Dentin formation Flashcards
dentin definition
1) bone like matrix
2) closely packed dentinal tubules that traverse entire thickness of dentin
3) contain the cytoplasmic extension of odontoblasts that once formed the dentin and maintain it
dentin composition
1) 70% inorganic
2) 20% organic
3) 10% water
dentinogenesis
1) dentin formation begins during the early bell stage
2) from apex of the tooth, the dentin formation spreads down slopes of cusp
3) differentiation of odontoblasts from ectomesenchymal cells of the dental papilla
odontoblast differentiation
1) the growth factors from the epithelial cells cause daughter cells to become odontoblasts
2) less stimulated cells remain undifferentiated
- stem cell properties in the dental pulp
dentinogenesis componenets
1) predentin
- unmineralized matrix near the pulp
2) inorganic component
- calcium hydroxyapatite
3) dentin matrix
- organic components
dentin matrix
1) collagen type I, small amounts of III and IV
2) non collagenous proteins
- DMP 1
- proteoglycans (prevent premature mineralization)
- DSPP (dentin sialophosphoprotein)
dentin sialophosphoprotein
1) DPP
- dentin phosphoprotein
2) DSP
- dentin saloprotein
initial dentin formation
1) mantle
2) circumpulpal dentin
- parallel to DEJ
- collage type I
mantle dentin
1) collagen, proteoglycans, lipids, and non collagenous protein
2) deposition of first collagen fibers to form coronal mantle predentin
3) deposit of von korff’s fibers
- type III and fibronectin
tome’s fiber
1) left behind in the forming dentin matrix as the odontoblast moves away toward the pulp
circumpulpal dentin pattern of mineralization
1) lineral mineralization
- mineralization front appears uniform
2) globular mineralization
- deposition of crystals in several areas
- crystals enlarge and eventually fuse
dentinogenesis imperfecta
1) mutation in dentin sialophosphoprotein (DSPP)
2) inherited disorder
3) dentinal tubules are irregular and larger in diameter
4) uncalcified matrix areas are seen
predentin
1) unmineralized
2) near the pulp
3) light brown
primary dentin
1) mantle dentin
- outer layer - near enamel or cementum
2) circumpulpal dentin
3) bulk of dentin
- produced during tooth development
secondary dentin
1) develops after root formation
2) continuous but much slower
tertiary dentin
1) response to injury
2) reactive or reactionary
- pre-existing odontoblasts
3) reparative dentin
- newly differentiated odontoblast like cells
separation between primary and secondary dentin
1) slight change in direction
tertiary dentin shape
1) sparse irregular tubules
root dentin
1) forms at a later stage of development
2) open apex
- roots are not formed yet
3) by the time the tooth reaches its functional position, about 2/3 of root dentin is formed
4) completion in primary teeth occurs around 18 mo after eruption
5) complete in permanent teeth 2-3 years after eruption
hertwig’s epithelial root sheath
1) from cervical loops
2) initiated the differentiation of odontoblasts that form root dentin
3) cementoblasts derived from the dental follicle
4) epithelial cell rests of malassez are remnants of hertwig’s epithelial root sheath
role of epithelial cell rests of malassez
1) can eventually differentiate to bone, cementum, and PDL
cementum
1) about 45-50% hydroxyapatite
- collagen and noncollagenous
cementum classification
1) primary
- acellular
2) secondary
- cellular
—
1) fibrular
- intrinsic fibers (parallel to root surface)
- extrinsic fibers (sharpey’s fibers)
2) afribrillar
cementum layers
1) acellular afribrillar
- over enamel and dentin at CEJ
2) acellular extrinsic fiber
- cervical margin to apical third of the root
- sharpey’s fibers
3) cellular intrinsic fiber
- middle to apical third and furcation
4) cellualar mixed types of cementum
- apical portions and furcation
hyaline layer
1) intermediate cementum
- between dentin and primary acellular cementum
cementoenamel junction configuration
1)cementum is over enamel
- 60%
2) cementum meets enamel
- 30%
3) cementum, exposed dentin, enamel
-10%
dentinal tubules histology
1) dentinal tubules
- house odontoblastic process
2) migration of odontoblasts to smaller area
- S curve shape in cross section “primary S curve”
intertubular dentin x peritubular dentin
1) peritubular dentin
- surrounds the dentinal tubules
2) intertubular dentin
- in between
interglobular dentin histology
1) areas of unmineralized or hypomineralized
2) failed to fuse into homogenous mass of dentin
sclerotic dentin histology
1) dentinal tubules have become occluded with calcified material
2) glassy or transparent
dead tracts histology
1) empty dentinal tubules
2) odontoblast regression from tubules or death
3) most often in coronal dentin
incremental lines histology
1) lines of von ebner
- at right angles to dentinal tubules
- similar to lines of retzius
2) lines of owen
- accentuated deficiencies in mineralization
- physiological stress
granular layer of tomes histology
1) found only in root dentin
2) a special arrangement of collagen and non-collagenous matrix proteins at the interface between cementum and dentin
dentin pulp complex
1) vital portion of the tooth
2) zones
3) ECM has collagen I and III
4) apical foramen / accessory foramen have blood vessels
5) nerve plexus in the cell free zone is called the subdodontoblastic plexus of raschkow
6) nerves are sympathetic branches from superior cervical ganglion and sensory nerves of TG nerve
zones of the pulp
1) odontoblastic zone
2) cell free zone
3) cell rich zone
4) pulp core
- type II collagen
fibroblasts are most common cell type
dentin sensitivity
1) dentin is directly innervated by nerves through dentinal tubules
2) odontoblasts themselves transmit pain information to nerves
3) fluid in the dentinal tubules will be modified due to pressure and heat => stimulate receptors of subodonticblastic plexus of raschkow (MOST ACCEPTED THEORY)
age changes in the dental pulp
1) reduction in size due to secondary dentin formation
2) increase in fibrous and decrease in cellular components
3) increase in dead tracts and sclerotic dentin
4) young pulp recovers factor from injury than older ones
5) calcification of dentin “pulp stones”
pulp stones
1) calcified masses that are comparable to dentin in the pulp
2) hard to get past in root canals
- have to be removed first
