dentin Flashcards
dentin is ____% mineral by volume and ____% organic matrix by volume
50; 30
of the organic matrix of dentin, about 90% is _____ by weight
collagen-I
90% of the non-collagenous protein of dentin is derived from _____
DSPP (dentin sialophosphoprotein)
other components of dentin:
dentin matrix protein (DMP1) osteonectin (SPARC) bone sialoprotein (BSP) osteopontin (OPN) proteoglycans
odontoblasts differentiate from _____
dental papilla cells
a long cytoplasmic extension encased in dentin
odontoblastic process
rate of deposition of dentin
about 4 micrometers/day
incremental (daily) lines in dentin are called:
incremental lines of Owen (or von Ebner)
dentin formation occurs throughout life, reducing the sizes of the ____ and ____
pulp chambers; root canals
microscopic zones in the pulp
odontoblastic layer (beneath the dentin)
cell-free zone (nerve and capillary plexus)
cell-rich zone (extensive vascular system)
pulpal core
lines of von Ebner are oriented in the ____ axis at approx ____ angles to the dentinal tubules which run in the ____ axis
horizontal; right; vertical
dentin tubules contain ____ which mediate dentin sensitivity
odontoblastic processes
more terminal branching of dentinal tubules occurs in ____ compared to ____
root dentin; coronal dentin
_____ have an S-shaped curvature
coronal tubules
dentin tubules are ____ in diameter
1 to 3 micrometers
more dentin tubules are in the ____ relative to the ____
crown; root
more dentin tubules are near the ____ than the ____
pulp; surface
the fibrillar organic matrix before its calcification
predentin
odontoblasts exhibit a ____ shape, with their nucleus at the ____ region
tall columnar; basal
predentin is always interposed between the ____ and the _____
odontoblasts; mineralizing front
dentin made during tooth formation
primary dentin
primary dentin is also called _____; makes up most of the tooth; outer layer is called _____
circumpulpal dentin; mantle dentin
forms by the slower, continuing deposition of dentin by odontoblasts following completion of the root
secondary dentin
junction betw primary and secondary dentin is characterized by a change in the ______
direction of dentinal tubules
deposition of secondary dentin is fastest on the ____ and _____ of the _____, leading to pulp recession
roof; floor; pulp chamber
local reaction to attrition, caries, or dental restoration
tertiary dentin
subtypes of tertiary dentin
reactionary dentin and reparative dentin
reactionary dentin (least severe) is formed by ____
preexisting odontoblasts
reparative dentin is formed by newly differentiated _____; these cells can be included in the hard tissue, which is called _____
odontoblast-like cells; osteodentin
dentin that has become translucent due to calcification of the dentinal tubules as a result of normal aging or injury; also called _____
sclerotic dentin; transparent dentin
patterns of dentin mineralization
linear or globular
____ occurs at high rates of dentin deposition; best seen in the mantle dentin
globular mineralization
globular mineralization results in an irregular mineralization front at the _____ interface
predentin-dentin
localized areas of hypomineralized dentin, often just beneath the mantle dentin, where globular zones of mineral fail to fuse into a homogeneous mass
interglobular dentin
interglobular dentin can be caused by ____ and _____
decreased vitamin D ; high fluoride
dentinal tubules pass through interglobular dentin, but ____ dentin is not present in these areas
peritubular
peritubular dentin (PTD) is lower in ____, higher in ____, and more highly ____ than intertubular dentin (ITD)
collagen; DSPP; mineralized
where is ITD harder?
ITD is harder at the DEJ than at the pulp (about 4x)
where is PTD harder?
PTD has equal hardness at DEJ and pulp
is PTD or ITD harder?
PTD is harder than ITD at both the pulp (about 20x) and the DEJ (about 5x)
odontoblasts line the ___ surface of dentin
pulpal
the dental phenotype in persons afflicted with osteogenesis imperfecta
dentinogenesis imperfecta type I (DGI-I)
mutations in the ____ and _____ genes cause osteogenesis imperfecta
COL1A1; COL1A2
COL1A1 and COL1A2 mutations can:
- reduce the amount of collagen (less severe phenotype)
2. produce defective collagen molecules (more severe phenotype)
COL1A1 gene mutation causes _____ osteogenesis imperfecta
autosomal-dominant
classic radiographic features of DGI-I (dental phenotype of someone with osteogenesis imperfecta)
bulbous crowns, pulpal obliteration, short roots, and tooth impactions
mutations in DSPP cause:
DD-II (dentin dysplasia type II)
DGI-II
DGI-III
2 structural domains of DSPP
dentin sialoprotein (DSP) - proteoglycan dentin phosphoprotein (DPP)- acidic protein
expression of DSPP in teeth
expressed in preameloblasts, preodontoblasts, and odontoblasts
Dspp (-/-) mice show features similar to human ____
DGI-III
dspp (-/-) mice show enlarged ____, reduced thickness of ____ and increased thickness of ____ (similar to human DGI-III)
pulp cavities; mineralized dentin; predentin
____ is distinct from OI as only the teeth are affected; caused by mutations in DSPP
DGI-II
