Module 1: Reading Assignment 1: Pulp Biology Flashcards
What is the embryonic cell structure that the tooth buds form from?
Oral epithelium
What is formed when the oral epithelium invaginates
Dental Lamina
After the epithelial based bud has formed, what types of cells begin to condense around it?
Ectomesenchyme Cells
What embryonic structure do ectomesenchyme cells come from?
Neural Crest
When the bud invaginates, what developmental stage has been reached?
Cap
What is the name of the bell shaped structure in the Bell stage?
Enamel organ
What does the ectomesenchymal tissue inside the invagination of the enamel organ eventually become?
The pulp
What is the name of the future pulp tissue while it is in the bell stage?
Dental Papilla
During the bell stage, what do the inner layer of enamel organ cells become?
Ameloblasts
During the bell stage, what do the cells of the outer layer of the dental papilla differentiate into?
Odontoblasts
During which stage do odontoblasts begin to deposit dentin?
Bell Stage
Once dentin is deposited by the odontoblasts, what is the dental papilla officially known as
the Dental Pulp
After the pulp is formed, a layer of cells forms around the enamel organ and the pulp….what is it called
Dental Follicle
What does the dental follicle eventually become?
The periodontal attachment
Several genes control the histodifferentiation of cells during embryonic development of the teeth, what are 3 developmental defects that can occur due to gene expression disorders at this stage of development?
Anodontia
Amelogenesis imperfecta
Odontogenesis imperfecta
From what cells do odontoblasts arise from?
Undifferentiated ectomesenchyme cells
What cells interact with the ectomesenchyme cells in order to stimulate them to differentiate into odontoblasts?
The ectodermal cells of the Inner Enamel Epithelium (Enamel Organ)
When the odontoblasts have completed their differentiation what part of the enamel organ disappears?
The basal lamina which contained the cells stimulating the odontoblast’s differentiation
Odontoblasts are joined together in a “line” due to what types of connections?
Tight Junctions
Desmosomes
Gap
The newly matured and linked odontoblasts are ready to do what?
Deposit dentin
The deposition of enamel signals the ameloblasts in the IEE of the enamel organ to do what?
Start depositing enamel
At what end of the tooth does unmineralized dentin deposition begin?
At the cusp tip, moving in an apical direction
What circumstance determines the shape of the crown of the future tooth?
The genetically predetermines proliferation pattern of the cells in the Inner Enamel Epithelium
What is the first thin layer of dentin that is deposited called?
Mantle Dentin
How does mantle dentin differ from Circumpulpal dentin?
The direction and size of the collagen fibers
What is predentin, and where is it located
It is unmineralized dentin located immediately next to dentinal layers
Does dentin formation ever stop?
No, but its rate slows with age
What can increase the rate of dentin formation?
The presence of a toxic insult that has invaded the dentin
What is the name of the point where the IEE and OEE meet?
The Cervical Loop
The cervical loop demarcates the border between what two future tissue layers?
Crown and Root
What is the name of the structure that arises from the cervical loop and initiates root formation
Hertwigs Epithelial Root Sheath
How does the root sheath actually help “build” the root?
It stimulates odontoblasts
What determines the shape of the root structure
The genetically determined pattern of proliferation of the root sheath cells
How do multiple roots form
When opposing parts of the root sheath proliferate vertically and horizontally
What is formed by opposing horizontal segments of the root sheath
The epithelial diaphragm which results in a single root tooth
If the root sheath stimulates odontoblasts, how does cementum get formed?
Once the first dentin of the root has been laid down, the root sheath’s basement membrane breaks down and inner sheath cells secrete hyaline over the new root dentin.
After that the root sheath breaks down and allows dental follicle cells to contact the new root dentin and become cementoblasts
The new cementoblasts will deposit what subtype of cementum?
Acellular
This acellular cementum will serve as the achor material for what tissue
principal fibers of the PDL
When epithelial remnant of the root sheath get caught in the PDL, what are they called?
Epithelial rest cells of Malassez
Rest cells of Malassez are normally function less but under certain inflammatory conditions they can give rise to
Radicular Cysts
What are Lateral or Accessory Canals
They are communication channels between the pulp and the PDL
How are lateral canals formed
When localized areas of the root sheath fragmented before the root dentin was deposited
What part of the root is the most likely area to find Lateral Canals?
Apical Third
Why are Lateral Canals clinically significant?
They provide a pathway for disease to travel from the pulp to the periradicular tissues
After a tooth is fully formed is the apical foramen at the very bottom of the root?
No is is slightly coronal, and it gets pushed further towards the crown as apical cementum is formed during life
When there are multiple apical foramina in one root, what do we call them?
The largest one remains the apical foramen, smaller ones are called accessory canals
What do you call the combination of all of the foramina in a root?
The apical delta
What is the diameter of an average adult apical foramen
.3-.6 mm
Where is the largest apical foramen in the mouth found?
Distal root of mandibular molars
Palatal root of max molars t
What type of embryonic tissue does the PDL arise from
Ectomesenchymal cells of the dental follicle
What are Sharpey’s fibers, and where do they come from?
They are bundles of collagen secreted by fibroblasts of the dental follicle. The fibers get “trapped” in the new cementum and become the principle fibers of the PDL
If one end of Sharpey’s fibers are anchored in cementum, what is anchoring the other end?
Osteoblasts differentiate from the dental follicle and form bundle bone that “grabs” the other end of the fibers.
What type of cementum is formed after the PDL fibers have been formed?
Cellular
The pulp space is split into these two primary divisions
Coronal and Radicular
Coronal pulp is subdivided into these two spaces
Pulp Horns
Pulp Chamber
Why do young, partially developed teeth have a better chance to survive trauma then adult teeth?
They have better blood flow to the pulp
What is the apical constriction?
It is the narrowest portion of the pulp canal, which is usually narrower than the apical foramen
What anatomical landmark does the apical constriction coincide with?
The CDJ
What are the 5 functions of the pulp?
- Induction
- Formation
- Nutrition
- Defense
- Sensation
What is the pulps role in Induction of the tooth development?
The initial deposition of dentin begins amelogenesis
What is the pulps role in formation of the tooth
Odondoblasts make dentin
What is the difference between Secondary Dentin and Tertiary Dentin
Secondary dentin is very similar to primary dentin and it forms after the root is complete
Tertiary dentin is much less organized structurally and is formed in response to injury
What are the two types of Tertiary Dentin
Reactionary
Reparative
How does reactionary and reparative dentin differ
Reactionary dentin is tubular and formed by original odontoblasts
Reparative is atubular and formed from new odontoblasts differentiated to replace killed odontoblasts
How does the pulp function to defend the tooth
The odontoblasts form dentin is response to injury
The pulp can process and identify foreign substances and elicit an immune response
What are the three layers of pulp? (Only true in coronal pulp)
Odontoblast layer
Cell Free Zone of Weil
Cell Rich Zone
What structures make up the pulp core?
Fibroblasts
Nerve and Blood Vessels
How are odontoblasts arranged in the pulp
In a single layer around its periphery
How does the concentration and shape of odontoblasts change in different parts of the pulp
Coronal odontoblasts are heavily concentrated and columnar in shape
In the root the odontoblasts are less concentrated and flatter in shape
Do odontoblasts undergo cell division?
No, they are end cells
What are the two main parts of an odontoblast?
Cell body and Cell Processes
Does the odontoblast have more than one process?
Yes, only one large one that occupies the dentin tubule, but there are many smaller processes that link the cell to other odontoblasts, and perhaps fibroblasts too
What organelles are prominent in an active odontoblasts
Golgi
ER
Mitochondria
Vesicles
What type of odontoblasts receptors allow an immune response
TLR2 and TLR 4 (Gram Positive Bacteria)
They release pro inflammatory cytokines when bound
What receptors may allow the odontoblast to act as a nociceptor?
TRPV1 and TRK-1 which can detect the movement of hot and cold induced fluid movementWh in the tubule
What is the cellular origin of the stem cells in the pulp
They are undifferentiated ectomesenchymal cells, aka preodontoblasts
Pulp stem cells primarily replace killed odontoblasts, but what other cells can they differentiate into?
Osteoblasts
Adipocytes
Cardiac muscle cells
Neurons
What are the most common type of cell in the pulp?
Fibroblasts
What is the purpose of the fibroblasts?
Pulp is a loose connective tissue, they provide the collagen and ground substance that allows the pulp to function
What are the most numerous immune cells found in the pulp?
Dendritic cells are the main APC in the pulp
What other immune cells can be found in the pulp
T cells
Resting Macrophages called Histiocytes
What are the primary non cellular components of the pulp?
Collagen Fibers
Glycosaminoglycans
Calcifications
What is the primary collagen type in the pulp
Type I at 55%
Type III is a close second at 45%
Odontoblasts only produce this type of collagen
Type I
What are the three types of pulp stones
Free Stones
Attached Stones
Embedded Stones
This type of Pulp stone is attached to dentin but not surrounded by it
Attached stones
This type of pulp stone is completely surrounded by tertiary dentin
Embedded stones
Why might pulp stones be important clinically
They can block access to the canals during RCT
What are the largest blood vessels that enter the tooth?
Arterioles
What is the only classic inflammation response that is not vascular in nature?
Pain
What branch of the autonomic nervous system controls the precapillary sphincters of the arterioles supplying the pulp?
Sympathetic
What teeth are sometimes innervated by a nerve other than V2 or V3
Mandibular molars are sometimes innervated by C2-C3
Where does the trigeminal sensory neuron travel once it leaves the tooth
- To the trigeminal ganglion
- Then to trigeminal sensory nucleus in the brainstem
- Then to specific nuclei in the thalamus
- Finally they reach the sensory cortex as 3rd Order Neurons
Where does the pulps sympathetic motor innervation come from?
T1 fvia the superior cervical ganglion
Is there any parasympathetic innevation in the pulp?
No.
What type of Neurons make up the vast majority of the myelinated neurons in the pulp?
Slow speed Alpha Gamma (95%)
What percent of the myelinated fibers in the pulp are fast speed Alpha Beta axons?
5%
Where in the pulp do the myelinated nerve fibers terminate?
Either adjacent to the odontoblasts bodies, in the tubule next to the process, or in the Subodontoblastic plexus of Raschkow
What percent of tubules in a young tooth contain nerve axons
27% in the area of the pulp horn
11% Mid Crown
8% Cervical Crown
0% Root
