1 periodontal ligament future

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1 periodontal ligament future

  1. 1. Theperiodontal Ligament
  2. 2. Periodontium: Is the investing and supporting attachment system of the teeth. :It consists of Two soft tissues Two hard tissues Gingiva -1 Cementum -1That part covers the neck of thetooth and part of the alveolar covers the anatomical root.bone Alveolar Bone -2 The bone of the jaw that Periodontal Ligament -2 surrounds the root of the tooth Strong ligament that attachesthe tooth to the alveolar bone
  3. 3.  Definition: The periodontal ligament is the dense fibrous connective tissue that occupies the periodontal space between the root of the tooth and the alveolus.•Inflammation from the dental pulpand gingiva could spread to involvethe PDL and other apical supportingtissues.
  4. 4. Width of the periodontal ligament:It ranges from 0.15-0.21 mm.The narrowest area is at the mid-root ( Fulcrum ).The region at the alveolar crest is the widest areafollowed by the apical region. The width generally reduced in: •Non-functional teeth. •Un-erupted teeth. While increased in: Bone Dentin *Teeth subjected to an occlusal stress within the physiological limits . *Deciduous teeth
  5. 5. The periodontal ligament resemblesimmature, fetal-like connective tissues inthe following features:1- High rate of turnover.2- Large volume of ground substance.3- The presence of oxytalan fibers.4- High cellularity.5- Similar biomechanical propereties.
  6. 6. Knocked out toothThe length of time before a tooth is reimplanted (within half anhour) and how it is transported to the dentist (in saline) arecritical in successfully saving and re-implanting the tooth.The periodontal ligament will regenerate and revascularize.A tooth that is replaced within half an hour has a 90% chance of successful re-implantation.
  7. 7. Development Of PDL: •Dental follicle consists of1-Dense fibrous and cellulartissues immediatelyencapsulate the developingtooth (Cementum)2-Perifollicular mesenchyme (PDL ,Alveolar bone)
  8. 8. Histological structureThe periodontal ligament is formed of : Intercellular cells substancesSynthetic Fibers,Resorptive ground substancesProgenitor blood vessels,Defensive nerves & lymphatics.
  9. 9. A- The principal fibers: They are formed of collagen bundles, which are wavy in course and are arranged in three groups.a) Gingival fibers.b) Transseptal or interdental ligament.c) Alveolodental ligament which is subdivided into the following five groups: 1- Alveolar crest group. 2- Horizontal group. 3- Oblique group. 4-Apical group. 5- Interradicular group.
  10. 10. A- The principal fibers: a- The gingival fibers:1- Dento-gingival fibers: extend from the cervical cementum into the Dento- gingiva. gingival Alveolo-2- Alveolo-gingival group: extends gingival from the alveolar crest into the gingiva. Circular fibers3- Circular group: a small group of fibers that encircles the tooth and interlaces with the outer fibers.4- Dento-periosteal fibers: they Dento- extend from the cementum directed periosteal over the bone crest and then incline Alveolar apically between the periosteum of bone the alveolar bone and the gingiva.
  11. 11. Function of gingival fibers:They form a rigid cuff around thetooth that can add stability and resistgingival displacement.
  12. 12. b- The transseptal ligament:*It connects two adjacent teeth. Dentin*The ligament runs from the cementum of one tooth over the crest of the alveolus to the cementum of the adjacent tooth. Bone*Function: DentinResists mesial and distaltooth separation.
  13. 13. c- The alveolodental ligament:1-Alveolar crest group: radiate from the crest of the alveolar process and attach themselves to the cervical part of the cementum.Function: resists vertical andintrusive forces. Bone Dentin2-Horizontal group:The fiber bundles run from thecementum to the bone at rightangle to the long axis of thetooth.Function: resists horizontal and tipping forces.
  14. 14. 3- Oblique group:The fiber bundles run obliquely.Their attachment in the bone issomewhat coronal (higher)than the attachment in thecementum. boneThe greatest number of fiber dentinbundles are found in this group.Function:*Performs the main supportof the tooth against masticatoryforces.*Resists vertical and intrusive forces.
  15. 15. 4- Apical group:The bundles radiate from the dentinapical region of the root tothe surrounding bone boneFunction: resists verticalforce.5- Interradicular group: dentinThe bundles radiate from theinterradicular septum to thefurcation of the multirootedtooth. boneFunction: resists vertical and lateral forces.
  16. 16. B- Accessory fibers:They are collagenous in nature and run from boneto cementum in different planes, more tangentially toprevent rotation of the tooth and found in theregion of the horizontal group.
  17. 17. 2- Oxytalan fibersThese are immature elastic (pre-elastic) fibers.They need special stains to bedemonstrated.They tend to run in an axialdirection, one end being embeddedin bone or cementum and theother in the wall of blood vessels.At the apical region they form acomplex network.
  18. 18. The functions of oxytalan fibers:1-Support nerves. 2- Support blood vessels.3- Help fibroblasts migration.
  19. 19. Histological structureThe periodontal ligament is formed of : cells Intercellular substancesSynthetic Fibers,Resorptive ground substancesProgenitor blood vessels,Defensive nerves & lymphatics.
  20. 20. The cells Synthetic fibroblasts, osteoblasts and cementoblasts. cellsResorptive cementoclasts , osteoclasts and fibroclasts. cells Note that fibroblasts perform both synthetic and resorptive activities.Progenitor undifferentiated mesenchymal cells cells Epithelial cells remnants of the epithelialDefensive macrophage, lymphocytes root sheath of Hertwig cells and mast cells
  21. 21. Synthetic Cells of PDL Fibroblasts Cementoblasts Osteoblasts
  22. 22. PDL Fibroblasts • Oriented parallel to collagen fibers •Are motile due to contractile properties •Show numerous microtubules & microfilaments •Assembles procollagen molecules •Perform fibroclastic function •Ingestion collagen fibers •Contains intracellular collagen profiles & vacoules •Contains lysosomal system
  23. 23. Cementoblasts OsteoblastsBoth are rich in alkaline phosphatase activity.
  24. 24. Resorptive Cells of PDL• osteoclasts• cementoclastsBoth are rich in acid phosphataseactivity.
  25. 25. Progenitor cells .U. M. C• Can undergo mitotic devision• Can differentiate to different types of cells• Have small, closed- face nucleus• Little amount of cytoplasm• Found close to blood vessels
  26. 26. Defensive Cells of PDLMacrophages Mast cellslymphocytes Note: There are no plasma cells.
  27. 27. Epithelial Cells: remnants of the epithelial .root sheath of Hertwig•They are separated from thesurrounding connective tissue by abasal lamina.•They show low cells turnover,although they may proliferate to formcysts or tumors.
  28. 28. Histological structureThe periodontal ligament is formed of : cells Intercellular substancesSynthetic Fibers,Resorptive ground substancesProgenitor blood vessels,Defensive nerves & lymphatics.
  29. 29. Interstitial tissues*They are found between thefibers of the periodontalligament.*They are areas thatcontain some of the bloodvessels, lymphatic andnerves.*They are surroundedby loose connective tissue.
  30. 30. Blood supplyThe arterial blood supply of the periodontal ligament is derived from 3 sources: 1- Branches from the gingival vessels. 2- Branches from the intra-alveolar vessels, these branches run horizontally and these constitute the main blood supply. 3- Branches from the apical vessels that supply the dental pulp.
  31. 31. Nerve supply: The nerve supply of periodontal ligament comes from either the inferior or superior dental nerves.1- Bundles of nerve fibers run from the apical region of the root towards the gingival margin.2- Nerves enter the ligament horizontally through multiple foramina in the bone.
  32. 32. Are responsible forSmall nerve fibers pain sensation Are responsible forLarge nerve fibers touch & pressure (mechanoreceptors)•Stimulation of the mechanoreceptors initiates a reflex jawopening.•This reflex is a protective mechanism to prevent forcesapplied to the teeth from reaching damaging levels.
  33. 33. Functions of the periodontal ligament:1- Supportive: Through the collagen fibers and the blood vessels. [*Periodontal ligament permits the teeth to withstand the considerable forces of mastication.*As the force is applied on the teeth, the wavy course of the collagen fibers gradually straightening out and then acting as inelastic strings. *Also periodontal fibers being non elastic prevent the tooth from being moved too far.
  34. 34. *Blood vessels and all the components of theligament act together as a hydraulic damperor shock absorber with the groundsubstance and the tissue fluid.
  35. 35. Dental implants lack periodontal ligament fibersand they have a rigid connection to bone(Osseointegration).
  36. 36. Periimplant tissues Titanium implant Sulcular epithelium Juunctional epithelium Connective tissue Bone
  37. 37. 2- Sensory:The periodontal ligament having the mechanoreceptors contributes to the sensation of touch and pressure onthe teeth. proprioceptive reflexsudden overload inhibition of the activity of the masticatory muscles Opening the mouth
  38. 38. 3- Nutritive:The blood vessels in the periodontal ligament providenutrient supply required by the cells of the ligament andto the cementocytes and the most superficial osteocytes.4- Formative:The fibroblasts are responsible for the formation of newperiodontal ligament fibers and dissolution of the oldfibers Cementoblasts and osteoblasts are essential in building up cementum and bone.
  39. 39. 5- ProtectiveThe protective function of the periodontal ligament is achieved by:a- The principal fibers.b- The blood vessels.c- The nerves.a- The principal fibers: The arrangement of the fiber bundles in the different groups is well adapted to fulfill the functions of the periodontal ligament.The alveolodental ligament transforms the masticatory pressure exerted on the tooth into tension or traction on the cementum and bone.If the exerted force on a tooth is transmitted as pressure this will lead to differentiation of osteoclasts in the pressure area and resorption of bone.
  40. 40. b- The blood vessels:The capillaries form a rich network, they are arranged in form of a coil and attached to bone and cementum through the oxytalan fibers.This arrangement makes it possible when pressure is exerted on the tooth, the blood does not escape immediately from the capillaries and thus buffering the pressure action before it reaches the bone.The behavior of the blood in the capillaries may be simulated to a hydraulic brake.c- The nerves:By its mechanoreceptors nerves.
  41. 41. The Age Changes of periodontal ligament*The periodontal ligament through aging shows Vasuclarity Cellularity Thickness*It may contain cementicles.
  42. 42. The cementicles appear near the surface of cementum may be free , attached or embedded in the cementum.They have nidus favoring the deposition of concentric layers of calcosphrite as degenerated cells, area of hemorrhage and epithelial rests of Malassez.Cementicles are usually seen in periodontal ligament by aging but in some cases they may be seen in a younger person after local trauma.
  43. 43. Thank you &good luck

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