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Periodontal ligament 牙周韌帶

Periodontal ligament 牙周韌帶. 何坤炎副教授：高醫醫學大學 口腔醫學院牙醫學系 07-3121101 轉 7004 , 7029 kuyeho@kmu.edu.tw. 學習目標：. 牙周組織解剖結構及顯微結構 牙周組織的進化與發展 牙周組織的神經、血管 牙周組織的功能. 學習資源： 1. Ten Cate’s Oral histology. sixth edition, pp 241-274

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Periodontal ligament 牙周韌帶

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  1. Periodontal ligament 牙周韌帶 何坤炎副教授：高醫醫學大學 口腔醫學院牙醫學系 07-3121101轉 7004 , 7029 kuyeho@kmu.edu.tw

  2. 學習目標： • 牙周組織解剖結構及顯微結構 • 牙周組織的進化與發展 • 牙周組織的神經、血管 • 牙周組織的功能 學習資源： 1. Ten Cate’s Oral histology. sixth edition, pp 241-274 2. Rateitschak, Wolf, and Hassel: Color Atlas of Periodontology. 1st edition, 1985 3. Berkovitz BK , Holland GR, Moxham BJ.: Color atlas & textbook of oral anatomy. 1978 4. Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p133 -140

  3. Periodontium(牙周組織) Periodontal ligament Gingiva(牙齦) Cementum (牙骨質) Alveolar bone (齒槽骨) Rateitschak, Wolf, and Hassel: Color Atlas of Periodontology. 1st edition, 1985, p 1

  4. Periodontal ligament *It is attached to the dentine of the root by cementum and to the bone by alveolar bone. 牙周韌帶藉著牙骨質與牙本質附著,藉著 齒槽骨與骨頭附著 *It acts as adapting apparatus for support of the teeth during function 當行使功能時，作為適應的工具以支持牙齒

  5. 1. PDL located between the cementum and the periodontal surface of the alveolar bone. 2. It surrounds the necks and roots of teeth. 3. It is a fibrous connective tissue, abundant with cellularity and vascularity. Ten Cate’s Oral histology. sixth edition, p 261,Fig.9-20

  6. PDL contains a heterogeneous population of • mesenchymal cells , when triggered appropriately, • can differentiate toward an cementoblast or • osteoblast phenotype, that can promote formation • of bone and cementum • Perivascular and endosteal fibroblasts when • appropriately induced, have the capacity to form • PDL, cementum, and bone

  7. Compelling (令人信服的) evidence indicating that • populations of cells within the PDL, during • development and during regeneration, secrete factors • that can regulate the extent of mineralization • Factors secreted by PDL fibroblasts may inhibit • mineralization and prevent the fusion of tooth root • with surrounding bone; for example, ankylosis

  8. PDL * It ranges in width from 0.15 to 0.38 mm, with thinnest portion around middle third of the root(最窄部分在 牙根中間1/3處) * A progressive decrease with age * Tension and pressure site Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p139, Fig. 11-18 From KMUH

  9. Sharpey’s fibers (夏庇氏纖維) These fibers are embedded in the cementum and serve as an attachment for the tooth to the surrounding bone. 夏庇氏纖維埋在牙骨質做為牙齒與周遭 骨頭之附著

  10. Sharpey’s fibers (夏庇氏纖維) The principal fibers are more numerous but smallerat their attachment to cementum than at the alveolar bone

  11. Evolution of PDL • The central points of coordinated in the jaws is the radical reconstruction of the mandible. • In ancestral reptiles(爬蟲類)the teeth are ankylosed (連黏) to the bone. In mammals they are suspended (懸掛) in their sockets by ligaments. • The mandibular articulation is formed by a separated bone of mandible , articulare and quadratum.

  12. Evolution of PDL (cont’) 3. Dentary attains larger proportion of mandible → finally forms mammalian mandible. articulare → malleus (槌骨), quadratum →incus (砧骨) Dentary growing a condylar process, formed a new temporomandibular joint (顳顎關節)

  13. Evolution of PDL (cont’) 4. In reptile, the growth of mandible is “suture” in mammal the cartilage of the condylar as the most important growth site of the mandible. 5. In reptile, the growth of mandiblar body in height occurs in mandibular sutures where in mammals is occurred by growth at the free margins of the alveolar process.

  14. Development of PDL * The cells of the dental follicle give origin to fibroblasts of the developing PDL. The formation of PDL occurs after the cells of Hertwing’s epithelial root sheath (HERS) have separated, forming the epithelial rests of Malassez.

  15. Development of PDL A.Epithelial root sheath B. Undifferentiated mesenchyme of dental papilla C. Dental follicle D. Odontoblasts E. Epithelial rests F. Cementoblasts G. Developing alveolar bone H. Developing cementum J. Developing PDL Berkovitz BK ,Holland GR, Moxham BJ.: Color atlas & textbook of oral anatomy. 1978, p170 Fig. 443

  16. Cells of PDL * It divided into various categories: • Synthetic cells: 1. fibroblasts 2. osteoblasts 3. cementoblasts B. Resorptive cells: 1. fibroclasts 2. osteoclasts 3. cementoclasts C. Progenitor(原始細胞) D.Epithelial rests of Malassez E.Other: 1. mast cells 2. macrophages

  17. Synthetic cells(合成細胞) * Synthesizing proteins for secretion 1. a large open-faced or vesicular (胞狀的) nucleus containing prominent nucleoli (核仁) 2. cytoplasm---hematoxyphilic---interaction of RNA with acid hematin in H&E stain 3. clear, unstained Golgi membrane

  18. Fibroblasts(成纖維細胞) * They are surrounded by fibers and ground substance and orientated parallel to the orientated bundles of collagen fibers Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p138 Fig. 11-16

  19. Osteoblasts (造骨細胞) * Covering the periodontal surface of the alveolar bone constitute modified periosteum Berkovitz BK , Holland GR, Moxham BJ.: Color atlas & textbook of oral anatomy. 1978, p117, Fig. 302

  20. Cementoblasts(造牙骨質細胞) * Similar to the distribution of osteoblasts on the bone surface Berkovitz BK ,Holland GR, Moxham BJ.: Color atlas & textbook of oral anatomy. 1978, p117 Fig. 300, 301

  21. Osteoclasts(破骨細胞) * Large and multinucleated, or small and mononuclear (大而多核巨細胞) * The characteristic multinucleated giant cells exhibit eosinophilic cytoplasm. * It occupy in Howship’s lacunae, or surround the end of a bone spicule in light microscope. Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p149 Fig.12.16

  22. * Osteoclasts are seen regularly in normal functioning PDL, in which the cell play an art in removal and deposition of bone that constitutes its remodeling (重塑形) * Characteristic folds is termed ruffled or striated border.It disappears in inactive osteoclasts

  23. Osteoclasts (cont’) • Resorption occurs in : stage 1: demineralization at the bone margin stage 2: disintegration (不結合) of the exposed organic matrix

  24. Cementoclasts (破牙骨質細胞) • In PDL but undergo continual deposition during life. • The cells located in Howship’s lacunae and the surface of the cementum. From KMUH

  25. Progenitor cells * Undifferentiated and have the capacity to undergo mitotic division(有絲分裂) * Stimulated appropriately, they undergo division and one of the daughter cells differentiated into a functional type of connective tissue cell

  26. Epithelial rests of Malassez • Remnants of the epithelium of HERS • Network, strands, tubules rapid proliferation to producecyst (囊腫) and tumors Berkovitz BK , Holland GR, Moxham BJ.: Color atlas & textbook of oral anatomy. 1978, p118 Fig. 304,305

  27. Extracellular substance * Fibers: collagen (膠原纖維) oxytalan (抗酸纖維) * Ground substance: Proteoglycans (酸性黏多醣) Glycoproteins(醣蛋白)

  28. Ground substance(基質) of the PDL 1. It is occupied the space between the cells fibers, bloods and nerves 2. Comprises two major groups 1) proteoglycans or acid mucopolysaccharides(酸性黏多醣) 2) glycoproteins(醣蛋白)

  29. Fibers of the PDL Many of collagen fibers are gathered together to form bundles, each bundle or principal fiber having a diameter of about 5µm, though smaller bundles may be seen.

  30. Principal fibers of the PDL • Alveolar crest group(齒槽向組) • Horizontal group(水平組) • Oblique group (斜向組) • Apical group (根尖組) • Interradicular group (根間組) Ten Cate’s Oral histology. sixth edition, p 266, Fig.9-25A

  31. Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p134 Table 11-1

  32. Interstitial space (裂縫間隙) Contain a network of blood vessels, nerves, lymphatics, also a network of finer fibers interlace (交錯) and support the dense collagen bundles Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p133 Fig. 11-2B

  33. Interstitial space Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p137 Fig. 11- 13, 11-14

  34. Oxytalan(抗酸纖維) • They are immature elastic fibers（彈性纖維） • Run in an axial direction, one end embedded in cementum and the other often in the wall of a blood vessel. 3. Function in supporting the blood vessel and collagen fibers

  35. Oxytalan(抗酸纖維) Berkovitz BK , Holland GR, Moxham BJ.: Color atlas & textbook of oral anatomy. 1978, p115 Fig. 294 Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p133 Fig. 11-3

  36. Structure of PDL A. Blood vessels • from apical vessels • from intra-alveolar vessels • from gingival vessels *在齒槽骨端較牙骨質端多 * 在韌帶之尖端及頸部有 豐富血管網

  37. Nerves 2. Two types of nerve fibers : 1) Large and myelinated(髓鞘), have knob- like (節瘤狀的)endings 2) Small and may not be myelinated, and end in branch 3) The larger fiber appear to be concerned withtouch and the small one with pain Berkovitz BK ,Holland GR, Moxham BJ.: Color atlas & textbook of oral anatomy. 1978, p119 Fig. 306B

  38. Functions of the PDL * Supportive • During mastication the compressed PDL provides support for the loaded tooth. 咀嚼時被壓縮的牙周韌帶提供牙齒的支持 • Collagen fibers and ground substance act as a cushion for the displaced tooth.膠原纖維及基質作為位移牙齒之襯墊

  39. Functions of the PDL * Supportive • Pressure of blood vessels provides a hydraulic mechanism for support of the tooth.血管的壓力提供支持牙齒的水力學機轉 * Nutritive Blood vessel provide anabolites andremove the catabolites

  40. Functions of the PDL (cont’) * Sensory Through nerve supply, it can detect the most delicate forces to the tooth and very light displacement of the tooth, and protects the tissue from the effects of excessively vigorous masticatory movement.

  41. Functions of the PDL (cont’) * Homeostatic（恆定） • The cell of the periodontal ligament have a capacity to resorb and synthesize extracellular substance of the connective tissue of the ligament. • If homeostatic mechanism are upset will result in ankylosis bone and tooth • If the balance between synthesis and resorption is disturbed, the quality of the tissue will be change.

  42. Homeostatic (cont’) 4. If loss of homeostasis function, much of extracellular substances of the ligament is lost, the width of the periodontal space is decreased.

  43. Clinical considerations 1. The thickness of PDL seems to be maintained by the functional movement of the tooth 2. Thin in functionless and embedded teeth wide in teeth that are under excessive occlusal stresses 3. Pulp inflammation apical granuloma (肉芽腫) or cyst(囊腫)

  44. 結論 1. PDL provides an attachment for the tooth to bone of the jaw while permitting the teeth to withstand the considerable forces of mastication 2. The balance between formation and maintenance of mineralized tissue versus soft connective tissue of PDL require finely regulated control over cells in the local area.

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