Tissue reaction in orthodontics /certified fixed orthodontic courses by Indian dental academy


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Tissue reaction in orthodontics /certified fixed orthodontic courses by Indian dental academy

  1. 1. TISSUE REACTIONS IN ORTHODONTICS INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
  2. 2. INTRODUCTION • Orthodontic Appliances have been in use for a very long time. Since then the mode of action of appliances have been the same. Appliances have been fabricated and used in various designs to apply a therapeutic force which would move teeth through the bone to their intended positions. • Irrespective of the type of appliance - a spring, an arch wire or an elastic the mechanical-biological transduction and the following tissue changes of the periodontium are generally the same. This presentation deals with the tissue changes in the periodontium and the biology of tooth movement.
  4. 4. PERIODONTAL LIGAMENT 0.25mm wide cellular and vascular connective tissue rich in fibres connecting the root surface to the alveolar bone wall The fibres are : Principle fibres, Elastic fibres and indifferent fibre plexus Principle fibres are made of collagen and form the basis of the attatchment apparatus Principle fibres are divided into Apical, Oblique,Horizontal and Alveolar crestal fibres.
  5. 5. PERIODONTAL LIGAMENT Collagen fibres are synthesised from fibroblasts. Fibroblasts synthesise Tropocollagen fibril molecules which are later organised into fibres and fibre bundles. The collagen turnover rate is higher than any other tissue in the body- 3 to 23 days. The collagen turnover rate in the gingiva is also high but comparitively slower than the PDL.
  6. 6. PERIODONTAL LIGAMENT Elastic fibres are: Oxytalan and Eluanin. They are immature Elastin fibres. Oxytalan fibres run vertically parallel to the root surface and get embedded coronally into the cementum. Oxytalan fibres control the vascularity of the Periodontal ligament as they intermingle with the blood vessels.
  7. 7. PERIODONTAL LIGAMENT • CELLS: Fibroblasts Mesenchymal cells Epithelial cell rests Defence cells
  8. 8. PERIODONTAL LIGAMENT Fibroblasts are stellate shaped cells with interconnecting peripheral processes. They are responsible for the synthesis and destruction of the collagen fibres and the extracellular matrix. Thus they are responsible for the tissue turn over.
  9. 9. PERIODONTAL LIGAMENT Mesenchymal cells form the reserve for all connective tissue cells like fibroblasts, osteoblasts and osteoclasts. Their number decreases with age. Osteoblasts and Osteoclasts are seen lining the socket wall. Mesenchymal cells form the reserve for all connective tissue cells like fibroblasts, osteoblasts and osteoclasts. Their number decreases with age.
  10. 10. PERIODONTAL LIGAMENT The extracellular matrix is made of Glycosaminoglycans which hold the tissue fluid within itself and is responsible for the viscoelastic properties of the PDL.
  11. 11. GINGIVA Parts of the Gingiva: Free Gingiva, Attached Gingiva, Interdental Papilla.
  12. 12. GINGIVA Composition: 65% Connective tissue fibres. 5% Fibroblasts. 35% Nerves, Vessels and Matrix.
  13. 13. GINGIVA Collagen in the Gingiva has two types of arrangements: Bundles and Networks. The Bundles are: Dentogingival Dentoperiosteal Transseptal Circular
  14. 14. GINGIVA Collagen composition: 90% Type I Collagen 8% Type II Collagen 2% Type IV,V,VI & VII Collagen
  15. 15. GINGIVA Collagen fibre Bundles: Gingival collagen has a high turnover rate but not as high as the PDL. However the rate of turnover of the transseptal fibres is similar to that of the PDL.
  16. 16. GINGIVA • Connective tissue matrix: Proteoglycans: similar to Glycosaminoglycans found in the PDL. Glycoproteins: Fibronectin and Laminin: Extracellular multiadhesive proteins necessary for cell migration, differentiation and healing. SPARC(Secreted Protein Acidic and Rich in Cysteine) or Osteonectin: A Calcium binding protein which disrupts CellECM interactin and found at sites of cell migration, proliferation and morphogenesis.
  17. 17. ALVEOLAR BONE Parts of the alveolar bone: Alveolar bone proper Cancellous bone Outer cortical plate
  18. 18. ALVEOLAR BONE Cells of the Alveolar Bone: Osteoblasts Osteoclasts Osteocytes Osteoprogenitor cells
  19. 19. ALVEOLAR BONE Osteoblasts: Bone forming cells Derived from Osteoprogenitor cells Later mature to form Osteocytes
  20. 20. ALVEOLAR BONE Osteoclasts: Bone resorbing cells Haemopoetic in origin derived from monocyte precursors Multinucleated with ruffled border
  22. 22. TISSUE RESPONSE TO NORMAL FORCES • The periodontal ligament is a fluid filled chamber with porous walls of limited permeability. The PDL thus acts as a shock absorber within physiological limits due to it’s viscoelastic properties. • During masticatory function teeth meet force values between 2kg to 50kg of very short duration may be 1 second or less. During this time the tooth is not displaced within the PDL but the PDL acts as a shock absorber and transfers the forces to the alveolar bone producing bone bending. • But however if a similar amount of force is applied for a longer time the tooth moves within the PDL space with excursion of the extracellular fluid into the marrow spaces resulting in close approximation of the root surface with the alveolar bone proper resulting in pain. • The PDL is well adapted to physiological forces and maintain the integrity of the arches. But when a therapeutic force is applied for a long duration of time the physiological limit is crossed and tooth movement takles place.
  23. 23. REACTION OF THE PERIODONTAL LIGAMENT TO PHYSIOLOGICAL FORCES TIME IN SECONDS REACTION <1 PDL fluid incompressible Alveolar bone bends Peizoelectricity 1 to 2 PDL fluid expressed Tooth moves within the PDL space 3 to 5 PDL fluid squeezed out Tissues compressed Pain
  24. 24. TISSUE RESPONSE TO ORTHODONTIC FORCES • Tissue reaction to Orthodontic forces depends on the following factors Force magnitude Force duration Morphology of the supporting structures • As the tooth is being moved through a biological medium using a force the basic laws of physics donot hold good. Higher forces donot produce faster tooth movement nor do lighter forces cause slower tooth movement.
  25. 25. FORCE DISTRIBUTION • Orthodontic forces applied on a tooth are not evenly distributed through the Root surface. Force distribution for each type of tooth movement -Tipping,Translation,Rotation, Intrusion and Extrusion are different. • Force distributions are represented by a Loading diagram.
  26. 26. FORCE DISTRIBUTION DURING TIPPING Only one half of the PDL surface area is loaded. Concentration of pressure in limited areas- beneath the alveolar crest and near the apical third of the root. Tensile forces present opposite to areas of pressure. force value decreases from the loaded areas towards the region of the centre of rotation and reaches a value of zero at the centre of rotation Force value:35 to 60g.
  27. 27. FORCE DISTRIBUTION DURING BODILY MOVEMENT PDL area is uniformly loaded. Two times more force is required than tipping as the area loaded is two times more. A uniform area of pressure on one side and a uniform area of tension on the other side is seen. Force value: 70 to 120g
  28. 28. FORCE DISTRIBUTION DURING TORQUING Initially the pressure area is located close to the middle region of the root due to the variation in thickness of the PDL. Later a uniform area of pressure is seen along the surface of the root. Force value: 50 to 100g.
  29. 29. FORCE DISTRIBUTION DURING ROTATION Force can be distributed over the entire PDL area. Larger forces can be applied. Usually two pressure areas and two areas of tension are seen. Force value: 35 to 60g
  30. 30. FORCE DISTRIBUTION DURING EXTRUSION Ideally should produce no areas of compression. Force value: 35 to 60g.
  31. 31. FORCE DISTRIBUTION DURING INTRUSION Light force is required as it is concentrated in a very small area. Force value: 10 to 20g.
  32. 32. TISSUE REACTIONS IN THE PERIODONTAL LIGAMENT The tooth alone does not move but so does it’s attachment apparatus. Tooth movement is basically a periodontal ligament phenemenon and all tissue reactions are mediated through the periodontal ligament. The role of the periodontal ligament is explained by the PressureTension theory which is the classical theory of tooth movement. Other theories that explain tooth movement are the Peizoelectric theory and Streaming potential which are concerned with Bioelectricity.. The role of the periodontal ligament will be explained in relation to the Pressure tension theory.
  34. 34. RESPONSE TO A SUSTAINED THERAPEUTIC FORCE Light force: TIME RESPONSE Less than 1 sec Alveolar bone bending and peizoelectric signals are generated 1 to 2 sec PDL fluid expressed Tooth moves within the PDL space 3 to 5 sec Vascular changes Fibres and cells mechanically distorted Minutes Blood flow altered Oxygen tension altered PG and cytokines released
  35. 35. RESPONSE TO A SUSTAINED THERAPEUTIC FORCE Light force: TIME RESPONSE Hours Metabolic changes Chemical messengers alter cellular activity Cellular enzymes released 4 Hours Cellular differentiation detectable in the PDL 2 Days Tooth movement begins as bony socket is remodelled
  36. 36. RESPONSE TO A SUSTAINED THERAPEUTIC FORCE Heavy force: TIME RESPONSE < 1 sec Alveolar bone bending and peizo electricity 1 to 2 sec Tooth moves within the PDL space 3 to 5 sec Blood vessels totally occluded Minutes Blood flow totally cut off to the compressed area
  37. 37. RESPONSE TO A SUSTAINED THERAPEUTIC FORCE Heavy force: TIME RESPONSE Hours Cell death in compressed area 3 to 5 days Cell differentiation in adjacent marrow spaces 7 to 14 days Undermining resorption removes the lamina dura adjacent to compressed PDL and tooth movement occurs
  38. 38. TOOTH MOVEMENT AND TISSUE CHANGE Tooth movement can be divide into three phases : Initial tooth movement, Lag phase and Post lag phase Initial tooth movement is due to movement of the tooth within the PDL space Lag phase is the period during which the hyalinised area is cleared up Post lag phase is the period of frontal resorption
  39. 39. TRANSDUCTION OF MECHANICAL FORCE INTO BIOLOGICAL SIGNALS. • Many transduction mechanisms have been studied: cAMP dependent second messenger system Prostaglandin E dependent second messenger system Other Eicosanoids Phosphatidylinositol pathway Cytoskeletal-Matrix interaction Neuropeptides
  40. 40. cAMP DEPENDENT MECHANISM Mechanical forces cuse cell membrane pertubrations which cause an influx of Calcium ions The influx of Calcium ions causes production of cAMP cAMP stimulates differentiation of osteoblasts and osteoclasts from osteoprogenitor cells cAMP appears only 4 to 6 hours after application of sustained force
  41. 41. PROSTAGLANDIN E DEPENDENT SECOND MESSENGER SYSTEM Prostaglandins are derived from cell membrane phospholipids called Arachinodic acid They are produced by the cyclooxygenase pathway which produce inflammatory mediators. A pathway that is blocked by common NSAID’s The pathway is stimulated by a mechanical disturbance of the cell membranes Prostaglandin E which is then produced can stimulate Osteoclasts after 48 hours and later stimulate the osteoblasts . So first a wave of resorption is seen followed by a wave of bone deposition. Prostaglandins can also stimulate Inteleukin1 which later stimulates the cAMP mechanism QuickTime™ and a GIF decompressor are needed to see this picture.
  42. 42. OTHER EICOSANOIDS Recent studies have shown that tooth movement cannot be explained by the role of cAMP and PGE alone. QuickTime™ and a GIF decompressor are needed to see this picture. Other second messengers like leukotrienes which are also metaboluites of Arachidonic acid are now known to play a role. PGE and Leukotrienes belong to the same family of compounds called Eicosanoids.
  44. 44. Phosphatidylinositol Pathway
  45. 45. NEUROPEPTIDES Experiments have shown that cAMP levels can be increased not only by mechanical stimuli but also by endogenous chemical stimulus Neuropeptides like Substance P, Vasoactive intestinal polypeptide and Calcitonin gene relared polypeptide are released from sensory nreve endings in the PDL. Substance P bind to osteoblast cell receptors and also cause vasodilation
  46. 46. TISSUE RESPONSE OF THE GINGIVA Gross gingival changes are seen after closure of an extraction space or after rotation or excessive labial movement. After space closure accumulation of gingival tissue and enlargement of the interdental papilla is seen due to retraction and compression of the gingival tissues of the extraction space. At the mesial surface of the orthodontically retracted tooth a triangular red patch is seen. This is the Reduced enamel epithelium that has peeled off. After space closure vertical invaginations and clefts are formed by both the epithelium and connective tissue on the Buccal and lingual aspects.
  47. 47. ULTRASTRUCTURAL CHANGES Studies done by Transmission Electron microscopy have shown that there is an increase in the diameter of collagen fibres in areas of pressure and tension. Degraded collagen fibres are seen in areas of compressed papillae. There is an increase in the number and size of elastic fibre on the pressure side. Fewer elastic fibres are seen on the tension side. After tooth movement there is an increase in interstitial matrix content, collagen and elastic fibres. A pappillary epithelial hyperplasia is seen in the extraction space after space closure. The transseptal fibres in the extraction space are coiled and compressed and have a football shape. Stretched supracrestal fibres are not responsible for relapse but it is the increase in Elastic fibres and ground substance in the region of compressed areas that are responsible for
  51. 51. CHANGES IN THE ALVEOLAR BONE Apposition front
  53. 53. CHANGES IN THE ALVEOLAR BONE Bone resorption and deposition are always coupled. Uncoupling of resorption and deposition takes place during tooth movement. IL-1 is responsible for uncoupling Bone resorption is the limiting factor of tooth movement There are two waves of bone resorption. The first wave of resorption is from precursor cells present within the PDL. The second wave is from precursor cells from the blood vessels Always osteoclasts are stimulated first followed by osteoblast
  54. 54. CHANGES IN THE ALVEOLAR BONE After 93% of appliance activity is over a second wave of bone remodelling is seen. - BIPHASIC BONE REMODELLING. Bone has STRAIN MEMORY which is created by mechanical distortion of it’s extracellular matrix. So cells are stimulated even after the mechanical stimulus is removed. Short exposures to mechanical signals can stimulate substantial amounts of bone remodelling. Cyclic or pulsating forces can produce tooth movement similar to those produced by continuous forces.
  55. 55. SERUM MARKERS AND OTHER BIOMOLECULES Serum markers of Osteoblast activity: Osteocalcin Alkaline phosphatase Serum markers of Osteoclast activity: Acid Phosphatase
  56. 56. BIOMOLECULES STIMULATING BONE CELLS Stimulating Osteoclasts: Interleukin-1 Tumor Necrosis Factor - alpha Metabolites of VitaminD Stimulating Osteoblasts: Tumor Growth Factor - beta Insulin like Growth factor - I Platelet Derived Growth Factor
  57. 57. WAVES OF BONE ACTIVITY PERIODS OF DELAY INITIAL 7 DAYS CELL ACTIVITY Increased in number of osteoclasts Increased serum acid phosphatase Increased serum alkaline phosphatase and osteocalcin DAYS 10 to 14 No resorption Increased Osteoblast bone formation DAYS 14 TO 18 Tooth movement Resorption Inhibition of formation 18th DAY
  58. 58. PEIZOELECTRICITY AND STREAMING POTENTIAL Peizoelectricity is a phenomenon common to all crystalline structures. When any crystalline structure undergoes stress induced deformation a current is produced within the crystalline structure due to displacement of the electrons within it. The alveolar bone can also be considered as a huge crystal of hydroxyapatite molecules and peizoelectric currents induced in them by forces - physiological or therapeutic. As the alveolar bone bends concave areas become electropositive and resorption takes place whereas convex areas become electronegative and bone deposition takes place.
  59. 59. CLINICAL IMPLICATIONS Force duration Differential anchorage Differential force philosophy Adult Orthodontics Relapse
  60. 60. FORCE DURATION Intermittent force Interrupted force Continuous light force
  61. 61. INTERMITENT FORCE Force levels decrease abruptly to zero when the appliance is removed by the patient.- RA, Headgear, Elastics
  62. 62. INTERRUPTED FORCE Force levels decline to zero between activations
  63. 63. CONTINUOUS LIGHT FORCE Force maintained at some appreciable fraction of the original from one appointment to the next
  64. 64. FORCE DURATION A force duration of atleast 4 hours is required to produce second messengers In humans clinical experience has shown that atleast 6 hours of sustained force is necessary Continuous forces produce the most efficient tooth movement Interrupted forces give enough time for tissues to regenerate and reorganize In case heavy forces are used, which most often happens undermining resorption would take atleast 7 to 14 days so appliances are not to be reactivated within 3 weeks
  65. 65. DIFFERENTIAL ANCHORAGE Anchorage potential of a tooth may vary according to the density of the alveolar bone and the cross section of the root The volume of osseous tissue that should be removed is a tooths anchorage value Maxillary molars have lesser anchorage value than mandibular molars Thin cortices and trabeculae of maxillary alveolar bone Bone formed during mesial movement of the molar is more dense in the mandible
  66. 66. DIFFERENTIAL FORCE PHILOSOPHY Storey and Smith first studied the effects of force variation in orthodontics The concept was later adopted by Begg into his Light arch wire technique
  67. 67. ADULT ORTHODONTICS Due to Bone loss the PDL area decreases so the same force will cause higher Pressure So the absolute force magnitude used should be less The centre of resistance is more apically located so the moment of any force would increase. Thus the countermoment magnitude should be increased. Overall the M:F ratio is increased Decreased blood flow and decreased vascularity of the PDL provide an explanation for the insufficient source of progonitor cells Cortical bone becomes more dense and the cancellous bone changes from a trabecular pattern to a network Initial forces should be low as the immediate pool of cells available is less. Light continuous intrusive force to be maintained if marginal bone loss is seen
  68. 68. RELAPSE Stretched gingival fibres play a major role Increased Oxytalan fibres and ECM in compressed areas are also a reason Gingival fibres take 232 days to totally remodel Rotation corrections and closure of spaces have a high relapse rate
  69. 69. CONCLUSION Tissue reactions in Orthodontics form the basis of our clinical procedures - How much force? and What type of Force? A sound knowledge of the tissue reactions is necessary to know how we really move teeth through bone. Though most of the research done is based on animal studies the use of these results in a clinical setting seem promising. The use of NSAID’s like indomethacin to inhibit tooth movement and locally administered Prostaglandins to accelerate tooth movement in humans can be tried. With improved histological techniques and better research methods used, our knowledge of the tissue reactions will improve.
  70. 70. Thank you For more details please visit www.indiandentalacademy.com