Periodontium Flashcards
Periodontium consists of…
- Cementum
- Periodontal ligament
- Bone that lines alveolus socket
Cementum
Functions
Composition
General
Function
- Seals tubules of root dentin
- Attachment for periodontum fibers to keep tooth in socket
Composition
- Inorganic
- 50% Calcium hydroxyapatite
- Organic
- 50% type I collagen, water, proteins
Generally thickest at root apex and interradicular areas of teeth w/ multiple roots
Thinest near CEJ
Limited to root of teeth
Acellular (primary) Cementum
Thin layer that surrounds the root next to dentin
Cellular (secondary) Cementum
Less mineralized
Thicker
Prevalent around apical root and interradicular areas
Intermediate Cementum Formation
Initially called intermedium cementum or cementoid
Formed by inner enamel epithelial root sheath cells during root dentin formation
Made of enamelin, hard
Acellular Cementum formation
Function
After intermedium cementum
Thin layer of acellular cementum is formed and attaches to intermedium
All of the cementoblasts in the acellular cementum migrate to periodontal ligament
Function: Provide attachment for tooth
Cellular Cementum Formation
Function
Forms when cementoblasts become embeded in the matrix as cementocytes
Function
- Adaptive role in response to tooth wear and movement
- Helps repair periodontal ligament
Cementocytes
Development
Features
Cementoblasts enclosed in a self-generated matrix
Matrix mineralizes and cementoblasts lose thier secretory ability and become cementocytes
Features
- Have cytoplasmic process within a canaliculi
- Canaliculi- small fingers extend from lacunae
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Root Development
Cervical loop brings about development
- Consists of IEE and OEE
Hertwigs Epithelial Root Sheath is formed by
- Growth of cervical loop deep into mesenchyme of dental sac
- Encloses more dental papilla
- Cementum forms on root after HERS disintegrates
Epithelial Rests of Malassez
Clusters of residual cells from HERS
Enamel Pearl
Defect in HERS
Cementoenamel Junction Varoation
Enamel and cementum overlap
Edge to edge
Enamel and cementum do not meet
Periodontal Ligament Formation
Formed from ectomesenchyme
Present within Dental follicle
Differentiate into fibroblasts
- Create collagen fibers
- Sharpey’s fibers (type I collagen)
- Form the PDL
Periodontum Ligament Function
Nutritive
- pdl has blood vessels to supply nutrients to
- itself, alveolar bone, cementum
Maitenance
- pdl heals rapidly
Sensory
- Receptors to detect movement and pressure
Supports tooth during occlusal movement
Cells of periodontum Ligament
- Fibroblasts
- Most abundant
- pdl has high collagen content
- provide rapid replacement of fibers
- Macrophages, mast cells, eosinophils
- Osteoclasts
- Imp in orthodontic movement
- Bone resorption in periodontal disease
- Undifferentiated Mesenchyme
- Cementoblasts, cementoclasts
Fibroblasts, function
Make new collagen fibers, some can break down as well
Maintains cell framework and tone of tissue
Amount of collagen in a tissue can be tested by its hydroxyproline content
Properties of Periodontal Ligament
Mostly collagen type I
Some amounts if type III and XII
Rich blood supply
Periodontal Ligament Innervation
- Sensory Nerves
- pdl nerve endings perceive propioception
- by mechanoreceptors
- Pain
- Nociceptors
- pdl nerve endings perceive propioception
- Autonomic Nerves
- Help regulate periodontal blood flow
- Theres mylenated (sensory) and unmyelinated (sensory or autonomic) nerves
Principle Fibers
Collagen bundles that attach teeth to bone or gingiva
(Exception transseptal fiber attaches teeth=teeth)
2 Main groups
Gingival Group and Dentoalveolar Group
Subcategorized into fibers
Dentoalveolar Group
- Apical –> resist vertical forces
- Oblique–> Resist vertical and intrusive force
- Horizontal —> Resists horizontal and tipping forces
- Alveolar Crest—> Resist vertical and intrusive force
- Interradicular —> Resist vertical and lateral force
Gingival Fiber Group
- Transseptal–> Resist mesial distal movement
- Circular–> band around tooth
- Dentogingival–>extends cervical cementum-lamina propria attach free gingiva
- Alveologingival–> bone to lamina propria
- Dentoperiosteal–>
Not strictly part of pdl
Aid gingiva in resisting displacement
Collectivel called Gingival Ligament
Oxytalin Fibers
Made of
Location
Function
Type of elastic fiber
run in oblique fashion, cementum to blood vessels
Play role in vascular flow
Sharpey’s Fibers
Collagenous fibers embedded in cementum and alveolar bone proper
Alveolar Bone/Process
Function
Parts
- Supports teeth
- Alveolus
- tooth socket
- Alveolar Bone Proper
- bone lining tooth socket
- lamina dura in X-ray white
- Constantly remodeled due to occlusion
- Supporting Bone
- Cancellous bone that underlies the alveolar proper
