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What is the main function of the periodontal ligament in terms of protecting vessels and nerves?
What percentage of the ground substance is made up of water?
What is the name of the calcified masses that may be present in the periodontal ligament?
What is the main component of the ground substance in the periodontal ligament?
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Which nerve is responsible for innervating the periodontal ligament?
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Where do the blood vessels in the periodontal ligament come from?
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What are the terminal portions of the principal fibers that insert into cementum and bone called?
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What is the characteristic of the fibers that form a continuous anatomizing network?
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Which type of fibers run from the cementum of one tooth to the cementum of an adjacent tooth?
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What is the function of alveolar crest fibers?
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Which type of fibers are the largest group and extend from the cementum in a coronal direction obliquely to the bone?
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What is the characteristic of apical fibers?
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What is the function of the true periodontal ligament fibers?
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What is the characteristic of the fibers that run in all directions, forming a plexus?
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What is the primary function of the periodontal ligament?
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What is the approximate width of the periodontal ligament?
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What is the shape of the periodontal ligament?
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What is the main component of the periodontal ligament fibers?
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What is the function of the principal fibers of the periodontal ligament?
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What is the radiographic appearance of the periodontal ligament?
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What is the state of the periodontal ligament?
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What is the width of the periodontal ligament affected by?
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Study Notes
Periodontal Ligament
- A connective tissue structure that surrounds the root and connects it to the bone.
- Continuous with the gingival fibers, and communicates with the bone through vascular channels.
- In a healthy tooth, it covers the root up to the cemento-enamel junction.
- Appears as a radiolucent line paralleling the root surface in radiographs.
- The width of the periodontal ligament varies from tooth to tooth and within the same tooth, approximately 0.25 mm (range 0.2-0.4 mm).
- The width of the periodontal ligament decreases with age.
- The shape of the periodontal ligament is an hourglass, narrowest at the mid-root level.
Functions of PDL
- SUPPORT: Supports teeth in their socket, preventing loosening.
- MASTICATORY LOAD: Permits teeth to withstand the considerable forces of mastication.
- SENSORY: Supplied by abundant receptors and nerves that sense movement when teeth are in function, helping in proper positioning of the jaws.
- NUTRITIVE: Blood vessels provide essential nutrients for the ligament's vitality and hard tissue of cementum and alveolar bone.
Microscopic Feature
- The periodontal ligament is formed of cells and an extracellular component.
- The extracellular compartment consists of well-defined collagen fiber bundles embedded in the ground substance, comprising glycosaminoglycans, glycoproteins, and glycolipids.
PDL Fibers
- Mainly formed of collagen fibers, with other fibers including oxytalan fibers and indifferent fiber plexus.
- The predominant collagens of PDL are types I, III, arranged in distinct and definite fiber bundles.
- The principal fiber bundles consist of individual fibers that form a continuous anatomizing network.
Principal Fiber Bundles of PDL
- Fibers are grouped into:
- Transeptal fibers: run from the cementum of one tooth to the cementum of an adjacent tooth.
- Alveolar crest fibers: extend obliquely just apical to the junctional epithelium to the alveolar crest.
- Horizontal fibers: extend at right angles to the long axis of the tooth.
- Oblique fibers: extend from the cementum in a coronal direction obliquely to the bone.
- Inter radicals fibers: fan-out in multirooted teeth.
- Apical fibers: do not occur on incompletely formed roots.
Cellular Elements
- Cells can be grouped into four groups:
- C.T cells: fibroblast, cementoblast, osteoblast.
- Epi.Cells: rest of Malassez, distributed close to the cementum.
- Defence cells: macrophages, mast cells.
- Cells associated with neurovascular elements.
Ground Substance
- Has two main components: glycosaminoglycans (hyaluronic acid and proteoglycans) and glycoproteins (fibronectin and laminin).
- Water content is 70%.
Physical Function
- Provision of a soft tissue "casing" to protect the vessels and nerves from injury by mechanical forces.
- Attachment of the teeth to the bone.
- Maintenance of the gingival tissues in their proper relationship to the teeth.
- Transmission of occlusal forces to the bone.
- Resistance to the impact of occlusal forces (shock absorption).
Nerve and Blood Supply
- Nerves of the periodontal ligament are responsible for pain, tactile sensation, proprioception, and pressure, innervated by the IV cranial nerve.
- Blood vessels come from the supra-alveolar and infra-alveolar artery.
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Description
This quiz covers the anatomy and characteristics of the periodontal ligament, a connective tissue structure surrounding the root of a tooth. Learn about its functions, appearance in radiographs, and variations in width.
