117404156 pain and pain pathways

7/29/2019 117404156 Pain and Pain Pathways

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Pain and pain pathways


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CONTENTS

Introduction

History

Levels of pain processing

Neural pathways of pain

Theories of pain

Types of pain

Measurment of pain

Management of pain

Studies

References


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The most fundamental and primitive sensation

Pain impairs the lives of millions of people

In 1984 Bonica reported that 1/3 of the worlds

population suffers from pain of some etiology

We dentists are concerned with teo of the most

common pains:

1st

Acute orofacial pain arising from teeth andassociated structures

2nd Chronic orofacial pain , which is belived to

account for 40% of all chronic pain problems


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Responsibility of the dentist:

To identify the cause

To treat ( by dental or multidiciplinary

approach)


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History

Root : from greek word Poin derived from latin

Poena

Dorlands Medical dictionary defined pain as A

more or less localised sensation of discomfort,distress or agony, resulting from stimulation of

specialised nerve endings.

It serves as a protective mechanism in so far as

it induces the suferer to remove or withdraw

from the source


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An unplesant sensation associated with acuteor potential tissue damage and mediated by

spefic nerve fibers to the brain wheere its

conscious appreation may be modified byvarious factors

Pressure to seek aid for pain increases when

patient is under greater than usual stress

Degerr of pain is not related to amount of injury.

. . . . . But on attention given by patient


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Levels of pain processing

Nociception

Pain

Suffering Pain behaviour

Pain is presently recognised as anexperience rather than a sensation


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Neural pathways of pain

Feilds has noted that subjective experience of

pain arises from 4 distinct processes

Transduction Noxius stimuli electric activity in sensory neuron

Transmission 1st order neurons: sensory organ spinal chord

2nd order neurons: spinal chord thalamus

3rd order; interaction

Modulation

Perception


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Fibers carrying pain impuls:

A delta fibers:

Myelinated

Mechanical stimulus

C fibers

Unmylinated

Chemical and thermal stimuli


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Theories of pain

Intensity theory When sensation is beyond a level

Speficity theory Spefic nociceptors + center in brain

Pattern theory Nan specialised receptors; excitation thresholds,

adaptation ranges,distribution of branches

Protopathic and epicritic theory Primitive system + advanced system


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Gate control theory 1965, Melzack and Wall

Activity in several interacting neural pathways

Cells in substantiagelatinosa

Dorsal column fibersthat project towards

the brain

First central transmission(T) cells in spinal chord

Gate control system

modulates efferent

paterns before they

influnce T cells

Central control trigger

activates areas in brain

influnces modulating

prop of GCS

Activates neural

mechanism for perception

- Threashold


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Orofacial pain classification: Axis I (Physical conditions)

I. Somatic pain

Superficial somatic pain

Cutananeous pain

Mucogingival pain

Deep somatic pain

Musculoskeletal pain

Muscle pain

Protective co contraction Local muscle soreness

Myofacial pain

Myospasm

Centrally mediated myalgia

Temporomandibularjoint pain

Ligamentous pain

Retrodiscal pain

Capsular pain

Arthritic pain

Osseous /periosteal pain

Soft connective tissue pain

Periodontal dental pain

Visceral pain

Pulpal dental pain

Vascular pain

Neurovascular pain

Visceral mucosal pain

Glandular, ocular, auricular pain


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II Neuropathic pain

Episodic neuropathic pains

Paroxysmal neuralgia pain

Trideminal neuralgia

Glossopharyngeal neuralgia

Geniculate neuralgia

Superior laryngeal neuralgia

Nervus intermidus

Occipital neuralgia Neurovascular pain

Continuous neuropathic pain

Peripherally mediated pain

Entrapment neuropathy Deafferentiation pain

Traumatic neuroma pain

Neuritic pain

Peripheral neuritis

Herpes zoster

Centrally mediated pain

Burning mouth disorder

Atypical odontalgia

Postherpetic neuralgia

Metabolic polyneuropathies

Diabetic neuropathy

Hypothyroid neuropathy

Alcholic neuropathy

Nutritional neuropathy

Axis II (psychologic conditions)

Mood disorders Anxiety disorders

Somatoform disorders

Other conditions


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Measurment of pain

Pain perception threashold (PPT)

Severe Pain Threashold (SPT)

Variability

Scales for measurment

Category scale Rupee analog scale

Numeric rating scale

Visual analog scale


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Visual analog scale:

Pain score

No pain Worst possible pain10 cms

0- no pain

1 Probabaly no pin

2 Mild discomfort

3 Mild pain or discomfort

4 Mild to moderate pain

5 Moderate pain

6 Increased moderate pain

7 moderate to severe pain

8 Severe pain

9 Severe to excruciating pain

10 Worst possible pain


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Management of pain

Therupatic modalities:

Pharmacologic therapy

1) Analgesic agents

2) Anesthetic agents

3) Anti inflamatory agents

4) Muscle relaxants

5) Antidepressants

6) Anti anxity agents

7) Vasoactive agents8) Non epinephrine blockers

9) Antimicrobial agents

10) Antiviral agents


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11) Antihistamine agents

12) Anticonvulsants

13) Neurolytic agents

14) Uricisuric agents15) Dietary considerations

Physical therapy Psychologic therapy

1) Modalities 1) Counclling

Sensory stimulation 2) Behaviour modification

Ultrasonic * Stress releiving training

Electrogalvanic stimulation * Relaxation training

Deep heat * Physical self regulation

2) Manual techniques Massage

Spray and streach technique

Exercise

Physical activity


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Analgesic agents:

Shouldnt eliminate pain. . . . But make it tolerable

Non narcotic analgesics:- 4 basic actions

- Inhibition of COX PG E2 formation

- PGs induce hyperalgesia

- Temperature in fever

- Inhibits PGE2 formation in hypothalamus

- Prolongs bleeding time

- Synthesis of platelet aggregator factor TXA2

- No tolerance, physical dependence

- Have celing effect

- Toxicity: gastric mucosal damage, bleeding, Renal blood flow,

aggrevates Asthma &anaphylactoid reactions

Eg: Asprin, Iboprofen, Ketoprofen (short t1/2)

Nabumetone, naproxen (long t1/2)

Acetaminophen (adv)


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Most commonly used for acute dental pain

Mild-moderate pain + inflamation : Paracetamol + low

dose Iboprofen

Post extraction pain : Ketorolac/ diclofenac / nimesulide/asprin

Gastric intolerance to NSAIDs: Celecoxib/ Raficoxib/

Paracetamol

With history of asthma; anaphylaxis to NSAIDs:Nimesulide

Children: only Paracetamol/ Asprin/ Ibuprofen(asprin in

viral infections: Reyes syn)

Pregnancy: paracetamol is safest; 2nd choice low doseasprin


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Asprin dose: 300-500 mg TDS/QID

ASSPRIN, DISPRIN 350 mg tabS

Paracetamol: 500mg-1g TDS CROCIN 500mg; 1g, METACIN,PARACIN 500mg

tabs; CROCIN PAIN RELIF: paracetamol 650mg+

Caffine 50mg tabs

Diclofenac 50 mg TDS VOVERAN, DICLONAC, MOVONAC 50 mg entric

coated tabs

Celecoxib 100-200 mg BD

CELACT, REVIBRA 100mg 200mg caps


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Narcotic analgesics

- Act through CNS receptors. . . . . Induce peripheral

analgesia

- Depress nociceptor neurons

- Have inhibitory influnce on release of substance P

- Tolerance should be noted- May cause constipation, physical dependence, addiction,

Acute morphine poisoning (R naloxone)

- Should be given on strict time schedule

- Used only for severe acute pain, chronic cancer pain- Eg ; morphine, codine, Pentazocine, Tramadol


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Anesthetic agents :

- For diagnostic and therupatic

Topical anesthesia- Solutions / spraya / lozenges

- Alovera juice inflamatory pain

- Analgesic balms : Balsam of peru, eugenol, guaiacol .- Use

- Eg: Xylocaine 4% topical solution

- Topical LA mixed with other medication

- Eg: Peripheral neuropathy: lignocain + amitriptyline +

Carbamazepine (Tegretol)

Injectable LA


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Injectable LA

Low potency short duration: Procaine

Intermediate Potency and duration: Lignocaine

Prilocaine

High potency, long duration : TetracaineBupivacaine

Ropivacaine

Mechanism of action: Reduces Na entry during AP

depolarization dosent reach threashold no APRate of rise of action potential

Lignocaine2% + adrenalin :commonly used

pulpal anesthesia obtained in 2-3 mins; lasts for 40-60 mins

Soft tissue anesthesia 2-3 hrs

Analgesia may not be acheived in very sensitive teeth, marked

inflamation

Lignocaine10% spray: for impressions

Bupivacaine 2% + adr 1: 200000

High lipid soluble- low bone penetrationanesthesia in >5 mins lasts for


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Anti Inflamatory agents

By inhibiting PGs

Devar reported that locally applied steroidrapidly and eeffectively arrested pain

Corticosteroids potent; but immune system

Uses: reccurent oral ulcers;

Phemphigus;erosive lichenplanus; pain from

exposed dental pulp; Hydrocortisone may be

injected into TMJ to relive refractory pain and

stifness Contraindicated in systemic fungal and herpesinfections


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Muscle relaxants

- in myogenous pain

- Potential agents (succinyl choline, methocarbamol)restricted to hospitalised pts

Anti depressants

- In Chronic pain with depression- Tricyclic anti depressants action: availability of 5HT,

norepinephrine, dopamine in CSF

- Eg: low dose of amitryptaline before sleep on

prolonged use reduces chronic pain ( nt acute pain)- Amitryptaline : post herpetic neuralgia

- Newer antidepresants SSRIs eg: fluoxetine, venloflaxine


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Antianxity agents

Reduces modulating effect of pain and

apprehension Major tranquilizer : Phenothiazine

Minor tranquilizers: Diazepam,Meprobamate

Have muscle relaxant action also

Potential for drug tollerance,dependence

When used for analgesia best prescribed for

limited period

Clonazepam

Has analgesic effect in certain neuropathic pains

Effective in burning mouth syndrome


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Vasoactive agents:

In neurovascular pain

Somatostatin has inhibitory action on substance P

B adrenergic blockers are proven effective in

phantom limb pain, migrane

adrenergic blocking drugs( eg: ergotamine

tartarate) : stimulating effect on b.v Used in cluster headache

Caffine has enhancing effect on its action


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Norepinephrine blockers:

Block reuptake of norepinephrine

Block stellate ganglion : control ofsympathetically maintained pains of orofacial

region

Guanethidine commonly usedAlso effective in rheumatoid arthritis


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Antimicrobial agents

Reduce pain by resolving

Intrinsic analgesic effect

Pain

Long term therapy - only if infection present

Antiviral agents

Effective in primirary infection of HSV, HZV

Eg Acyclovir, Famcyclovir Famcyclovir effectively reduces all symptoms

Drug of choice even in immunocompromised, HIV


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Anti histamine agents

In allergic reactions and neurovascular pain

Also has some analgesic effectAntihistamine + acetaminophen greater

analgesia than acetaminophen alone

Anticonvulsants Useful in neuropathic pain

Eg: Carbamazepine- primary mediator in

inflamatory pain

Neuropathic pain also treated by: Gabapentin;

oxycarbamazepine; Topiramate


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Neurolytic agents

Treat pain by destroying neves

Deafferentiation pain: Pain caused bydestroying nerves

Eg: 95% ethyl alchol (may not prevent

regeneration of peripheral axons) Glecerol injected into retro gasserian spc for

treating trigeminal neuralgia

It demyleanetes neurons responsible for trigeminal

neuralgia


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Uricosuric agents:

Used in hyperurecemia causing TMJ pain

Colchicine: subsides acute attacks of gout and relives

pain Probenicide: for for chronic gout arthritis

Acts by inhibiting reuptake of urates by kidney

Gout can involve TMJ


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Dietary considerations: Dietary supplementation of L-tryptophan : elevated pain

tollerence

Tryptophan competes with other amino acids for passage

across BBB

2% plasma tryptophan Tryptophan hydroxylase

. Tryptophan

Brady et al: 10 chronic pain patients included in study obtained

pain relif by taking 4g of L tryptophan per day and consuming

low-protein, low-fat, high carbohydrate diet for 8 weeks

CNS seratonergic neurons are actively involved in nociceptive

response

Seltzer et al: reduction in clinical pain and elevated pain

tolerance among randomly selected patients suferring from

chronic maxillofacial pain as a result of 4 weeks tryptophan

supplement therapy

Vit B6


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Physical therapy Sensory stimulation Cutaneous

Trans cutaneousPercutaneous

Cutaneous stimulation

Effect occurs by stimulation of thick mylinated afferents ;

A- neurons chiefly Many forms of cutaneous stimulation effectively

attenuate pain

Rubbing skin

Superficial massage

With alchol, menthol

Counter irrigation

Muster plaster

Mixture of aconite + iodine : stimulation of nociceptive fibers :

analgesic effect

Vapocoolant therapy


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Vapocoolant therapy

Useful in reliving myofacial trigger point pain

Interrmittancy is esseential

Act By stimulating cutaneous nociceptors and thicker A

fibers Eg: ethyl chloride spray

Alternative applications of heat & cold for brief periods

Eg : moist heat application over painful areas. When heat isnt

effective ice may be tried Infra red heat

Warm saline moutwashes for pain relif after chord insertion

for gingival retraction

Mechanical vibrations

Reported to give complete pain relif in 1/3 of patients with

dental pain

Hydrotherpy

Especially in neck & back pain of muscle origin

Effect of warm saline mouth washes on reduction of pain after packingchord for gingival retraction ;J of Mashhad dentistry 2007

Transcutaneous stimulation


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Transcutaneous stimulation

Low intensity current of high frequency

Mild tingling vibration

50 70% pain relif Action is immediate , restricted to segment

Acupuncture

By stimulating endogenous antinociceptive system

Electro acupuncture: low intensity, high frequency

current

Acupoints

Stimulates muscle nociceptors anti

nociceptive system

Induction period: 15-20 mins. Effect segmental or

generalised

Acupoint of oral cavity: inte orbital bridge + Ho Ku

point

Per cutaneous stimulation:


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Per cutaneous stimulation:

By electrodes that penetrate skin:

Subcutaneous nerve stimulation

Prolonged analgesia, no tollerance

Lawrence :

electric stimulation of perriosteum by insulated needles

9 122 V at 100-300 Hz for 45 mins Reported it was better than EA &TENS for chronic pain

Ultrasound

tissue temperrature at interrface

blood flow, seperates collagen fibers

Has better effect on deeper tissueskin

Phonophoresis: ultrasound used to administer drugs

through

Eg 10% hydrocortisone cream + Ultrasound


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EGS:

Uses electric stimulation to cause muscle contracture

Repeated involuntary contraction+ relaxation of muscles

Help in breaking up myospasm and increasing blood flow tomuscles

Reported to yield good results in MPDS

Deep heat therapy

Phisiotherapy in form of penetrating heat

Especially useful inflamatory pain

In form of ultrasound and diathermy

In myospasm and myofacial trigger point pain

Manual techniques:

Massage:

Gentle massage

Deep massage preceeded by 10 15 mins deep moist heat

effective in releiving trigger point pain and relaxing muscles


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Spray and streach technique

Muscle is streaxhed short of pain

Vapocoolant is applied in parallel sprays in one

direction travelling towards refrence area

Procedure

After 3 sweeps muscle is rewarmed

After treatment moist heat applied and range of

movement exercise done

Exercise

Forceful contraction of anagonist muscle causes

reflex relaxation of agonist Used for treating masticatory muscle spasm

For mucle to maintain normal resting length occational

stimulation of receptors is necessary


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Studies

A study to determine prevelence of joint diseases in 2

forms of myofacial pain( with limited mouth opening and

without) showed that patients with myofacial pain and

limited mouth opening often had joint diseases that were

not detected with clinical examination Study on modulation of myofacial pain by reproductive

harmones showed that pain levels were constant when

harmone levels were constant wheras they varied with

harmone levels in nonusers Posture corrections when given along with cognitive

behaviour intervention were seen to treat myofacial pain

better


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Maping of pressure pain threasholds (ppt) in edentulous

mucosa showed that ppt from ant post alveolus but

decreased from ant palate to post palate. Ppt reduced

from ridge crest to buccal vestibule

Another study conducted in 1993 showed that intraoralappliance (IA) was more effective than BF/SM in treating

TMJ disorders with pain and depression but after 6 mnts

IA group significantly relapsed wheras BF/SM

maintained and continued improvement Neeraj Madan, ijdr, 2001 :Denture wearing patients with

pain in oral musculature &tmj could be attributed to

improperly recorded vertical jaw relations


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O.gabbert 2005 : case report of pt who developed

neuropathic pain after implant placement: underwent

multiple RCTs, extraction, long term opoid therapy .

Finally CT,MRI showed perforation of mandibular cannal

by implant.


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Thank you

117404156 pain and pain pathways

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