NJDS: Histology - Dental Pulp
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- What is the dental pulp?
- The dental pulp is the connective tissue that lies within and provides support for the dentin
- What are the three zones of the peripheral dental pulp?
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1. Odontoblastic Zone
2. Cell Free (poor) Zone of Weil
3. Cell Rich Zone -
Name this zone:
Its composed of a single layer of odontoblasts that line the pulp and lies next to the predentin. Each cell has a single process that rests within a dentinal tubule - The Odontoblastic Zone
- What are the types of junctions located in the odontoblastic zone?
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zonula occludens, zonula adherens, desmosomes, and gap junctions
Note: The location of the gap junctions chance according to the functional state of the odontoblast - What are the various characteristics of Odontoblasts?
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-long-lived and last until tooth remains vital
-don't divide -
Name this zone:
A thin layer underneath the odontoblastic zone without many cells. It is occupied by blood vessels, nerve fibers, and fine fibers - The Cell Free zone of Weil
- What are the characteristics of the Cell Rich zone?
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-about 3-5 layer thick
-composed of flattened stellate or fusiform cells
- has many fibroblasts and undifferentiated mesenchymal cells
-the undifferentiated mesenchymal cells can differentiate into odontoblasts - What is the subodontogenic nerve plexus that is located only in the coronal pulp?
- The nerve plexus of Raschkow
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True or False:
1. The Nerve plexus of Raschkow has both myelinated and unmyelinated axons and dendrites
2. sensory afferent fibers do not come from the trigeminal nerve
3. The nerve plexus does not contain sympathetic branches of the -
1. True
2. False
3. False
Note: The nerve plexus also has parasympathetic fibers
The superior cervical ganglion has a role in regulation of blood flow -
Name the two types of nerve fibers.
Hint: We learned it in the pain section in physio -
1. A delta fibers- fast conducting, larger diameter, myelinated, associated with sharp pain
2. C fibers- unmyelinated, slow conduction,smaller diameter, associated with dull diffuse pain - What happens to the nerves as they approach more coronal portions of the pulp?
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1. Myelinated nerves lose their myelin sheaths and terminate as unmyelinated nerve endings
2. They intermingle with the odontoblasts and dentinal tubules--> dentin sensitivity - What are the characteristics of the vascular plexus?
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-enter and leave pulp through apical foramen and sometimes through the accessory canals
-Most of the arterioles branch off into capillaries that supply the subodontoblastic region
-vascular elements also include venules and lymphatics - Name the other types of cells in the dental pulp.
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1. Fibroblasts
2. Undifferentiated Mesenchymal Cells
3. Macrophages
4. Lymphocytes
5. Dendritic Cells - Fibroblasts
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-most numerous in dental pulp
-most commonly seen in coronal portion-->make up cell-rich zone
-provide support for pulp and help form its matrix - Undifferentiated Mesenchymal Cells
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-can be recruited to form odontoblasts of fibroblasts
-also found in the cell-rich zone and the core of the dental pulp next to blood vessels - Macrophages
- located near the pulp core
- Lymphocytes
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-Only T lymphocytes are found in the pulp
-Non-Pathological - Dendritic Cells
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- are antigen-presenting cells and share the same function as Langerhans Cells
Unerupted: associated with odontoblast layer
Erupted: migrate towards pulp core and thus are below odontoblast layer - What does the pulp matrix consist of?
- Collagen fibers and ground substance
- What is the function of the ground substance? What does it contain?
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1. Functions in support and nutrient and waste transport between cells and blood vessels
2. contains GAGs, glycoproteins, and water
Note: Supported by fibroblasts - What type of collagen fibers are in the pulp matrix?
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-most of the fibers are type I; thick and stained with eosin
-fine fibers are made of type III (reticulin); thin and stain with silver - Dentin sensitivity is a response to _____________,_________, ________
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1. thermal change
2. mechanical contact
3. dehydration - What does the hydrodynamic theory state?
- This theory states that the flow of fluid through dentinal tubules causes a distortion in the pulpal environment, stimulating the free endings of Raschkow's nerve plexus
- What are pulp Stones?
- calcium salt masses in the pulp that have a similar degree of mineralization to dentin
- What are the characteristics of pulp stones and why are they a problem?
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-can be solitary or multiple
-found in pulp chamber orifice or root canal
-form around dead cells, collagen, or blood clots
-may have dentinal tubules within them
They are a problem when doing endodontic procedures because they obstruct the root canal. -
Pulp Stones:
What are the differences between:
1. True vs. False
2. Discrete vs. indiscrete
3. Attached vs. Free -
True- has dentinal tubules
False- doesnt have dentinal tubules
Discrete- well defined borders
Indiscrete- just a smear, no well defined borders
Attached- attached to wall of dentin
Free- in the pulp - What are the 4 changes in the pulp associated with increasing age?
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1. Decrease in pulp volume: caused by pulp stones or secondary dentin formation
2. Decrease in cellularity: caused by loss of odontoblasts
3. Reduction in nerve fibers: you become less sensitive
4. Dystrophic Calcification- a way of forming pulp stones