Periodontium brian


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Periodontium brian

  1. 1. PERIODONTIUM Oral mic anatomy and embyrology BEE
  2. 2. PERIODONTIUM Pulp cavity EnamelCementum DentinPDL GingivaAlveolar boneSharpeys fibers CementumAttachmentorgan Periodontal ligament Root canal Alveolar bone Apical foramen Alveolar vessels & nerves
  4. 4.  Four tissue supporting the tooth in the jaw ◦ Cementum ◦ Periodontal ligament ◦ Alveolar bone ◦ GingivaePeriodontium
  5. 5.  Thin layer of calcified tissue covering the root in the human teeth Present in the crowns of some mammals ◦ Adaptation to herbivorous diet One of four tissues supporting the tooth (periodontium) The least known of ◦ Periodontium tissues ◦ All mineralized tissuesCementum
  6. 6. 1) It covers and protects the root dentin (covers the opening of dentinal tubules) 2) It provides attachment of the periodontal fibers 3) It reverses tooth resorptionRole of Cementum
  7. 7.  Varies in thickness ◦ Thick @ apex (50-200 µm) & inter-radicular regions ◦ Thin cervically (10-15 µm) Contiguous with PDL Firmly adherent with root dentine Highly responsive mineralized tissue ◦ Maintenance of root integrity ◦ Maintenance of functional position of tooth ◦ Tooth repair & regenerationCementum
  8. 8. Varies in thickness: thickest in the apex andIn the inter-radicular areas of multirootedteeth, and thinnest in the cervical area10 to 15 m in the cervical areas to50 to 200 m (can exceed > 600 m) apically
  9. 9.  Slowly-formed throughout life Allowing continual reattachment of PDL fibers Cementum can be regarded as a mineralized component of PDL Precementum - a thin mineralized layer on the surface of the cellular cementum Similar to bone, however - ◦ Avascular & not innervated ◦ Less rapidly resorbed – orthodonticsCementum
  10. 10. Cement- enamel junction Pattern I ◦ Cementum overlaps enamel for a short distance ◦ Most predominant – 60% of sections Pattern II ◦ Enamel meet cementum at butt joint ◦ Occurs in 30% of sections Pattern III ◦ Enamel fails to meet cementum ◦ Dentine between them is exposed ◦ 10% of sections
  11. 11.  Pale yellow Softer than dentine Permeability ◦ Varies with age and type of cementum ◦ Decreases with age ◦ Cellular is more permeable ◦ More permeable than dentine Readily removed by abrasion after gingival recessionPhysical properties
  12. 12. Chemical properties Inorganic Organic Water By weight 65% 23% 12% By volume 45% 33% 22% Hydroxyapatite crystals similar to those in bone More concentration of trace elements (F) at surface F levels higher in acellular Collagenous organic matrix, primarily type I Molecules involved in PDL fiber reattachment &/or mineralization ◦ Bone sialoprotein, osteopontin & cementum-specific elements
  13. 13. Cellular and Acellular Cementum Acellular cementum: covers the root adjacent to dentin whereas cellular cementum is found in the apical area Cellular: apical area and overlying acellular cementum. Also common in interradicular areas Cementum is more cellular as the thickness increases in order to maintain Viability The thin cervical layer requires no cells to maintain viability as the fluids bathe its surface A: Acellular cementum (primary cementum) B: Cellular Cementum (secondary cementum)
  14. 14. A: Acellular cementum B: Hyaline layer of Hopwell-Smith C: Granular layer of Tomes D: Root dentinCellular: Has cellsAcellular: No cells and has no structureCellular cementum usually overlies acellular cementum
  15. 15. Acellular CellularVariations also noted where acellular and cellular reverse in positionand also alternate
  16. 16. CEMENTUM Canaliculus GT Lacuna of cementocyte DentinAcellular cementumCellular cementumHyaline layer(of Hopewell Smith)Granular layer of tomes Dentin with tubules
  17. 17. Cementoblast and cementocyteCementocytes in lacunae and the channels that their processes extend arecalled the canaliculiCementoid: Young matrix that becomes secondarily mineralizedCementum is deposited in increments similar to bone and dentin
  18. 18. Are acellular and cellular cementum formed from two differentsources?One theory is that the structural differences between acellular and cellularcementum is related to the faster rate of matrix formation for cellularcementum. Cementoblasts gets incorporated and embedded in the tissueas cementocytes.Different rates of cementum formation also reflected in more widelyspaced incremental lines in cellular cementum
  19. 19.  Presence or absence of cells ◦ Cellular cementum ◦ Acellular cementum Nature & origin of organic matrix ◦ Extrinsic fiber cementum ◦ Intrinsic fiber cementum ◦ Mixed fiber cementum CombinationsClassification of cementum
  20. 20.  Most common pattern- adjacent to dentine Structureless Afibrillar cementum ◦ Exists between  Acellular cementum  Hyaline layer (of Hopewell-Smith) ◦ Mineralized GS ◦ Covers cervical enamel ◦ Results following loss of REEAcellular cementum
  21. 21. •Fibres of Periodontal Ligament•Epithelial •CementumRests Acellular cementum •Root dentine
  22. 22.  Most common pattern ◦ Apical area ◦ Inter-radicular areas ◦ Overlying acellular dentine Cementocytes ◦ Inactive ◦ In lacunae – appear dark in GS ◦ Processes present in canaliculi ◦ Processes connected via gap junctionsCellular cementum
  23. 23. Cellular cementum
  24. 24.  Organic fibrous framework, groundsubstance, crystal type, development Lacunae Canaliculi Cellular component Incremental lines (also known as “resting”lines; they are produced by continuous but phasic, deposition of cementum)Cementum simulates bone
  25. 25. Clinical CorrelationCementum is more resistant to resorption: Important in permittingorthodontic tooth movement
  26. 26. Cementocytes vs.osteocytes Cementocytes ◦ More widely dispersed ◦ Randomly arranged ◦ Canaliculi oriented towards PDL – nutrition Osteocytes ◦ Osteon – Haversian system ◦ Organized cells ◦ Circumferential lamellae
  27. 27.  More common pattern ◦ Acellular – cervically ◦ Acellular closer to dentine ◦ Cellular – apically ◦ Cellular covers acellular Less common patterns ◦ Alternating ◦ Acellular overlies cellularRelationship between acellular& cellular cementum
  28. 28.  Extrinsic fiber cementum ◦ Fibers derived from inserting Sharpy’s fibers of PDL Intrinsic fiber cementum ◦ Run parallel to root surface at right angles to extrinsic fibers ◦ Fibers derived from cementoblastsExtrinsic & intrinsic fibercementum
  29. 29.  AEFC Over cervical half – 2/3s of the root Bulk of cementum in premolars First formed cementum - acellular Thickness of 15 µm All collagen are from Sharpy’s fibers Though GS from cementoblasts Fibers well-mineralizedAcellular extrinsic fibercementum
  30. 30.  CIFC Fibers deposited by cementoblasts Fibers run parallel to root surface No role of tooth attachment In apical 1/3 & inter-radicular areas May be ◦ Temporary – extrinsic fibers gain reattachment ◦ Permanent – without attaching fibersCellular intrinsic fiber cementum
  31. 31.  If cementum forms slowly in CIFCAcellular intrinsic fiber cemetum
  32. 32.  Alternating AEFC with CIFC Root apex Furcation areasCellular mixed stratifiedcementum
  33. 33.  Collagen fibers derived from ◦ Extrinsic fibers ◦ Intrinsic fibers Intrinsic fibers run between the extrinsic fibers Two types – rate of formation ◦ Acellular mixed-fiber cementum  Well mineralized fibers ◦ Cellular mixed-fiber cementum  Less well mineralized fibersMixed-fiber cementum
  34. 34.  Irregular rhythm of deposition Not related to activity & quiescence Related to ◦ Difference in the degree of mineralization ◦ Composition of organic matrix Imprecise periodicity Acellular – closer, thinner & regular lines Cellular - farther apart, thicker & irregular linesCemental incremental lines
  35. 35. Development of Cementum Cementum formation occurs along the entire tooth Hertwig’s epithelial root sheath (HERS) – Extension of the inner and outer dental epithelium HERS sends inductive signal to ectomesen- chymal pulp cells to secrete predentin by differentiating into odontoblasts HERS becomes interrupted Ectomesenchymal cells from the inner portion of the dental follicle come in with predentin by differentiating into cementoblasts Cementoblasts lay down cementum
  36. 36. How cementoblasts get activated to lay down cementum is not known3 theories:1. Infiltrating dental follicle cells receive reciprocal signal from the dentin or the surrounding HERS cells and differentiate into cementoblasts2. HERS cells directly differentiate into cementoblasts3. What are the function of epithelial cell rests of Malassez?
  37. 37.  Derive from dental follicle  Transformation of epithelial cellsCementoblasts
  38. 38. Incremental lines Cementum is formed rhythmically and can be seen as being composed of layers
  39. 39.  Less susceptibility to resorption than bone Localized resorption areas occur Could be caused by microtrauma May continue to root dentine By multinucleated odontoclasts Resorption filled by mineralized tissue (resembles cellular cementum) Reversal lineResorption & repair of cementum
  40. 40.  Wider uncalcified zone Less mineralized Smaller crystals Calcific globules are presentDifferences are related to different speed of formationReparative cementum vs.cementum
  41. 41.  Cemental callus ◦ Root fracture ◦ No remodeling to original dimensions of the root Cementicles ◦ Free or attached pieces in PDL ◦ Microtrauma ◦ Apical & middle 1/3s of root ◦ Root furcationClinical considerations
  42. 42. Clinical considerations Supra-eruption of teeth Tooth wear Local hypercementosis ◦ Reaction to PA inflammation ◦ Difficulty in extraction ◦ Paget’s disease – multiple teeth with hypercementosis Cementum narrowing root canal and shifting the junction between dental pulp & PDL cervically ◦ Pulp removal in RCT up to that point
  43. 43.  Dense fibrous connective tissue Occupies the area between the root of the tooth and the walls of the alveolar socket Derived from the dental follicle Continuous with ◦ the connective tissue of the gingiva above the alveolar crest ◦ The dental pulp at the apical foramenPeriodontal ligament PDL
  44. 44.  Variable in width, average 0.2 mm looks hourglass in shape Reduced in unerupted & non-functional teeth Increased in teeth subjected to heavy occlusal stress Narrows slightly withPeriodontal ligament agespace Narrower in permanent teeth
  45. 45.  Attachment Has a role in tooth eruption and support Its cells repair the alveolar bone & cementum Neurological control of mastication through itsFunctions of PDL mechanoreceptors
  46. 46.  Fibers Ground substance CellsComponents of PDL
  47. 47.  Collagen ◦ Type I (70% of fibers) ◦ Type III (20% of fibers)  Found in the periphery of Sharpy’s fibers attachment into alveolar bone ◦ Small amounts of type V, VI as well as basement membrane collagen IV & VII associated with the epithelial rests ◦ Highest turnover of collagen is in PDL  Higher near apex  Even across the width of PDL  Rate could be related to the amount of occlusal stress Oxytalan (in humans) or elastinFibers of PDL ◦ Attached into cementum ◦ May have a role in tooth support
  48. 48.  Fibers exist as bundles (principal fibers) running in different orientations in different regions ◦ Dentoalveolar crest fibers ◦ Horizontal fibers ◦ Oblique fibers ◦ Apical fibersPrincipal fibers of PDL ◦ Interradicular fibers  From crest of interradicular septum to furcation
  49. 49. Principal fibers of PDL
  50. 50.  Principal fibers embedded into cementum and bone More numerous but smaller at cemental end Mineralized andSharpy’s fibers unmineralized parts
  51. 51.  60% of PDL by volume Main components ◦ Hyaluronate GAGs ◦ Proteoglycans ◦ Glycoproteins Functions of GS ◦ Ion and water binding & exchange ◦ Control of collagen fibrillogenesis & fiberGround substance of orientation ◦ Tooth support & eruption - high tissue fluidPDL pressure
  52. 52.  Fibroblasts ◦ Fusiform cells with many processes Cells of PDL ◦ Functions – secretion and turnover of fibers  Regeneration of tooth support apparatus  Adaptive responses to mechanical loading Cementoblasts ◦ Cement-forming cells lining cemental surface ◦ Cuboidal cells Osteoblasts ◦ Bone-forming cells lining tooth socket ◦ Resemble cementoblasts
  53. 53.  Cementoclasts & osteoclasts ◦ Resorbing cells ◦ Howship’s lacunae Epithelial rests cells ◦ Cuboidal cells that stain deeply ◦ Close to cemental surface Defence cells ◦ Macrophages ◦ Mast cellsCells of PDL ◦ Eosinophils
  54. 54.  Separate from those entering pulp Some from alveolar bone through foramina Some from pulp through accessory canals Major vessels lie between principal fiber bundle close to alveolar bone Capillary plexus around the tooth Crevicular plexus of capillary loops Veins do not follow arteries but drain into intraalveolar venous networksBlood vessels of PDL
  55. 55.  Sensory ◦ Nociception ◦ Mechanoreception  Sensitivity to occlusal loads  Guidance to intercuspation Autonomic ◦ Associated with blood vesselsInnervation of PDL
  56. 56.  The alveolar process develops during the eruption of teeth Grows at a rapid rate at the free border Proliferates at the alveolar crest No distinct boundary exists between the body of the maxilla or mandible and the alveolar process If teeth are lost the alveolar bone disappearsAlveolar process
  57. 57. Development of bony crypt Deciduous tooth & permanent successor initially share crypt Bone subsequently forms to encase permanent tooth