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BIOLOGY OF TOOTH MOVEMENT.ppt
- 1. Dr. Rohit Madan 1 BIOLOGY OF TOOTH MOVEMENT
- 2. 2 CONTENTS INTRODUCTION CLASSIFICATION OF TOOTH MOVEMENT THEORIES OF TOOTH MOVEMENT HISTORY OF STUDIES PERTAINING TO TOOTH MOVEMENT BILOLOGICAL CONSIDERATIONS HISTOLOGICAL STRUCTURE OF CEMENTUM PERIODONTAL LIGAMENT ALVEOLAR BONE BIOLOGICAL EVENTS DURING TOOTH MOVEMENT
- 3. 3 CLINICAL CONSIDERATIONS FACTORS AFFECTING TOOTH MOVEMENT ANCHORAGE RELAPSE FUTURE OF ORTHODONTIC TOOTH MOVEMENT CONCLUSION
- 4. 4 Introduction The specialty of Orthodontics is based on the fact that it is possible, by applying appropriate forces, to move the teeth through the alveolar bones of the jaws Over the years, several studies have been conducted to analyze the biological mechanisms of tooth movement, however, even now the detailed mechanisms are far from being completely understood
- 5. 5 Introduction Tooth movement involves a cascade of tissue reactions and is a result of several complicated and highly organized interactions at molecular level Extensive research is progressing towards analyzing and enhancing tooth movement at the ultra-structural level
- 6. 6 Classification of tooth movement Physiologic tooth movement • Eruption • Drifting Pathologic tooth movement • Periodontal Pathology • Oral pathologies ( Cysts, Tumors etc ) Orthodontic tooth movement • Tooth Movement under external clinical forces
- 7. 7 Studies pertaining to tooth movement Experimental studies Laser holography studies Finite element analysis studies
- 8. 8 History of tooth movement studies Sandtedt ( 1904 to 1905 ) was probably the first to investiate the phenomenon of tooth movement by histological examination of supporting structures. He found that the under gentle pressure, bone resorption took place on the pressure side and bone deposition on the tension side Oppenheim’s( 1911 ) experiments further supported the conclusions made by Sanstedt
- 9. 9 In 1932, Schwarz concluded from his experiments that the most favorable tooth movement was produced by forces not greater that capillary blood pressure, such forces being insufficient to collapse the capillaries in the PDL Reiten (1951) carried out a series of experiments on dogs and human subjects to determine the tissue reaction during tooth movement and discovered changes in the cellular level including the phenomenon of hyalinization.
- 10. 10 With passing years, studies were performed in depth regarding changes at the molecular level By 1983, various chemical mediators were identified to be the cause of cellular differentiation during tooth movement and different theories of tooth movement were postulated Extensive research still continues to identify the mediators and signaling molecules responsible for tooth movement
- 12. 12 The Periodontium Includes the tissues supporting and investing teeth. Cementum The periodontal ligament The bone lining the alveolus and That part of the gingiva facing the tooth
- 13. 13 Cementum Layer of calcified tissue covering the dentin of the root Specialized connective tissue similar in physical and chemical properties to the bone but is avascular and has no innervations First demonstrated in 1835 by two pupils of Purkinje
- 15. 15 Cementum is less readily resorbed compared to alveolar bone, a feature that is important for permitting orthodontic tooth movement The reason for this feature is unknown but it may be related to: Differences in physicochemical or biological properties between bone and cementum The presence of an unmineralized layer the “cementoid” on the surface of the cementum The increased density of Sharpey’s fibres (particularly in acellular cementum) The proximity of epithelial cell rests to the root surface
- 16. 16 Physical characteristics Light yellow color with a hardness less than that of dentin Composition 45%-50% inorganic substances Calcium and phosphate ( in the form of hydroxyapatite ) Numerous trace elements Highest fluoride content in the body 50%-55% organic substances Type I collagen Proteoglycans ( protein polysaccharides )
- 17. 17 Structure Types ( under light microscope ) Acellular cementum Do not incorporate the spiderlike cementocytes Covers the root dentin from the CEJ to the apex but is often missing at the apical third. Cellular cementum Incorporates cementocytes in spaces called lacunae A typical cementocyte has numerous cell processes or canaliculi, radiating from its cell body These branch or anastamose with other processes mostly directed towards the periodontal surface of the cementum
- 18. A – ACELLULAR CEMENTUM B – CELLULAR CEMENTUM
- 19. 19 Collagen fibres • Arranged in both cellular and acellular cementum in a very complex fashion •In some areas relatively discrete bundles of collagen fibrils are seen, particularly in tangential sections •These are Sharpeys fibres
- 20. 20 Function of cementum Primary function – furnish a medium for attachment of collagen fibers that bind the tooth to the alveolar bone. There is a continuous deposition of cementum (unlike bone, it does not resorb under normal conditions) New cementum is laid down as the most superficial layer ages ( hence keeps the attachment apparatus intact)
- 21. 21 Also serves as a major reparative tissue for root surfaces Root damages ( minor fractures , resorptions can be repaired by deposition of new cementum )
- 22. 22 Periodontal Ligament Soft, specialized, unique connective tissue Situated b/w the cementum covering the root of the tooth & the bone forming the socket wall Width ranges from 0.15 to 0.38 mm which varies with the location of the tooth and the age of the patient Principle function is to support teeth in their sockets and at the same time permit them to withstand the considerable masticatory forces
- 24. 24 Cells Extracellular matrix Structure
- 25. 25 Importance has always being given to the anatomy of the fiber bundles of the PDL at the expense of both the cellular and non fibrous components. The fiber bundles are, of course important, but the cells have an equal or greater role to play in the ligament function Surrounding cells must be viable so there can be tooth movement Cells
- 26. 26 Types : Synthetic cells Fibroblasts Osteoblasts Cementoblasts Resorptive cells Fibroblasts Osteoclasts Cementoclasts Epithelial cells Epithelial cells of malassez Other cells Mast cells macrophages
- 27. 27 Fibroblasts Principle cells of the PDL Characterized by an ability to achieve an exceptionally high rate of turnover of the extracellular compartment, in particular collagen Large cells with an extensive cytoplasm containing in abundance all the organelles associated with synthesis and secretion ( eg. Rough ER, several golgi complexes, many secretory vesicles )
- 28. 28 They also have a well developed cytoskeleton with a particularly prominent actin network ( indicates functional demands placed on them, requiring change in shape and migration Lined along the general direction of the fiber bundles and with extensive process that wrap around the fiber bundles In PDL, the remodeling of collagen is achieved by a single cell - the fibroblast, which is capable of simultaneously synthesizing and degrading collagen.
- 29. 29 One probable main reason of alveolar bone remodeling and tooth movement takes place because of the unique property of the PDL A healthy PDL always tries to maintain a width and orientation of fibers that would best enable the tooth to maintain an equilibrium state The fibroblast cells of the PDL tightly cling along the principle fibers These fibroblasts are very sensitive to the mild variations in vascular flow or fiber orientation
- 30. 30
- 31. 31 Bone and cementum cells Although technically situated within the periodontal ligament, bone and cementum cells are associated with the hard tissues they form Osteoblasts/osteoclasts Line the bone surface of the ligament May be either functional or resting, depending on the functional state of the ligament This variation in the distribution of bone cells along the socket wall reflects the constant rate of flux of the alveolus
- 33. 33 Remnants of the hertwig’s epithelial root sheath Occur as lacy strands close to the cementum surface Easily recognized by the H & E stained sections because their nuclei stain deeply Known as the epithelial rest cells of malassez ( discovered by Mallassez in 1884 ) Have no known function Epithelial cells
- 34. 34 An important cellular constituent of the PDL They have a perivascular location within 5 microns of the blood vessels They are believed to give rise to daughter cells that differentiate into fibroblasts, cementoblasts and osteoblasts Undifferentiated mesenchymal cells/progenitor cells
- 35. 35 Fibers Collagen of the PDL - mixture of Type I and Type III Individual fibrils have an average diameter of 55 nm Vast majority of fibrils are arranged in definite and distinct fiber bundles Each bundle resembles a spliced rope Individual strands can be continually remodeled while the overall fiber maintains its architecture and function This way fiber bundles are able to adapt to the continual stresses placed on them
- 36. 36 Groups of periodontal fibers Alveolar crest group From cementum just below CEJ – run downward and outward – insert into rim of alveolus Horizontal group Apical to the alveolar crest group – run at right angles to the long axis of the tooth till the bone just below the alveolar crest Oblique group Most numerous group of fibers – run from cementum in an oblique direction to insert into bone coronally
- 37. 37 Apical group Radiate from the cementum around apex of root to bone – forming the base of the socket Interradicular group Found only between roots of multirooted teeth – run from cementum into bone, forming the crest of the interradicular septum
- 38. 38 Transseptal group of fibers Run interdentally from cementum just apical to the base of the junctional epithelium of one tooth over the alveolar crest and insert into a comparable region of the cementum of the adjacent tooth Collectively, they form an interdental ligament connecting all the teeth of the arch The supracrestal fibers – in particular the transeptal fiber system are implicated as a major cause of post retention relapse of orthodontically positioned teeth
- 39. 39 The probable cause of this is the inability of these fibers to undergo physiologic rearrangement at a rate as fast as the other PDL group of fibers Hence usually a sufficiently prolonged retention period following orthodontic tooth movement would allow reorganization of these fibers
- 40. 40 Bone
- 41. 41 Hard connective tissue, the major component of almost all skeletal systems in adult vertebrate animals. Appears to be nonliving—in fact, the word skeleton is derived from a Greek word meaning “dried up” However, bone actually is a dynamic structure composed of both living tissues, such as bone cells, fat cells, and blood vessels, and nonliving materials, including water and minerals Accounts for 14 percent of the body’s total weight.
- 42. 42 Composed of an intricately layered structure that gives them the strength of steel, but a weight much closer to that of aluminum A central, honeycomb network called spongy bone provides strength without adding excessive weight. A layer of denser bone called compact bone surrounds the spongy bone Compact bone is composed of many units called osteons. Osteons consist of a central canal surrounded by closely packed concentric layers called lamellae
- 43. Each osteonic canal houses blood vessels and nerves. A final layer, a thin membrane called the periosteum, protects the bone and houses the nerves and blood vessels responsible for detecting pain and supplying the bone with nutrients
- 44. 44 Alveolar Bone That bone of the jaws which contains the sockets for the teeth Consists of an outer cortical plate A central spongiosa bone lining the alveolus referred to as the bundle bone (provides attachment for the PDL fiber bundles)
- 45. 45 Cortical plate consists of fine fibered lamellar bone supported by compact harversian system bone of variable thickness The bone occupying the central part of the alveolar process also consists of fine – fibered membrane bone disposed in lamellae Bundle bone That part into which the fiber bundles of the PDL insert Also sometimes referred to as the cribriform plate as it is perforated by many foramina which transmit nerves and vessels
- 47. 47 Compostion 65 % inorganic 35% organic 88-89% collagen 11-12% non collagen
- 48. 48 Cells Osteoprogenitor stromal cells Osteoblasts Osteocytes Bone lining cells Osteoclasts
- 49. 49 Osteoprogenitor cells Derived from pluripotential stromal cells present in the bone marrow and other connective tissues Can differentiate into osteoblasts prior to bone formation Resemble young fibroblasts Two types : Committed osteoprogenitor Inducible osteoprogenitor – may diiferentiate into fibroblasts, myoblasts, adipose cells, chondroblasts etc
- 50. 50 Biological events / Tissue reactions during tooth movement
- 52. 52 After the development of teeth, for them to become functional, considerable movement is required to bring them to the occlusal plane Preeruptive tooth movement Eruptive tooth movement Posteruptive tooth movement Eruption
- 53. 53 Made by deciduous and permanent tooth germs within tissues of the jaw before they begin to erupt These movements are thought of as the means by which the teeth are placed in a position within the jaw for eruptive movement Analysis reveal that they result as a combination of 2 factors Total bodily movement of the tooth germ Growth – in which one part of the tooth germ remains fixed while the rest continues to grow, leading to a change in the center of the tooth germ Preeruptive tooth movement
- 54. 54 Brings about axial and occlusal movement of the tooth from its development position within the jaw to its final position in the occlusal plane Rate of tooth eruption varies depending on the tooth’s location Avg of 1 – 10 micron meter per day during the interosseous phase 75 micron meter per day once the tooth escapes from its bony cell – persists till the tooth reaches the occlusal plane Eruptive tooth movement
- 59. 59 Theories of eruption Root formation Hydrostatic pressure Selective deposition and resorption of the bone around the tooth Pulling of the tooth into occlusion by the cells or fibers ( or both ) of the PDL
- 60. 60 Periodontal traction Theory Available evidence strongly indicates that the force for the eruptive tooth movement strongly resides in the PDL The frequent cell to cell contacts that occur between PDL fibroblasts permit summation of the contractile forces This force can be translated into eruptive tooth movement provided that the collagen fiber bundles have an oblique orientation and that this orientation is maintained
- 61. 61 In summary, the force moving the tooth is most likely generated by the contractile property of the PDL fibroblasts However a number of other conditions are needed to translate this contraction into tooth movement, such as root growth, PDL formation and bone and collagen remodeling. Eruption therefore must be considered a multifactorial phenomenon
- 62. 62 Post eruptive tooth movement Made by the tooth after it has reached its functional position in the occlusal plane Divided into three categories : Those to accommodate the growing jaws Those to compensate for continued occlusal wear Those to accommodate interproximal wear
- 63. 63 Physiologic Drifting The position of teeth, after eruption, are governed by the different physiological forces that act on them These include An anterior component of occlusal force Soft tissue pressure Contraction of transeptal fibers between teeth
- 64. 64 Throughout life, teeth achieve an equilibrium position relative to these forces This maintenance requires and leads to what is known as ‘drifting’ of teeth The anterior component of occlusal force When teeth are brought into contact ( clenching ), an anteriorly directed force is generated This force is result of • Mesial inclination of most teeth • Summation of intercuspal planes ( producing a forward directed force ) • Transeptal fibers of the PDL
- 65. 65 Contraction of the Transeptal fibers Play an important role in maintaining tooth position Evidence suggests that if these fibers are removed then the relapse, post orthodontic treatment, is reduced to a great extent Also it has been demonstrated experimentally that in bisected teeth the two halves separate from each other; but if the transseptal fibers are previously cut, this separation does not occur
- 66. 66 Experiments reveal that if a tooth is slenderized interproximally, and its opposing tooth is removed, the mesial drift of this tooth is slower than if the opposing tooth is not removed Taking the current evidence into consideration, it can be assumed that the mesial drift is achieved by a contractile mechanism associated with the transeptal fibers and enhanced by occlusal forces
- 67. 67 Soft tissue pressures Pressures generated by the cheeks and tongue may push teeth mesially Though soft tissue does not play a major role in creating a mesial drift, nevertheless this soft tissue pressure does influence the position of the tooth
- 68. 68 Theories of tooth movement Two possible elements in the PDL affect the blood flow Biological electricity Pressure tension These are the basis of the two major theories of Orthodontic tooth movement Bioelectric Theory Pressure Tension Theory
- 69. 69 Bioelectric Theory Relates Tooth Movement to change in bone metabolism controlled by the electric signals that are produced when the alveolar bone flexes and bends Piezoelectricity : phenomenon observed in many crystalline materials in which a deformation of the crystal structure produces a flow of current as electrons are displaced from one part of the crystal lattice to another
- 70. 70 These are due to migration of electrons within the crystal lattice as it is distorted by pressure Electrons migrate from one location to another and an electric current is observed Crystal is stable as long as the force is maintained Characteristics of piezoelectric signals
- 71. 71 When force is released, the crystal returns to its original shape & a reverse flow of electrons is seen Hence a rhythmic activity would produce a constant interplay of electric signals, whereas occasional application and release of force would produce only occasional electric signals
- 73. 73 Fluids bathe the living bone The ions contained by these fluids interact with this complex field This results in temperature changes as well as formation of electric signals Both convection and conduction currents can be detected in the extracellular fluids The small voltages observed are called “streaming potential”
- 74. 74 These stress-generated signals are important in the general maintenance of the skeleton Without such signals, bone mineral is lost and general skeletal atrophy ensues In astronauts, the bone flexing is not as much in the weightless environment as is under gravity. This usually leads to skeletal atrophy In the oral cavity, regular mastication leads to generation of signals by the bending of the alveolar bone This is important for the maintainance of the bone around the teeth
- 75. 75 Orthodontic force, once applied, creates only a brief production of electric signals and as this force is sustained, nothing happens Hence considering this aspect, a vibrating type of orthodontic force should be more beneficial to achieve tooth movement However, studies have found that there is little or no benefit of vibrating forces over sustained forces for tooth movement These stress generated signals may have little to do with orthodontic tooth movement.
- 76. 76 Pressure-Tension Theory Most accepted theory of tooth movement Relies on chemical rather than electric signals as the stimulus for cellular differentiation and tooth movement Sustained pressure causes tooth to shift position within the pdl space Some areas of the ligament get stressed, some compressed
- 77. 77 Blood flow decreases in the compressed areas and increases or is maintained in the areas under tension Blood flow alteration leads to quick changes in the chemical environment ( eg. reduced Oxygen levels in compressed region ) These chemical changes act either directly or by stimulating the release of other biologically active agents that stimulate cellular differentiation and activity,
- 78. 78 PHASES OF TOOTH MOVEMENT INITIAL PHASE LAG PHASE PROGRESIVE TOOTH MOVEMENT PHASE
- 79. 79 Application of Orthodontic Force Areas of compression (Catabolic modeling ) Areas of Tension (Anabolic modeling) Initial period Secondary period
- 80. 80 Macro level
- 82. 82 TOOTH MOVEMENT UNDER LIGHT FORCES UNDER HEAVY FORCES DIRECT RESORPTION INDIRECT RESORPTION/ UNDERMINING RESORPTION
- 83. 83 Initial period of tooth movement Impeding vascular circulation and cell differentiation Degeneration of cells and vascular stuctures Changes in cells ( swelling of mitochondria and ER) Rupture and discoloration of cytoplasmic membrane Isolated Nuclei remnants ( Pyknosis – first sign of hylanization ) Occurrence of mild inflammation
- 84. 84 Hyalinization zone Cells unable to differentiate into osteoclasts No bone resorption from Periodontal membrane Tooth movement halts until adjacent bone has resorbed and hyaline structure is removed and areas repopulated by cells Peripheral areas of hylanized tissue are removed by invasion of cells and blood vessels from adjacent undamaged PDL Hyalinized material ingested by phagocytic activity of macrophages and removed Adjacent bone removed by cells that have differentiated into osteoclasts Reestablishment of tooth attachment – wider ligament space
- 85. 85 Secondary period of tooth movement PDL widened considerably Osteoclasts attack the bone surface over a much wider area Further bone resorption – predominantly direct Reorganization of fibrous attachment apparatus Complete reorganization of the fibrous system throughout the membrane Light force maintained
- 87. 87 Stretching of PDL fibers Formation of osteoblasts along stretched fiber bundles Cell proliferation Deposition of osteoid tissue on the tension side Original periodonal fibers become embedded in the new layers of prebone or osteoid which mineralizes in the deeper parts Deposition of new bone till the width of the membrane is returned to normal limits Orthodontic force
- 89. 89 Osteoblasts Basophilic, roughly cuboidal mononuclear cells 15-30 micron meter across Found on forming surfaces of growing or remodeling bone Responsible for the synthesis, deposition and mineralization of bone matrix A proportion of them, on becoming embedded in the matrix, finally change to osteocytes
- 90. 90 Ultra structurally, they have features typical of protein secreting cells One major activity is secretion of organic matrix – type I collagen and small amounts of type V collagen Collagen synthesis occurs in the RER and the golgi apparatus
- 91. 91
- 92. 92
- 94. 94 Other products secreted Osteocalcin Osteonectin Osteopontin RANKL (receptor activator of nuclear factor kappa B ligand ) Macrophage colony stimulating factor ( M-CSF ) osteoprotegerin (OPG)
- 95. 95 Osteoblasts contain on their surface receptors for Parathormone (PTH) 1,25 dihydroxy vit D3 PGE2
- 96. 96 Osteoclasts Functionally responsible for local removal of bone during bone growth and subsequent remodeling of osteons and surface bone Large ( 40 micron meter or more ) polymorphic cells Variable no. of ( 15-20 ) oval, closely packed nuclei Lie in close contact with bone surface in pits termed as resorption bays
- 97. 97 Contain numerous mitochondria and vacuoles which are phosphatase containing lysosymes Cause demineralization by proton release - an acidic local environment and organic matrix and destruction by releasing lysosomal and non - lysosomal ( collagenase ) enzymes. Contain the receptor RANK (receptor activator of nuclear factor kappa B) on their surfaces.
- 100. 100 Pressure side ( osteoclast formation )
- 101. 101 Mechanical distortion of PDL cells and fibers Partial compression of blood vessels in PDL Orthodontic force Alteration of blood flow and oxygen levels INFLAMMATION Cascade of chemical mediators
- 102. 102 Chemical Mediators Histamine Serotonin Plasma proteases neuropeptides Kinins Eicasonoids ( prostaglandins , interleukins ) Nitrous oxide Cytokines
- 103. 103 Other Biological factors responsible for bone remodelling Hormones Polypeptide Hormones Parathyroid hormone Calcitonin Insulin Growth hormone Steroid hormones 1,25 Di-hydroxyvitamin D3 Glucocorticoids Sex steroids Thyroid hormones Growth Factors Insulin-like growth factor ( IGF I and II ) TGF-b Including BMP Fibroblast growth factor (FGF) Platelet derived growth factors ( PDGF) Selected Cytokines
- 104. 104 What triggers Osteoclasts? Osteoclasts may get activated directly by the action of chemical mediators like interleukins But latest research shows that the cells responsible for both recruiting and restraining of Osteoclasts are osteoblasts Osteoblasts contain receptors for PTH, PGE2, Vit D3 etc Once these attach to their respective receptors, osteoblasts release secondary messengers called “RANKL” and “M-CSF”
- 105. 105 Osteoclasts have on their surfaces, receptors for RANKL and M-CSF Recent research reveals that the main cytokine responsible for activation of osteoclasts is RANKL and also that the major source of RANKL are the osteoblast cells Under the influence of RANKL, ostoclasts get recruited and start to function
- 106. 106 Research also shows that not only are Osteoblasts responsible for recruiting osteoclasts, they are also responsible for restraining them This occurs when the osteoblasts get activated and in turn release the secondary messenger “OPG” OPG has a strong affinity for and gets attached to the RANKL molecules which in turn prevents the activation of osteoclasts
- 109. Hormonal Control of Bone Resorption: Pro-Resorptive and Calcitropic Factors
- 110. 110 Summary of tissue changes on pressure side
- 111. 111 Pressure Side Compressed vessels INFLAMMATION Reduced oxygen, changes in pH Release of chemical mediators of inflammation Attachment to osteoblasts Osteoclast activity and bone resorption Simultaneous periodontal ligament remodelling Release of RANKL and CSF Activity of PDL fibroblasts Periodontal width maintained
- 112. 112 Molecular changes on the Tension side
- 113. 113 Unloading/ tension Perturbation of periodontal cells Change in influx of sodium and calcium ions into cells Neuropeptides – substance p, vasoactive intestinal polypeptide VIP, calcitonin dene related peptide (CRGP) Formation of ‘secondary messengers’ – cAMP, cGMP Release of BMP Endogenous signalling Mechanical stimulus
- 115. 115 Hormonal Control of Bone Resorption: Anabolic and Anti-Osteoclastic Factors
- 116. 116 Summary of tissue changes on tension side
- 117. 117 Unloading/ tension Perturbation of periodontal cells Formation of ‘secondary messengers’ – cAMP, cGMP Release of BMP Differentiation of bone forming cells Simultaneous remodelling of PDL fibers Release of OPG Restraining of osteoclasts Bone formation Tension side
- 121. 121 Factors Influencing Orthodontic tooth movement • Force • Drugs/medications • Age of Patient • Facial Pattern
- 122. 122 Force Magnitude of force Light forces should always be used to move teeth Heavier forces lead to complete compression of the vessels of the PDL leading to hyalinization Heavier forces do not increase the rate of tooth movement
- 123. 123 Instead, heavier forces have a number of drawbacks Pain Increased undermining resorption Increased chances of root resorption Chances of debonding of orthodontic brackets Research shows that heavy orthodontic forces cause the cementum adjacent to the hyalinized areas of the PDL to be “marked” and that clast cells attack this marked cementum when the PDL is repaired leading to severe root resorption
- 124. 124 Light forces on the other hand, keep pain, hyalinization and root resorption to a minimum and are more easily accepted by the patient The optimum force levels for orthodontic tooth movements should be just high enough to stimulate cellular activity without completely occluding blood vessels in the PDL
- 126. 126 Continuous Interrupted intermittent Duration
- 128. 128 Orthodontic forces should be light and continuous
- 129. 129 Effect of drugs/medications on tooth movement Orthodontic Tooth Movement enhancers • Vitamin D administration enhances Tooth Movement • Direct injection of prostaglandin into the PDL has shown to increase the rate of tooth movement ( Painful ) Orthodontic Tooth Movement Depressors • Bisphosphonates ( used for Rx of osteoporosis eg. Alendronate ) • Prostaglandin Inhibitors ( eg. Indomethacin used for arthtritis treatment )
- 130. 130 Osteoporosis • A problem faced by many post menopausal Females & also aging individuals of both sexes • Medication –Estrogen ( older women ) –Bisphosphonates
- 131. 131 Estrogen Has little of no effect on impact on orthodontic Movement
- 132. 132 Bisphosphonates They are synthetic analogues of pyrophosphate that bind to hydroxyapatite in bone Act as specific inhibitors of osteoclast-mediated bone resorption. Eg. Alendronate Physicians of Older Women on these drugs and who require orthodontic treatment should be consulted regarding the possibility of switching over to estrogen, at least temporarily
- 133. 133 Prostaglandins Play an important role in the cascade of signals that lead to tooth movement Two categories of drugs affect prostaglandin activity : • Corticosteriods and NSAIDS (interfere with prostaglandin synthesis) • Other agents with mixed agonistic and antagonistic effects on various prostaglandins
- 135. 135 Other drugs affecting prostaglandin synthesis Tricyclic antidepressants ( doxepin, amitriptyline, imipramine) Anti-arrhythmic agents ( procaine ) Anti malarial drugs ( quinine, quinidine, chloroquine) Methyl Xanthines Anticonvulsant drug phenytoin Some tetracyclines ( doxycycline ) inhibit osteroclast recruitment.
- 136. 136 It is of prime importance to include a detailed medical history of the patient during the diagnosis phase of the orthodontic treatment. A sound knowledge of the effect of different regularly used drugs will aid the clinician to take the required precautions and in turn make the orthodontic treatment as efficient as possible.
- 137. 137 Other factors affecting tooth movement AGE OF THE PATIENT GROWTH PATTERN YOUNG ADULT VERTICAL HORIZONTAL
- 138. 138 Controlling tooth movement ( Anchorage) Defined as “ resistance to unwanted tooth movement “ In clinical practice, anchorage control is probably one of the most critical aspects of the treatment In planning orthodontic therapy, it is simply not possible to consider only the teeth whose movement is desired. Reciprocal forces throughout the dental arches must be carefully analyzed , evaluated and controlled.
- 139. 139 Retention & Relapse Post orthodontic treatment completion, retention is of utmost importance Orthodontic treatment results may potentially be unstable PDL reorganization is important for stability that normally controls tooth position
- 140. 140 Causes of relapse Differential jaw growth Cheek/lip tongue pressure Elastic recoil of gingival fibers Intra-arch irregularity Changes in occlusal relationship
- 141. 141 Future of Orthodontic Tooth Movement New biological/chemical materials (Prostaglandins etc) Research to increase rate of tooth movement UV radiation Electricity/electromagnetic Nitrous Oxide Stem cell research
- 142. 142 CONCLUSION Sound knowledge of the basics of tooth movement “Tissue conscious” Keep in touch with the recent advances pertaining to tissue research
- 143. 143 THANK YOU
- 144. 144 REFERENCES Gray’s Anatomy, 39th edition Contemporary Orthodontics, William R. Profitt, 3rd edition Oral Anatomy, Histology & Embryology, B.K.B. Berkovitz, 3rd edition Oral Histology, Ten Cate, 6th edition Inflammation, Henry Towbridge, 5th edition
- 145. 145 Orthodontics, Current principles and Techniques, Graber Vanarsdal Textbook of Orthodontics, F.D. Foster Bristol University post graduate notes in Orthodontics, MSC/MOrth Programme, 2nd edition Bone Remodelling, J.A. Hill et al, BJO vol 25/1998/101- 107 The Periodontal Ligament: a unique, multifunctional connective tissue, Periodontolgy 2000, Vol 13, 1997, 20-40