Quiz 5: Dentin & Pulp

clinical relevance of Dentin

tubules help explain dentin sensitivity and can keep forming in response to irritation

odontoblast ___ the ___ and ___ dentin

odontoblast “line” the “pulp” and “form” dentin

physical properties of Dentin:

• makes up the bulk of the tooth

• 2nd hardest tissue

• somewhat radiopaque

• slightly elastic

• yellow

How does dentin support the overlying enamel?

by being slightly elastic, serves as a resilient cushion for the enamel

dentin main function

prevents the hard but brittle enamel from fracturing off the tooth by dissipating occlusal forces

dentin additional functions:

• provides support to the enamel

• protects the pulp

the apical portion of the dentin is covered by what?

cementum

the coronal portion of the dentin is covered by what?

enamel

what makes up the bulk of the tooth?

dentin

what is the 2nd hardest tissue?

dentin

what is the 1st hardest tissue?

enamel

what is the 3rd hardest tissue?

cementum

what type of tissue is dentin?

mineralized, specialized CT

Components of Dentin:

• associated cells

• ExtraCellular Matrix

is dentin avascular or vascular?

avascular

how does dentin receive its nourishment?

blood vessels from the pulp

associated cell of dentin

odontoblasts

pulp dies =

odontoblast die, no new dentin made

ECM components

• fibers

• gr. sub.

• HA crystals

organic matrix of dentin name:

predentin

inorganic matric of dentin name:

dentin

scientific term for dentin formation

dentinogenesis

% of organic components of dentin

30%

% of inorganic components of dentin

70%

cell that produce dentin

odontoblast

components of predentin:

• type I collagen fibers

• gr. sub

component of inorganic portion of dentin

HydroxyApatite crystals

the two steps of dentinogenesis:

1. Apposition/Formation of Predentin

2. MIneralization of Predentin

1. Apposition of organic matrix of dentin

odontoblast produce Type I Collagen + gr. sub. to form a layer of predentin

2. Mineralization of Predentin:

• odontoblast pump out Ca + PO₄ ions which form HA crystals in predentin → becomes mineralized/mature dentin

• Another layer of predentin is formed underneath where the odontoblasts are

where do odontoblast differentiate?

at the future DEJ/DCJ

where do odontoblast move as new dentin is formed?

pulpally & apically

when does dentinogenesis occur?

during and after tooth development provided the tooth is vital

outline of the DEJ is ___

scalloped

why is the DEJ border scalloped?

increases the strength of junction between the dentin & enamel

Dentinogenesis Imperfecta

DEJ is straight rather than scalloped → dentin is defective and cannot provide a healthy foundation for the enamel

Dentinogenesis Imperfecta is a ___

genetic disorder/hereditary

shape of odontoblast cell body

columnar

odontoblastic process

cell processes of odontoblasts extending through the entire thickness of dentin from the cell body to the DEJ/DCJ

odontoblastic processes occupy ___

dentinal tubules

primary odontoblastic process

main cell process of odontoblast

secondary odontoblastic process

branches of primary odontoblastic processes

lateral branches

processes arising at right angles to the primary odontoblastic process; considered as secondary odontoblastic process

what branch is more extensive in root dentin?

lateral branches

where do odontoblastic processes direct themselves?

pulpally and apically

enamel spindles

extensions of odontoblastic processes into the enamel; considered as secondary

dentinal tubules

main structural element of dentin; small channels extending from the DEJ/DCJ to the pulp

what do dentinal tubules have inside?

primary odontoblastic process

why do dentinal tubules form in the dentin?

During dentin formation, dentin is deposited around the odontoblastic cell processes, which create the dentinal tubules

primary S Curvatures

shapes of odontoblastic processes and dentinal tubules; shows the main pathway taken by odontoblasts; move pulpally & apically

secondary S curvatures

delicate curves in the course of the odontoblastic processes and dentinal tubules; shows minor deviations in the movement of odontoblasts of their pathway

how does the S Curvatures affect the spread of caries in dentin?

• decay spreads faster

• pattern of decay spreads pulpally & apically following the S curves

how do dentinal tubules affect the location of secondary dentin formation?

causes the formation to be apical to the stimulus following the S curves

IVE and CLO are ___ to the dentinal tubules

perpendicular

incremental/ imbrication lines of Von Ebner (IVE)

relines that reflect the normal diurnal appositional activity of odontoblasts; form between the increments of dentin when odontoblasts slow down their activity at night

contour Lines of Owen (CLO)

the accentuated dark bands in dentin which represent a disruption in the normal apposition activity of odontoblasts; areas where less dentin is formed and is less mineralized

Neonatal line

accentuated CLO occurring at or near birth; disruption of odontoblasts occurs with abrupt change in environment

how is tetracycline stain incorporated in the dentin?

during tooth development along the CLO

primary dentin

all dentin formed during tooth development until completion of apical foramen

secondary dentin

formed throughout the life of the tooth after formation of apical foramen

secondary dentin can be classified as?

regular or irregular

mantle dentin:

• first few increments (20 um) of dentin formed next to the DEJ/DCJ during tooth development

• first layer of dentin to form

• outer most layer of dentin

circumpulpal dentin

consist of ALL dentin formed around the pulp EXCEPT for the mantle dentin

majority of dentin is ___

circumpulpal

circumpulpal dentin can be?

primary or secondary dentin

which dentin is more mineralized? mantle or circumpulpal

circumpulpal

which dentin is uniformly(evenly) mineralized? mantle or circumpulpal

mantle

Von Korff’s fibers

• produced by pulp fibroblasts

• incorporated into dentin as it forms

• thicker fibers

• perpendicular to DEJ

Peritubular dentin

dentin immediately surround the dentinal tubules

Intertubular dentin

main body of dentin located between the dentinal tubules

which dentin is more mineralized? peritubular or intertubular

peritubular

which dentin forms first? peritubular or intertubular

intertubular

calcification of dentin

when there is an uneven mineralization pattern in dentin, globular and interglobular dentin will be seen

calcification patterns of dentin can be found in?

circumpulpal dentin of the crown

globular dentin

zone of dentin that did not mineralized uniformly; has a “globular: appearance of the calcospherities which do not fuse completely

interglobular dentin

zone of dentin that was hypomineralized and found between calcified globules of dentin

microscopically, interglobular dentin will look like ___

dark spaces

collagen fibers are delicate and oriented perpendicular to dentinal tubules

peritubular dentin

collagen fibers are thick and more randomly oriented

intertubular dentin

Tomes’ Granular Layer

the granular appearance of zone underlying the cementum covering the root

Tomes’ granular layer is what type of dentin?

interglobular

Sclerotic dentin

areas of dentin where the dentinal tubules have mineralized by being filled with HA crystals

another name for Sclerotic dentin

transparent dentin

when does transparent dentin occur?

in response to a low-grade or noxious stimulus mainly in peripheral root dentin

how does sclerotic dentin look?

tissue looks transparent due to obliteration of dentinal tubules

dead tract

a group of dentinal tubules in which the odontoblastic processes have degenerated

how does dead tract occur?

in response to a noxious stimulus

regular secondary dentin

• forms slowly in response to low grade stimulus (gradual attrition)

• does not form uniformly along pulpal wall

irregular secondary dentin

• forms rapidly in response to a noxious stimulus (caries, trauma)

• forms apical to stimulus

another name for irregular secondary dentin

tertiary, reactive dentin

microscopic features of regular secondary dentin:

• more mineralized than primary dentin

• abrupt change in direction of dentinal tubules is evident, yet neat arrangement

• fewer tubules

• odontoblast remain outside of dentin

microscopic features of irregular secondary dentin:

• not as mineralized

• even fewer tubules

• odontoblasts may become entrapped in dentin

where are sensory nerve endings of the pulp extend in the dentinal tubules?

pass the cell body but not beyond the pulpal one-third of the dentin/ dentinal tubules

what kind of tissue is pulp?

non-mineralized, specialized CT

components of pulp:

1. associated cells

2. ECM

3. blood vessels

is the pulp vascular or avascular?

vascular

the fibrous matrix of the pulps does NOT contain:

• elastic fibers

• adipose tissue

associated cells of pulp:

• pulpal fibroblast

• odontoblast (cell body only)

• mast cells

• macrophages

• wandering/defense cells

• pulp stem cells

fibroblast

produce/turnover the fibrous matric and gr. sub in pulp

mast cells

reside in the vicinity of blood vessels; release granules with chemical mediators when pulp is injured