Microscopic Anatomy of Enamel, Dentin, Pulp Flashcards
Exam 2 Prep OBJECTIVES
What is the function of enamel?
- Hardest material in body
- Provides hard surface for chewing and speech
- Resists diseases such as dental caries as well as fractures
What are the components of dentin?
- Dentinal Tubule
- Dentinal Fluid
- Odontoblastic Process
How is enamel produced?
- Enamel is produced by ameloblasts
- Is laid down in layers
- Begins at the crown tips and moves cervically
Discuss the use of fluorides in prevention and
remineralization
Post-eruptive maturation/mineralization of enamel is due to mineral deposition such as fluoride and calcium from the saliva into
hypomineralized areas of enamel
Enamel matrix
30% mineralized
What are the different pulpal zones?
Odontoblastic Layer
Cell-free zone
Cell-rich zone
Pulpal Core
Discuss the changes to the pulp that come with aging
DECREASE in cellular substance as it fills with increased amount of collagen fibers
- Decrease in numbers of undifferentiated mesenchymal cells
- Pulp becomes more fibrotic with age
- Pulp cavity may be made smaller by the addition of secondary or tertiary dentin
Outer layer of crown
enamel
Composed of a crystalline material that is the
hardest material in the body
enamel
Avascular
enamel
Crystalline formation consists of mainly calcium hydroxyapatite
enamel
96% inorganic
Enamel
Provides hard surface for chewing and speech
Enamel
Resists diseases such as dental caries as well as fractures
Enamel
Outer pulpal wall, consists of cell bodies of odontoblasts
Odontoblastic layer
What is the cell-free zone?
Contains fewer cells than
odontoblastic layer; nerve and
capillary plexus is located here
What is the cell rich zone?
Contains increased density of
cells and has a more extensive
vascular system
What is the pulpal core?
Located in the center of the pulp chamber, has many cells and an extensive vascular supply
What is the function of dentin?
- Absorbs forces, shock, absorber
describe the location of pulp
- Contained within pulp chamber
- Coronal Pulp/Pulp Horns
- Radicular Pulp/Canals
- Apical Foramen/Opening from pulp at the root tip
- Accessory canals
What is the function of pulp?
- Nutritive and supportive layer
- Cells can transform into fibroblast and odontoblast if needed after injury
Location of dentin
-Middle layer of crown and root
Location of enamel
Is laid down in layers
-Begins at the crown tips and moves cervically
What are enamel rods and where are they located?
- Keyhole shape stacked in rows
- Extend from enamel from the DEJ to the outer surface
What are dentinal tubules and where are they located?
Long tubes in dentin that extend from DEJ and DCJ to pulp
Where is the dentinal fluid located?
Located in tubule and surrounds the odontoblastic process
What and where is the odontoblastic process ?
Cellular extension of odontoblast located in tubule
What are the components of pulp?
- Fibroblasts are largest group of cells, followed
by odontoblasts
-Pulp also contains undifferentiated cells
Describe the processes/features of apposition
and maturation dentin?
- Dentinal tubules extend from the DEJ or DCJ to the outer wall of the pulp
- Odontoblastic process located within the dentinal tubules
What does odontoblasts lay down?
pre-dentin
What do mesenchymal cells make?
fibroblast
What are pulp stones?
calcified masses of
dentin; can be free or attached to the dentin
What do the undifferentiated calls transform into?
These cells can transform into fibroblasts and odontoblasts if needed after injury
describe the lines of Retzius
incremental lines that stain brown on prep, show bands on the enamel rods; looks like growth rings in a tree
describe the neonatal line
accentuated line of Retzius that reflects the stress or trauma experienced by the ameloblasts during birth
describe the enamel spindles
result from odontoblasts that crossed the basement membrane; dentinal tubules become trapped in enamel matrix
describe the hunter-scheger bands
Enamel gets its strength from the crystals in the rod groups bending right and left in slightly different areas than the surrounding groups
describe enamel tufts
look like small dark brushes with their bases near the DEJ; are an anomaly of crystallization, have no
describe enamel lamellae
partially calcified vertical sheets of enamel matrix that extend from DEJ to outer surface
What is the crystalline structural unit of enamel called?
enamel rods
What are the raised ridges in enamel?
imbrication lines
What are the grooves in enamel?
perikymata
What percentage inorganic is dentin?
70%
What are the processes of enamel maturation/apposition?
Enamel tufts, enamel lamellae, imbrication lines, hunter-scheger bands, lines of reitzus, neonatal line, and enamel spindles
What is Attrition?
loss through tooth-to-tooth wear
List the diseases that effect enamel?
Attrition Erosion Abrasion Caries Abfraction
What is abfraction?
loss through tensile and compressive forces during tooth flexure
What are caries?
loss through chemical means from cariogenic bacteria (also acid)
What is erosion?
loss through chemical means not involving bacteria (ex. Soda or gastric acid)
What is abrasion?
loss through friction from toothbrushing and/or toothpaste
What are the types of dentin?
Peritubular Dentin Intertubluar Dentin Mantel Dentin Circumpulpal Dentin Primary Dentin Secondary Dentin Tertiary Dentin (reparative dentin)
What is the first pre-dentin that forms called?
Mantel dentin
Describe Peritubular Dentin
wall of tubules
Describe Intertubluar Dentin
between the tubules
Describe Mantel dentin
outermost layer
Describe Circumpulpal Dentin
layer around outer pulp wall
Describe Primary dentin
Formed before completion of apical foramen
Describe secondary dentin
Formed after completion of apical foramen
Describe Tertiary Dentin (reparative dentin)
formed as result to injury
What are the stages of Dentin maturation?
primary mineralization
secondary mineralization
What happens during dentin primary mineralization?
the collagen fibers of the predentin, expanding and fusing together
What happens during dentin secondary mineralization?
new areas of mineralization occur as globules form in the partially mineralized predentin. regularly layered on the initial crystals
What is globular dentin?
where both primary and secondary mineralization have occurred
What is interglobular dentin?
areas where only primary mineralization has occurred
What are the different types of curvature tubules of dentin?
Primary curvature
Secondary curvature
Describe the primary curvature of dentin?
overall tubule course, resembling a large S-shape
Describe the secondary curvature of dentin?
smaller curves reflecting smaller daily changes in odontoblastic direction
List the microscopic features of dentin?
Imbrication lines of Von Ebner
Contour lines of Owen
describe the imbrication lines of Von Ebner
incremental lines or bands that stain darkly and can be likened to growth rings (like lines of Retzius in enamel)
Describe the contours lines of Owen
a number of adjoining parallel imbrication lines that are present in stained dentin; they represent a disturbance in body metabolism that affects the odontoblasts (most pronounced is neonatal line)
How much of population has an overlap of gingiva over CEJ?
60%
How much of population has their MEET the CEJ?
30%
How much of population has an gap of gingiva and can clearly see the CEJ?
10%