less & Pressing of root against the cortical plate Risk factors â˘Conical roots with pointed apices â˘Distorted root form â˘History of trauma â˘Root apices in contact with cortical bone â˘Excessive force during orthodontic treatment 0 = No apical root resorption 1=Slight blunting of root apex 2=Moderate blunting upto 1-4th 3=Excessive blunting beyond 1-4th Contemporary Orthodontics â WILLIAM R. PROFIT 5 th EDITION
- 38. Tissue response in sutures ⢠Rapid Max expansion & the traction generated by orthopedic forces stimulate the sutural growth & widens the midpalatal suture and changes in orientation of fiber bundles. ⢠Increase in the osteoid and new bone formation occurs. ⢠Tranduction of mechanical force into bone formation occurs by influx of Ca & Na ions & decreases cAMP & promotes the cellular proliferation and DNA synthesis. Orthodontics, current principles and techniques by Graber & Vanarsdall -5th edition
- 39. Tissue response in TMJ ⢠McNamara has shown that TMJ is capable of functional adaptation when the mandible is displaced in a Forward direction. ⢠Hypertrophy and hyperplasia of the prechondroblastic and chondroblastic layers of condylar cartilage are seen in the posterior border of the condyle. ⢠A mandibular retrusion by chin cup therapy in the rat revealed a reduced thickness of prechondroblastic zone & decrease in no.of dividing cells cause reduced length of the mandible . Orthodontics, current principles and techniques by Graber & Vanarsdall -5th edition
- 40. Tissue reactions seen in retention and relapse ⢠Remodelling of the gingival connective tissue is not as rapid as the PDL, slower turn over rate of gingival fibers are seen stretched and unremodeled as 232 days after the experimental tooth rotation. ⢠To avoid relapse, a tooth should be retained until total rearrangement of the structures involved has Occurred.
- 41. CONCLUSION Tooth movement is a highly conserved physiological mechanism for continuous adaptation of the dentition. Orthodontic tooth movement is a biomechanical exploitation of the physiologic mechanisms for developing and maintaining optimal occlusal function. The tooth continues to move until it achieves equilibrium with natural and applied loads.
- 42. REFERENCES ⢠Contemporary orthodontics by William Proffit- 5th edition ⢠Orthodontics, current principles and techniques by Graber & Vanarsdall - 6th edition ⢠Biologic mechanism of tooth movement by Krishnan 2nd edition ⢠Caranzaâs clinical periodontology by Michael Neuman and Caranza â 10th edition ⢠Vinod Krishnan and Davidovitch. Cellular, molecular & tissue level reactions to othodontic force. AJODO 2006:129;469e.1-469e32
Editor's Notes
- Tooth & their supporting tissues have a lifelong ability to adapt to functional demands & hence drift through the alveolar process. it is a slow process that occurs usually in mesial & occlusal direction. Pa Tm ârefers to tooth displacement tat result when balance among factors tat maintain PTP is disturbed by PDL disease. 3) OTM wch is COMPLX process,whr 1 Cs (tooth) moves through another Cs (bone) by applicatio of OFr ,by creation of compression & tension in PDL whr B R in 1 surface & B D in another surface ,remodeling phase is intiated by conversion of ME into Biological sig .
- which stated that OTM in the socket depends on R and D of bone, but it took >60 years to have the 1st HPic of this phenomenon, which was provided by Sandstedtâs exp studies of tooth movements in dogs , showing the site of PDL compression, including an osteoclastic & necrotic (hyalinized) areas. Â OPPENEIM - only light forces should be applied to teeth for optimal exploitation of the cellular remodeling of the bone.SCHWARZ COINEDÂ term optimal force in orthodontics and concluded from his histologic studies of tooth movement in dogs that orthodontic forces should not > capillary blood pressure.
- Dep on Mag, Dirc, Dura -â Periodontium -Gingiva , PDL , Root cementum Alveolar bone PDL serves as dual function of providing attachment of tooth to alveolar bone . 1.TS , AC, H ,O,AP, IR â Run at angle farther apically on tooth rather on adjacent alvelor bone ,which resist displacement during normal function. 2..UD mesenchymal cells - fibroblasts, cementoblast, osteoblasts , osteoclasts, Defence cells, epithelial cells 3.The extracellular matrix is made of Glycosaminoglycans which hold the tissue fluid & it is responsible for the viscoelastic properties of the PDL
- Are usually not balancedâŚ.. Active stabilization produced by metabolic effects in the PDL probably explains why teeth are stable in the presence of imbalanced pressures that would otherwise cause tooth movement.
- Orthodontic mechanotherapy is mainly aimed at tooth movement by⌠Craniofacial orthopedics is aimed at delivering
- Initial â starts from time of application of force till eliminatio of bone below hyalnized tissues ,& nxt the tooth movement which occurs after hyalinisation is called 2* period. IP âMagnitude of force has no effect on this stage. Light does not produce lag phase .
- FR takes place after 2 days
- Form of tissue degeneration characterized by formation of a clear, eosinophilic homogenous substances- Denotes a compressed and locally degenerated PDL. - Reversible process -It lasts for a period of 7 -14 days . Tooth will move again only after bone beneath hyalinised area undergoes resorption.. Reason for late tooth movement â differentiation & activation of osteoclast take more time ,& thickness of bone to b removed is more from underside
- Hyalinized zone will b invaded by the cells of osteoclast adjacent to bone marrow spaces ,cells from PDL , initiate resorption from underside of bone adjacent to hyalinized PDL zone .
- Osteoblast are derived from paravascular connective tissue cells ,closely related to blood vessels. Organic acids such as citric acid ,lactic acid ,H ions are secreted by ruffeled border of osteoclast ,which increse the solubility of hydoxyappetite crystal leadind to decalcification & nxt degradation of matrix is brought by cathepsin B-1 ,Finally breakdon products are transpoted to EC fluid & blood vascular system.
- Obseved in crystalline material , both C & H ap QDR- Force â piezoeectricity is generated wch Imed goes to 0 ,even force is continously applied . RP â crystal r deformed ,Electron flow frm one location to another & produce Elec current .when force removed ,crstal after returing to original position ,produce Electron flow in Opp direction ..in ortho role of PIEZO is doubtful
- Electric fields r generated when bone bent & later ions in the fluid surrounding living bone interact with it & produce currents of small voltage are called SP. Doubtful in ortho. 2) Force â bending of bone â becomes electricaly charged .concave â Negative polarity(deposition) ,convex + polarity(resorption)
- Tooth movement occurs as a result of alterations in fluid dynamics in the periodontal ligament. Bien characterized three distinct but interacting fluid systems in the PDL: 1. Vascular system 2. Cellular system 3. Interstitial fluid system. When a force of short duration is applied to a tooth, the fluid in the PDL space escapes through tiny vascular channels. When the force is removed, the fluid is replenished by diffusion from capillary walls.
- Whenever a tooth is subjected to an orthodontic force, it results in areas of pressure and tension.
- 1)Decreased vascularity & overstrecthing of PDL & tissue truma occurs which induces chemical changes & inflammatory tyoe of response , 2)ATP to c-AMP & opening of Ca ion channel & activate Ca. 3)Differentiaton of OsteoB & C which produce remodelling of bone & tooth begins to move
- This is flow chart of sequence of OTM ,illustrating roles played by mineralised ,non mineralised tissues along with associated blood vessels & neural elements
- 1)Application of a single force to the crown of a tooth creates rotation around a point approx halfway down the root. Heavy pressure is felt at the root apex and at the crest of the alveolar bone, but pressure decreases to zero at the center of resistance. The loading diagram,i.e, consists of 2-triangles as shown. 2)Bodily movement of a tooth requires that the PDL space be loaded uniformly from alveolar crest to apex, creating a rectangular loading diagram. Twice as much force applied to the crown of the tooth would be required to produce the same pressure within the PDL for bodily movement as compared with tipping.
- A torquing movement of a tooth involves tipping of the apex .During the initial movement of torque, the pressure area usually is located close to the middle region of the root. After resorption of bone areas corresponding to the middle 3rd , the apical surface of the root gradually begins to compress adjacent periodontal fibers, and a wider pressure area is established .. if more torque is incorporated in the archwire, the force will increase and may result in resorption and fenestration of the buccal bone plate 2) Formation of two pressure sides and two tension sides. B, Demarcation line between old and new bone layers; C, pressure side with root resorption. B, Arrangement of free gingival fibers after rotation.
- 1) Extrusive tension results in added bone at alveolar crest. B, New bone layers at the alveolar fundus. 2)No areas of compression ,, Relaxation of the free gingival fibers during intrusion (arrow). A, Bone spicules laid down according to the direction of the fiber tension; B, relaxed supraalveolar tissue.
- Drugs tat affect PG Activity is NSAIDS & Corticosteroids (phospholipase activity ) , aspirin indomethacin inhibit cyclo-oxygenase pathway Bisphosphonate inhibit osteoclast mediated bone resorption ,so remodelling slower during medication. Acetaminophen recommended as it act on cental PG not on pheripheral PG Fluoride increases bone mass and mineral density, and because of the actions, it has been used in the treatment of metabolic bone disease, osteoporosis
- Most of the teeth exhibit some loss of root resorption after orthodontic treatment , max incisor is high compared to other During tooth movement, clast cells attack cementum as well as bone, creating defects in surface of the roots. During the repair phase,these defects fill back in with cementum. Shortening of the root occurs when cavities coalesce at the apex, This is why, apex of the root experience resorption, roots become shorter but not thinner as a result of orthodontic tooth movement
- A, category 1, slight blunting; B, category 2, moderate resorption, up to 1/4 of root length; C, category 3, severe resorption,greater than 1/4 of root length.
- Modification of neuromuscular pattern was observed with the skeletal adaptation to the forward displacement of Mandible.
- -Most relapse tendency is caused by the structures related to marginal third of the root whereas Little relapse tendency exists in the area adjacent to the middle and apical thirds. Hyalinised zones are seen after tipping the teeth without retention.