Periodontal ligament
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The document provides information about the periodontal ligament (PDL). It defines the PDL as the specialized connective tissue that surrounds tooth roots and attaches them to the alveolar bone. The summary discusses that the PDL is composed of collagen fibers, fibroblasts and other cellular elements embedded in a ground substance. It has an average width of 0.2mm and develops along with root formation. The principal collagen fibers of the PDL, including alveolar crest fibers, horizontal fibers, oblique fibers and apical fibers, develop from the cementoblast surface and resist various forces on the teeth.
Periodontal ligament
- 1. GOOD MORNING
- 2. PERIODONTAL LIGAMENT A SEMINAR Presented By- Dr. Sneha Sharan MDS 1st year Department of Periodontology Seema Dental College & Hospital, Rishikesh
- 3. CONTENTS 1. Introduction 2. Definitions Of PDL 3. Synonyms 4. Structure 5. Average Width 6. Development Of PDL 7. Structural Components Of The PDL 8. Periodontal Fibers 9. Development Of Periodontal Fibers 10.Cellular Elements 11.Functions 12.Blood Supply 13.Nerve Supply 14.Clinical Correlation 15.References
- 4. Introduction ● Specialized fibrous connective tissue ● Surrounds & attaches roots of teeth to the alveolar bone ● Composed of complex vascular & highly cellular connective tissue ● Continuous with the connective tissue of the gingiva ● Avg. Width - 0.2mm ● Diminished around teeth that are not in function & in unerupted teeth
- 5. DEFINITIONS OF PDL ➢ Periodontal Ligament is composed of soft complex vascular & highly cellular connective tissue that surrounds the tooth roots & connects to the inner wall of the alveolar bone (Mc Culloch CA, Lekic P, Mc Kee MD Periodontal 2000 24:56, 2000) ➢ It is that soft, specialized CT situated between the cementum covering the root of the tooth & bone forming the socket wall. (A.R Tencate 1971) ➢ It is a narrow & highly cellular CT that form is the interface between alveolar bone & cementum. ( Periodontal 2000, vol. 3, 1993)
- 6. ➢Soft ,richly vascular & cellular connective tissue which surrounds the roots of the teeth & joins the root cementum with the socket wall. (Jan Lindhe 5th ed) ➢The periodontal ligament occupies the periodontal space, which is located between the cementum & the periodontal surface of alveolar bone & extends coronally to the most apical part of the lamina propria of the gingiva. (Orban’s)
- 7. SYNONYMS ❏ Gomphosis ❏ Desmodent ❏ Pericementum ❏ Dental Periosteum ❏ Alveo-dental ligament ❏ Periodontal membrane
- 8. Structure ● Hourglass shaped ● Widest cervically ● Dense, fibrous connective tissue ● Bears heavy occlusal stress ● Thickness decreases with age
- 9. AVERAGE WIDTH ● DEPENDING ON AGE: AGE AVERAGE WIDTH 11-16yrs 0.21mm 32-52yrs 0.18mm 51-67yrs 0.15mm
- 10. AVERAGE WIDTH ● According to the functional state of the tissues: Functional State AVERAGE WIDTH Time of eruption 0.1-0.5mm At Function 0.2-0.35mm Hypo Function 0.1-0.15mm
- 11. As the root formation continues, cells in the perifollicular mesenchyme gain their polarity, cellular volume & become widely separated Actively synthesize and deposit collagen fibrils & glycoproteins in developing PDL Type I Collagen is secreted Assembles as collagen bundles on the bone and cementum surface Establish Continuity across the ligament space DEVELOPMENT OFPDL
- 12. DEVELOPMENT OF PDL Jan Lindhe, Niklaus P.Lang, Thorkild Karring Clinical Periodontology & Implant Dentistry 5th Edition
- 13. Cellular Elements Periodontal Fibers Ground Substance 1. Synthesizing Cells: Fibroblasts, Cementoblasts, Osteoblasts 1. Principal Fibers Alveolar Crest Fibers , horizontal fibers, oblique fibers, apical fibers, interradicular fibers 1. Glycosaminoglycans a. Hyaluronic acid b. Proteoglycans 2. Resorptive cells: fibroblasts, cementoblasts, osteoclasts 2. Other Fibers Oxytalan fibers, elaunin fibers 2. Glycoproteins a. water b. fibronectin c. c. laminin 3. epithelial cell rests of malassez, progenitor cells, defense cells, such as mast cells & macrophages The structural components
- 14. Periodontal Fibers ● Most important element of PDL- Principal Fibers ● PRINCIPAL FIBERS: - Collagenous - arranged in bundles - follow wavy course (when viewed in LS)
- 15. Originate at surface of newly formed root dentin in close relation to highly polarized fibroblasts Nascent fiber bundles are tightly packed by action of cementoblasts during initial development of Acellular extrinsic fiber cementum. As PDL Matures, fringe fibers merge across the width of ligament to form principal fiber bundles Closely related to root formation DEVELOPMENT OF PRINCIPAL FIBERS
- 17. DEVELOPMENT OF PRINCIPAL FIBERS…. ❏ Terminal portions of principal fibers that insert into cementum and bone are termed as Sharpey’s fibers. ❏ The principal fibers embedded in the cementum have a small diameter but are more numerous than those embedded in the alveolar bone proper. ❏ In addition to these fiber types, small collagen fibers associated with larger principal fibers have been called as “Indifferent fiber plexus of Shefforfold”
- 18. ❏ Terminal portions of the principal fibers that are inserted into the cementum & bone are termed as - SHARPEY FIBERS
- 20. SHARPEY FIBERS ● Calcify to a significant degree ● associated with abundant noncollagenous proteins-typically found in bone
- 21. ALVEOLAR CREST GROUP ● Extend obliquely from the cementum just beneath the JE to the alveolar crest ● Prevent extrusion of the tooth and resist lateral tooth movements.
- 22. Transseptal Fibers ● Extend interproximally over the alveolar bone crest ● Embedded in cementum of adjacent teeth ● reconstructed even after destruction of alveolar bone ● do not have osseous attachment
- 23. Horizontal Fibers ● Extend at right angles to the long axis of the tooth from the cementum to the alveolar bone. ● Prevent Lateral tooth movement
- 24. Oblique Fibers ● Comprise the largest group in periodontal ligament ● Extend from cementum in a coronal direction obliquely to the bone ● Bear vertical masticatory stresses ● Transform such stresses into tension on the alveolar bone
- 25. Apical Fibers ● Radiate in irregular manner from cementum to the bone at the apical region of the socket ● Do not occur on incompletely formed roots. ● Prevent tipping ● Resist forces of luxation ● Protect blood, lymph & nerve supply
- 26. Interradicular Fibers ● Fan out form the cementum to the tooth in the furcation areas of multirooted teeth. ● Resist tipping of tooth. ● Forces of luxation & rotation
- 27. ● Other well-formed fiber bundles interdigitate at right angles between regularly arranged fiber bundles. ● Less regularly arranged collagen fibers are found in the interstitial connective tissue between the principal fiber groups; this tissue contains the blood vessels, lymphatics & nerves.
- 29. ● PDL does not contain mature elastin, 2 immature forms are found: oxytalan & elaunin ● OXYTALAN FIBERS: - Run parallel to root surface in a vertical direction - bend to attach to the cementum in the cervical third of the root - Regulate vascular flow ● Principal Fibers are remodeled by PDL cells to adapt to physiologic needs & in response to different stimuli.
- 30. ELASTIN FIBERS Restricted to walls of blood vessels in humans PDL fibers do not contain mature elastin but two immature forms are found oxytalan and eulanin.
- 31. OXYTALAN FIBERS ● Are micro fibrils ● Run in apico-coronal direction to bend and attach at cervical third of root (Fulmer et al. 1974) ● Diameter – 0.5-2.5mm ● Volume – 3% ● No cross banding seen ● Function - regulate vascular flow - play a role in tooth support - guides cell migration
- 32. Oxytalan fibers(stained dark purple) running in the apico occlusal direction. Note that their course does not correspond with that of the collagen fibers in the periodontal ligament.
- 33. ELUANIN FIBERS ● Are immature elastic fibers consisting of micro fibrils within small quantity of elastin ● An elastic meshwork has been described in the PDL as being composed of many elastin lamellae with peripheral oxytalan & eulanin fibers ● Functions - Regulate vascular flow - Role in tooth support - Facilitate fibroblast attachment and migration
- 34. RETICULIN FIBERS ● Reticular fibers, reticular fibres or reticulin is a type of fiber in connective tissue composed of type III collagen secreted by reticular cells. Reticular fibers crosslink to form a fine meshwork (reticulin). This network acts as a supporting mesh in soft tissues such as liver, bone marrow, and the tissues and organs of the lymphatic system. ● Reticular fiber is composed of one or more types of very thin and delicately woven strands of type III collagen. These strands build a highly ordered cellular network and provide a supporting network. Many of these types of collagen have been combined with carbohydrate. Thus, they react with silver stains and with periodic acid-Schiff reagent but are not demonstrated with ordinary histological stains such as those using hematoxylin. The 1953 Science article mentioned above concluded that the reticular and regular collagenous materials contains the same four sugars – galactose, glucose, mannose, and fucose – but in a much greater concentration in the reticular than in the collagenous material.
- 35. RETICULIN FIBERS
- 36. CELLULAR ELEMNTS
- 38. FIBROBLASTS ● Most common cells in the PDL ● Appear as ovoid / elongated cells oriented along the principal fibers ● Exhibit pseudopodia-like processes. ● Synthesize collagen ● Regulates collagen turnover
- 39. SEM IMAGE OF PDL FIBROBLASTS
- 40. FIBROBLASTS... ● Most common cells in PDL ● Occupies about 30% of the volume of the periodontal ligament space in rodents (Beertsen W, Brekelmans M, Everts V. 1978) ● Appear as ovoid or elongated cells oriented along the principal fibers, exhibiting pseudopodia like processes. ● In cross section, they may exhibit a stellate appearance with cytoplasmic process segregating individual fiber bundles of collagen fiber.
- 41. FIBROBLASTS... ● Phenotypically distinct & functionally different sub populations of fibroblasts exist in adult PDL. ● They may have different functions like secretion of different collagen types & production of collagenase. ● Importantly in inflammatory situations, an increased expression of MMP occurs that aggressively destroys collagen. ● Thus attractive therapies for controlling this may include host modulators to inhibit MMP.
- 42. FIBROBLASTS... ● The PDL fibroblasts are large cells with an extensive cytoplasm containing in abundance, all organelles associated with protein synthesis and secretion. ● They also have well developed cytoskeleton with a particularly prominent actin network. ● ATTACHMENTS The fibroblasts of PDL are interconnected by gap junctions or adherence type of junctions. ● The cells may attach to collagen via a fibro nexus type of attachment plaque and are likely to have the capacity to orient extracellular matrix.
- 43. FIBROBLASTS... ● The migratory and contractile activity of fibroblast is because of the presence of contractile protein actin and myosin in their cytoskeleton. ● It may: -Remain stationary and pull on adjacent structures -Crawl and cause the environment in which it lies to wrinkle.
- 44. FIBROBLASTS... ● Chemoattractants produced locally or by the hard tissues bordering the ligament may have a role in this process. ● Directed migration of cells is associated with polarity of organelles, the nucleus usually in the trailing portion of cell and golgi apparatus and centrioles are towards the leading edge of the cells. ● They appear to be rich in alkaline phosphatase activity an enzyme along outer plasma membrane that plays a key role in phosphate metabolism, probably in the mineralization process and in Acellular cementum formation.
- 45. Add Text Add Text Epithelial Rests Of Malassez ● Form a latticework in the PDL ● Appear as either isolated clusters of cells/interlacing strands ● Considered remnants of the hertwig’s root sheath ● Distributed close to the cementum ● Diminish in no. with age by undergoing calcification ● Surrounded by a distinct lamina ● Participates in formation of periapical cysts & lateral root cysts
- 47. ● Osteoblasts, Cementoblasts, osteoclasts & odontoclasts are also seen in the cemental & osseous surfaces of the PDL ● Defense Cells in the PDL include neutrophils, lymphocytes, macrophages, mast cells & eosinophils
- 48. Osteoblasts & Cementoblasts ● Although technically situated within the PDL, bone and cementum cells are properly associated with the hard tissues they form. ● Osteoblasts line the bone surface of the ligament and may be either functional or resting, depending on the functional state of the ligament. ● Cementoblasts are responsible for formation of cellular cementum.
- 50. Resorptive Cells ● Fibroblasts : - Exhibit lysosomes that contain fragments of collagen that appear to be undergoing digestion. - Dual action ● Osteoclasts & Cementoclasts: - Osteoclast cells resorb bone and tend to be large and multinucleated. - Cementoclasts resemble osteoclasts and are occasionally found in normal functioning PDL.
- 51. Progenitor Cells ● Cell division ---- daughter cell ---- undifferentiated progenitor CHARACTERISTICS ❏ Small cells ❏ Close faced nucleus ❏ Very little cytoplasm ❏ Highest concentrations' close to blood vessels ❏ Burst of mitosis occurs when pressure is applied
- 52. Defense Cells ❏ Include neutrophils, lymphocytes, macrophages,& eosinophil's. MAST CELLS ● Small round or oval cell; Diameter 12-15µm. ● Contain numerous cytoplasmic granules(0.5-1 µm) that stain metachromatically with dyes like azure A and positively by PAS reaction. ● Contain heparin & histamine. ● Role of heparin is not clear. Histamine plays a role in inflammatory reaction. Occasionally seen in healthy PDL. It may cause proliferation of endothelial & mesenchymal cells.
- 53. Defense Cells
- 54. Macrophages CHARACTERISTICS ● Found adjacent to the blood vessels ● Nucleus has a regular contour and may be horse shoe or kidney shaped with a dense peripheral layer of chromatin. ● Surface may be raised in microvilli. ● Sparse RER with widely spaced polysomes. ● Golgi apparatus is not well developed ● DUAL ROLE 1. Phagocytosing dead cells 2. Secreting growth factors that regulate the proliferation of adjacent fibroblasts.
- 55. Cementicles ● Calcified masses, adherent to or detached from the root surfaces (O.J. Mikola, Wm.H. Bauer,1949) ● Represent dystrophic calcification (example of regressive or degenerative change) ● Develop from: calcified epithelial rests, calcified Sharpey’s fibers, Calcified, thrombosed vessels within the PDL, around small spicules of cementum or alveolar bone traumatically displaced into the PDL
- 56. Cementicles... ● Too small to be seen on IOPA, seldom being larger than 0.2- 0.3 mm. in diameter. ● No clinical significance. ● Actually a variety of calcified bodies may occur in the PDL, not all of which have the morphologic characteristics of cementum. Nevertheless, they have all been commonly known as cementicles. ● The pattern of calcification often gives the appearance of a circular lamellated structure.
- 57. EXTRACELLULAR COMPONENTS FIBERS GROUND SUBSTANCE Collagen Proteoglycans Elastic Glycoproteins Reticular Secondary Indifferent Fiber Plexus Oxytalan
- 58. COLLAGEN ● Is derived from the French word collagene to designate connective tissue constituents that produce glue. ● Collagen molecule is rigid and resists stretching. Therefore it is utilized in tissues where mechanical forces should be transmitted without loss. ● Organization of collagen depends upon the specific functional requirements in various tissues.
- 59. COLLAGEN... STRUCTURE ● All collagens are composed of 3 polypeptide chains coiled around each other to form the typical triple helix configuration. Variations are brought about by ● Differences in assembly of the basic polypeptide chains ● Different lengths of helix ● Various interruptions in helix ● Differences in the terminations of the helical mains
- 60. UNIQUE STRUCTURAL PROPERTIES THAT DISTINGUISH COLLAGEN FROM OTHER PROTEINS ● Made up of 3 polypeptide chains ● α chains that are left handed chains assembled into a triple helix with a right handed twist. May be a homo-trimer or hetero-trimer. ● Has a repeating gly-X-Y amino acid sequence in which X and Y are usually amino acid other than glycine. ● Contain 2 unique amino acid hydroxy proline and hydroxy lysine along with glycine & proline (Carneiro J, Fava de Moraes F , 1955) ● Collagen molecules are covalently linked through lysine derived intra and inter chain crosslink.
- 61. COLLAGEN... ● The amount of collagen in a tissue is determined by its hydroxy proline content. ● There are at least 19 recognized collagen species encoded by at least 25 separate genes, dispersed among 12 chromosomes (Embery et al 2000) Collagen classes a. Interstitial collagens ---- Type I,II,III b. Basement membrane type ---- Type IV,VI,VII c. Short chain collagens ---- Type IX,X
- 62. COLLAGEN... ● Type I, III, V, XII – Periodontal Ligament ● Type VI, II – cartilage ● Type IV - Basement membrane ● Type VI – Ligaments, skin, bone ● Type VII - Anchoring fibrils of basement membrane ● Type IX - Cartilage ● Type X, XI - Cartilage, Bone ● Type XIII - Epidermis Cartilage
- 64. COLLAGEN... ● The ligament fibers and Sharpey’s fibers are composed of interstitial collagen type III and I ● Collagen V is associated with these fibrils and is either buried within these fibrils or is found in the spaces between the fiber bundles. ● Type VI - microfibrillar component associated with oxytalan fiber system. ● Type XII contribute to the construction of 3-dimensional fibril arrangement- hence closely associated with regeneration of PDL
- 65. Formation Of Collagen Fiber Synthesized by - Fibroblasts, chondroblasts, osteoblasts, odontoblasts and other cells. The steps involved in biosynthesis of collagen fiber involve - Intra cellular pro collagen synthesis - Extra cellular collagen biosynthesis & fibril/fiber formation.
- 66. GROUND SUBSTANCE ● The ground substance is the gel like matrix synthesized by the fibroblasts family & fills the space between the fibers & cells. COMPOSITION ● Consists of a biochemically complex , highly hydrated semi solid gel. ● Water content of 70% ● Glycosaminoglycans- hyaluronic acid, ● Proteoglycans(versican,decorin) ● Glycoproteins-fibronectin,laminin,vibronectin,tenascin
- 67. GROUND SUBSTANCE ● Fills the space between the fibers and cells ● Overlooked possibly because difficult to investigate and not recognized in routine methods COMPOSITION ● Consists of a biochemically complex, highly hydrated, semisolid gel. ● Water content of 70% Glycosaminoglycan's – hyaluronic acid, proteoglycans( versican , decorin ) ● Glycoproteins -- fibronectin , laminin , vibronectin , tenascin
- 68. PROTEOGLYCANS ● Large group of anionic macromolecules that consists of a protein core to which are attached hexose amine containing polysaccharide called gag chains. ● Distribution in PDL is similar to gingival tissue. FUNCTIONS a. Cell adhesion b. Cell-cell & cell- matrix adhesion c. Cell repair d. Binding to various growth factors
- 69. GLYCOPROTEINS ● The primary function of these molecules is to bind cells to extracellular elements. ● Most widely studied is FIBRONECTIN ● Exists in one form as an insoluble connective tissue matrix protein which promotes the attachment and subsequent spreading of cells that bind to a fibronectin – collagen complex. ● The attachment and spreading of cells within the PDL collagen matrix is a pre requisite for both alignment of collagen fibers and for cell migration.
- 70. GLYCOPROTEINS... ● TENASCIN is an adhesive glycoprotein synthesized at specific times and location during embryogenesis. ● In adult its distribution is specific and restricted. ● It binds to fibronectin and to proteoglycans. ● It blocks the binding capacity of syndecan and thereby enables the cell to move freely
- 71. ➢PHYSICAL FUNCTIONS ➢FORMATIVE & REMODELING FUNCTION ➢NUTRITIONAL & SENSORY FUNCTIONS ➢REGULATION OF PERIODONTAL LIGAMENT WIDTH FUNCTIONS OF PDL
- 72. PHYSICAL FUNCTIONS ● Provision of a soft-tissue “casing” to protect the vessels & nerves from injury by mechanical forces. ● Transmission of occlusal forces to the bone ● Attachment of the teeth to the bone ● Maintenance of the gingival tissues in their proper relationship to the teeth ● Resistance to the impact of occlusal forces (i.e, shock absorption)
- 73. RESISTANCE TO IMPACT OF OCCLUSAL FORCES ( Shock Absorption): Two theories pertaining to the mechanism of tooth support have been considered: 1) TENSIONAL THEORY ❖ States that the principal fibers of the PDL are the major factors in supporting the tooth & transmitting forces to the bone ❖ When a force is applied to the crown,the principal fibers first unfold & straighten, & then they transmit forces to the alveolar bone, thereby causing an elastic deformation of the bony socket. ❖ Finally, when the alveolar bone has reached its limit, the load is transmitted to the basal bone.
- 74. 2) VISCOELASTIC THEORY ❖ States that the displacement of the tooth is largely controlled by fluid movements, with fibers having only a secondary role. (Bien SM,1996 & Bim H, 1966) Force applied on tooth Extra-cellular fluid from PDL escapes to marrow spaces Depletion of fluid, Fibers absorb slack & tigthen Blood vessels stenosis Arterial back pressure created Balloning of vessels Passage of blood ultra filtrates Lost fluid replenished
- 76. TRANSMISSION OF OCCLUSAL FORCES TO BONE ❏ Arrangement is like suspension bridge/Hammock ❏ The oblique fibers alter their wavy pattern & sustain the major part of the axial force AXIS OF ROTATION: ● Single rooted tooth at junction of middle & apical 3rd of the root. ● Multirooted tooth in the bone between the roots below furcation
- 78. ❏The apical portion of the root moves in a direction opposite to the coronal portion ❏Areas of tension- Principal fibre bundles are taut rather than wavy ❏Areas of pressure- Fibres are compressed, the tooth is displaced & a corresponding distortion of bone exists in a direction o tooth movement.(Picton DC, 1967)
- 79. Formative & Remodelling Function ● Occur during physiologic tooth movement, during the accomodation of the periodontium to occlusal forces, & during the repair of injuries. ● Variations in cellular enzyme activity are correlated with the remodelling process. ● PDL is constantly undergoing remodeling. ● Old cells & fibres are broken down & replaced by new ones. ● Rate of formation & differentiation of the fibroblasts affects the rate of formation of collagen, cementum & bone. ● Rate of collagen synthesis is twice as fast as that in the gingiva & four times as fast as that in the skin.
- 80. NUTRITIONAL ❏ Supplies nutrients to cementum, bone & gingiva by way of the blood vessels ❏ Provides lymphatic drainage ❏ PDL is highly vascularized tissue ❏ Rich network of arcades are more evident in the PDL space adjacent to the bone and cementum.
- 81. SENSORY ❏ PDL provides the most efficient proproceptive mechanism. ❏ 4 types of neural transmissions are seen 1) Free nerve endings-pain 1) Ruffini like mechanoreceptors(apical area) 1) Meissner's Corpuscles- mechanoreceptors (middle 3rd) 1) Spindle like pressure & vibration endings (apex)
- 82. REGULATION OF PDL WIDTH ❏ Adaptability to rapidly changing applied force ❏ Capacity to maintain its width at constant dimensions throughout its lifetime. ❏ Ability of PDL cells to synthesize & secrete a wide range of regulatory molecules is an essential component of tissue remodeling & PDL homeostasis.
- 83. BLOOD SUPPLY ● Branches of the intraseptal vessels-perforate the lamina dura & enter the ligament. ● After entering the PDL perforating rami anastomose & form a polyhedral network which surrounds the root like a stocking
- 84. ● Inferior & superior alveolar arteries to the mandible & maxilla reaches the PDL from 3 source: 1)Apical vessels (Dental Artery) 2)Transalveolar vessels( rami perforates - penetrating vessels from alveolar bone) 3)Intraseptal vessels (anastomosing vessels from the gingiva)
- 85. NERVE SUPPLY ● The nerve follow almost the same course as the blood vessels. ● Nerve bundle divide - myelinated fibers - lose their myelin sheath - end in one of the 4 types of neural termination
- 86. 1. Free nerve endings - terminal arborization of thick/fine myelinated fibers -0,21 um in diameter - fine, nonmyelinated fibers only type of ending in tooth pulp - classic model of pure nociception. 1. Ruffini- like - apical area 1. Meissner’s corpuscles- mid-root, for tactile perception 1. Spindle shaped(Krause type end bulbs)- temperature receptor, present at apex of the tooth
- 87. ● Development of a new technique in which the axons can be radioactively labeled & visualized by radioautography ● The PDL has double innervation: ➢Axons arising both from the mesencephalic nucleus - Unconscious reflex pathways & proprioceptors- position control of the mandible ➢Axons from the trigeminal ganglion - Conscious sensation of touch, pain & temperature
- 88. CLINICAL CORRELATION ❏ Trauma to the ligament due to mechanical separation can produce pathological changes such as fracture or resorption of the cementum, tears of fiber bundles, hemorrhage and necrosis. ❏ This result in resorption of bone and periodontal ligament is widened, so the teeth become loose. ❏ Orthodontic tooth movement depends on resorption and formation of both bone and periodontal ligament- ->stimulated by both tension and pressure Application of large forces->necrosis of periodontal ligament(28)
- 89. CLINICAL CORRELATION ❏ In SCLERODERMA, the periodontal ligament is uniformly widened at the expense of surrounding alveolar bone. ❏ Malignancy, both primary and metastatic, can affect the alveolar ridge and often presents as periodontal disease. ❏ A uniform widening of the periodontal ligament can be an early sign of osteosarcoma. Irregular destruction of the periodontal bone without tooth displacement is frequently the result of squamous cell carcinoma or metastatic carcinoma.
- 90. PDL Relationship With Implants ● Implants do not employ a gomphosis to provide support & attachments to the jaw bones as does the PDL, but still it serves as a replacement for natural teeth . ● The absence of PDL around implants- absence of resilient connection between teeth & jaw bones thus any occlusal disharmony will have repercussions at bone to implant interface. ● No intrusion or migration can compensate for the eventful presence of a premature contact. ● Absence of PDL leads to: reduced tactile sensitivity reduced reflex functions ● Even if certain degree of perception is present- Osseoperception
- 92. PDL WITH IMPLANTS Periodontitis is the inflammation of hard and soft tissues of periodontal structures; if left untreated may lead to the tooth loss. Replacement of the missing tooth with an implant has gained immense popularity in the last few decades. Currently, development of a periodontal ligament (PDL) attachment around dental implants has now become an important new therapeutic tool to replace lost teeth. PDL houses various vital cells that are all important in the dynamic relationship between the tooth and the bone. Thus, ligaplants are now an available option to improve the biological performance and to prolong the life of the prosthesis.
- 93. CONCLUSION ● The periodontal ligament is a fibrous connective tissue forming important part of periodontium. ● The PDL is a physically small, but functionally important tissue in tooth support,proprioception, & regulation of alveolar bone volume. ● The PDL is an absolute requirement for rapid remodelling of alveolar bone when forces are applied to the teeth. ● Cell of the periodontal ligament are pluripotent & helps in the regeneration of all the components of the Periodontium lost in the periodontal disease process.
- 94. REFERENCES ● Carranza’s Clinical Periodontology, 10th Edition ● Clinical Periodontology and Implantology by Jan Lindhe, 5th edition ● Oral Histology and Embryology by Orban, 11th edition ● Tencate oral histology, 5th edition ● Fundamentals of Periodontics, 2nd Edition, by Thomas G. Wilson, Kennath S. Kornman ● Hassel TM. Tissues and cells of periodontium. ● Periodontol 2000, Vol. 3, 1993, 9-38. The Periodontium - Hubert E Schroeder