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158 Cards in this Set
- Front
- Back
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formed from odontoblasts that originate from ectomesenchyme (remember neural crest);
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dentin
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2 parts of dentin
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coronal
root |
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appear at other parts of the dentin; these may also carry blood vessels; these canals (openings) represent a potential compromise to pulp (bacteria entry)
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lateral canals
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what makes up dent ? %
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70% inorganic
20% organic 10% water |
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extensions of odontoblasts, called ?, occupy dentin tubules
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odontoblast processes
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junctions dentin makes
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dentinoenamel Junction
dentinocementum junction |
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3 types of dentin
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primary
secondary tertiary (reparative) |
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Mantel dentin: first formed dentin; outer-most layer (150 microns thick) differs from rest of primary dentin (mineralized from matrix vesicles, contains loosely packed collagen fibrils, less mineralized)
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primary
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root dentin
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secondary
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dentin is harder than ? and softer than ?
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bone
enamel |
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crown dentin formation begins in what stage
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late bell
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where does the formation of dentin start
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cusp of the tooth
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dentin immediatly beneath the enamel
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crown dentin
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IEE and OEE come together to form ? which brings about differentiation of root odontoblasts to form root dentin
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Hertwigʼs Epithelial Root Sheath (HERS)
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? dentin formation begins later than ? dentin formation and is slower
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Root
Crown |
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steps of dentinogenesis
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ectomesenchyme cells
preodontoblasts odontoblasts dentin |
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how does ectomesenchyme become preodontoblast?
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cell elongates and develops organelles
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how does preodontoblast become odontoblast?
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cytoplasm and protein synthesizing organelles increase
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how does mantel dentin differ from primary dentin?
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mineralized from matrix vesicles
contains loosely packed collagen fibrils less mineralized |
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where do growth factors bind in the basement membrane?
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heparin sulfate
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growth factors secreted by IEE cells
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TGF (transforming growth factor)
BMP2 (bone morphogenic growth factor) IGF (insulin-like growth factor) |
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what develops growth factor receptors?
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preodontoblasts
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Odontoblasts differentiate where?
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environment of ground substance
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type 3 collagen synthesized by odontoblasts first appear in
ground substance and extend to inner enamel epithelium |
large fibers (von Korff's fibers)
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collagen type 1 fibrils synthesized by odontoblasts also appear; these fibrils run parallel to future dentin enamel junction
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small fibers
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what buds off of odontoblasts?
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matrix vesicles
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odontoblast processes that pass through basement membrane into the enamel matrix, where they become trapped in the future enamel
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enamel spindles
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what always precedes mineralization?
Mineral formation always lags behind the formation of ? What always appears before dentin formation? |
matrix formation
organic matrix predentin |
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how thick in mantel dentin
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150-200 microns
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what type of capillaries are in dentin
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fenestrated
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how does mineralization continue w/o matrix vesicles?
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Ca brought into dentin by capillaries
presence of alkaline phosphotase and Ca ATP |
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Inorganic ions likely reach the mineralization front through ?
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odontoblast
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two patterns of dentin mineralization
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globular
linear |
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mantel dentin laid down in globs and globs come together
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globular dentin
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globs that have joined to form a mineralization front that move together or conversely, the front can move in a globular pattern
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linear
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where do odontoblastic processes lie within?
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canaliculi dentin tubules
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which way are dentin tubules tapered
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towards enamel
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Odontoblasts attach to neighboring odontoblasts
by a ? |
terminal web composed of actin filaments
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The odontoblast process is encased in a tube or canaliculus called a
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dentin tubule
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The odontoblast process extends to the DEJ and may penetrate the DEJ where it forms an ?
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enamel sipndle
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course of dentin tubules in the crown of the tooth is ? due to the crowding of the odontoblasts as they get squeezed into a smaller space near the pulp cavity.
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S-shaped
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Tubules run straight in the root where ? is not an issue
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crowding
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main product of odontoblasts, network of type I collagen fibrils, randomly arranged parallel to dentin tubules
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intertubular
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forms a highly mineralized collar (40% more mineralized, than intertubular dentin) around the tubule
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peritubular dentin
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Dentinoenamel junction: two hard tissues come together forming a ?
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scalloped profile
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odontoblast processes trapped in enamel
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enamel spindles
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tubules often become blocked with calcified material, increases with age, consistent with continued mineralization by peritubular dentin, and likely protects the pulp.
- takes on glassy appearance - translucent to light |
sclerotic dentin
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areas in dentin that fail to mineralize or hypomineralized dentin where globular zones fail to fuse
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interglobular dentin
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what causes interglobular dentin?
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Vit d deficiency
exposure to high fluoride during dentin |
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what remain present in interglobular dentin?
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tubules
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only seen in ground sections, only seen in root dentin adjacent to cementum
- possible interpretations include: - hypomineralized regions of interglobular dentin - looped terminal ends of dentin tubules found only in root - arrangement of collagen and non-collagenous matrix proteins between dentin and cementum |
tomes granular layer
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air filled spaces from loss of odontoblast process or death of the odontoblast.
- tubules filled with air - seen in ground sections - age related - blackened tubules alone or in combination with other tubules |
dead tracts
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Dentin is laid down incrementally to form ?
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growth lines
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5 day cycles in dentin produce shifts in orientation called
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incremental lines of von Ebner
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Growth lines run ? to dentin tubules
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at right angles
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accentuated variations in metabolism cause deficiencies in mineralization
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contour line of owen
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what becomes pulp when dentin is first laid down?
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dental papilla
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soft connective tissue that supports dentin
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pulp
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2 regions of the pulp
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coronal pulp (crown)
radicular pulp (root) |
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4 pulp zones
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odontoblast zone
cell free zone cell rich zone pulp core (vessels and nerves) |
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principle cell types in pulp
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odontoblasts
fibroblasts nerve blood vessels macrophages lymphocytes matrix ground substance |
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supports cells in pulp and transport for nutrients to cells and metabolites from cells to blood
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ground substance
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Blood vessels enter tooth via ?
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apical foramen (accessory)
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source of blood vessels
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external carotid
interior alveolar arteries |
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What and What from trigeminal ganglion enter as myelinated nerve bundles
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Inferior and superior alveolar nerves
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Inferior and superior alveolar nerves branch extensively to form what?
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Raschkow nerve plexus in the subodontoblastic space
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enter the pulp to supply blood vessels
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sypathetic nerves
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Dentin innervated directly
• Odontoblast acts as a receptor that is coupled to nerves in pulp • Receptors found in pulp are stimulated by movement of fluid through tubules (pressure in tubule pushes against free nerve endings in pulp) |
dentin sensitivity; 3 hypothesis
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where do ameloblasts derive from?
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oral epithelial cells of ectodermal origin
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? are lost as the tooth erupts into the oral cavity and therefore are not ?
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ameloblasts
renewable |
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what are the units of enamel
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rods and interrods
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what are rods made of?
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crystals
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are rods and interrods similar in structure?
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yes
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rods are ? in shape; contain crystals that run along the ?
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cylinder-like
long axis |
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parts of the rod
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rod
rod neck rod tail |
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what are found at the boundary between rods and interrod regions
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rod sheaths
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what do the rods sheaths contain that remain following enamel development?
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proteins
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2 steps of enamel formation process
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partial mineralization (30%) at full thickness of immature enamel
full mineralization |
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- Cubodial (or low columnar)
- Contain central nucleus - Poorly developed Golgi; mitochondria are present - Contain a terminal web (junctional complex near stratum intermedium) |
inner enamel epithelial cells
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- Differentiate from IEE cells
- Elongated (columnar) - Contain a polarized nucleus near stratum intermedium - Highly developed Golgi ( migrates distally), endoplasmic reticulum increases - Second junctional complex (terminal web) forms at the distal end - Basement membrane fragments and disintegrates during mantel predentin formation |
ameloblasts
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what do ameloblasts secrete
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enamel protein
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When do inner enamel epithelial (IEE) cells become ameloblasts?
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At the time when preodontoblasts elongate and become odontoblasts.
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Three Stages in Enamel formation
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I. Presecretory Stage
II. Secretory Stage (Structure and Structure-less enamel formation) III. Maturation Stage |
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what does ameloblast secrete besides enamel protein
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dentin protein
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what forms junctional complex formed?
second junctional complex(terminal web)? |
IEE
ameloblast |
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First enamel is ?; NO rod formation occurs
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structure-less enamel
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With formation of distal ?, protein matrix is secreted at both proximal and distal sites
- enamel formation at the proximal site begins before enamel formation at the distal site |
Tomes Process
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tomes proximal end form?
tomes distal end forms? |
inter rod region
rods |
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End Stage of Enamel Formation
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structure-less enamel formation
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(Only at Proximal Tomes Process)
Laid down adjacent to dentin: protein deposited on dentin Crystallization directly from dentin crystals in mantel dentin |
first matrix
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(Tomes Process)
Presence of distal Tomes process Formed slightly later at a distal site |
second matrix
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Secretion forms ? (distal site) and ? (proximal site)
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RODS
WALLS |
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where do enamel proteins synthesize?
packed into vesicles? |
RER
golgi |
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As ameloblast loses its ?, the last-formed enamel is structureless
enamel; as it was in the initial formation; no rod formation occurs |
tomes process
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Enamel hardening that occurs before tooth eruption results from ?
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growth in width and thickness of crystals
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During Maturation Stage ? are degraded and removed and are mostly absent from mature enamel
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enamel matrix proteins
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Amelogenesis can take up to ? years to complete in permanent teeth
? of this time is taken up in the Maturation Stage |
5
2/3 |
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when does the maturation stage begin?
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full thickness of immature enamel
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Distal end of the ameloblast modulates between ? and ? edges
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rough
smooth |
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Ameloblasts with ? serve to introduce inorganic material (mineral) to the enamel
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ruffled edges
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Root of the tooth consists of ? covered by ?
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dentin
cementum |
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Root formation begins after ?
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complete formation of the crown
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IEE and OEE come together at cervical loop to form ?
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Hertwig's epithelial root sheath (HERS)
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functions to induce differentiation of adjacent pulp cells to become odontoblasts and lay down root dentin
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HERS
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determines the shape and number of roots
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HERS
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when does HERS disintegrate?
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when dentin is formed, allowing cells from dental sac to move in contact with root dentin
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differentiate to become cementoblasts which lay down cementum
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follicle cells
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Remnants of HERS persist in periodontal ligament where they are called ?
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epithelial cell rests of Malassez
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Cell growth takes place within the ?
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root sheath
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Root Sheath breaks down before dentin forms (dentin fails to form) timing: too early
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accessory root canal
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Root Sheath fails to breakdown (cementum fails to form) timing: too late
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areas of exposed dentin
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Root Sheath adheres to some regions of the dentin timing: too lat
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enamel pearls
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those tissues supporting the tooth
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periodontium
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specialized fibrous joint formed by cementum periodontal ligament alveolus gums
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gomphosis
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Periodontium is of ? origin
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ectomesenchymal, neural crest
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ectomesenchyme produces what four things
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dental papilla
odontoblasts dentin dental sac/follicle |
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what do the layers of the dental sac/follicle produce?
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inner-cementum
middle-PDL outer-alveolar bone proper |
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gingival facing tooth comes from what 3 things
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enamel epithelium
oral epithelium connective tissue |
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hard, avascular tissue, connective tissue, covering the root
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cementum
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two types of cementum
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primary acellular
secondary cellular |
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part of cementum that provides attachment for tooth
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primary acellular
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part of cementum that provides adaptive role in tooth movement, repair, and regeneration of periodontal tissues (some teeth don't have)
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secondary cellular
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what provides signal to transform dental follicle cells into cementoblasts?
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dentin
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Cementoblasts align themselves next to ?
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unmineralized mantel predentin
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Cementoblasts then extend ? into the predentin matrix where they deposit collagen fibrils which mix with fibrils given off by odontoblasts.
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processes
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Mineralization of the mantel dentin takes place adjacent to odontoblasts and spreads throughout the matrix until the cementoblast fibrils are also mineralized. This region is named the ?
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DCJ
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Cementoblasts move away from the forming mineralization front but give off ? as they move away. ? are also secreted around the fibers.
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fiber bundles
Noncollagen proteins |
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PDL ends get mineralized in the cementum where they are called ?
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sharpey's fibers
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PDL fiber bundles next enter into the fibrous fringe laid down by the migrating cementoblasts
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primary cellular cementum
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provides adaptive role in tooth movement, repair, and regeneration of periodontal tissues
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secondary cellular cementum
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when does secondary cementum occur?
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after occlusion
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Secondary cementum deposited as unmineralized matrix
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cementoid
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As cementum forms, cementoblasts become trapped; trapped cementoblasts are called ?
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cementocytes
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Cementocytes occupy hollow spaces called ?
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lacunae
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Cementocytes give off processes which project toward the PDL where they receive nourishment by diffusion from the PDL. These processes are contained in small tubes in cementum called
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canaliculi
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Cementoblasts lay down ? randomly at first, but then arrange the fibrils parallel to the root surface
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collagen fibrils
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that part of bone containing tooth sockets
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alveolar process
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when does alveolar bone formation begin?
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8th week
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3 components of the alveolar process
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outer cortical plate
central spongiosa alveolar bone proper |
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part of the alveolar bone that acts as attachment of skeletal muscles
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outer cortical plate
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bone lining alveolus
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alveolar bone proper
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2 layers of the alveolar bone
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bundle bone
lamellar bone |
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directly lines socket and bundles of PDL fibers attach to it
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bundle bone
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Alveolar bone proper and outer cortical plate meet at ?
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alveolar crest
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soft CT that lies between cementum and alveolar bone
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PDL
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derives from dental sac/follicle in ectomesenchyme
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PDL
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begins as unorganized connective tissue located in a centralized ligament space
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PDL
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primary collagens in PDL
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type 1, 3, and 7
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Collagen fibrils arranged in bundles
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spliced rope
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principle bundles of PDL
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trans-septal
alveolar crest fibers horizontal fibers oblique fibers apical fibers |
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connect cementum between adjacent teeth
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trans-septal fibers
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attach cementum to alveolar bone
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alvoelar crest fibers
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fibers with right angles to long axis of the tooth
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horizontal fibers
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fibers around the apex of the root
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apical fibers
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only between multi-rooted teeth
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interradicular fibers
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Superior/Infervior alveolar arteries branch to become ?
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interalveolar arteries
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Interalveolar arteries pass through bone; enter PDL as ?
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perforating arteries
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nerve in PDL
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trigerminal nerve
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