Dentin formation

Question 1

dentin definition

Answer 1

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

Question 2

dentin composition

Answer 2

1) 70% inorganic
2) 20% organic
3) 10% water

Question 3

dentinogenesis

Answer 3

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

Question 4

odontoblast differentiation

Answer 4

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

Question 5

dentinogenesis componenets

Answer 5

1) predentin
- unmineralized matrix near the pulp
2) inorganic component
- calcium hydroxyapatite
3) dentin matrix
- organic components

Question 6

dentin matrix

Answer 6

1) collagen type I, small amounts of III and IV
2) non collagenous proteins
- DMP 1
- proteoglycans (prevent premature mineralization)
- DSPP (dentin sialophosphoprotein)

Question 7

dentin sialophosphoprotein

Answer 7

1) DPP
- dentin phosphoprotein
2) DSP
- dentin saloprotein

Question 8

initial dentin formation

Answer 8

1) mantle
2) circumpulpal dentin
- parallel to DEJ
- collage type I

Question 9

mantle dentin

Answer 9

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

Question 10

tome’s fiber

Answer 10

1) left behind in the forming dentin matrix as the odontoblast moves away toward the pulp

Question 11

circumpulpal dentin pattern of mineralization

Answer 11

1) lineral mineralization
- mineralization front appears uniform
2) globular mineralization
- deposition of crystals in several areas
- crystals enlarge and eventually fuse

Question 12

dentinogenesis imperfecta

Answer 12

1) mutation in dentin sialophosphoprotein (DSPP)
2) inherited disorder
3) dentinal tubules are irregular and larger in diameter
4) uncalcified matrix areas are seen

Question 13

predentin

Answer 13

1) unmineralized
2) near the pulp
3) light brown

Question 14

primary dentin

Answer 14

1) mantle dentin
- outer layer - near enamel or cementum
2) circumpulpal dentin
3) bulk of dentin
- produced during tooth development

Question 15

secondary dentin

Answer 15

1) develops after root formation
2) continuous but much slower

Question 16

tertiary dentin

Answer 16

1) response to injury
2) reactive or reactionary
- pre-existing odontoblasts
3) reparative dentin
- newly differentiated odontoblast like cells

Question 17

separation between primary and secondary dentin

Answer 17

1) slight change in direction

Question 18

tertiary dentin shape

Answer 18

1) sparse irregular tubules

Question 19

root dentin

Answer 19

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

Question 20

hertwig’s epithelial root sheath

Answer 20

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

Question 21

role of epithelial cell rests of malassez

Answer 21

1) can eventually differentiate to bone, cementum, and PDL

Question 22

cementum

Answer 22

1) about 45-50% hydroxyapatite
- collagen and noncollagenous

Question 23

cementum classification

Answer 23

1) primary
- acellular
2) secondary
- cellular
—
1) fibrular
- intrinsic fibers (parallel to root surface)
- extrinsic fibers (sharpey’s fibers)
2) afribrillar

Question 24

cementum layers

Answer 24

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

Question 25

hyaline layer

Answer 25

1) intermediate cementum - between dentin and primary acellular cementum

Question 26

cementoenamel junction configuration

Answer 26

1)cementum is over enamel - 60% 2) cementum meets enamel - 30% 3) cementum, exposed dentin, enamel -10%

Question 27

dentinal tubules histology

Answer 27

1) dentinal tubules - house odontoblastic process 2) migration of odontoblasts to smaller area - S curve shape in cross section "primary S curve"

Question 28

intertubular dentin x peritubular dentin

Answer 28

1) peritubular dentin - surrounds the dentinal tubules 2) intertubular dentin - in between

Question 29

interglobular dentin histology

Answer 29

1) areas of unmineralized or hypomineralized 2) failed to fuse into homogenous mass of dentin

Question 30

sclerotic dentin histology

Answer 30

1) dentinal tubules have become occluded with calcified material 2) glassy or transparent

Question 31

dead tracts histology

Answer 31

1) empty dentinal tubules 2) odontoblast regression from tubules or death 3) most often in coronal dentin

Question 32

incremental lines histology

Answer 32

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

Question 33

granular layer of tomes histology

Answer 33

1) found only in root dentin 2) a special arrangement of collagen and non-collagenous matrix proteins at the interface between cementum and dentin

Question 34

dentin pulp complex

Answer 34

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

Question 35

zones of the pulp

Answer 35

1) odontoblastic zone 2) cell free zone 3) cell rich zone 4) pulp core - type II collagen fibroblasts are most common cell type

Question 36

dentin sensitivity

Answer 36

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)

Question 37

age changes in the dental pulp

Answer 37

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"

Question 38

pulp stones

Answer 38

1) calcified masses that are comparable to dentin in the pulp 2) hard to get past in root canals - have to be removed first