oral histology - dental pulp

Dental pulp

organisation

• Loose c.t • Odontoblasts (periphery)• Nerve terminals(trigiminal afferents)

(periphery )• Specialized antigen presenting cells periphery)• The rest of the cells act as a support system !

• Blood vessels and nerves >apical foramen

• Root>at least one canal !

• Vascular canals between roots (furcation) in multirooted teeth

composotion

• Cells + (more)extracellular matrix(fibers in a semi-fluid gel)

• So :1)cells2)fibers3)non-fiberous matirx (gel)

• 75% water 25% organic .• Compostition change during development and vary

between teeth types

Extracelluar matrix

• Extracellular matrix:• Polysaccahrides ,proteins >>>forming a

stabilizing scaffold that is far from inert >>>affecting cells :development ,migration division ,shape and function .

• Collagen 25-32% dry weight

Fibers

• Collagen type 1 (bone,cementum,skin,dentine)

Irregular except at the periphery where They become parallel to predentine . (early in development >>right angles to predentine “von kroff ”.

Collagen fibers

Collagen I

• α1, α 2 chains• 56% (of pulpal collagen )

Collagen III

• α1• 41%

Fibers

• Collagen IV • Collagen V• Microfibrils (fibrillins)beaded large glycoproteins.

Non-fibrous matrix

• Glycosaminoglycans • Proteoglycans• Other adhesion molecules:Fibronectin,laminin.

Glycosaminoglycans

GAG’s :polysacchrides chains composed of repeating disacchrides linked covalently to proteins.

bulky,hyrophilic,fills most of the extracellular space, swell when hydrated which : >>contributes to the high fluid pressure >> gives high support >> facilitates easy movement of water soluble materials and cells.

GAG’sGAG’s Developing

tooth Info: Functions Mature pulp

Chondrotin sulphate

Major GAG 12%

Dermatan sulphate

Small amounts 20%

hyalorunan Minor component

Only GAG found unbound to prtns.

MechanicalCell migration During development .

60%

Heparan sulphate

Proteoglycans

• Core protein of variable sizes surrounded by GAG’s and other sugars .

• They are part of a larger group called GLYCOPROTEINS :have GAG’s as part of their side chains.

Other adhesion proteins

• Fibronectin :Glycoprtn . attaching cells to extracelluar matrix regulating cell shape ,migration ,differentiation part of integrins (cell adhesion molecules )

• Laminin (integrin) in basement membranes (binding epi to extracelluar matrix ,binding some signaling molecules) found around endothelial cells and schwan cells Odontoblasts cell bodies and processes are coated with laminin

Cells

• Odontoblasts• Fibroblasts • Defense cells • Undifferentiated cells • Blood vessels • Nerve cells

Odontoblasts

• Dentine formation

• Post mitotic cells (cannot divide)

• If the insult was too high >>odontoblast death>> Subodontoblastic cells divide to form tertiary dentine.

ODONTOBLASTS

• Columnar cells(crown ),cuboidal(radicular).

• Single long cell process through tubule> predintine and dentine .

Odontoblastscell junctions

• (provide integrity, render odontoblastic layer permeable )

1.Desmosomes (mechanical union )Intracellular >between fibrils Intercellular>between cells

2.Adherens Small molecules between cells Play a role in synchronizing activity of odontoblasts .

Odontoblasts cell junctions

1.dendritic antigen presenting cells .Nature of the relationship is unknown but could be that odontoblasts producing proinflammatory mediators .

2.Nerve cells Chemical synapse .Electrical synapse by gap junctions . (no high evidence )

3.odontoblast-odontoblast juntions

4.odontoblast-fibroblast junctions Odontoblast-mesenchymal cells junctions .

Odontoblasts

• First cells to encounter dental pathogens

• Express IL-8 recruitment of neutrophils .

Fibroblasts

• adherens(junctions)Fibroblast-fibroblast /fibroblast-odontoblast Arms of stars

• Stellate (shape)

Fibroblasts..

• Play a role in the:1. production of fibers and matrixTheir production is low ,turnover is low, so few organells .2.They produce a hard tissue after turnover resemling bone more than dentine (stones?)3.Growth factors and cytokines during development 4.Cell division 5.Apoptosis (programmed cell death )

Defence cells

1)T-lymphocytesusually few in number but increase after injury to pulp.

2)Macrophages (histocytes in resting form)Hard to be distinguished from fibroblasts Mostly around endothelial cells and odontoblasts

3)Mast cells (absent in pulp)

4)Dendritic antigen presenting cells 3 main processes Around endothelial cells and odontoblasts Stimulate division of t-lymphocytes May travel with trapped antigens to regional lymph nodes .

Note..

• Pulp’s response to injury has both inflammatory and immune components.

Immune +neural system relationship

Blood vessels of pulp

• (architecture similar to nerves )

• Enter from :1)apical foramen 2) lateral canals

• Stay in in a bundle in the root ,branch profusely when reaching pulp chamber .

• Arterioles and venules

• Vasoconstrictors from nerve endings to endothelial smooth muscles to control pulpal blood flow .

• Calcitonin (vasodilator)

• Subodontoblastic capillary plexus :

• Insultrelease of vasoactive molecules .

• With and underneath odontoblasts and between odontoblasts and predentine .

• doesn’t enter tubules .

• Capillaries with class II molecule expressing dendritic cells around them:

1.Antigen presenting 2.Phagocytes pulpal blood flow is 6-20-ml/min per 100g of tissue.High pulsatile interstitial tissue pressure to wash out toxins from outside .

Nerves of dental pulp • Heavely innervated

• 2500 axons enter the apical foramin of a mature premolar .

• 25% are myleinated afferents of trigiminal gangelion

90% narrow Aδ fibers (1-6ɱm in diameter )10%wider Aβ fibers

• Close association to blood vessels

• Branch profusely in coronal pulp chamber

• Plexus beneath odontoblasts “raschkaw plexus” is evident after eruption of the tooth .

• Marginal plexus between odontoblastic layer and predentine .

• Some nerves enter dentinal tubules with odontoblastic processes

• Branching increases surface area for activation • Schwan cell covering many axons so axon-axon

interaction is possible .

Nerve fiber types 1. Myleinated trigiminal afferents Carry sharp pain centrally .

2.Aβ afferents Non-noxious stimuli.

3.C-fibers : non myleinated afferents carry noxious information centrally.sympathetic afferents that supply arterioles smooth muscles and mediate their vasoconstrictive effects by :a)Noradernaline b)Neuropeptides

VASODILATORS :Parasympathetic (acetylcholine) low evidence of their presence in dental pulp .Mostly axon reflexes and build up of metabolites locally cause vasodilation.Nitric oxide is the principle molecule to induce vasodilation .(tissue hypoxia)

Nerve endings

• Autonomic nerves end in smooth muscles of arterioles .

• Aδ afferents enter tubules of dentine and predentine and detect stimuli outside dentine

(marginal plexus).

• some end in junctions with odontoblasts(low evidence of this junction)

Nerve endings

• All nerves in area of predentine –pulp border are NAKED :

• lost their 1) schwan cells 2) axolemmas .So they are exposed to extracellular environment . And any changes in extracellular environment results in NEUROPEPTIIDE (Ex. Calcitonin gene related peptide GCRP) release .. which has a functional role in regulation rather than sensation .

Molecules

• GCRP:From cell bodies in trigeminal ganglion and moves by axonal transport to the dental pulp.Vasodilator Control hard tissue production

• NGF+receptors From fibroblasts mostly Attract leucocyte after insult (chemo attractant).

Regions of dental pulp

Outiside

Inside

Predentine

Supraodontoblastic region

Odontoblastic layer

Subodontoblastic zone : cell free zoneCell rich zone

Bulk of the dental pulp

Regions • Supraodontoblastic region :ArtifactSecond after odontoblast to receive stimuli .Made of :1)Unsheathed axons (crown )Predentinal axons of “bradlaw”their function is :End within tubules to detect changes in extracellular matrix and fluid movements in tubules . (which otherwise would be delayed due to the barrier properties of the odontoblastic layer )2)Dendritic antigen presenting cells

• Cell free zone of “weil” :Artifact.Absent in radicular pulp.

• Cell rich zone :Artifact ?Cells of capillary and nerve plexus ,schwan cells,endothelial cells ..Bulk of pulp Loose c.t

Age related chnges

• With age Pulp becomes more fibrous ,less vascular and less innervated ,we start noticing stones

stones

Stones:They are mineralized Age related and not pathological If one tooth presents with stones,other teeth within sameperson might exhibit stones.

stones

Appearance :Tiny spicules (snow storm)Discrete pulp stones (single/groups)Resemble dentine ,tubular ,(true denticles )Resemble bone,cells embeded within them (false denticles )

Role of pulp

• Produce dentine Primary Secondary Tertiary

Thank you …..