histoloy of dentine and pulp e lec Flashcards
how can dentine be studied
in both ground sections and demineralised sections
what are ground sections
where the mineral is retained and the section is unstained
what are demineralised sections
where the mineral is removed and the section is stained
how can pulp be studied
only in demineralised sections
what is a characteristic feature of dentine
the dentinal tubules which run from the pulp to the outer dentinal surfaces
what do the tubules contain
contain fluid and odontoblasts
what shape do the dentinal tubules follow
they follow an S shape called the primary curvature
what is on top of the primary curvature
the secondary curvature is superimposed on the top of the primary curvature
what does the secondary curvature look like
more frequent and small wave like deviations
what might happen to the tubules
the tubules might be branched
where is branching more evident
it is evident at the ADJ especially under the enamel in the tooth crown
why does interglobular dentine form
arises due to incomplete fusion of calcospherites
what is the mineral front as
dentine is laid down and mineralised
what does the fusion trap do
it traps areas of poorly mineralised dentine in the form of arches which reflect the spherical nature of the calcospherites
where can calcospherites be seen visibly
at the mineralisation front of forming dentine
what can dentine be divided into
primary or secondary dentine
what dentine is found in circumpulpal dentine
primary dentine
secondary dentine
which is the first dentine laid down adjacent to the ADJ
mantle dentine
how are the collagen fibres arranged in the mantle dentine
they are located perpendicular to the ADJ
where do the collagen fibres in the mantle dentine arise from
some people think it arises from sub odontoblastic mesenchyme origin and not odontoblasts
where is the evidence that the collagen fibres come from sub odontoblastic mesenchyme
from von korff fibres which are evident when to developing tooth is stained with silver
how do we see the von korff fibres
when the developing tooth is stained with silver
what lays down the basic shape of the dentine
primary dentine
what is primary dentine
it lays down the basic shape of the dentine
what happens once the tooth erupts
a slower rate of dentine production at the pulpal surface happens and the root is completed
what is the dentine called that is produced slowly after the tooth erupts
regular secondary dentine
what is the junction between the two types of dentine shown by
by a change in the direction of dentinal tubules
how do dentinal tubules pass through from the ADJ to the pulpal surface
by following a shape called the primary curvature
what might happen in the ground section
some tubules might be black
why might tubules be black
due to the fact that they are no longer filled with fluid and fill with debris
what might the tubules look like in a carious area
the tubules might look black due to odontoblasts being affected and form dead tracts
the pulp dentine interface is composed of from exterior to interior
mineralised dentine
pre-dentine (unmineralised except for the presence of calcospherites)
odontoblasts
cell free zone (of Weil)
cell rich zone
body of the pulp (a loose, vascular and well innervated connective tissue)
what is predentine
it is the collagenous matrix before mineralisation
what lies between the mineralised layer and odontoblast layer
a layer of predentine
what is the cell responsible for forming dentine
odontoblasts
how is dentine formed
initially predentine is formed
which is then mineralised by calcospherites
what projects into the dentinal tubule
a process from the distal end of the cell
what happens to pulp size as dentine mineralises
becomes smaller
why does the pulp reduce is size
due to the dentine pseudostratified
what happens to the cell count as dentine production continues
the cell count decreases as dentine goes from primary dentine to regular secondary dentine
what does the odontoblast layer contain
capillary loops
unmyelinated nerve fibres
where do capillary loops and unmyelinated nerve fibres orginate from
sub odontoblastic plexus
what are calcospherites
small isolated globular structures which fuse with predentine to form mineralised dentine at the mineralisation front
where does the cell free zone lie
below the odontoblast layer
what is the H&E stain
hematoxin and eosin stain
is the cell free zone real
many people think its artefactual due to shrinkage of the pulp layer away from the odontoblast layer
what does the cell rich zone have
a high amount of cell nuclei
what does the body of the pulp contain
the loose connective tissues
what is the predominant cell type
fibroblasts
what other cells nmight be present
macrophages
what is also located in sub odontoblastic layers
undifferentiated mesenchyme
the pulp also has
nerves and capillary loops which also supply the odontoblast layer
where do nerves and capillaries enter the pulp from
the apical foramen
where do the nerves have endings
between odontoblasts and within the dentinal tubules
what might happen to the capillaries
they may become fenestrated
why does the lesion in the dentine spread wider than the enamel
due to the way the enamel prisms around the fissure and lie adjacent to the ADJ
why does sclerotic dentine arise
due to the dentinal tubules being completely occluded by peritubular dentine by odontoblasts
why does peritubular dentine get deposited
as a againg process or as a reactionary process( defensive process) in a response to the overlying carious lesion
when does the defensive process occur
if the lesion develops slowly which allows the dentinal tubules to fill slowly with peritubular dentine
what is a dead tract
if the dentinal tubules cannot allow for this form of defence they retract and the tubule is empty and leads to the formation of a dead tract
why does a dead tract occur
if the odontoblast cannot mount a defence it will withdraw the processes and form a dead tract. the dead tract can fill with debris and air during the grinding process and appears black
what will happen if the odontoblast cell is still alive
it will try to seal the pupal end of the dentinal tubule with reparative dentine
what happens if the odontoblast cells are dead
cells like sub odontoblastic cells produce a bone like material
when is reparative dentine put down
reparative dentine is put down when the odontoblasts make an attempt
what else is reparative dentine called
irregular secondary dentine
what is reactionary dentine
it is when extant odontoblast cells lie down reparative dentine
what should reparative dentine be reserved for
when the odontoblast cells have died and subodontoblastic cells replace them and lie down reparative dentine
what does reparative dentine not have
it does not have dentinal tubules
