Periodontal Ligament Histology PDF 13/10/2021

13/10/2021 Histology of the Periodontal Ligament Intended Learning Outcomes By the end of the session students should be able to:  Define the periodontal ligament and explain its functions.  Explain how the periodontal ligament develops and part of tooth development.  Discuss the cellular...

13/10/2021 Histology of the Periodontal Ligament Intended Learning Outcomes By the end of the session students should be able to:  Define the periodontal ligament and explain its functions.  Explain how the periodontal ligament develops and part of tooth development.  Discuss the cellular and extra cellular components to the periodontal ligament.  Explain the nerve and blood supply to the periodontal ligament.  Discuss location, origin, insertion and significance of principal fibres of the periodontal ligament. 2 1  13/10/2021 Formative Summative  Class contribution  Quiz  E-assessment  Unseen case 3 GDC Learning Outcomes 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their application to patient management 4 2  13/10/2021 What is the periodontal ligament?  The periodontal ligament is the connective tissue that surrounds the root and connects it with the bone.  It is continuous with the connective tissue of the gingiva and communicates with the marrow spaces through vascular channels in the bone.  At the root apex, the PDL merges with the dental pulp. 5 Functions of periodontal ligament Sensory Physical Formative & Nutritive (remodelling)resorptive 6 3  13/10/2021 Average width of PDL – 0.2mm (range 0.15mm to 0.38mm) Width of PDL in different loading conditions Width of PDL Heavy loaded Normally loaded Functionless Near crest of 0.35mm 0.14mm 0.10mm alveolus Middle of alveolus 0.28mm 0.10mm 0.06mm Near fundus of 0.30mm 0.12mm 0.06mm alveolus 7 PDL on a radiograph  The ligament appears as the periodontal space on radiographs  Radiolucent area between the lamina dura of alveolar bone proper and radiopaque cementum  Narrower in permanent teeth than deciduous teeth 8 4  13/10/2021 The PDL forms from the dental follicle shortly after root development begins 9 Development of PDL  As crown comes to oral mucosa fibroblasts in follicle become active & produce….  Initially fibres lack organisation but then become oblique to tooth  1st fibres are apical to CEJ & give rise to gingivodental fibres.  As eruption progresses more fibres develop and become attached to new cementum and bone. 10 5  13/10/2021 Development of PDL  In eruption cemental Sharpey’s fibres appear first followed by Sharpey’s fibres in bone.  SF’s in bone are fewer and model spaced.  After, alveolar fibres extend into the middle zone to join the lengthening cemental fibres & gain their thickness & strength when in occlusal function. 11 Structural elements of PDL PDL Extra Cellular Cells Substance Synthetic Fibres Resorptive Ground Substances Progenitor Defence Epithelial Rests of Malassez 12 6  13/10/2021 Blood supply to periodontal ligament  Principal blood supply - superior & inferior alveolar arteries. i. Apical vessels ii. Penetrating vessels from the alveolar bone iii. Anastomosing vessels from the gingiva.  These vessels anastomose freely within the ligament, occupying the interstitial spaces. 13 Nerve supply to periodontal ligament  2 types of nerves: 1. Sensory 2. Autonomic Branches of second & 3rd division of 5th cranial nerve (trigeminal nerve) 14 7  13/10/2021 Fibres of periodontal ligament  All made from collagen  PDL wider near apex and cervical margin of tooth  Most are principal fibres – organised into groups according to orientation and function (resemble spliced ropes)  Distribute forces of mastication & speech  Principal fibres of PDL embedded into cementum & bone = Sharpey’s fibres 15 Principal fibre groups  Main principal fibres Consist of 5 groups: 1. Alveolar crest group 2. Horizontal group 3. Oblique group 4. Apical group 5. Interradicular group  Overall function to resist rotational forces 16 8  13/10/2021 Alveolar Crest Group Fibres Location Just beneath junctional epithelium Origin Cementum, below CEJ Insertion Runs downwards & outwards & inserts into alveolar crest Significance Prevents extrusion of tooth from socket and resists lateral, tilting & intrusive tooth 17 displacement Horizontal Group Fibres Location th Limited to coronal one 4 of PDL Origin Cementum, apical to the alveolar crest group Insertion Runs at right angles to long axis of the tooth & inserts into the bone apical to the alveolar crest Significance Resists horizontal & tipping forces 18 9  13/10/2021 Oblique Group Fibres Location 2 thirds of length of the PDL Origin Cementum Insertion Runs obliquely in coronal direction & inserts into alveolar bone Significance Is the largest group Resists the vertical masticatory forces, thereby 19 preventing intrusion of the tooth Apical Group Fibres Location Root tip Origin Cementum, around the apex of the tooth Insertion Fans out in an irregular fashion and is inserted into the apex of the socket Significance Not found in incompletely formed roots Resists vertical, luxative & twisting forces Protect delicate nerves and vessels at the apex 20 10  13/10/2021 Inter-radicular Group Fibres Location Found in multi rooted teeth Origin Cementum Insertion Inter-radicular septum Significance Resists vertical & lateral movement Tipping, torquing & luxation are also resisted 21 Periodontal disease – total loss of fibres Interdental ligament or transseptal fibres  Important fibres which run through gingival mucosa to connect neighbouring teeth  Insert interdentally into cervical cementum of neighbouring tooth over alveolar crest  Fibres travel from cementum to cementum with no bony attachment  Resist rotational forces & keep teeth in alignment 11  13/10/2021 Gingival fibre group  Name given to separate but adjacent fibre groups found within lamina propria of marginal gingiva  Revise Gingival Histology Lecture Ground Substance Content Functions  Collagen fibres  Exchange of metabolites  Ion & water binding  Water 70%  Fibre orientation  Tooth support and binding mechanisms  Tissue fluid pressure high, 10mm Hg above atmospheric pressure 24 12  13/10/2021 Ages changes 25 Age changes  Decrease in cells  Increase in fibrous tissue  Decrease in vascularity, mitotic activity  Narrowing of width of PDL  Scalloping seen on calcified tissues (bone, cementum)-pdl attached to the peaks of these scallops 26 13  13/10/2021 Clinical Considerations 27 Given new knowledge what can you see the clinical considerations being when thinking about the PDL? PUT ON DISCUSSION BOARD 28 14  13/10/2021 Image references  https://www.slideshare.net/jazxh/radiographic-interpretation- 38070055  https://www.slideshare.net/DrJohnnKazimm/pdl-29808197  https://pocketdentistry.com/fundamentals/  Periodontal ligament in health, its structure and functions (periobasics.com)  Periodontal Ligament PDL [Quick Notes With Charts and Diagrams For Exams]  (dentomedia.info) 11. Periodontium: Periodontal ligament | Pocket DentistryIs  Aging Reversible? Scientists Find Way to Reverse Aging in Cells - Industry Tap 29 15