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Structure and Function of the Periodontal Ligament (PDL)
What is the Periodontal Ligament (PDL)?
A soft, connective tissue situated between the alveolar bone proper and the cementum covering the root of the tooth.
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Structure and Function of the Periodontal Ligament (PDL)
How does the PDL communicate with the dental pulp?
Through the apical foramen of the tooth.
What is the role of fibroblasts in the PDL?
They secrete collagen and are responsible for the high turnover of proteins, particularly collagen.
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Alveolar Bone Structure and Function
What is alveolar bone proper?
The bone of the alveolar process that lines the sockets for teeth (alveoli).
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Alveolar Bone Structure and Function
Why does alveolar bone proper appear radiopaque?
Due to the presence of thick bone without trabeculations.
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Orthodontic Tooth Movement Mechanisms
What occurs on the opposite side of the tooth during orthodontic movement?
The periodontal ligament fibers are compressed, causing inflammation and upregulation of RANKL, leading to bone resorption.
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Principal Fiber Groups of the PDL
What are the principal fiber groups of the periodontal ligament (PDL)?
They include the alveolar crest group, horizontal group, oblique group, apical group, and interradicular group.
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Alveolar Bone Structure and Function
What is bundle bone?
The inner aspect of alveolar bone proper that is more compact.
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Alveolar Bone Structure and Function
What are Sharpey's fibers?
Periodontal ligament fibers embedded in alveolar bone proper and mineralized at their periphery.
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Principal Fiber Groups of the PDL
What is the function of the apical group of PDL fibers?
They radiate from the cementum around the apex of the root to the bone, forming the base of the socket.
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Principal Fiber Groups of the PDL
Where is the interradicular group of PDL fibers found?
Only between the roots of multirooted teeth.
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Development of Alveolar Bone Proper
From where do osteoblasts that form the alveolar bone proper originate?
They differentiate from the dental follicle as part of the periodontium.
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Development of Alveolar Bone Proper
What is the embryological origin of the alveolar process?
It has the same embryological origin as the body of the mandible and maxilla, formed from intramembranous bone formation from ectomesenchymal cells.
What types of cells are present in the PDL?
Osteoblasts, osteoclasts, fibroblasts, epithelial cell rests of Malassez, macrophages, undifferentiated mesenchymal cells, and cementoblasts.
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Blood Supply and Innervation of the PDL
Where are more blood vessels found in the periodontal ligament?
In the gingival area compared to the rest of the PDL.
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Structure and Function of the Periodontal Ligament (PDL)
What are the formative and remodeling functions of the PDL?
Formation and resorption of cementum and bone during physiologic tooth movement.
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Structure and Function of the Periodontal Ligament (PDL)
What occurs in the PDL under heavy occlusal stress?
The space is widened and collagen bundles thicken to accommodate the increased force.
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Alveolar Bone Structure and Function
What is the alveolar process?
The bone of the jaws that contains the sockets for the teeth.
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Alveolar Bone Structure and Function
What is the difference in spongiosa between posterior and anterior regions of the alveolar bone?
There is more spongiosa in the posterior regions (near molars), while the anterior region has no spongiosa.
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Alveolar Bone Structure and Function
What happens to the compact bone of the alveolus as you move anteriorly?
It fuses with the compact bone of the cortical plates.
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Collagen Synthesis and Vitamin C Role
What happens to the PDL when there is a deficiency of Vitamin C?
It can lead to rapid loss of the supporting tissue of the tooth, as seen in scurvy.
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Gingival Ligament Fibers
What is the role of the transseptal fiber system during orthodontic treatment?
It requires significant remodeling and is implicated in post-retention relapse of orthodontically treated teeth.
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Blood Supply and Innervation of the PDL
What is the main blood supply to the periodontal ligament (PDL)?
The inferior and superior alveolar arteries.
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Gingival Ligament Fibers
What does the circular group of fibers do?
It binds the free gingiva to the tooth.
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Collagen Synthesis and Vitamin C Role
What enzymes are responsible for the hydroxylation of proline and lysine in collagen formation?
Prolylhydroxylase and lysylhydroxylase.
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Orthodontic Tooth Movement Mechanisms
What is the role of force in orthodontic tooth movement?
A force is used to move a tooth in a certain direction, placing tension on the periodontal ligament fibers.
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Collagen Synthesis and Vitamin C Role
What role does Vitamin C play in collagen formation?
It is required for the proper functioning of collagen synthesis enzymes.
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Impact of Periodontal Diseases on PDL
How does chronic inflammation in periodontal diseases affect collagen?
It increases the expression of matrix metalloproteinase enzymes that destroy collagen.
What are the epithelial cell rests of Malassez?
Remnants of HERS that form a network around the root of the tooth in the PDL.
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Principal Fiber Groups of the PDL
What is the function of oxytalan fibers in the PDL?
Their function is unknown but they are thought to regulate vascular flow.
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Structure and Function of the Periodontal Ligament (PDL)
What are the anatomical borders of the periodontal ligament?
Superiorly continuous with gingival connective tissue and inferiorly with pulp tissues.
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Structure and Function of the Periodontal Ligament (PDL)
What are the physical functions of the PDL?
Transmission of occlusal forces, attachment of teeth to bone, maintenance of gingival tissue, resistance of occlusal forces, and protection of vessels and nerves.
p.4
Gingival Ligament Fibers
What is the transseptal fiber system?
Fibers that run interdentally from cementum just apical to the junctional epithelium of one tooth to the adjacent tooth.
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Collagen Synthesis and Vitamin C Role
What is the consequence of vitamin C deficiency on collagen synthesis?
It affects the function of enzymes, leading to issues like mobile teeth due to high turnover of collagen fibers in the PDL.
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Alveolar Bone Structure and Function
What are the components of the alveolar process?
An outer cortical plate, a central spongiosa, and bone lining the alveolus.
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Principal Fiber Groups of the PDL
Where does the alveolar crest group attach?
It attaches to the cementum just below the CE junction.
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Principal Fiber Groups of the PDL
What is the orientation of the horizontal group of PDL fibers?
They run at right angles to the long axis of the tooth.
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Blood Supply and Innervation of the PDL
What are the foramina in the alveolar bone used for?
They contain neurovascular structures, which is why it is also referred to as the cribriform plate.
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Alveolar Bone Structure and Function
Why must the alveolar bone constantly adapt?
Due to constant minor tooth movements.
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Structure and Function of the Periodontal Ligament (PDL)
What is the significance of the extracellular matrix in the PDL?
It consists of collagenous fibers and a non-collagenous extracellular matrix that supports the structure of the PDL.
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Blood Supply and Innervation of the PDL
How do the interalveolar arteries contribute to the PDL's blood supply?
They run horizontally and penetrate the alveolar bone to enter the PDL as perforating arteries.
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Development of Alveolar Bone Proper
What is the initial composition of the ligament space in the PDL?
Unorganized connective tissue with short fiber bundles extending from the cementum and alveolar bone proper surfaces.
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Orthodontic Tooth Movement Mechanisms
What happens to the periodontal ligament fibers on the side where force is applied?
They are stretched, pulling on the adjacent alveolar bone and promoting bone formation.
p.2
Collagen Synthesis and Vitamin C Role
What enzymes are essential for collagen synthesis in the PDL and alveolar bone?
Prolylhydroxylase and lysylhydroxylase.
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Orthodontic Tooth Movement Mechanisms
What is the result of the force applied to the periodontal ligament?
Bone deposition on one side of the tooth and bone resorption on the other side, allowing tooth movement.
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Orthodontic Tooth Movement Mechanisms
Why is cementum more resistant to resorption than bone?
Cementum is avascular and does not have neural innervation.
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Orthodontic Tooth Movement Mechanisms
What happens if the forces applied to the tooth are too great?
The cementum of the tooth will also resorb, causing root resorption.
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Gingival Ligament Fibers
What is the function of the alveologingival group?
It radiates from the bone of the alveolar crest into the lamina propria of free and attached gingiva.
p.2
Structure and Function of the Periodontal Ligament (PDL)
What nutritional and sensory functions does the PDL serve?
Carries nutrients to cementum, bone, and gingiva; provides proprioceptive and tactile sensitivity.
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Principal Fiber Groups of the PDL
What are Sharpey's fibers?
Collagen fiber bundles embedded into the bone and cementum on either side of the PDL.
p.4
Gingival Ligament Fibers
What is the role of gingival ligament fibers?
They maintain the integrity of the periodontium and are found in the lamina propria of the gingiva.
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Gingival Ligament Fibers
What does the dentogingival group connect?
It connects the cervical cementum to the lamina propria of free and attached gingiva.
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Principal Fiber Groups of the PDL
What does the interradicular group of PDL fibers form?
It forms the crest of the interradicular septum.
p.8
Alveolar Bone Structure and Function
What is the lamina dura?
It is a radiographic term referring to the dense bone lining the tooth socket, identifiable on periapical radiographs.
p.4
Gingival Ligament Fibers
What is the path of the dentoperiosteal group?
It runs apically from cementum over the periosteum of the outer cortical plates and inserts into the alveolar process.
