Chapter 20 Flashcards
where does the ameloblasts lay down a matrix of mucopolysaccharide and organic fiber next to the dentin matrix?
Dental papilla
Where is the CEJ formed?
Dental Papilla
What has genetic control over the tooth shape?
Dental papilla
What is the hardest structure of the body?
Enamel
Enamel is generally what color?
White
Enamel can appear what color at times and why?
yellowish because of the reflection of the underlying dentin
Composition of enamel is
96% inorganic (Hydroxyapatite)
Other 4% of enamel is composed of what
Water and fibrous organic material
Enamel rod is made up of what?
Hydroxyapatite crystals.
What is the primary unit of enamels structure?
Enamel Rod
a column of enamel that runs from the Dentinoenamel Junction to the surface of the tooth
Enamel Rod
Enamel rod is Perpendicular to
The DEJ and the surface of the crown
Lays down matrix to form enamel
Ameloblasts
where does Ameloblasts begin to lay down Matrix
At the tip of the cusp and then further toward the cervical line
Ameloblast lying down matrix is referred to as
the mineralization stage of enamel rod calcification
The second stage of calcification is called the
Maturation stage
what happens in Maturation stage
Crystals should grow in size until they are tightly packed together
When is there a change in development of the enamel rod
every 4 days
when change in development of enamel rod occurs and a brownish line develops in the enamel it is called
Striae of retzius
On the labial surface of the crown you can se horizontal lines on the crown due to
Striae of Retzius
Horizontal lines that can be seen on crown of Anterior teeth are called
Imbrication lines.
Imbrication lines are
surface manifestations of the striae of retzius
The final job of ameloblasts is to
lay down a protective layer over the enamel
Protective layer of the enamel created by ameloblasts is called
Primary enamel cuticle
Another name for Primary enamel cuticle is
Nasmyths membrane
Nasmyths membrane (Primary Enamel Cuticle) covers
the crown and remains there for many months after eruption until worn away by toothbrushing and other abrasion
when spots or entire areas of the teeth appear white to whitish yellow in color
Hypocalcified enamel
hypocalcified enamel the result of
insufficient growth of the enamel crystals or an insufficient number of crystals originally deposited in the matrix
hypocalcification can be termed
Soft teeth
soft teeth (hypocalcification) can decay
More rapidly
Density is normal but enamel is thin in
Hypoplastic enamel
teeth with hypoplastc enamel look what color
Enamel of tooth will have a yellow to gray hue
Enamel will look thinner than normal radio graphically due to
hypoplastic enamel
Cracks in the enamel
Enamel lamellae
Enamel lamellae clinically appear
as hairline cracks in enamel that extend all the way through the enamel and even into the dentin
small area of hypocalcified enamel seen at the DEJ
Enamel tuft
enamel tuft is only foud
in the histologic section of the tooth
Enamel spindle is an
odontoblastic process
Cellular extension of the odontoblast that becomes trapped between ameloblasts in early developed
Enamel spindle
Enamel spindle is found only
histologically
Hard yellowish substance
Dentin
Composiion of dentin
70 % inorganic hydroxyapatite
30 % primarily organic (composed of collagen, mucopolysaccharide ground substance, and water)
Three distinct areas of dentin
- ) dentinal tubule
- ) peritubular dentin
- ) intertubular dentin
A long tube running from the DEJ to the pulp containing odontoblastic process
Dentinal Tubule
an area of higher crystalline content immediately surrounding the dentinal tubules
Peritubular dentin
the bulk of the dentinal material
Intertubular dentin
Distinct areas of dentin are all
Microscopic structures
dentin that has formed by the time the tooth has ruptured into the oral cavity
Primary dentin
Dentin that continues to be formed
secondary or reparative dentin
layer of dentin formed inside the regular dentin and positioned closest to the pulp
secondary dentin
secondary dentin starts forming when
About the time the tooth erupts and comes into contact with the opposing tooth
what happens as secondary dentin forms
it causes the overall sixe of the pulp chamber to decrease
Newly erupted teeth have
prominent pulp horns and large pulp chambers
Dentin formed in response to local trauma
Repairative dentin
repairative dentin is located
immediately beneath the trauma
Trauma that triggers repairative dentin can be
Occlusal Mechanical or chemical
the condition that exists when one tooth or part of a tooth is subjected to more occlusal stress than normal
Occlusal Trauma
The result of cavity preparations in the tooth
Mechanical trauma
brought about by the acids produced by the bacteria that cause dental caries
Chemical trauma
dentinal tubules that are empty because of the death of the odontoblasts that originally occupied them
Dead Tracts
Dead tracts can only be seen
Microscopically
Dead tracts provide
a pathway to the pulp for bacteria involved in decay
Dentinal tubules become filled with dentin material
Sclerotic dentin
Sclerotic dentin is related to
Occlusal trauma or decay
Pulp consists of
Blood vessels, lymphatic vessels, nerves, fibroblasts and collagen fibers.
Nerves of the pulp are
Primarily sensory
Nerves of the pulp transmit
only one type of sensation– Pain
Primary abnormality seen in pulp
Pulp stones
Small circular calcified areas found in the pulps
Pulp stones
Pulp stones are found in about
about 80% of older persons age 70-80 years
True pulp stones
originate from odontoblasts and are very rare
False pulp stones
The most common type and probably originate from dead cells with concentric layers of calcium phosphate around them.
What does a false stone look like under the microscope
resembles an onion cut in the cross section
Free pulp stones are found
In the middle of the pulp
Pulp stones may be seen as
Small globular radiopacities on the microscope
the only problem that may occur with pulp stones
Would be in the endodontic treatment of a tooth with pulp stones (RCT- root canal therapy. )
