Flashcards in Periodontium Deck (61)
What structures make up the periodontium?
Gingiva facing the tooth
What are the two types of gingiva that face the tooth?
What is the only perio structure not attached to the tooth
What immediately precedes periodontal development?
What is the coordination of periodontal development?
Cementoblasts and osteoblasts secrete their organic matrix
Then PDL fibroblasts secrete their organic matrix
Then the bone and cementum mineralize
How does the PDL develop during tooth eruption?
Collagen fiber bundles are added apically
The orientation of collagen fiber bundles change - they start obliquely, then horizontal, and then coronally oblique
How does the PDL develop after tooth eruption?
The thickness of collagen fiber bundles increase
What are the two types of cementum?
Forms as the tooth is erupting
covers the coronal 2/3 of the tooth
Most important in attachment
Formed after at least half the root is formed, around the time the tooth emerges in the oral cavity
Apical 2/3 of the root
More important in adaptation
T/F - Primary and Secondary Cementum overlap in the middle 1/3 of the root
True - The Secondary cementum overlies the Primary
Why is cementum and dentin so firmly attached?
It is a consequence of the collagen fibers of the tissues intermingling between mineralization
As primary cementum is laid down, what happens to the cementoblasts?
They retreat towards the future PDL
They don't become entrapped in the cementum, but persist in the adult PDL
Epithelial Rests of Mallasez
Fragments of HERS that remain in the PDL
What is the main difference between primary and secondary cementogenesis?
In secondary cementogenesis, the cemntoblasts become trapped in cementum matrix - they're then called cementocytes
What does the sulcular epithelium derive from?
Embryonic oral epithelium
What does the junctional epithelium derive from?
Reduced enamel epithelium
Do cementoblasts derive from the dental follicle or the HERS?
We don't know - maybe both?
What is at the mineralization front of periodontal development?
Hard connective tissue that covers the dentin of the root - similar to bone
How much of cementum is organic
(90% collagen - mostly type I)
How much of cementum is inorganic?
T/F - Cementum is secreted through life and not normally resorbed
True - Can triple in size from age 16-70
What are the functions of cementum
Attach tooth to the jaw
Protect the root dentin
Adapt to masticatory forces
How thick is the cementum in the CEJ v the apex of the root.
CEJ = thin (20-50um)
Apex = thicker (150-200um)
What are the types of joints at the CEJ?
Cementum overlaps enamel (60%)
Cementum buts up agains enamel (30%)
Gap between the cementum and enamel (10%)
Acellular extrinsic fiber cementum
Importance in attachment
Collagen fibers are at right angles to cementum surface
Has Sharpey's Fibers
Fibers of the PDL that extend into the mineralized area
Cellular intrinsic cementum
Important in adaptation
Collagen fibers are parallel to the surface of cementum
Called intrinsic fibers because fibroblasts get caught in the cementum and are called cementocytes