Histo- Cementum & Pulp
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What is the embryological origin of pulp?
Dental papilla (derived from ectomesenchyme)
What is in the cellular and interceullar components of pulp?
- Cellular- Odontoblasts, Fibroblasts, mesenchymal cells (which make new odontoblasts), and immunologic cells
- Interceulluar- collagen fibers and ground substance
In addition to the cellular and intercellular components of pulp, what are two other main parts of this tissue?
- Blood vessels- for nutrients and oxygen
- Nerve supply- sensory (mediate pain) and motor (supply blood vessels)
What cells are involved in the inflammatory aspect of pulp?
Lymphocytes, mast cells, neutrophils, macrophages, and dendritic cells
How does the volume of the pulp change with different teeth/age?
- Molars have more volume than incisors
- pulp volume decreases with age
What main divisions can the pulp be divided into?
- 1. Coronal pulp
- 2. radicular (root canal) pulp
How are coronal and radicular pulp different?
- Coronal pulp- similar in contour to dentin and may possess a roof, pulp horns, and floor in this area
- Radicular pulp- tube shaped (bc in root canal!), is continuous with the periodontal CT at the apical forament
Name the zones of the pulp. Where are all these zones?
- All zones found w/in the crown of the teeth
- 1. Odontoblastic layer
- 2. Cell free zone of Weil
- 3. Cell rich zone
- 4. Pulp core
What is the funciton of the odontoblastic zone and where is this located in the pulp?
- Zone is adjacent to the dentin and is made of a single layer of odontoblasts.
- Fxn: make dentin and be area for sensory nerves to treminate
What is in the cell free zone of the pulp?
intercellular matrix, nerve fibers, capillaries and tissue fluid
What is in the cell rich zone of the pulp? What do these cells do?
- Fibroblasts and undifferentiated cells that will become odontoblasts. Also nerve plexus here.
- These cells form reparative dentin or replace odontoblasts.
What is found in the pulp core zone?
- Bulk of the pulp.
- Loose CT with fibers, cells and ground substance.
How can calcifications such pulp stones/denticles be classified? Based on...
Location and structure
Where are the three places that a pulp stone could be?
- Free in the pulp.
- Attached to the dentin.
- Embedded in the dentin.
What are the names of the three different strucutres/forms of pulp stones?
- True denticles
- False denticles
- Diffuse calcifications
What are TRUE denticles made of? What are their predecesors?
- Made of dentin, but formed from induction of remnants of Hertwigs root sheath trapped in the pulp.
- For these, odontoblasts differentiate in the pulp and make dentin= true denticles.
Which is the most rare type of pulp stone?
True denticles- big red ovals
What does a False Denticle look like?
- Concentric layers of calcified tissue surrounding dead cells or collagen bundles.
- Pink circles
What makes a diffuse calcificaiton? What does it look like?
Made from calcification of collagen bundles. Squamous, irregular looking
How is cementum similar and different from bone?
similar in that it is 50% mineralized (bone is 60), but different bc cementum is avascular.
Where is cementum thinnest and thickest?
- Thinnest- cervix
- Thickest- apex
Why is cementum considered part of the periodontium?
It serves as an attachment site for PDL fibers
What are the two big functions of cementum?
- 1. Anchors root to the socket
- 2. Continuously produces itself throughout life, which helps the tooth continuously erupt through life (helps w/ enamel loss), helps the PDL fibers maintain width, and helps repair root injuries.
What cells are in cementum?
What is in the extracellular matrix of cementum?
- Organic matrix
- inorganic matrix
- Sharpey's fibers
Where are cementoblasts found and what do they do?
- Found at the surface of the cementum
- Lay down organic matrix (cementoid) on the surface of root dentin.
What are cementocytes? where are they located?
- Cementocytes are cementoblasts that have become embedded in the cementum.
- They live in lacunae and have processes called canaliculi.
What is the function of cementoclasts? What other type of cell do they resemble?
- Cementoclasts are large, multinucleated cells that are derived from monocytes.
- They demineralize and remove cementum- they are located in the PDL.
- Similar to osteoclasts.
What is the name of the organic matrix in cementum? what is it made of and where is it located?
Cementoid- ground substance and collagen fibers which are produced by and located underneath the cementoblasts
What is the name of the inorganic matrix and what is it made of?
Cementum- formed from hydroxyapatite depositing on the collagen fibers of the cementoid (organic matrix) and of the PDL.
What is an extracellular component of cementum that is unique to this part of the tooth?
Sharpey's fibers- extrinisic collagen fibers of the PDL that become embedded in the cementum as the cementum grows outward
What is the embyronic orgigin of cementum?
Dental Sac (follicle) which is derived from ectomesenchyme
How does the process of cementogenesis occur?
- Root shealth breaks down after root detin forms. (reminants called epithelial rests)
- This allows mesenchymal cells, fibroblasts, and collagen, in the dental sac to move toward the dentin.
- Dentin turns these cells into cementoblasts and they then secrete cementoid.
What two sources to collagen fibers from early cementum come from?
- 1. from fibroblasts in the dental sac
- 2. later, from newly differentiated cementoblasts
What is the name of the collagen fibers from the dental sac that come from fibroblasts?
Sharpey's fibers of the PDL. These fibers are not really fibers of the true matrix. These fibers are anchored into calcified cementum and help anchor the tooth into the alveolar bone.
What is the function of the collagen fibers that come from cementoblasts?
The cementoblasts, when mature, lay down the collagen fibers that secrete the organic matrix for the mineralization of cementum.
What are the two basic types of cementum?
Cellular and Acellular
Where is acellular cementum located and what does it contain?
- Located in the cervical 1/3 of the root.
- Covered by cementoid and cementoblasts. (NO CEMENTOCYTES). No cells in this matrix, just covered by them.
- This is the first cementum produced, and is usually just a thin layer.
Where is acellular cementum deposited?
on dentin surface- in upper 1/3 root
Where is the cellular cementum and what does it contain?
- Located in apical 1/3 of root
- Covered by cementoid and cementoblasts (same as acellular), but cementocytes are distributed throughout it in lacunae(different from acellular).
- Cementocytes processes extend toward PDL
When in life, and how does cementum grow?
- Grows throughout life.
- Most recently formed cementum has Sharpey fibers.
- Grows in Incremental lines that have periods of rest (cementoblasts retreat) and then resumed cementum formation.
- These lines follow the contour of the tooth.
What happens to cementum in response to stress?
- More layers of cementum are deposited in response to stress- LAMELLAE. This appears as heavier resting lines.
- Can be cellular or acellular.
What are the three ways that the CEJ can be formed?
- 1. Cementum overalps enamel (60% of the time). Happens due to the early degeneration of the REE during development/ early breakdown of epithelial root sheath.
- 2. Cementum and enamel abut eachother (30%) Well formed. Proper.
- 3. Cementum is lacking (10%). Exposed dentin. Due to delayed breakdown of epithelial root sheath.
What are ceminticles and what are they formed as a result of?
- Calcified bodies located on or in the cementum or PDL.
- Formed via induction from remnants of epithelial rests.
- May be formed from local trauma, hyperactivity and increasing age.
Name the 3 types of ceminticles adn where they are located.
- 1. Free- lie in the PDL
- 2. Attached- stone is attached to cementum
- 3. Embedded- stone is embedded in cementum
What are the clincially significant factors of cementum?
- 1. Anchors teeth in the socket
- 2. Allows for repair at root surface
- 3. Seals the ends of the dentinal tubules
- 4. Is more resistance to resorption than bone
- 5. Permits orthodontic movement
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