Periodontium Flashcards
What structures make up the periodontium?
Cementum
PDL
Bony socket
Gingiva facing the tooth
What are the two types of gingiva that face the tooth?
Junctional epithelium
Sulcular epithelium
What is the only perio structure not attached to the tooth
Sulcular epithelium
What immediately precedes periodontal development?
Root dentinogenesis
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?
Primary Cementum
Secondary Cementum
Primary Cementum
Forms as the tooth is erupting Mainly acellular covers the coronal 2/3 of the tooth Most important in attachment More mineralized
Secondary Cementum
Formed after at least half the root is formed, around the time the tooth emerges in the oral cavity Mainly cellular Apical 2/3 of the root Less mineralized 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?
Sialoprotein
Cementum
Hard connective tissue that covers the dentin of the root - similar to bone
How much of cementum is organic
45-55%
90% collagen - mostly type I
How much of cementum is inorganic?
50-55%
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
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
Mixed fiber cementum
Some intrinsic, and some extrinsic
Make up most of the secondary cementum - made in the second wave of secondary cementum and found closer to the root apex
Cementocytes
Cementobalsts that got caught in the organic matrix
No longer make cementum - may be inactive
Periodontal ligament
Soft connective tissue between the cementum and the bony wall of the socket
Made up of large collagen fiber bundles with ends embedded in cementum/bone
Continuous with the gingival connective tissue cervically and apical foramen apically
How thick is the periodontal ligament?
.15-.40 mm (thin)
gets thinner with age
What cells are most numerous in the PDL?
Fibrobalsts
What do fibroblasts do in the PDL?
Secrete and degrade collagen
Cell-Cell junctions
Cell-ECM junctions
What non-fibroblasts cells are found in the PDL?
Cementoblasts Osteoblasts/clasts Epithelial rest of Mallasez Immune cells Stem cells
What is the collagen turnover in Gingiva v PDL?
Gingiva = 5 weeks PDL = 1 week
What is the cell volume of Gingiva v. PDL?
Gingiva = 8% PDL = 40%
What is the proliferation rates of Gingiva v. PDL?
Gingiva = lower PDL = higher
What is the importance of Cell-ECM junctions
Functional link between occlusal forces and fibroblasts
Translate forces applied to fibroblast into physiological responses
Maintain orientation of fibroblasts in PDL
What is the structure of Cell-ECM junctions?
There are a variety of different junctions
They all interact with collagen in the ECM either by a single transmembrane molecule or several
Where are cementobalsts in the PDL?
Near cemetnum
Where are the osteoblsats and osteoclasts located in the PDL?
At the interface of the PDL and alveolar bone
Undifferentiated Mesenchymal Cell characeristics in the PDL
Perivascular location
Pluripotent
What types of fibers are in the ECM of the PDL?
Types I and III Collagen
Oxytalin
What is in the ground substance of ECM of PDL?
PGs and the associate GAGs
Glycoproteins
Cementicle
Spherical calcified mass in the PDL
Similar to pulp stones in the pulp
What are the principal fiber groups of the PDL?
Alveolar crest Horizontal fibers Oblique fibers Apical fibers Interradicular septum
Alevolar crest fibers
Attach cementum to the crest
Horizontal fibers
Attach cementum to the alveolar bone just below the crest
Oblique fibers
Attach cemntum to the alveolar bone in an oblique orientation that suspends the tooth in the socket
Apical fibers
Attach the apex of the tooth in the alveolar bone
Interradicular septum
Only found in teeth with multiple roots
Extend between the cementum and interredicular septum of alveolar bone
Gingival ligament
Important for maintaining the PDL and supporting the toth
Transseptal ligament
From cementum of tooth, arching over the alveolar bone, and attaching to the cementum of the adjacent tooth
T/F - The tooth is heavily vascularized
True
What are the 2 routes taken by blood vessels to supply the PDL?
1) Enter the alveolar bone and then pierce the foramina in the wall of the bony socket - via perforating arteries
2) Branch near the apical foramen and directly enter the PDL
What fibers signal pain in the PDL?
Small fibers
- A-delta
- C
What fibers signal proprioception in the PDL?
Large fibers
-A-beta
What are features of A-beta PDL fibers
Intermingle with collagen fibers Highly sensitive Code for the amount of force Code for the direction of force Send info to CNS regarding chewing Underlie out ability to localize stimuli applied to teeth
Alveolar processes
Bone of jaw that contains sockets for teeth
Spongy bone
