Class 4 Dentin Flashcards
what are the structural components of dentin and their relative percentages
-70% mineral/inorganic
-20% organic
-10% water
what makes up the mineral/inorganic component of dentin
-calcium hydroxyapatite and trace amounts of calcium carbonate, fluoride, magnesium and zinc
what makes up the organic dentin matrix
-type 1 collagen with trace amounts of type 3 and 5
-50% non-collagenous proteins are phosphoprotein
-sialoprotein and silophophoprotien
-proteoglycans (biglucan and decorin) and glycosaminoglycans (chondroitin 4 sulfate and chondroitin 6 sulfate)
-osteonectin
-osteopontin
-receptor binding sequence arginine-glycine-asparagine (RGD) binding complex
what orientation does type 1 collagen in dentin run in relation to the basal lamina
parallel
what are the differences in type 1 collagen in dentin vs bone
- higher ratio or proline and hydroxyproline
-higher prevalence of molecular cross-linking
-higher level of bound water
-random orientation of the hydroxyapatite crystals
what are the life cycle stages of dentin
-pre-odontoblast
-secretory odontoblast
-transitional odontoblast
-resting odontoblast
what happens with fibronectin in the pre-odontoblast stage
-stimuli is derived from fibronectin from pre-ameloblasts located within the basal lamina of the inner enamel epithelium and growth factors derived from the IEE
-the fibronectin receptors on pre-odontoblasts allow the cells to align themselves along the basal lamina, assume polarity and differentiate into secretory cells
what do fibronectin receptor help do
align pre-odontoblasts along basement membrane with pre-ameloblasts on opposite side
what is odontoblast differentiation stimulated by
growth factors secreted by the IEE
what are the growth factors secreted by the IEE in odontoblast differentation
-transforming growth factor
- bone morphogenic protein
- IGF
-fibroblast growth factor
what happens in odontoblast differentiation in the pre-odontoblast stage
-complete differentiation of odontoblasts required a set number of replications to express necessary receptors to recognize growth factors
- the GF then help odontoblasts differentiate resulting in a mature odontoblast and a daughter cell that is forced into the subodontoblastic layer
what is the subodontoblastic cell layer and what is it responsible for
layer under the primed replicated pre-odontoblasts, “back up layer”, responsible for reparative dentin formation via reparative odontoblasts that differentiate from pulpal cells
what protects the subodontoblastic cell layer from growth factors
the layer above it
when is the subodontoblastic layer activated
when something injures the odontoblastic layer growth factors will trickle down to this layer causing maturation
describe the cells and their role in the subodontoblastic layer
they represent ectomesenchymal cells exposed to the entire cascade of developmental controls for odontoblastic differentiation except for the inductive influence of the growth factors with the IEE
describe the mature odontoblasts in the secretory odontoblast stage
tall columnar cells with extensive junctional complex and gap junctions formed
what do the mature odontoblasts in the secretory odontoblast stage do
-formation/crystallization of hydroxyapatite
-secrete type 1 collagen and trace type 3 and 5
- secrete matrix vesicles
how does formation/crystallization of hydroxyapatite by odontoblasts occur
significant alkaline phosphatase activity
what do the matrix vesicles secreted by odontoblasts contain
-alkaline phosphatase, phospholipids, phosphoproteins, pyrophosphatase
-calcium and phosphate
-annexin
-calcium hydroxyapatite crystals
what does annexin do
mediates flow of calcium into the matrix vesicle and serves as a collagen receptor that binds matric vesicles to collagen
what is mantle dentin and describe it
-first formed dentin
-50-100 um thick layer
- consists of type 1 and 3 collagen
how are the collagen fibers in mantle dentin arranged in orientation to the basal lamina of the IEE
perpendicular
what is the mantle dentin secreted by and then what happens
odontoblasts which then stimulates ameloblasts to secrete enamel matrix
how often is the organic matrix of dentin deposited
incrementally at a rate of 4-8 um per 24 hours
what are incremental lines in dentin and what is another name for them
-lines of von ebner
-represent a hesitation in matrix formation and subsequent altered mineralization that occured after 4-20 days of matrix deposition
what are neonatal lines/contour lines of owen
deficiencies and irregularities in dentiogenesis resulting in areas of hypomineralization in the dentin matrix
what are incremental lines in dentin a counterpart to and what does it occur
striae of retizius of enamel happening every 4-8 days
where are odontoblastic processes/dentin tubules located in the secretory odontoblast
extend out, trapped in dentin and branches out connecting to basal lamina. always remains connected with the basement membrane
where are anastomoses/branches in secretory odontoblast located
occurs as the tubule gets closer to the basement membrane. increases surface area/attachment points
what are the anastomoses/branches in the secretory odontoblast important in
bonding agents for composite
where does mineralization in dentin tubules occur
around the odontoblastic process
how are the dentin tubules tapered
narrower (0.9 um) near the DEJ and wider (2.5 um) as it nears the pulpal surface (and 1.2 um at mid-length)
dentinal tubules per unit area increases as ___
you reach the pulp due to pulpal chamber decreasing in size
where are dentinal tubules greater
near the pulpal surface (40,000) and about 20,000 near the DEJ
what are the types of dentin near the tubules
peritubular dentin and intertubular dentin
describe peritubular dentin
-more calcified/harder and more resistance to etch
-greater content of inorganic salts/more mineralized
describe intertubular dentin and its location
demineralized
-located between the tubules
what are the patterns of mineralization of dentin
linear
-globular/interglobular
describe linear mineralization
calcified uniform manner and has solid appearance
describe globular/interglobular mineralization
has areas of unmineralized and hypomineralized dentin between normal calcified dentinal layers
where is globular/interglobular mineralization typically seen
in root surfaces and crowns of teeth
does globular/interglobular mineralization indicate that somethings wrong
no just a different mineralization pattern
what is tome’s granular layer
dentin that is formed globularly found in the root just adjacent to the cementum
what is tomes granular layer used to distinguish
root dentin from crown dentin
what is primary dentin
all the dentin (except mantle dentin) formed up to the time the tooth achieves functional occlusion
what is secondary dentin
all the dentin formed (except tertiary/reparative dentin) formed after the tooth achieves functional occlusion
what are dead tracts, what are they filled with and what do they look like
dentinal tubules that are void of the odontobalstic processes
-either filled with air or organic debris
-appear black in transmitted light microscope
what is sclerotic dentin
dentin in which the tubules are occluded with mineral (no odontoblasts) the dentin is non-tubular and is nearly transparent
when does sclerotic dentin occur
incidence occurence increases with increasing age of patient
how often are incremental lines of von ebner depositied
increments of 4-8 um every 24 hours
when do incremental lines of von ebner occur and what are they
4-20 days of matrix deposition and are thought to represent hesitations in matrix deposition and therefore altered mineralization
what are contour lines of owen caused by
exaggerated von ebner lines caused by hesitations in maturation stages of the dentin
what is the neonatal line
exaggerated von ebner line caused by trauma from birth
-whatever part of the tooth was forming at the time of birth will hold and then continue on
what is tetracycline staining
lines/change in color of tooth occurs due to tetracycline taken at formation of certain tooth development
what kind of stain results from tetracyclin
deep intrinsic stain
what is reparative dentin/tertiary dentin
dentin deposited by newly differentiated odontoblasts at the site of pulpal trauma
-a defensive reaction attempting to wall off the pulp from the site of injury (caries)
where does reparative/tertiary dentin form
when carious lesion reaches DEJ it will form at the pulp interface of the dentin
what is the process of reparative dentin formation
cells in the subodontoblastic layer once exposed to growth factros released by stimulated pulpal cells differentiate and form the matrix of reparative dentin
what is the goal of reparative dentin
wall off the site of injury and protect the pulp from more damage
what is pulp capping/pulpotomy
process of removing infected pulp and pulp capping it. caused injury to pulp so a bridge of reparative dentin in root canal can form to protect the tooth and save it from having to get a root canal
what is dentinogenesis imperfecta
hereditary defect that results in bluish gray teeth with an apalescent sheen
describe the enamel and dentin in dentinogenesis imperfecta
-the enamel is normal but chips off due to lack of support by the abnormal dentin
- very little connection between enamel and dentin due to lack of enamel tufts
describe the pulp chambers in dentinogenesis imperfecta
pulp chambers and canals are usually obliterated by defective dentin formation
what is dental attrition due to bruxism
loss of wear of surface caused by tooth to tooth contact during mastication of parafunction
which wears faster in dental attrition due to bruxism: enamel or dentin
same rate
is dental attrition due to bruxism cold/temperature sensitive
yes
what is dental erosion
loss of hard dental tissue by chemical processes
describe what dental erosion looks like
-broad concavities with cupping of occlusal surfaces and dentin exposure
- incisal translucency as well as wear on non-occluding surfaces
- amalgam restorations appear raised and have non-tarnished appearance
what is the caries balance
the balance between pathological and protective factors
what does the hydroxyapatite core consist of
a more soluble carbonate apatite
where does the carbonate subsitution occur in hydroxyapatite core
at the phosphate site
what is the core of carbonated apatite eroded by
acids due to its greater susceptibility to dissolution
what does fluoride replace and do in hydroxyapatite
may substitute hydroxyl ions in hydroxyapatite conferring greater stability and resistance to acidic dissolution
how is bacteria responsible for dental caries (mechanism)
-bacteria ferments carbohydrates
-excrete acids
-acid attacks hydroxyapatite core and weakens it
what bacteria are responsible for enamel and dentin caries
-streptococcus mutans
-streptococcus sorbinus
-streptococcus gorgonoid
-lactobacillus acidophilus
what bacteria are responsible for root caries
actinomyces viscosus
what is the dental caries process from enamel to dentin to pulp
enamel: a substantial cavitation is produced beneath the adjacent enamel surface. initally the caries lesion exhibits a small opening in the enamel and a pyramidal shaped dentin lesion with the apex of the pyramid pointing towards the tooth pulp
dentin: as it reaches DEJ it spreads laterally due to branching of dentinal tubules at the DEJ and then penetrates towards the pulp within the dentinal tubules
pulp: pulp necrosis can occur due to overwhelming of the pulpal tissue with carious lesions
how much of the population is affected by dentinal sensitivity
1 in 5 people
what teeth are most commonly affected by dentinal sensitivity and why
canine and premolars usually due to occlusal forces
what stimuli are associated with dentinal sensitivity
-cold/hot beverages
-sweet/sour food
- aggressive brushing
-acidogenic plaque bacteria
-cosmetic bleaching of teeth
-clenching or bruxism
what causes sensitivity in free nerve endings
excitability
what are the dentinal sensitivity theories
-direct innervation theory
- transduction theory
- brannstroms hydrodynamic theory
what is the direct innervation theory
direct stimulation of nerve endings in dentinal tubules
what is the transduction theory
stimulation of odontoblasts that are coupled to nerves in the pulp
what is brannstroms hydrodynamic theory
stimulation of dentinal tubules or exposed odontoblastic cell processes causes movement of tissue fluids within dentinal tubules that stimulate nerve endings in close associcated with dentin at the dentin/pulpal interface
what is brannstroms hydrodyanmic theory rooted in and what is it
charles law- the volume of gas or fluid is directly protportional to the amount of heat applied at a constant pressure
what does charles law say if heat is applied to the tooth
the volume of the fluid in the tubules increases stimulating nerve endings
what does charles law say if cold is applied to the tooth
volume of fluid in the tubules decreases stimulating nerve endings
