FUNCTIONS OF THE PERIODONTIUM <ul><li>Attachment & support </li></ul><ul><li>Nutritive </li></ul><ul><li>Sensation </li></...
ATTACHMENT & SUPPORT  <ul><li>Principal collagen fibre bundles attach the tooth to the jaw </li></ul><ul><li>Cementum, PDL...
Physiological tooth movement and PDL <ul><li>All components of PDL act together as a SHOCK ABSORBER </li></ul><ul><li>Ceme...
Intra – socket tooth movements <ul><li>Teeth of opposing jaws come together </li></ul><ul><li>- APPLYING FORCE - </li></ul...
Tooth movement under force v time
Intra – socket movements  <ul><li>Direction and amount of movement depend on direction and amount of force </li></ul><ul><...
<ul><li>REMEMBER :–  </li></ul><ul><li>TOTAL TIME TAKEN FOR A TOOTH TO RETURN TO ITS ORIGINAL POSITION IS GREATER THAN THA...
Physiology during tooth movement  OR “whats going on ?” <ul><li>3 components of PDL in the system of tooth support </li></...
GROUND SUBSTANCE <ul><li>Allows rapid movement </li></ul><ul><li>Operates first </li></ul><ul><li>Resistance provided by f...
BLOOD AND BLOOD VESSELS <ul><li>Blood forced from vessels in ligament to those in alveolar bone marrow </li></ul><ul><li>R...
PRINCIPLE FIBRE BUNDLES <ul><li>Only involved after ground substance and other tissue fluids have responded to forces </li...
Other changes  <ul><li>Increase in periodontium function :– </li></ul><ul><li>50% increase in PDL thickness </li></ul><ul>...
What happens of we have a second force applied to the tooth after the first force? <ul><li>Occurs during chewing! Forces l...
Tooth movement with second force
TRANSLOCATORY TOOTH MOVEMENT <ul><li>Resultant of forces so that tooth moves permanently </li></ul><ul><li>Socket is remod...
<ul><li>Remodelling of PDL = metabolic turnover across  whole width of PDL </li></ul><ul><li>- FORCE - </li></ul><ul><li>P...
So what happens to alveolar bone & cementum? <ul><li>Alveolar bone </li></ul><ul><li>In areas of COMPRESSION, osteoclasts ...
Compression Compression Tension Tension
CLINICAL IMPLICATIONS <ul><li>Varying structure of alveolar bone means different types of movement needed to extract diffe...
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FUNCTIONS OF THE PERIODONTIUM Attachment

  1. 1. FUNCTIONS OF THE PERIODONTIUM <ul><li>Attachment & support </li></ul><ul><li>Nutritive </li></ul><ul><li>Sensation </li></ul><ul><li>All components of the periodontium form a FUNCTIONAL SYSTEM that provides attachment for the tooth to the bone of the jaw AND permits the tooth to withstand the forces of mastication </li></ul>
  2. 2. ATTACHMENT & SUPPORT <ul><li>Principal collagen fibre bundles attach the tooth to the jaw </li></ul><ul><li>Cementum, PDL and alveolar bone involved in accommodating any tooth movement </li></ul><ul><li>Teeth held in jaws and supported against functional stresses </li></ul><ul><li>BUT </li></ul><ul><li>Allow for tooth movement </li></ul><ul><li>Intrasocket & Translocatory </li></ul>
  3. 3. Physiological tooth movement and PDL <ul><li>All components of PDL act together as a SHOCK ABSORBER </li></ul><ul><li>Cementum and Alveolar bone respond to stresses at specific sites </li></ul><ul><li>Ground substance </li></ul><ul><li>Tissue fluid / blood </li></ul><ul><li>Fibre bundles of PDL </li></ul><ul><li>Secretion and resorption </li></ul><ul><li>Corresponding to areas of tension / compression </li></ul>
  4. 4. Intra – socket tooth movements <ul><li>Teeth of opposing jaws come together </li></ul><ul><li>- APPLYING FORCE - </li></ul><ul><li>Teeth move within sockets </li></ul><ul><li>- REMOVING FORCE - </li></ul><ul><li>Teeth move back to their original position </li></ul>
  5. 5. Tooth movement under force v time
  6. 6. Intra – socket movements <ul><li>Direction and amount of movement depend on direction and amount of force </li></ul><ul><li>When force applied – rate of movement rapid initially but DECREASES WITH TIME </li></ul><ul><li>- no further movement occurs - </li></ul><ul><li>When force removed – rate of movement rapid and DECREASES WITH TIME </li></ul><ul><li>- tooth returns to original position - </li></ul>
  7. 7. <ul><li>REMEMBER :– </li></ul><ul><li>TOTAL TIME TAKEN FOR A TOOTH TO RETURN TO ITS ORIGINAL POSITION IS GREATER THAN THAT TAKEN TO MOVE UNDER THE IMPOSED FORCE </li></ul>
  8. 8. Physiology during tooth movement OR “whats going on ?” <ul><li>3 components of PDL in the system of tooth support </li></ul><ul><li>GROUND SUBSTANCE </li></ul><ul><li>TISSUE FLUID / BLOOD and BLOOD VESSELS </li></ul><ul><li>PRINCIPLE FIBRE BUNDLES </li></ul><ul><li>Operate and function in that order </li></ul>
  9. 9. GROUND SUBSTANCE <ul><li>Allows rapid movement </li></ul><ul><li>Operates first </li></ul><ul><li>Resistance provided by friction between large individual PG molecules and between PGs and collagen fibres </li></ul><ul><li>Alterations in molecular structure occur </li></ul><ul><li>Ground substance - compressed & displaced into other regions of ligament - depending on direction of force </li></ul>
  10. 10. BLOOD AND BLOOD VESSELS <ul><li>Blood forced from vessels in ligament to those in alveolar bone marrow </li></ul><ul><li>Resistance provided by friction between blood and vessel walls </li></ul><ul><li>Again acts as a damper when force applied as blood displaced through vessels through cribriform plate to alveolar bone marrow </li></ul>
  11. 11. PRINCIPLE FIBRE BUNDLES <ul><li>Only involved after ground substance and other tissue fluids have responded to forces </li></ul><ul><li>Fibres become straightened out and absorb axial stress – can increase in number and thickness </li></ul><ul><li>Are inelastic – allow no further tooth movement </li></ul><ul><li>Prevent direct apposition of cementum and bone surfaces so prevents complete closure of periodontal space </li></ul>
  12. 12. Other changes <ul><li>Increase in periodontium function :– </li></ul><ul><li>50% increase in PDL thickness </li></ul><ul><li>Alveolar bone increases in thickness </li></ul><ul><li>Reduction in function :- </li></ul><ul><li>PDL narrows, fibre bundles decrease thickness </li></ul><ul><li>Alveolar bone decreases in thickness </li></ul>
  13. 13. What happens of we have a second force applied to the tooth after the first force? <ul><li>Occurs during chewing! Forces later than the first occur before teeth have returned to their resting positions </li></ul><ul><li>Collagen fibres prevent complete closure of periodontal space </li></ul><ul><li>Proteoglycans become increasingly viscous with increasing rates of loading </li></ul><ul><li>Teeth move further than after initial force - longer to return to resting position when force removed </li></ul>
  14. 14. Tooth movement with second force
  15. 15. TRANSLOCATORY TOOTH MOVEMENT <ul><li>Resultant of forces so that tooth moves permanently </li></ul><ul><li>Socket is remodelled to move with tooth and accommodate new position </li></ul><ul><li>Tooth eruption </li></ul><ul><li>Adaptation to jaw growth </li></ul><ul><li>Physiological mesial drift </li></ul><ul><li>Orthodontic tooth movement </li></ul>
  16. 16. <ul><li>Remodelling of PDL = metabolic turnover across whole width of PDL </li></ul><ul><li>- FORCE - </li></ul><ul><li>PDL fibres breakdown – new ones synthesized </li></ul><ul><li>Anchored to cementum and bone by Sharpey’s fibres </li></ul><ul><li>New layer of cementum secreted and alveolar socket wall remodelled (resorption and deposition of bone) </li></ul><ul><li>Staggered replacement of PDL fibres as </li></ul><ul><li>tooth attachment maintained during any movement </li></ul>
  17. 17. So what happens to alveolar bone & cementum? <ul><li>Alveolar bone </li></ul><ul><li>In areas of COMPRESSION, osteoclasts RESORB bone to accommodate tooth movement </li></ul><ul><li>In areas of TENSION osteoblasts SECRETE bone to fill space left </li></ul><ul><li>Cementum </li></ul><ul><li>In areas of TENSION, cementoblasts increase SECRETION of cementum to fill space left </li></ul><ul><li>In areas of COMPRESSION cementum is RESORBED </li></ul>
  18. 18. Compression Compression Tension Tension
  19. 19. CLINICAL IMPLICATIONS <ul><li>Varying structure of alveolar bone means different types of movement needed to extract different teeth – in direction of thinnest bone </li></ul><ul><li>Direction of PDL fibres means extraction force is APICALLY directed (push not pull) </li></ul><ul><li>Rapid rate of PDL turnover and activity of cementoblasts & osteoblasts means re-attachement of teeth possible </li></ul><ul><li>Epithelial rests of Malassez can proliferate = radicular cysts and occasionally more serious pathology </li></ul>
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