Histology & neurophsiology of the dentino-pulpal complex ian Trantor bds



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HISTOLOGY & NEUROPHSIOLOGY OF THE DENTINO-PULPAL COMPLEX

  • Ian Trantor BDS(Syd), MDSc(Melb)

AIM

  • REFRESH

  • Histology/Anatomy of Dental Pulp

  • DEVELOP

  • understanding of dentinopulpal interface response to trauma

OVERVIEW

  • Histology of Dental Pulp

  • Causes of pulpal/dentinal injury

  • Pulpal response to injury

  • Clinical classification/diagnosis of pulpal disease

HISTOLOGY OF THE PULPO-DENTINAL COMPLEX

  • Dentinal walls

  • Loose CT

  • mesenchymal origin

  • Enclosed

  • low compliance environment

  • pulp relatively incompressible

  • ltd. capacity for increased blood flow without local damage

STRUCTURAL ASSANGEMENT

  • Dentine

  • Pre-Dentine

  • Odontoblast layer

  • Cell free zone

  • Cell rich zone

  • Pulp proper

DENTINE

  • Inorganic(70%)

  • hydroxy apatite -Ca10(PO4)6 (OH)2

  • Organic(30%)

  • collagen(I,V)

  • phosphoproteins, proteoglycans, glycoproteins, growth factors, lipids

DENTINE

  • TYPES

  • primary(developmental)

  • secondary

  • tertiary(reparative)

  • interglobular

  • ANTOMY

  • peritubular

  • intertubular

DENTINAL FLUID

  • 22% of volume of dentine

  • Ultra-filtrate of plasma-blood

  • Pulpal tissue pressure 14mmH2O

  • outward pressure gradient

DENTINE PERMEABILITY

  • Density

  • Diameter

  • Location

NERVES IN DENTINE

  • Gunji T. 1982

  • subodontoblastic plexus

  • fibres into DT’s in predentine

  • complex fibres branching extensively into predentine

  • intratubular extensions into dentine(pulp horn, 40% of tubules contain odontoblastic process

PREDENTINE

  • Unmineralised matrix

  • collagen(I, II)

  • PG, GAG, GP

  • growth factors

CELL POOR ZONE

  • Transversed by

  • capillaries

  • unmyelinated nerve fibres

  • Presence reflective of functional pulpal activity

CELL RICH ZONE

  • Prominent coronally

  • Rich in fibroblasts

  • Lymphocytes/macrophages

  • Formed by peripheral migration of cells from central pulp

  • Source of replacement cells for damaged pulp.

CELLS OF THE PULP

  • Odontoblast

  • Fibroblast

  • Macrophage

  • Dendritic Cells

  • Lymphocyte

  • Mast Cells

ODONTOBLAST

  • Dentinogenesis

  • collgen-proteoglycan mineralisation

  • extensive, RER, Golgi Complex

  • numerous mitochondria/secretory granules

  • Odontoblastic process

  • lateral branches interconnect

ODONTOBLASTIC PROCESS

  • Within tubules

  • Microfilaments, microtubules

  • function unclear

  • transport of materials

  • structural integrity

  • Extent of Process?

  • SEM, TEM, fluorescent carbocyanine dye, suggest inner 1/3 only in mature dentine.

PULP FIBROBLAST

  • Most numerous pulp cell

  • Synthesize

  • collagen(I, III)

  • proteoglycan, GAG

  • nerve growth factor

  • Capable of differentiation into odontoblastic precursor

IMMUNE CELLS

  • Lymphocyte

  • mainly T8(suppressor)

  • present in ‘healthy’ pulp

  • Dendritic cells

  • antigen presenting cells

  • more prevalent in lymphatic tissue

  • ?role in immunosurveillace

  • Mast Cell

  • ?present in ‘healthy’ pulp

PULP PROPER

  • Large blood vessels

  • Connective Tissue Cells

  • Fibres

  • Ground substance

PULPAL VASCULARITY

  • Regulation

  • sympathetic adrenergic vasoconstriction

  • -adrenergic vasodilation

  • antidromic vasodilation involving sensory fibres

  • no evidence of parasympathetic vasodilator mechanism)

PULPAL VASCULARITY

  • Pulpal arterioles

  • enter via the apical foramen

  • <100m

  • travel central, branches to the subodontolastic layer

  • Terminal capillary network(TCN)

  • Post capillary venule

  • Pulpal Venule - usually thin walled

PULP VASCULARITY

  • Arteriovenous anastamoses

  • direct arteriole/venule communication

  • 10m

  • bypass TCM network

  • ?shunt blood away from area of injury

CT FIBRES OF THE PULP

  • Collagen

  • I - skin, tendon, dentine

  • II - cartilage

  • III - unmineralised CT, mature pulp

  • IV, V - basement membrane

GROUND SUBSTANCE

  • Amorphous Gel

  • Extracellular Matrix(ECM)

  • matrix into which fibres are deposited

  • polyelectric-polysaccharide - responsible for ware holding characteristics of CT

  • Glycoproteins

  • fibronectin, lamanin, proteoglycan, tenascin

GROUND SUBSTANCE

  • Proteoglycan

  • supports cells, mediates cell interactions

  • protein core

  • GAG chains

  • mainly disaccharides

  • form rigid cores which hold water

CT FIBRES OF THE PULP

  • Elastin

  • Walls of arterioles

  • not part of the ECM

INNERVATION

  • Unmyelinated/myerlinated

  • Regardless of stimulus - PAIN

  • Afferent neurones - sensory

  • Autonomic fibres - neurogenic modulation of the microcirculation

  • superior cervical ganglion

  • stimulation - decreases blood flow

  • ?role in regulation of dentinogenesis

SENORY FIBRES

  • Enter via the apical foramen

  • follow path of blood vessels

  • eruption400 fibres

  • mature  700 fibres

  • branch(x8) inti Plexus of Raschkow

  • emerge from myelin sheath

INNERVATION

  • depressed excitability of A fibres

  • C fibres less affected

  • C fibres

  • relatively resistant to necrosis

  • function in the presence of hypoxia

  • may explain sensitivity in apparently necrotic canals

CAUSES OF PULPAL INJURY

RESPONSES OF THE PULP TO INJURY

  • Aspiration of odontoblatic nuclei into DT’s

  • movement of dentinal fluid in DT’s

  • sclerosis of tubule

  • reparative dentine formation

  • fibrosis, reduced cellularity/neural/blood supply

  • dystrophic calcification

  • inflammation

PULPAL INFLAMMATION

  • Acute Inflammation

  • abrupt onset

  • relatively short duration

  • predominantly PMN infiltrate

  • dependent on severity of injury not cause

  • Chronic Inflammation

  • longer duration

  • proliferative response - angioblasts/fibroblasts

  • mononuclear infiltrate

PULPAL INFLAMMATION

  • Vascular Response

  • Hyperaemia

  • blood vessels dilated and engorged

  • Increased Permeability

  • exudation of plasma proteins/fluids

  • leukocyte migration

  • AVA’s shunt blood away from injury site

PULPAL INFLAMMATION

  • NEUROGENIC INFLAMMATION

  • “…pathalogical change in the neurovascular relationship resulting in inflammation.”

  • Kim 1990

  • neural tissue is a dynamic complex

  • change number, size and cytochemistry of nerves inresponse to injury

  • ‘sprouting’ of neural tissue in reponse to injury(mediated by NGF produced by local fibroblasts)

NEUROGENIC INFLAMMATION

  • Neuropeptides(mediators of neurogenic inflammation)

  • e.g. Calcitonin Gene Related Peptide(CGRP), Substance P(SP), Neurokinin A(NKA)

  • release stimulated by - injury, Complement, Ag-Ab complex, antidromic stimulation of IAN

  • Role

  • Vasodilation

  • causes hyperalgesia

  • promote wound healing

  •  Pulpal Tissue Pressure

  • Pulpal blood flow

  • accumulation of mediators/vessel damage

  • pulpal inflamation

  • PULPAL DEATH

PULPAL INFLAMMATION

PULPAL INFLAMMATION

DENTINE SENSITIVITY

  • Short /sharp discomfort

  • induced by cold(heat/sweet)(+++)

  • non-lingering

  • removal of stimulus - relief of symptoms

  • Treatment

  • desensitising toothpaste

  • topical F

  • (restoration)

REVERSIBLE PULPITS

  • Short /sharp discomfort

  • induced by cold(heat/sweet)(++)

  • non-lingering

  • removal of stimulus - relief of symptoms

  • Treatment

  • occlusal adjustment

  • restoration

  • cuspal protection

  • improve marginal seal

  • caries control

IRREVERSIBLE PULPITS

  • Constant dull ache

  • temperature sensitivity - HOT (& COLD)

  • spontaneous pain

  • not relieved by removal of stimulus

  • Treatment

  • endodontics

  • extraction

PULPAL NECROSIS

  • Variable

  • asymptomatic

  • acute ache

  • spontaneous ache

  • Non-responsive to pulpal sensitivity testing

  • Treatment

  • extraction

  • endodontics

SUMMARY

  • PULPAL HISTOLOGY

  • CAUSES OF PULPAL TRAUMA

  • PULPAL REPONSE TO TRAUMA

  • CLINICAL CLASSIFICATION

  • DIAGNISTIC TOOL



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