Dental Anatomy, Histology, Physiology, and Occlusion Flashcards
Enamel formation is done via what process, and involves what cells?
Amelogenesis
Ameloblast
What embryonic germ layer does ameloblast derive from?
ectoderm
What location of the tooth has the thicker/thinner layer of enamel
Enamel is thicker at the incisal/occlusal areas and thins out until it reaches the CEJ (ranging 2-3mm in thickness)
Cusps develop from individual _______.
ossification centers, which form into developmental lobes
the separation of cusps result in _____ and ______.
grooves and fossae (areas of coalescence)
A functional cusp that opposes a groove or fossa occludes where
on enamel inclines on each side of the groove and not in the depth of the groove (leaves a v shaped escape path between the cusp and its opposing groove for the movement of food during chewing)
the failure/compromised coalescence of enamel results in
a fissure
noncoalesced enamel at the deepest point of a fossa is termed
pit
fissures and pits represent what type of areas
non-self-cleaning areas where acidogenic biofilm accumulates and predisposes the tooth to caries
what is the largest mineral constituent of enamel
hydroxyapatite
what is the % of hydroxyapatite in enamel
90-92%
mineral constituent of enamel
hydroxyapatite (90-92%)
organic matrix protein (1-2%)
water (4-12%)
Enamel rods
“prisms” that are the largest structural part of of enamel and are formed appositionally
Appositional deposition of enamel rods are called?
Striae of retzius
Lines of Pickerill
incomplete, alternatiting lines of retzius noticeable on the enamel surface
Perikymata
space in between the lines of Pickerill that are parallel to the CEJ
how many enamel rods are there?
5-12 million
how are enamel rods positioned?
perpendicular to the DEJ EXCEPT in the cervical region of permanent teeth, where they are oriented outward in a slightly apical direction
the cervical layer of the tooth is missing what? how are the hydroxyapatite crystals oriented?
the cervical layer of enamel is prism-less (known as prismless enamel), and crystals are parallel to one another and perpendicular to the striae of retzius
enamel rods are formed by what cells
ameloblast
what direction are enamel rods produced in
alternating clockwise and counterclockwise
Why are enamel rods produced in alternating patterns
minimizes the fracture of then in the axial direction
what is the term of the alternating deposition of bands in enamel
hunter-schreger bands
what is the nasmyth membrane
a membrane layer that covers the ends of the enamel rods
the nasmyth membrane is replaces by what structure
the pellicle and it is formed by salivary proteins
apatite crystals are arrange how (what is the degrees of the arrangement)
65-degree angle parallel to the long axis of the
what is the permeable route of transmission of ions and molecules within enamel
rod sheaths, enamel cracks
enamel lamellae
thin, leaflike faults between the enamel rod groups and are mostly made of organic material and predispose the tooth to caries.
enamel maturation
age-like maturation of the enamel matrix that decreases its permeability
when is enamel soluble (whats the environment?) and travels in what direction
in acidic conditions and goes from the enamel surface to the DEJ
what does fluoride ions do to enamel
these ions, during enamel formation or applied topically to its surface, DECREASES its solubility
fluoride concentration decreases in what direction
from the surface to the DEJ
fluoride can effect what properties of enamel
- hardness of the apatite mineral
- chemical reactivity
- stability
fluoride works to decrease/increase what things
- DECREASE acid solubility
- DECREASE rate of demineralization
The density of enamel also decreases in what direction
from the surface to the DEJ
enamel is a rigid surface that is both ____ and _____.
strong and brittle
enamel’s elastic modulus is
high
enamel’s compressive strength is
high
enamel’s tensile strength is
low
dentin’s elastic modulus is
low
dentin’s compressive strength is
high
dentin’s tensile strength is
high
the junction of enamel and dentin is described as having what kind of appearance
scalloped with enamel projections into the dentin
enamel rods that lack projection into dentin are classified as being
easy to fracture
enamel rods should be
supported by dentin
pulp and dentin are formed by what structure
the papilla of the tooth bud
what are the 4 main functions of the pulp
- formative/developmental
- nutritive
- sensory (protective)
- defensive/reparative
primary and secondary dentin is formed by what cells
odontoblast
dentin nociceptors are unique because
various stimuli elicit pain ONLY as a response - not differentiating between heat, touch, pressure, or chemicals
the pulp is lined on its periphery by
a cellular layer of odontoblast, the cell free zone, and the cell rich zone
dentin is formed by what cellular process and by what cells
dentinogenesis
odontoblast
tomes fibers
odontoblastic cells that are apart of the pulp cavity and extend in the tubules of the mineralized dentin
what happens/what are they called when odontoblasts cross into the enamel
enamel spindles
dentin formation begins before or after enamel formation
immediately before.
extracellular collagen is generated after they move away from ameloblast
the most recent layer of dentin is always formed on what surface
pulpal surface
new dentin is mineralized or unmineralized
unmineralized (pre-dentin)
primary dentin is typically completed when
3 years after eruption
where does secondary dentin form
on all internal aspects of the pulp cavity
(thicker on the roof and floor of multi-rooted teeth)
what is the composition of human dentin
50% inorganic material
30% organic material
the organic material of dentin is composed of what
90% type I collagen
10% noncollagenous proteins
the mineral content of dentin is less than____ but more than ______(s).
a. enamel
b. cementum and bone
the mineral content of dentin increases with
age
dentin is distinguished from enamel during tooth prep by
- color and opacity
- reflectance
- hardness
- sound
typically what color is dentin
yellow-white
(black or brown when exposed to oral fluids)
physical, thermal, chemical, bacterial, and traumatic stimuli are detected through what
fluid filled dentinal tubules (hydrodynamic theory)
hydrodynamic theory suggests what
stimulus initiated rapid tubular fluid movement within the dentin tubules accounts for nerve depolarization
which is more permeable - coronal or root dentin
coronal
what odontoblast are first to respond to lesion formation
primary odontoblast
a high concentration of inflammatory response mediators (cytokines and chemokines) may do what to primary odontoblast
signal death
occlusion of the tubules lumen does what to the ability of light to pass through
increases
tertiary dentin is what
reactionary
tertiary dentin can be classified as
reactionary and reparative(structually different)
overcontouring in tooth structure results in what
increased plaque retention that can lead to a chronic inflammatory state of the gingiva
what is the function of proximal contacts
they promote normal healthy interdental papillae filling the interproximal space
where is the proximal contact located
the incisal third of the approximating surfaces
where is the ‘col’ located
lying beneath the contact area
embrasures are covered by what type of epithelium
nonkeratinized
which embrasure is typically bigger - lingual or facial
lingual
what are dental caries
a preventable, chronic, and biofilm mediated disease modulated by diet
caries is caused primarily by
imbalance of the oral flora (biofilm) due to the presence of fermentable dietary carbohydrates on the tooth surface over time
the critical pH level for enamel is ____ and ____ for dentin
5.5 and 6.2
a low pH does what to tooth structure
remove calcium and phosphate (demineralization)
caries is a balance between
- time
- fermentable carbohydrates
- host
- cariogenic biofilm
dental plaque
soft tenacious film accumulation on the surface of teeth
