PULPAL & DENTAL PULPAL & DENTAL PAINPAIN

Oral physiologyOral physiology

Dent 207Dent 207

Dental pulpDental pulp

Specialized connective tissueSpecialized connective tissue Contained within the toothContained within the tooth Enclosed by dentineEnclosed by dentine Continuous with the periodontal ligament through:Continuous with the periodontal ligament through: Apical foramenApical foramen

• Narrow – only allows for passage of the neurovascular Narrow – only allows for passage of the neurovascular bundlebundle

Small volumeSmall volume• Total volume in all teeth is 0.40 mlTotal volume in all teeth is 0.40 ml

Pulpodentine complexPulpodentine complex

Functions of pulp & dentine are interlinkedFunctions of pulp & dentine are interlinked Functions of the pulpFunctions of the pulp

• Maintain dentinal health by supplying nutrientsMaintain dentinal health by supplying nutrients• Provide a pathway for sensory impulses from Provide a pathway for sensory impulses from

dentinedentine• Initiate & govern repair of dentine in injuryInitiate & govern repair of dentine in injury

OdontoblastsOdontoblasts

The layer of specialized cells immediately The layer of specialized cells immediately adjacent to dentineadjacent to dentine

Have processes that penetrate dentine for Have processes that penetrate dentine for varying distancesvarying distances

Responsible for formation of dentineResponsible for formation of dentine Involved in sensory perception of dentineInvolved in sensory perception of dentine

Components of pulpal tissueComponents of pulpal tissue FibersFibers

• CollagenCollagen Confers rigidityConfers rigidity Maintains 3D spatial relationship of cells, blood vessels & nervesMaintains 3D spatial relationship of cells, blood vessels & nerves

• Elastin in blood vessel wallsElastin in blood vessel walls CellsCells

• OdontoblastsOdontoblasts• FibroblastsFibroblasts• Undifferentiated mesenchymal cellsUndifferentiated mesenchymal cells• Macrophages, histocytes & lymphocytesMacrophages, histocytes & lymphocytes

Amorphous matrixAmorphous matrix• SupportSupport

Nerves & blood vesselsNerves & blood vessels

Pulp nervesPulp nerves Sensory fibersSensory fibers AAδδ & C fibers & C fibers Types of nerve terminals near blood vesselsTypes of nerve terminals near blood vessels

• Large fibersLarge fibers Contain small vesicles (resemble cholinergic endings)Contain small vesicles (resemble cholinergic endings)

• Medium fibersMedium fibers Numerous small dense-cored vesiclesNumerous small dense-cored vesicles Found in pulp horns & pulp chamberFound in pulp horns & pulp chamber

• Small fibersSmall fibers Numerous large dense vesicles (purinergic or peptidergic endings)Numerous large dense vesicles (purinergic or peptidergic endings)

Plexus of Raschkow (subodontoblastic plexus)Plexus of Raschkow (subodontoblastic plexus)• Individual axons divide into many branches in the plexusIndividual axons divide into many branches in the plexus

Pulp nerves during tooth formationPulp nerves during tooth formation

Fibers near base of dental papillaFibers near base of dental papilla At cap stageAt cap stage

• Fibers form a plexus - to dental follicle – to dental papillaFibers form a plexus - to dental follicle – to dental papilla At bell stage – unmyelinatedAt bell stage – unmyelinated At eruption - number of fibers & their average size increase - At eruption - number of fibers & their average size increase -

transition towards myelinationtransition towards myelination Continues to increase for a few years after eruptionContinues to increase for a few years after eruption Dentine is laid down – pulp reduced in size – nerve plexus Dentine is laid down – pulp reduced in size – nerve plexus

decrease in sizedecrease in size Ageing pulpAgeing pulp

• Decrease in number of axons entering pulpDecrease in number of axons entering pulp• Reduction in myelinated fiber sizeReduction in myelinated fiber size• Raschkow’s shows little changeRaschkow’s shows little change

Pulp nerves in primary teethPulp nerves in primary teeth

Number of axons is less than that in permanentNumber of axons is less than that in permanent Except primary canineExcept primary canine Number of axons decrease with resorption Number of axons decrease with resorption

until the tooth is sheduntil the tooth is shed

Neurotrophic substancesNeurotrophic substances Nerve growth factors – evidenceNerve growth factors – evidence

• Promote survival of neural crest cells in trigeminal Promote survival of neural crest cells in trigeminal ganglionganglion

• Produced in the maxillary process to maintain survival of Produced in the maxillary process to maintain survival of nerve axonsnerve axons

• No role in directing spread of fibersNo role in directing spread of fibers• Act on nearby nerves govern late invasion of pulp tissue by Act on nearby nerves govern late invasion of pulp tissue by

nerve fibersnerve fibers• Allow permanent teeth to recruit their nerve supply from Allow permanent teeth to recruit their nerve supply from

branches of axons previously supplying deciduous teethbranches of axons previously supplying deciduous teeth• Odontoblastic factors promote extension of new nerve Odontoblastic factors promote extension of new nerve

fibers into the subodontoblastic layer & dentine in fibers into the subodontoblastic layer & dentine in reimplanted teethreimplanted teeth

Functions of AFunctions of Aδδ fibers fibers

• MyelinatedMyelinated• Diameter: 1 – 4 µmDiameter: 1 – 4 µm• Rapidly conducting (>2 m/s)Rapidly conducting (>2 m/s)• Mediate sharp, piercing pain sensationsMediate sharp, piercing pain sensations• Responsible for dentinal sensitivityResponsible for dentinal sensitivity• Respond to any stimuli causing fluid movement in Respond to any stimuli causing fluid movement in

dentinal tubulesdentinal tubules Drilling, drying & application of osmotic solutionsDrilling, drying & application of osmotic solutions

Functions of C fibersFunctions of C fibers

UnmyelinatedUnmyelinated Diameter: < 0.5 µmDiameter: < 0.5 µm Slowly conducting (< 2 m/s)Slowly conducting (< 2 m/s) Polymodal: activated byPolymodal: activated by

• ThermalThermal• MechanicalMechanical• Chemical stimuli – histamine & bradykinenChemical stimuli – histamine & bradykinen

Mediate dull, longer standing & less well-Mediate dull, longer standing & less well-localizedlocalized

Neurotransmitters in dental pulpNeurotransmitters in dental pulp

Calcitonin gene-related peptide (CGRP)Calcitonin gene-related peptide (CGRP) Substance PSubstance P Neurokinin ANeurokinin A

Autonomic nerve supply in the pulpAutonomic nerve supply in the pulp

SympatheticSympathetic ParasympatheticParasympathetic

SympatheticSympathetic Majority of autonomicMajority of autonomic Some are cholinergicSome are cholinergic

• Removal of superior cervical ganglion – some decrease in Removal of superior cervical ganglion – some decrease in cholinesterase staining in the pulpcholinesterase staining in the pulp

In mouseIn mouse• ½ in pulp horn½ in pulp horn• 1/3 in pulp chamber1/3 in pulp chamber• Rest in root canalRest in root canal

FunctionsFunctions• Control pulp blood flowControl pulp blood flow• Regulation of odontogenesisRegulation of odontogenesis• Afferent transmission of impulses associated with pain sensationAfferent transmission of impulses associated with pain sensation

Evidences of functionsEvidences of functions• Anatomical: near blood vessels & odontoblastsAnatomical: near blood vessels & odontoblasts• Sympathectomy – vasodilatation & changed in dentine appositionSympathectomy – vasodilatation & changed in dentine apposition

ParasympatheticParasympathetic

Majority are cholinergicMajority are cholinergic• Resection of inferior alveolar nerveResection of inferior alveolar nerve

Abolish cholinesterase stainingAbolish cholinesterase staining Increased rate f tooth eruption (increased intrapulpal Increased rate f tooth eruption (increased intrapulpal

pressure)pressure)

Nociceptive response – substance PNociceptive response – substance P

Pulp reacts initially to stimulating dentinePulp reacts initially to stimulating dentine• ElectricallyElectrically• MechanicallyMechanically• ChemicallyChemically

C fibers stimulated - C fibers stimulated - Retrograde impulse in C branches – Retrograde impulse in C branches – Release of substance P at terminals – Release of substance P at terminals –

• Vasodilatation – tissue edemaVasodilatation – tissue edema• Release of histamine – increase capillary permeability & Release of histamine – increase capillary permeability &

fluid extravasationfluid extravasation

Nociceptive response - bradykininNociceptive response - bradykinin

Noxious stimulation of the pulp – Noxious stimulation of the pulp – Bradykinin formation – Bradykinin formation –

• Contribute to vasodilatationContribute to vasodilatation• May stimulate release of encephalins from pulpal May stimulate release of encephalins from pulpal

cellscells Encephalins – anti-inflammatory – inhibit Encephalins – anti-inflammatory – inhibit

bradykinin release – protective –ve feedback bradykinin release – protective –ve feedback mechanismmechanism

Nociceptive responce – ecosanoid Nociceptive responce – ecosanoid groupgroup

Are metabolites of arachidonic aidAre metabolites of arachidonic aid• ProstaglandinsProstaglandins• LeucotrienesLeucotrienes

PG I2 produced by endothelial cellsPG I2 produced by endothelial cells• Inhibit platelet aggregationInhibit platelet aggregation• VasodilatorVasodilator

Thromboxane A2 produced by platelets & fibroblastsThromboxane A2 produced by platelets & fibroblasts• Stimulate platelet aggregationStimulate platelet aggregation

In the pulpIn the pulp• PG PG II22, PG , PG FF2α2α , PG , PG EE22 • Thromboxane Thromboxane AA22

• Leucotrience 12-HETE, LTCLeucotrience 12-HETE, LTC44

Nociceptive response – prostaglandinsNociceptive response – prostaglandins

Bacterial/mechanical/chemical irritation – Bacterial/mechanical/chemical irritation – Increase in prostaglandin Increase in prostaglandin FF2α2α & & EE22 (found in high (found in high

conc. In inflamed pulp)conc. In inflamed pulp)• VasodilatationVasodilatation• Increase pain-producing properties ofIncrease pain-producing properties of

HistamineHistamine BradykininBradykinin SerotoninSerotonin

Pain relieving drugsPain relieving drugs

Aspirin – inhibitor of cyclo-oxygenase – Aspirin – inhibitor of cyclo-oxygenase – inhibition of PG synthesisinhibition of PG synthesis

Root canal medicamentsRoot canal medicaments• Phenol, p-Chlorophenol, cresol, thymol, guaiacolPhenol, p-Chlorophenol, cresol, thymol, guaiacol• Inhibit synthesis of PG & leucotrienesInhibit synthesis of PG & leucotrienes• Have antibacterial activityHave antibacterial activity

Eugenol – more effective than phenols in Eugenol – more effective than phenols in inhibition of prostaglandin synthesisinhibition of prostaglandin synthesis

Pulpitis & pulp necrosisPulpitis & pulp necrosis

Injury to dentine (cavity prep.)Injury to dentine (cavity prep.)• Nerve fibers & odontoblastic processes pulled by Nerve fibers & odontoblastic processes pulled by

hydrodynamic force – hydrodynamic force – • Separated from pulpal tissue – Separated from pulpal tissue – • Damaging nerve fibers & killing of odontoblasts – Damaging nerve fibers & killing of odontoblasts – • Pain in dentinePain in dentine

Small injurySmall injury

In small damaged areas / odontoblastic layer In small damaged areas / odontoblastic layer damage is slightdamage is slight• Reparative dentine may seal off small damaged Reparative dentine may seal off small damaged

areasareas Blocks re-innervationBlocks re-innervation Innervation of adjacent areas is increasedInnervation of adjacent areas is increased

• CGRP from reactive axons promote growth of new CGRP from reactive axons promote growth of new fibersfibers

• When the lesion heals - new fibers disappearWhen the lesion heals - new fibers disappear

PulpitisPulpitis Cavity reaches the pulpCavity reaches the pulp

• Odontoblastic layer destroyedOdontoblastic layer destroyed• Inflammation occurs locallyInflammation occurs locally• In small lesions, dentine bridge forms – inflammation In small lesions, dentine bridge forms – inflammation

resolves & pulp heals (reversible pulpitis)resolves & pulp heals (reversible pulpitis) Inflammation area demarcated by fibrous tissueInflammation area demarcated by fibrous tissue

• More severe stimuli / larger lesions – irreversible pulpitisMore severe stimuli / larger lesions – irreversible pulpitis Severe inflammation -inflammation area demarcated by fibrous Severe inflammation -inflammation area demarcated by fibrous

tissuetissue Lack of pain at a later stage of pulpitisLack of pain at a later stage of pulpitis

• CGRP-mediated growth of nerve fibers outside CGRP-mediated growth of nerve fibers outside inflammation areainflammation area

Hypersensitivity in early pulpitisHypersensitivity in early pulpitis Difficulty in achieving anesthesia a tooth with an inflamed pulpDifficulty in achieving anesthesia a tooth with an inflamed pulp

Pulp necrosisPulp necrosis

More severe pulpal exposureMore severe pulpal exposure• Irreversible pulpitis - necrosis occursIrreversible pulpitis - necrosis occurs• Necrosis area demarcated by fibrous tissueNecrosis area demarcated by fibrous tissue• CGRP-mediated growth of nerve fibers outside CGRP-mediated growth of nerve fibers outside

necrosis areanecrosis area Lesion extends to root apexLesion extends to root apex

• Nerve growth in periapical tissueNerve growth in periapical tissue• New fibers appear to be involved in pain sensationNew fibers appear to be involved in pain sensation

Pain of dental originPain of dental origin Exposed dentine – sensitivity - painExposed dentine – sensitivity - pain

• Dental caries or cavity prep.Dental caries or cavity prep.• Cemental layer wears awayCemental layer wears away

Any sensation through dentine – painAny sensation through dentine – pain Heat / cold may be perceived as separate sensations?Heat / cold may be perceived as separate sensations? Most sensitive areas in dentine as atMost sensitive areas in dentine as at

• EDJEDJ• Exposed dentine in cervical root areasExposed dentine in cervical root areas

Nerve fibers to dentine are limited to coronal dentineNerve fibers to dentine are limited to coronal dentine Nerve fibers numerous under cuspsNerve fibers numerous under cusps Nerve fibers extend for a short distance within dentineNerve fibers extend for a short distance within dentine Odontoblastic processes vary in extension through dentineOdontoblastic processes vary in extension through dentine

• Function as receptorsFunction as receptors

Three theories of dentinal Three theories of dentinal hypersensitivityhypersensitivity

Odontoblastic processes as receptorsOdontoblastic processes as receptors• Odontoblasts are neural crest in originOdontoblasts are neural crest in origin

Nerve fibers extend through dentineNerve fibers extend through dentine• Direct stimulationDirect stimulation• Deformation of odontoblasts by fluid movement promotes Deformation of odontoblasts by fluid movement promotes

potassium release – action potential in neighboring nerve potassium release – action potential in neighboring nerve fibersfibers

Hydrodynamic theoryHydrodynamic theory• Movement of fluids through dentinal tubules inward & Movement of fluids through dentinal tubules inward &

outwardoutward• Distortion of nerve endings in Raschkow’s plexusDistortion of nerve endings in Raschkow’s plexus

Referred painReferred pain

Sensation of pain resulting from a deep organ Sensation of pain resulting from a deep organ peripherally in areas derived from the same peripherally in areas derived from the same somitesomite• Pain of cardiac origin may be perceived in the armPain of cardiac origin may be perceived in the arm

Convergence of somatic & visceral sensory Convergence of somatic & visceral sensory impulses at one or more of 3 levelsimpulses at one or more of 3 levels• PrespinalPrespinal• SpinalSpinal• SupraspinalSupraspinal

Referred orofacial painReferred orofacial pain In trigeminal, levels areIn trigeminal, levels are

• PrepontinePrepontine• PontomedullaryPontomedullary• SuprapontineSuprapontine

No convergence within brainNo convergence within brain Pain within the oral cavity is referredPain within the oral cavity is referred

• Within the distribution of the specific divisions of the trigeminal nerve Within the distribution of the specific divisions of the trigeminal nerve • Doesn’t cross midline except in ramifications of nerve terminals Doesn’t cross midline except in ramifications of nerve terminals

(incisor region)(incisor region) Migrainous headache may be due to dental conditionsMigrainous headache may be due to dental conditions

• Not referred painNot referred pain• Because it is vascular in originBecause it is vascular in origin