Successfully reported this slideshow.
Your SlideShare is downloading. ×

The Biology of tooth movement (Orthodontics)

Loading in …3

Check these out next

1 of 58 Ad

More Related Content

Slideshows for you (20)

Viewers also liked (20)


Similar to The Biology of tooth movement (Orthodontics) (20)


Recently uploaded (20)

The Biology of tooth movement (Orthodontics)

  2. 2. PRESENTATION OUTLINE 1)Introduction to orthodontic tooth movement. 2)Periodontal and bone response to normal function. 3)Theories of tooth movement. 4)Phases of tooth movement. 5)Types of orthodontic forces. 6)Types of orthodontic tooth movement. 7)Definitions. 8)Deleterious effects of orthodontic forces. 9)Methods of enhancement orthodontic tooth movement.
  3. 3. INTRODUCTION TO ORTHODONTIC TOOTH MOVEMENT ORTHODONTIC TOOTH MOVEMENT: It is a biological response to interference in the physiological equilibirium of the dentofacial complex by an externally applied force. STIMULUS: Force applied to teeth for purpose of causing tooth movement. OPTIMUM ORTHODONTIC FORCE: 1)Produces rapid tooth movement 2)minimal patient discomfort 3)The lag phase is minimum 4)No marked mobility should be seen. 5)The vitality of PDL and other structures should be maintained 6)Initiates maximum cellular response. 7)Produces frontal resorption.
  4. 4. PERIODONTAL AND BONE RESPONSE TO NORMAL FUNCTION 1)Normal periodontal ligament space 0.25- 0.5mm 2)Component of PDL includes . a)PDL fibers(resists the diplacement of tooth) b)The cellular elements( fibroblasts and osteoblasts) C)The tissue fluids. 3)Tooth movement during mastication: a)<1 secs = PDL fluid incompressible,alveolar bone bends, peizoelectric signals generated. B)1-2 secs=PDL fluid expressed,tooth moves within PDL space. C)3-5 secs=PDL fluid sqyueezed out,tissues compressed; causes immediate pain. 4)Active stabilization phenomenon
  6. 6. THEORIES OF ORTHODONTIC TOOTH MOVEMENT 1)PRESSURE TENSION THEORY ( Relates tooth movement to cellular changes produced by chemical messengers, tradionally thought to be generated by alterations in blood flow through the PDL 2)BIOELECTRIC/BONE BENDING THEORY ( Relates tooth movement at least in part to changes in bone metabolism controlled by electric signals that are produced when alveolar bone flexes and bends
  7. 7. PRESSURE-TENSION THEORY BY Sandstedt 1904, Oppenheim 1911, Schwarz 1932 The pressure tension theory relates tooth movement to cellular changes produced by chemical messengers,tradionally thought to be generated by alterations in blood flow through PDL. Force applied alteration in blood flow with pressure and tension in pdl formation and release of chemical messengerscellular differentiation Remodelling [Resorption(pressure side), Deposition(tension side)] HISTOLOGICAL CHANGES DURING TOOTH MOVEMENT: 1)Changes following applicaton of mild force. 2)Changes following application of extreme force..
  8. 8. PRESSURE-TENSION THEORY BY Sandstedt 1904, Oppenheim 1911, Schwarz 1932 1)CHANGES FOLLOWING APPLICATION OF MILD FORCE: A)CHANGES ON PRESSURE SIDE: 1)Periodontal ligament gets compressed to almost 1/3rd . 2)A marked increase in vascularity of PDL due to inc in capillary blood flow. This increase helps in mobilazation of cells such as fibroblasts and osteoclasts. 3)Osteoclasts are bone resorbing cells that ine up along the socket wall on pressure side, and they start resorbing bone. 4)when the forces applied are within the physilogical limits, the resorption in the alveolar plate immediately adjacent to the ligament.this kind of resorption is known as FRONTAL RESORPTION. B)CHANGES ON TENSION SIDE: 1)Periodontal membrane on tension side get stretched & so distance between the alveolar process and tooth is widened. 2)Raised vascularity as on pressure side and causes mobilization of cells such as fibroblasts and osteblasts. Osteoid is laid down immediatley adjacent to lamina dura which later on mature to woven bone.
  9. 9. PRESSURE-TENSION THEORY BY Sandstedt 1904, Oppenheim 1911, Schwarz 1932 2)CHANGES FOLLOWING APPLICATION OF EXTREME FORCES: A)CHANGES ON PRESSURE SIDE: 1)When extreme forces are applied it results in crushing or total compression of PDL. 2)On the pressure side root closely approximates the lamina dura compresssed PDL occlusion of blood vesselsDec. nutrional supply regressive changes(Hyalinization). 3)In this case, bone resorpton occurs in the adjacent marrow spaces and in the alveolar plate behind and above the hyalinized zones. This kind of resorption is known as UNDERMINING RESORPTION. B)CHANGES OF TENSION SIDE: 1)On tension side, the periodontal ligament gets over stretchedtearing of blood vessels and ischemia.
  10. 10. BIOELECTRIC/BONE BENDING THEORY Relates tooth movement at least in part to changes in bone metabolism controlled by electric signals that are produced when alveolar bone flexes and bends. Force applied(alveolar bone bends and flexes)Electrical signals generated change in bone metabolismtooth movement. CHANGE IN BONE SURFACES: 1)PDL pressure side: Convex(electro positive, Osteoclastic activity). 2)PDL tension side: Concave(electro negative, Osteoblastic activity). BIOELECTRIC RESPONSES: 1)Piezoelectric phenomenon. 2)Streaming potential.
  11. 11. BIOELECTRIC/BONE BENDING THEORY 1)PIEZOELECTRICITY: Piezoelectricity is the phenomenon observed in many crystalline materials in which a deformation of crystal structure produces a flow of electric current as electrons are displaced from one part of crystal lattice to another. A small electric current is generated when bone is mechanically deformed. The possible sources of the electric current are: A)collagen. B)Hydroxyapatite. C)Collagen-Hydroxyapatite interface. D)Mucopolysacchride fraction of the ground substance. Piezoelectric signals have two unusual characterstics: A) Quick decay rate: When a force is applied , a peizoelectric signal is produced. This electric current quicly dies away to zero when though force is maintained. B)When the force is released, electron flow in opposite direction is seen.
  12. 12. BIOELECTRIC/BONE BENDING THEORY 2)STREAMING POTENTIAL: Ions in the fluidinteract with complex electric fieldBoth conduction and convection currents can be detectedthe small voltages obsereved are known as streaming potential. Fluid flow with long decay period.
  14. 14. CHEMICAL REGULATION OF OTM CHEMICAL MESSENGERS: It is because of both mechanical and compression of tissues and changes in blood flow can cause release of chemical messengers. What happens after force is applied? A)Release of First messengers. B)Role of Mechanoreceptors. C)Release of Second Messengers. D)Other Messengers.
  15. 15. Diagrammatic representation of increasing compression of blood vessels as pressure increases in the PDL. At a certain magnitude of continuous pressure , the blood vessels are totally occluded.
  16. 16. SEQUENCE OF EVENTS LIGHT FORCE: Within seconds: 1)movement of fluids from areas of compressionareas of tension 2)development of strain in cells and extracellylar matrix 3)Intracellular ca++ , Increase CAMP, increase Phospholipase activity. Within mintues: 1)blood flow altered and oxygen tension begins to change 2)Prostaglandins and cytokines release. Within hours: 1)Metabolic changes occur/enzyme release. 2)After 4 hours: Inc. CAMP levels are present & cellular differentiation begins within PDL. Within days: 1) 2days: Activation of cells to participate in remodellingtooth movement 2) 5-7 days: Days to remove necrotic bone.
  17. 17. SEQUENCE OF EVENTS HEAVY FORCES: Within Minutes: flow of blood cut off Within Hours: cell death occurs in compressed areas. Within Days: 1) 3-5 days: cell differentiation, undermining resorption. 2) 7-14 days: Undermining resorption in lamina dura adjacent to compressed PDL  tooth movement occurs.
  19. 19. PHASES OF TOOTH MOVEMENT Burstone categories the phases as 1)Initial Phase 2)Lag Phase 3)Post lag Phase
  20. 20. PHASES OF TOOTH MOVEMENT INITIAL PHASE: 1)Rapid tooth Movement is observed over a short distance 2)Represents displacement of tooth in PDL membrane space and bending of alveolar bone 3)Both light and heavy forces displace the tooth to same extent during this phase 4)Movement is about 0.4mm to 0.9mm in a weeks time 5)Time Duration: 24 hours to 2 days
  21. 21. PHASES OF TOOTH MOVEMENT LAG PHASE: 1)Duration : 4 to 20 days 2)Little or no tooth movement occurs 3)This phase is characterized by formation of hyalinizied tissue in PDL which has to be resorbed before further tooth movement can occur. 4)Duration of lag phase depends upon the amount of force use to move the tooth
  22. 22. PHASES OF TOOTH MOVEMENT POST LAG: 1)Tooth movement progresses rapidly as the hyalinized zone is removed and bone undergoes resorption. 2)Also known as accelerated phase 3)During this phase osteoclasts are found all over the large surface area resulting in direct resorption of bony surface facing the PDL 4)Duration: 40 days after initial force application
  24. 24. TYPES OF ORTHODONTIC FORCES There are 3 types of orthodontic forces that are delivered to the tooth by help of appliances. 1)Continuous force 2)Interrupted force 3)Intermittent force
  25. 25. TYPES OF ORTHODONTIC FORCES CONTINOUS FORCE: 1)achieved via fixed appliances 2)example : braces 3)It never declines to zero 4)Alveolar bone resorbed at the pressure sites 5)Deposition of new bone at the PDL tension site.
  26. 26. TYPES OF ORTHODONTIC FORCES Interrupted Force : 1)Achieved via removable appliances 2)force starts heavy then decline to optimal and after that may reach zero 3)short hyalinization periods are formed 4)small compression zone is formed
  27. 27. TYPES OF ORTHODONTIC FORCES INTERMITTENT FORCE : 1)Achieved via extra oral appliance 2)example : Headgear 3)semi hyalinization 4)force fall to zero when the appliance is removed 5)Forces resume when the appliance is reinserted
  29. 29. TYPES OF ORTHODONTIC TOOTH MOVEMENTS Orthodontic tooth movement are of various types depending on the amount of force and the time duration the force is applied for. There are 7 types of orthodontic tooth movements.
  31. 31. DEFINITIONS…
  32. 32. DEFINITIONS FORCE: A load applied to an object that will tend to move in a different position in space. MOMENT: 1)A measure of the tendency to rotate an object around some point . 2)Generated by a force acting at a distance 3)Moment =magnitude of force * distance (perpendicular distance from the center of resistance of the body to the line of action of the force) 4)Measure in units of grams-millimeters. CENTER OF RESISTANCE: 1)A point where the whole body weight is concentrated and is termed as center of gravity 2)Center of resistance for tooth is at the approximate midpoint of the embedded portion of the root
  33. 33. DEFINITIONS COUPLE: 1)Two equal forces acting in opposite directions. 2)Couple results in pure rotational movement about the center of resistance. CENTER OF ROTATION : 1)The point around which the rotation actually occurs when an object is being moved 2)Center of rotation could be at the center of resistance, apical or at infinity. 3)Its position will determine the type of tooth movement.
  36. 36. DELETERIOUS EFFECTS OF ORTHODONTIC FORCES PAIN: 1)On application of appropriate orthodontic forces, patient initially feels little to no pain IMMEDIATELY. 2)Mild aching pain develops SEVERAL HOURS LATER 3)Teeth are sensitive to pressure 4)Pain usually last 2 to 4 days 5)Pain is associated with orthodontic treatment is related to the development of ischemic areas in the PDL (which may undergo sterile necrosis) 6)Peri-apical inflammation and mild pulpitis may also be a contributing factor to pain after orthodontic forces are applied. 7)If light forces are used, the amount of pain experienced by the patient can be reduced by having them engage in repetitive chewing. This allows blood flow through compressed areas. 8)ACETAMINOPHEN can be used for pain management. 9)Drugs like NSAIDs, ibuprofen and other prostaglandin inhibitors are contraindicated.
  37. 37. DELETERIOUS EFFECTS OF ORTHODONTIC FORCES ALLERGIC REACTIONS: 1)Some patients develop allergic reactions to two objects; latex gloves and Nickel. 2)Nickel may be present in stainless steel wires and brackets 3)Allergic reaction manifest as erythema and swelling of oral tissue which develops usually in a day or two 4)Titanium can be substituted against Nickel in such patients.
  38. 38. DELETERIOUS EFFECTS OF ORTHODONTIC FORCES MOBILITY: 1)Mobility is observed due to effects of orthodontic forces on PDL fibers. 2)PDL space widens 3)PDL disorganize and reorganize themselves 4)Force is directly proportional to mobility. 5)Excessive forces may lead to undermining resorption
  39. 39. DELETERIOUS EFFECTS OF ORTHODONTIC FORCES PULP VITALITY: 1)Transient inflammatory response within the pulp may occur initially 2)This initial mild pulpitis has no long term significance 3) History of previous trauma 4) Heavy continuous forces → Undermining resorption → Blood vessels engorged at root apex→ Loss of Pulp vitality 5)Endodontically treated teeth can be moved for orthodontic purposes 6)Calcium Hydroxide is filled in tooth with intrusive trauma until tooth movement is completed.
  40. 40. DELETERIOUS EFFECTS OF ORTHODONTIC FORCES ROOT RESORPTION: 1)Cementum adjacent to hyalinized areas of the PDL undergo resorption by cementoclasts 2)Heavy continuous orthodontic forces can lead to severe root resorption 3)Even with most careful control of orthodontic forces, it is difficult to avoid creating some hyalinized areas 4)Excessive resorption by cementoclasts will cause dentine destruction 5) Once orthodontic forces are removed, repair occurs by the deposition of new cementum in the area of previous destruction 6)Dentin once lost will not be replaced 7)Loss of root structure occurs primarily at root
  41. 41. Root Resorption Moderate Generalized Severe Generalized Severe Localized
  42. 42. DELETERIOUS EFFECTS OF ORTHODONTIC FORCES WHITE SPOT LESION: 1)Sub surface enamel porosity 2)Most common on maxillary lateral incisors during young age 3)Predisposed by poor oral hygiene 4)Can be prevented by Fluoridated water,Fluoride Toothpaste, Fluoride Varnish.
  43. 43. DELETERIOUS EFFECTS OF ORTHODONTIC FORCES ENAMEL TRAUMA: 1)Enamel trauma can be caused by bracket application, bracket removal and de- bonding 2)Applying Ceramic brackets on lower incisors can cause trauma on the maxillary incisors. 3)Iatrogenic causes of enamel trauma include debonding. 4)To prevent de-bonding enamel trauma, debond carefully using carbon dioxide laser or electro-thermal techniques
  46. 46. PHAMACOLOGICAL: DRUGS WHICH ENHANCE OTM 1)Prostaglandins have shown to increase the rate of tooth movement. 2)However, application of prostaglandin injections in PDL is painful 3)Vitamin D administration have also proven to help in orthodontic movement
  47. 47. PHAMACOLOGICAL: DRUGS WHICH RETARD OTM BISPHOSPHONATES – for Osteoporosis – Alendronate (Half life of 12 years) PROSTAGLADIN INHIBITORS – Indomethacin – NSAIDs: Asprin and Ibuprofen TETRACYCLINES – Doxycycline TRICYCLIC ANTIDEPRESSANTS – Doxepine – Imipramine ANTIARRHYTHMIC agents – Procaine ANTIMALARIALS Drugs – Quinine – Chloroquine
  48. 48. BISPHOSPHONATES: 1)Act as specific inhibitors of osteoclast mediated bone resorption. 2)BIONJ 3)Bisphosphonate incorporate 1. in structure of bone 2. On surface of bone 4)Estrogen analogues can be used instead
  50. 50. SURGICAL: DISTRACTION OSTEOGENESIS 1)Ankylosed tooth movement is only possible if the bone moves. 2)In order to attain tooth movement, a segment of the bone surrounding the tooth is moved 3)Distraction of Alveolar Segment
  51. 51. SURGICAL: ACCELERATED OSTEOGENESIS ORTHODONTICS 1)Areas of decortication over facial surface of alveolar bone 2)Place bone grafting material; deminerialized freeze-dried bone 3)Demineralization-Remineralization phenomenon produces accelerated bone remodeling that allows faster tooth movement.
  52. 52. SURGICAL: MODIFIED CORTICOTOMY 1)Incisions are made in the interproximal gingiva, so reflecting flaps is not necessary 2)Peizoelectric knife is used to penetrate the cortical bone 3)A tunnel towards the medullary space is thus established 4)Graft slurry is injected into the are with syringe
  53. 53. OTHERS: VIBRATION OF TEETH: 1)Induction of Peizoelectric current 2)Frequency: 30Hz 3)20 mins per day 4)Stimulates cell differentiation and maturation
  54. 54. OTHERS: PHOTOTHERAPY 1)Uses light with wavelength of 800 to 850 nm for 20 mins per day 2)Infuses light energy directly into bone tissue 3)97% of light energy is lost before it penetrates, thus remaining 3% is said to have enough energy to excite intracellular enzymes and increase cellular activity 4)Also has been shown to increase blood flow.
  55. 55. OTHERS: THERAPUETIC ULTRASOUND 1)Reduced root resorption to facilitate OTM 2)Increased blood flow in PDL would decrease the formation of hyalinized area, thus increasing rate of bone remodeling and tooth movement

Editor's Notes

  • Orthodontic force– mild—24/7 ; orthopeadic force—high magnitude – 12-16 hours. Optimal orthodontic force—mechanical input= maximum rate of tooth movement and minimal irreversible tissue damage. Optimum orthodonti force: Produces rapid tooth movement, minimal pateint discomfort, the lag phase is minimum, no marked mobiltiy of teeth should be there histo : the vitality of pdl and other strcutures is maintained, initiates maximum cellular response, produces direct or frontal resorption levelling, space closure/molar correction,finishing Metabolic activity in PDL: Formation, cross linkage, and maturation shortening of collagen fibers
  • PDL FIBERS: these run at an angle,attahing farther apically on tha tooth than on the adjacent alveolar bone.This arrangement ofcourse resists the displacement of the tooth expected during normal function. CELLULAR ELEMENTS: principal cellular elements in the pdl are undifferentiate mesenchymal cells and their progeny in the form of fibroblasts and osteoblasts. Bone and cementum are removed by specialized osteoclasts and cementoclasts. PDL also contains unmylinetad nerve endings associated with perception of pain and the more complex receptors associated with pressure and positonal information(propioception). Pdl fluids: a fluid filled chamber with retentive but porous walls ould be a description of shock absorber, and in normal function, the fluid allows the pdl space to play just this role. 5-10gm/cm2
  • Movement can be translatory---- root and crown movs at same position tipping--- controlled– root apni jaga stable crown moves uncontrolled---opposite
  • Secondary remodellng changes: whenever force is applied to move teeth the bone immediately adjacent shows osteoclastic and osetoblast activity on the pressure and tension side addiion bony changes also takes place elsewhere to maintain the widhe or thickness of the alveolar bone. For example: if a toot his being moved in labial direction there is compensatory depostion of new bne in the outer sde of the labial alveolar bone and also a compensatory resorption on the lingual alveolar bone.
  • Collagen: in bone collagen exists in a crystalized state and thus can be a source of piezoelectricity when deformed. Hyrdoxypapatite: It also is crystalline in form and therefore can produce electricity when deformed. Collagen –Hyrdoxyapatite interface: the junction b/w collagen and hydroxypatite crystals when bent can be a source of piezoelectricity. The mucopolysacchride fraction of ground substance although not crystalline may also possess the ability to generate electric current when deformed
  • Bone deposition: Osteoid, bundle bone,lamelated bone, bone resorption: decalcification, degradation of matrix,transport of soluble products to extracellular fluid of blood vascular system
  • Post lag is further divided into accelerated phase and linear phase
  • Torque is labiolungual movement of root if in palatal direction: positive root torque if it s in labial direction: negative root torque bone bending: 1: in and out 2: mesiodistal: root uprigthing 3: labiolingual: Torque force: 50-100gm
  • Center of resistance: single rooted: 2/3rd distance from the apex molar: beneath trifurcation. Maxilla: between first and second premolar
  • Chewing: Fluid inside PDL incinflammatory mediators rduced blood supply goodpain less
  • Allergic: Brackets—aletrnatives:plastic,polycarbonate,titanium,ceramics wires--- titanium,molybdenum,nobium,polycarbonate,tiflon
  • blunting also known as root resorption: slight blunting moderate: 1/4rth root length severe: more than ¼ root length
  • White spot lesion: natrual remineralization upto 6 months external bleaching microabrasion(pumice and HCL slurry) restorative treatment.