Components of the Teeth - Dentine and Pulp Flashcards
give a brief outline on dentine and its features
dentine forms the bulk of the tooth, and is harder than both bone and cementum. it is softer than enamel.
it has great compressive and tensile strength. it is permeable, contains cell processes (making it a living tissue) and is yellowish in colour
describe the importance of the compressive and tensile strength of dentine
it is important for the cushioning of enamel
explain how dentine is permeable
it contains tubules. if the dentine is exposed, any material that can be exposed to the dentine will pass through it and go to the pulp. the permeability of the dentine depends on the depth
give a breakdown of the different components of dentine
- hydroxyapatite makes up about 70% of the weight, and 50% of the volume
- water makes up about 10% weight, 20% volume
- organic matrix makes up about 20% weight and 30% volume
what are the different contents of the dentinal tubules
odontoblast processes, unmyelinated nerve terminals, dendritic cells, and dentinal fluid
give a brief description of pulp and its contents
- pulp is the connective tissue “core” of the tooth.
- it contains cells, extracellular components, nerves, blood vessels and lymphatics
what cells are found in the pulp of the tooth
odontoblasts, fibroblasts, defence cells
what are the extracellular components of the dental pulp
fibres like collagen and oxytalan
the matrix, which includes proteoglycans, chondroitin, dermatan
what nerves are found in the pulp of the tooth
the peripheral nerve which is innervated by one of the trigeminal nerves
what are the different functions of dental pulp
nutrition
dentine growth
dentine repair
defence (immune cells and the lymphatic drainage system)
neural functions (sensory and control of dentinogenesis)
what is the difference between weight composition and volume composition associated with
the density of the different components
what is the mineral content of dentine like compared to enamel
there is less mineral content within dentine
what is the content of water and organic content like in dentine compared to enamel
there is more water and organic content in dentine compared to enamel
what can loss of water content in a tooth lead to
fragility in the dry tooth, as it is the dehydrated dentine that leads to this fragility, rather than the enamel.
what can the pulp be thought of as in relation to the tooth
it is like the core, the vascular bed of the tooth
how can the strength of a tooth after a root canal be compared to the strength before
it is weaker post root canal due to the loss of hydration after the removal of the pulp. this makes the restorative process more complex
in what direction does dentine grow
the dentinal tubules grow inward over time
what can be understood by the term lumen
the lumen is the space within “tubes” of the body, like tubules in dentine, veins, arteries etc. it is essentially just space where things can move
how does the shape of dentine change over time
the tubules slowly grow inward
what are the different shapes of dentine tubules found within normal dentine
narrow and wide are both found within the dentin. wide tubules are close to the pulp, and narrow tubules are near to the ameli dentino junction
what are the different ways that slides can be prepared for viewing dental tubules
there are ground sections, and demineralised sections. in the demineralised sections, a special treatment like an acid or chelating agent is used to remove the mineral content, and this can use the 30% of organic content within the dentin to stain pinkish. for ground staining, it is sanded down from either side, and any cells will no longer be there, but it is possible to see where the cells were due to the presence of black dots
what are the s shapes of the tubules that can be viewed when looking at the cross section of dentine
these are the tubules which run from the amelo dentino junction to the pulp. there are primary and secondary curvatures of the dentine - the primary is the s shape that they adopt. secondary curvature are smaller curves that can be viewed on the primary curvature which show the changed direction of odontoblasts
why is it important to note that the dentinal tubules adopt an s shape when going from the amelo dentino junction to the pulp
because any damage will not be linear, since the damage will travel along the s shape.
can you see dentine and pulp as separate things
not really unless you are looking to a restorative procedure
describe the inside of the pulp
it is a connective tissue, with fibroblasts being the intrinsic cell found within.
describe the production of dentine
odontoblasts function to produce dentine. the production of dentine is special because it means the space is reduced over time since it grows inward. the odontoblasts produce the matrix that mineralises into dentine, known as predentine.
what is the difference between dentine and predentine
dentine is just mineralised predentine
what can be understood by globular dentine
this is dentine before it has been completely mineralised
how are tubules formed
each odontoblast is responsible for a tubule, and each one will send an arm into the dentine which creates a tubule and produces a matrix. as more is produced, the arm moves further away
where can sensory unmyelinated nerve terminals be located in tubules
in some sections of the tissue
what can be found within the dentine
sensory unmyelinated nerve terminals
dendritic cells from the immune system
dentinal fluid
dentinal tubules which provide the nutrients
what cells can be found within the pulp
odontoblasts, fibroblasts and defence cells
what are the extracellular components of dental pulp
fibres like collagen and oxytalan
the matrix with proteoglycans, chondroitin, dermatan
what are proteoglycans
proteins with glycosaminoglycans attached to them, found mainly in connective tissue to provide structural support and hydration
what are glycoproteins
these are proteins with carbohydrates (sugars), where the stem is a protein chain and there are polysaccharide structures attached to it
what are glycoprotein structure and function
protein with short, simple oligosaccharide molecules attached to them.
found in cell membranes to provide receptoin, adhesion and transport.
what else can be located within the pulp that aid with the function of the pulp
lymphatics, which are a drainage system, and blood vessels
what are the functions of dental pulp
they provide nutrition, growth and repair of dentine. they also provide defence
how does the pulp repair the dentine
when dentine becomes exposed, there is a reaction from the odontoblasts to close the tubules. this is the repair action. this can also produce more dentin, but a strange form of dentine that lacks any tubules which is known as tertiary dentine
how does the pulp defend the tooth
through immune cells and lymphatics (support of the defence system)
how are nerve cells involved in pulp function
these have a sensory function but also help control of more dentine generation
what is dentinogenesis
the generation of dentin
describe the role of blood vessels within pulp
they are present but they do not perforate the dentine. this means there is a space between where the dentine is and where the odontoblasts are. this is important as it represents when you have gone from pulp to dentine.
how does tissue react to damage
there is redness, swelling, pain and heat ie an inflammatory response
what happens when there is damage to the pulp which leads to swelling
the swelling is in an enclosed space, where pressure will build up as there is an increasing volume that cant be controlled. the increased pressure of the tissue means that blood vessels cant work properly and are unable to exchange components like nutrients. this leads to stagnation of the system, which leads to cell starvation of the pulp
what can dentine be though of as
the mineralised connective tissue that forms the bulk of the tooth
how does the size of hydroxyapatite crystals in enamel compare to the size in dentine
they are smaller in dentine than in enamel
what can be found within the dentinal tubule
the odontoblast processes, dentinal fluid, a nerve fibre and a process from a dendritic cell
how is tertiary dentine formed
the recruitment of stem cells lying in the dental pulp in response to trauma
how does the combination of enamel and dentine aid the mouth
it provides a rigid, hard structure suitable for chewing and tearing that resists both abrasion and fracture
does dentine stop growing once the tooth has erupted
no, it develops throughout life at the expense of the pulp, as it grows inward
is dentine considered to be sensitive
yes
what is predentine compared to dentine
the unmineralised layer of dentine matrix at the pulpal surface
where does the cell body of odontoblasts lie
at the periphery of the dental pulp
what are the reasons for dentine and pulp being approached as a dentine-pulp complex
- they both originate from the dental papilla
- the structures pass from the dental pulp to the dentinal tubules like cell bodies of odontoblasts, nerve fibres and dendritic processes of the antigen presenting cells
- tissue fluid that passes along the dentinal tubules is derived from the vasculature of the dental pulp
- the responsiveness of dentine to the external stimuli resulting in the formation of tertiary dentine is mediated by the recruitment of stem cells within the dental pulp
why is dentine more resistant to the propagation of cracks than enamel
because of the intimate associated of the small apatite crystals with strong protein fibres. cracking will only occur in dentine when it has been weakened by caries or cavity preparation
which stresses are more likely to result in the fracture of dentine
those that are parallel to the direction of the tubules
what are the chemical properties of dentine
- consists of apatite crystals on an organic scaffold predominantly composed of collagen
- inorganic mineral component is in the form of calcium hydroxyapatite crystals
- crystallites are calcium poor and carbon rich in comparison to the pure hydroxyapatite, and are much smaller than those in enamel
- the crystallites also contain fluoride
- hydroxyapatite crystallites in mineralised dentine are found on and between collagen fibrils
where are the hydroxyapatite crystallites in the mineralised dentine foud
on and between the collagen fibrils
what do most of the collagen fibrils run in the direction of
they run in the direction parallel to the pulpal surface
what is found embedded in the organic matrix of dentine
crystallites
where are the fibrils of dentine found
embedded in an amorphous ground substance.
how are collagen fibrils in dentine assembled compared to many non mineralised connective tissues like tendons and periodontal ligament
they are not assembled into bundles in dentine
what are the non collagenous proteins that can be found in the organic matrix of dentine
- phosphoproteins
- proteoglycans
- gla-proteins
- other acid proteins and growth factors
what are many of the non collagenous proteins in the organic matrix involved in
mineralisation
what does dentine phosphoprotein refer to
highly phosphorylated protein species. they have a high phosphate content and a high calcium ion binding properties which implicates it in the process of mineralisation
what is dentine sialophosphoprotein responsible for
synthesising both dentine phosphoprotein and dentine sialoprotein.
give a brief outline on the phospholipids found in dentine
they are detected in both predentine and mineralised dentine. they are more heavily concentrated near the mineralising front. phospholipids are needlike crystal ghosts and may be involved in the formation and growth of crystals
what course do dentine tubules follow
they follow a curved, sigmoid course known as the primary curvature. the convexity of primary curvatures nearest the pulp chamber faces rootward
what is the dentine found between tubules called
intertubular dentine
what are secondary curvatures
these are small changes of direction found on the primary curvature
where do tubules branch most profusely and why
they do so nearest to the enamel dentine junction due to the numerous processes the early odontoblast has. some end blindly and some join with other branches
what causes obliteration of dentinal tubules
the formation of peritubular dentine
what does peritubular dentin lack
collagenous fibrous matrix
why will peritubular dentine be lost as dentine is routinely demineralised
it lacks the stabilising feature of collagen
what happens if dentine is fractured, and what does this suggest
fluid exudes from the tubules and forms droplets on the surface of the dentine.
this suggests that there is a positive force, presumably pulpal tissue pressure, that is exerted outward
what do the properties and composition of mineralised dentine vary with
distance from the predentine to the amelo dentino junction. mineral content of dentine decreases and thickness of the mineral crystals will increase toward the amelo dentino junction
what are the different regions of dentine
- mantle dentine
- interglobular dentine
- granular layer
- hyaline layer
- circumpulpal layer
- predentine
- secondary dentine
- tertiary dentine
where is mantle dentine found
the periphery of the dentiine in the crown
what is interglobular dentine found
in the outer part of the crown
where is granular dentine found
in the outer part of the root dentine beneath the hyaline layer
where is hyaline dentine found
the outermost part of the root dentine
where is circumpulpal dentine found
this is the bulk of the dentine in the crown and the root
where is predentine found
unmineralised innermost dentine in the crown and the root
where is secondary dentine found
innermost layer of dentine between the circumpulpal and predentine
where is tertiary dentine found
the inner layer of the dentine formed mainly in the crown in response to serious insult
give an outline on the regional dentine
underneath the dentoenamel junction there is mantle dentine. underneath this is the primary dentine (dentine made before birth). below this is secondary dentine, which is softer and grows continuously.
give an outline of dentinogenesis
- formation of dentine is inward, and begins with the formation of the mantle dentine
- odontoblasts form predentine, a soft organic matrix made of proteins
- fibroblasts assist by creating thick collagen fibres called korfs fibres, which create a framework for dentinogenesis
- odontogenic processes secrete calcium hydroxyapatite which forms crystals to mineralise predentine to make it strong and flexible
- the end result of this is mantle dentine
- after this, the odontoblasts get bigger and form primary dentine. the fibroblasts move to the pulp for rest. they form the primary from the outside in
which layer of dentine is the thickest
primary dentine
how do odonotblasts change once they have formed mantle dentine
they get bigger and make primary dentine.
when does secondary dentine form
after root formation, growing at a slow rate throughout life, maintaining tooth strength
what borders the pulp
predentine
where is tertiary dentine found
at sites of dental caries and attrition
how is blood supplied to the pulp
external carotid artery - branches to become maxillary artery. this provides both rows of teeth with blood.
- deoxygenated blood leaves the pulp and ends up in the maxillary vein which travels back toward the heart
- the apical foramen is the narrow passage at the centre of the apex of the root where blood vessels and nerves can enter
what are the two parts to pulp called
central and peripheral pulp
where is pulp found
the pulp chamber
what are the four functions of pulp
formation
nutrition
protection
defence
how does the pulp represent the tooth outline
it forms the layer of dentine evenly in every direction which means it reflects the external form of the enamel
what are odontoblast processes
cellular extensions of odontoblasts used to form dentine and dentinal fluid
where is peripheral pulp found
adjacent to the calcified dentine, and the compartment closes to the central pulp is cell rich with lots of fibroblasts and undifferentiated mesenchymal cells
how do undifferentiated mesenchymal cells support the population of odontoblasts
by proliferation and differentiation
what is peripheral pulp
the interface of the dentine pulp complex. it is a layer of columnar odontoblast cells.
how do dentine tubules go from the pulp to the enamel dentine junction
extend through the pulp, through the dentine, to the junction
what is central pulp outlined by
the edge of the cell rich layer of peripheral pulp
what is the function of central pulp
main support system for peripheral pulp. contains large blood vessels, nerves and fibroblasts
what is the primary function of columnar odontoblast cells
the development of dentine
how does dentine form over the lifetime of a person
incrementally
dentine is a living tissue. what does this suggest about it
that it is formed throughout life, sensitive and can react to trauma
how does dentine react to trauma
formation of tertiary dentine
can dentine be thought of as elastic
yes, as well as being rigid
what does it mean to say that dentine is heterogenous
it has different zones and different physical features.
what are the features of mantle dentine
it is less mineralised and the dentinal tubules branch profusely
what are the features of granular dentine
it is dark as the dentinal tubules may loop back on themselves. it is hypomineralised
what are the features of interglobular dentine
the globules deposited in the mineral in dentine fuse to form uniformly calcified tissue. the uncalcified tissue is interglobular dentine
how much of the composition of dentine is hydroxyapatite
70%
how much of the composition of dentine is water
10%
how much of the composition of dentine is organic
20%
what makes up the organic matter found in dentine
90% is collagen type 1 and 10% is non collagenous proteins like phosphoproteins
why do dentinal tubules reduce in diameter as they go develop
the lumen is narrowed by the formation of peritubular dentine
how are odontoblasts related to dentine
these are the cells responsible for forming dentine. their long processes extend into the dentinal tubules. their cell body lines the border between dentine and pulp
what forms the single layer of cells attached to the predentine surface
odontoblasts
describe the epithelial structure of an odontoblast when it is fully differentiated
polarised columnar with a long cell process
how does the odontoblast process extend into the dentine and pre dentine
through the dentinal tubules
how do the odontoblast cells form the layer attached to the predentine surface
through cell junctions
what are the different cell junctions between the odontoblasts on the cell layer attached to the predentine surface
- macula adheren’s junction
- tight junctions
- gap junctions
describe macula adherens junctions
these are desmosomes. they anchor fibrils to form a mechanical union
describe tight junctions
these create near fusion of the opposing cell membranes. it limits permeability of the cell layer
describe the gap junctions
these junctions allow the movement of small molecules between the adjacent cells
why are there cell junctions between the odontoblasts on the cell layer attached to the predentine
to provide integrity to the cell layer
where are capillaries located in the dentine pulp complex
they are found within and below the odontoblast layer.
what is the subodontoblastic capillary plexus
the capillaries found below the odontoblast layer on the predentine
why are there capillaries near the odontoblast layer
to supply oxygen and nutrients during dentinogenesis
do the capillaries enter the dentinal tubules
no
what are the blood vessels present in the dentine and pulp
there are arteriols and venules that enter via the apical foramina. they run longitudinally through the root canals.
what is the blood flow into pulp under the control of
nervous control. the smooth muscle of the arteriols is innervated by the terminals of the sympathetic nerves
how much of the weight of the pulp is water
75%
how much of the weight of pulp is organic material
25%
what is found at the periphery of pulp
a layer of odontoblasts, as well as elements capable of detecting external stimuli.
what are the elements at the pulp periphery that are able to detect external stimuli
nerve terminals of the trigmeninal affarents and specialised dendritic antigen presenting cells
what are the nerves of the pulp
there is sympathetic innervation within the pulp. nerve bundles run centrally in the pulp of the root in close association with one another, although some leave the central root and go to the periphery
what is the plexus of raschkow
a pronounced plexus of nerves beneath the odontoblasts
where are specialised dendritic antigen presenting cells located in the pulp
they are most densely found in the periphery, around nerves and blood vessels
what are the connective tissue cells found within the dental pulp
fibroblasts and fibronectin
what is fibronectin
a glycoprotein found in several forms that achors cells. may be important in determining shape.
why are fibroblasts important
they produce the extracellular fibres and ground substance for the dental pulp. they also participate in the degradation
what are the main fibres of the dental pulp
collagen
what is the composition of collagen types in the pulp
60% are type 1 and 40% are type 3
where is the arrangement of collagen within the pulp most organised
the periphery
what is compressive strength
compressive strength is the ability to resist force, absorb it, and then come back to normal position
what is tensile strength
tensile strength is associated with sheer movements, and the amount of strength required to break through
