The document discusses pain pathways and pain management. It begins with definitions of pain from IASP and classifications of pain such as nociceptive, neuropathic, acute and chronic. It then covers topics like neural pathways, neuroanatomy, theories of pain including specificity theory and gate control theory. Pulpal pain pathways and assessment tools for pain are explained. Finally, it discusses approaches to pain management and goals of pain therapy.

1. P A I N P A T H W A Y
D R S H R U T I S U D A R S A N A N
J U N I O R R E S I D E N T 1 S T Y E A R
P E D I AT R I C A N D P R E V E N T I V E D E N T I S T R Y
G D C K O T TAYA M
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2. CONTENTS
 Introduction
 Definitions
 Classification of pain
 Terminologies
 Neural pathways
 Neuroanatomy
 Neurophysiology
 Pain pathways
 Theories of pain
 Pulpal pain
 Measurement of pain in children
 Management of pain
 Conclusion
 References
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3. WHAT IS PAIN?
 The International Association for the Study of Pain (IASP) has defined
pain as: ‘An unpleasant sensory and emotional experience associated
with actual or potential tissue damage, or described in terms of such
damage’.
 sensory refers to the senses, such as touch, hearing, taste, smell or
 emotional is associated with the state of mind or with feelings, as well
the prevailing motivation at the time of the experience
 actual or potential tissue damage suggests that a tissue injury is not
required for the experience of pain . Thus it is not always tied to a
stimulus
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4. CLASSIFICATION OF
PAIN
CAUSATIVE
FACTORS
NOCICEPTIVE
SOMATIC
VISCERAL
NEUROPATHIC
CENTRAL
PERIPHERAL
INTENSITY
MILD PAIN
MODERATE
PAIN
SEVERE PAIN
DURATION
ACUTE
CHRONIC
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5. • Acute pain - The normal, predicted physiological response to
an adverse chemical, thermal or mechanical stimulus
with surgery, trauma and acute illness.
• Acute pain is defined as pain lasting less than three to six
months.
• Chronic/ long-lasting pain - Pain in one or more anatomical
regions that persists or recurs over a period longer than three
months and is associated with significant emotional distress or
significant functional disability (interference with activities of
daily life and participation in social roles) and that cannot be
better explained by another chronic pain condition.
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6. TERMINOLOGIES
• NOCICEPTORS- These are the receptors sensitive to painful
stimulus and are responsible for initiating the generation of pain.
• NOCICEPTION- It refers to the processing of a noxious stimulus
resulting in perception of pain by the brain.
• ALLODYNIA- Pain that is produced by a stimulus that is not
normally painful.
• HYPERALGESIA- Increase sensitivity to painful stimuli.
• HYPOESTHESIA- Reduced sensation in response to stimulus.
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7. • ANESTHESIA- Absence of sensation in response to a stimulus
• CAUSALGIA- is a condition in which spontaneous burning pain
sensation occurs after a long time in the area of even trivial injuries.
• NEURALGIA- It is the pain experienced In the tissue along the
nerve distribution.
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8. NEURAL PATHWAYS
The subjective experience of pain arises from 4 distinct processes :
1. Transduction : processes by which tissue-damaging stimuli activate
nerve endings.
2. Transmission : the relay functions by which the message is carried
from the site of tissue injury to the brain regions underlying
perception.
3. Modulation : recently discovered neural process that acts specifically
to reduce activity in the transmission system.
4. Perception : the subjective awareness produced by sensory signals; it
involves the integration of many sensory messages into a coherent and
meaningful whole. Perception is a complex function of several
processes, including attention, expectation, and interpretation.
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9. PAIN RECEPTORS
• NOCICEPTORS are the specialised sensory receptors
responsible for the detection of noxious stimuli, transforming
the stimuli into electrical signals which are then conducted to
the CNS.
• They are the free nerve endings of primary afferent Aδ & C
fibers.
• These receptive endings are widely distributed in the body
– Skin
– Viscera
– Dental pulp
– Periosteum
– Meninges
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10. NOCICEPTORS
• Help to identify site of tissue injury
• Response to stimuli such as Thermal, chemical or mechanical
• The nature is Polymodal – respond to multiple stimulus.
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A BETA FIBRES A DELTA FIBRES C FIBRES
• Large • Small • Small
• Myelinated • Lightly Myelinated • unmyelinated
• Fast conducting • Slow conducting to
heat, cooling
• Very slow conducting
• Low stimulation
threshold
• Respond pressure,
chemicals
• Respond to all types
of noxious stimuli
• Require high intensity
stimuli to trigger a
response
• Respond to light
touch
• sharp sensation of
pain
• Transmit prolonged
dull pain

11. QUALITATIVE TYPES OF PAIN
SENSATIONS
• two types: fast pain and slow pain.
1. Fast pain is a sharp, well-localized, pricking sensation that results from
activation of the nociceptors on the A fibres.
• The fast pain sensations travel faster and thus appear within 0.1 ms after
the application of stimulus.
• Accompaniments of fast pain are: Withdrawal reflex, which causes the
individual to move the involved body part away from the source of
painful stimulus.
– Sympathetic response, i.e. increased blood pressure, tachycardia and
mobilization of body energy supply.
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12. 2. Slow pain
Slow pain is poorly localized, dull, throbbing, burning sensation that
results from activation of nociceptors on the C fibres.
• It appears after one second or more following the application of
stimulus.
• Accompaniments of slow pain are: Emotional perception in the form of
unpleasantness, and in long-standing cases in the form of irritation,
frustration and depression.
– Autonomic symptoms in the form of nausea, profuse sweating,
vomiting and lowering of blood pressure.
– Generalized reduction in skeletal muscle tone.
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13. TRANSMISSION OF PAIN SIGNALS
• Each end organ has its pathway and its pathway
consists of:
I. First order neuron
II. Second order neuron
III. Third order neuron
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14. PATHWAYS OF PAIN SENSATION
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15. NEOSPINOTHALAMIC TRACT
• lateral spinothalamic
tract
• First-order neurons
• Second-order neurons
• Third-order neurons.
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16. DENTAL PULP:
INNERVATION OF DEVELOPING TOOTH
• The sensory nerve fibres traverse the dental papilla and on reaching the coronal pulp,
branch towards the periphery to form PLEXUS OF RASCHKOW.
• Located in the subodontoblastic zone.
• These are myelinated fibres
• Many nerves leave the plexus and extend into odontoblastic layer
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A delta fibres C fibres
Most apical myelinated axons
fast conducting Slow conducting
receptive field  pulpal periphery and
inner dentin
 pulp
Activated by hydrodynamic
mechanism
Conduct short, well localised sharp Transmit dull, poorly localised,

17. PULPAL PAIN
Generally 2 Types of pulpal pain as described by patient:
• Sharp, piercing and lancinating: A delta nerve fibres
• Dull boring, gnawing and excruciating pain: C nerve fibres
Localisation of pain
• Localised pain: patient can point to a specific tooth or site with
assurance and speed
– Sharp pain usually responds promptly to cold
• Diffuse pain: pt describes an area of discomfort
– Relates to dull boring pain
– Responds abnormally to heat more than cold
– Symptoms can be referred to other sites
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18. Duration of pain:
• Pain may last only as long as an irritant is present
• Other times, it lasts for minutes to hours
• Pain may be intermittent or constant
A tooth with fleeting pulpal pain that disappears on removal of the irritant
has an excellent chance of recovery without the need for endodontic
treatment.
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19. • Acute reversible pulpitis (hyperemia): pain of short duration
– Caused by specific irritant
– Pain disappears when irritant is removed
– Pain is usually localised
– More responsive to cold than heat
• Irreversible pulpitis: if pain persists or
– If it occurs without any apparent cause
– Patient will require endodontic therapy
– Spontaneous pain and pain of long duration are symptoms
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20. PATHWAY OF SENSATIONS FROM FACE
AND ORAL CAVITY
• The sensations of pain from the face and oral cavity including teeth and
proprioceptive information from the jaw muscles are carried by
trigeminal nerve.
• First-order neurons are located in the trigeminal ganglion, which is
equivalent to dorsal nerve root ganglia in the spinal cord.
• The peripheral processes of these neurons form three divisions of the
trigeminal nerve: ophthalmic, maxillary and mandibular which innervate
different areas of the facial skin
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21. • The central processes of these neurons of
trigeminal ganglia terminate in different
components of trigeminal sensory nucleus as
:
– Principal sensory trigeminal nucleus,
located in the pons, receives fibres
carrying tactile sensations.
– Spinal nucleus is elongated and extends
down to the upper spinal cord. It receives
fibres carrying pain and temperature
sensations.
– Mesencephalic nucleus, which extends
from the pons into midbrain, receives
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22. • Second-order neurons. Axons of these neurons cross to the opposite
side and ascend as trigeminal lemniscus to the ventroposterior medial
(VPM) nucleus of thalamus
• Third-order neurons are located in the VPM nucleus of thalamus. All
the sensations reaching this nucleus are carried primarily to sensory area
of cerebral cortex by fibres passing through the posterior limb of
internal capsule (superior thalamic radiations).
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23. THEORIES OF PAIN
 Specificity theory
 Pattern theory
 Intensity theory
 Gate control theory
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24. SPECIFICITY THEORY
• The fundamental tenet of the Specificity Theory is that each modality has
a specific receptor and associated sensory fiber (primary afferent) that is
sensitive to one specific stimulus (Dubner et al. 1978)
• non-noxious mechanical stimuli are encoded by low-threshold
mechanorecepetors, which are associated with dedicated primary
afferents that project to “mechanoreceptive” second-order neurons in
the spinal cord or brainstem (depending on the source of the input).
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25. INTENSITY THEORY
• The theory defines pain, not as a unique sensory experience but rather, as
an emotion that occurs when a stimulus is stronger than usual.
• Repeated tactile stimulation (below the threshold for tactile perception)
produces pain concluding that there must be some form of summation
that occurs for the subthreshold stimuli to become unbearably painful.
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26. PATTERN THEORY
• Goldscheider [1894]
• Proposes that pain is generated by non specified receptor.
• Pain sensation depends upon the spatio-temporal pattern of nerve impulses reaching
the brain.
• Nerve impulse entering CNS –Diff. For diff. region and will vary from from person to
person due to anatomical variation
• A stimulus evoke certain pattern that the brain receives and recognizes.
• Receptors not specialized as in SPECIFICITY theory
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27. GATE CONTROL THEORY
• In 1965, Ronald Melzack and Charles Patrick (Pat) Wall (Melzack and
Wall 1965) proposed a theory that would revolutionize pain research:
the Gate Control Theory of Pain.
• The gate in the spinal cord is the substantia gelatinosa in the dorsal
horn, which modulates the transmission of sensory information from the
primary afferent neurons to transmission cells in the spinal cord.
• This gating mechanism is controlled by the activity in the large and small
fibers. Large-fiber activity inhibits (or closes) the gate, whereas small-
fiber activity facilitates (or opens) the gate.
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28. PAIN SUPPRESSION SYSTEMS IN CNS
The degree of reaction to painful stimuli varies from individual to individual, mainly
because of existence of pain suppression systems in the central nervous system. The pain
suppression consists of two major components
• Spinal pain suppression system and
• Supraspinal pain suppression system
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29. A. SPINAL PAIN
SUPPRESSION SYSTEM
• Gate control hypothesis
• It has been observed that activation of large myelinated touch fibres (Aβ) reduces pain.
• Aβ fibres give collaterals which cause presynaptic inhibition of pain carrying (both type
C and Aδ) fibres, where they synapse in the dorsal horn
• such circuitry probably explains the relief of pain achieved by following manoeuvres:
– Rubbing or massage or pressure in the vicinity of painful area.
– Local application of warmth or cold.
– Local application of counterirritants, i.e. stimulation of skin.
– Acupuncture.
– Transcutaneous electric nerve stimulation (TENS) in which pain site or the nerves
leading from it are stimulated by electrodes placed on the surface of skin
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30. ROLE OF BRAIN IN GATE CONTROL
MECHANISM
Pain signals reach the thalamus through lateral
spinothalamic tract
Signals are processed in thalamus
Signal are sent to sensory cortex & perception of pain
occurs in cortex
Signals are sent from cortex back to spinal cord and
the gate is closed by releasing pain relievers such as
opioid peptides
Minimizing the severity & extent of pain
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31. 6/6/2022 31

32. ASSESSMENT OF PAIN
• Comprehensive history intake
– Medical history
– Physical history
– Family history
• Physical exam
• Questioning on characteristic of pain – onset, duration, location, quality,
severity & intensity
• Evaluation of psychological status
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33. PAIN ASSESSMENT TOOLS
• Pain may be accompanied by physiologic signs and symptoms and there are no
reliable objective markers of pain
• The severity of pain can be assessed by rating scales & multidimensional scales.
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RATING SCALES
Provide a simple way to classify the
intensity of pain and should be
selected based on the patients ability
to communicate
MULTIDIMENSIONAL
SCALES
Helpful information in obtaining about
the pain and impact on QOL, but are
more often time consuming to
complete

34. • Visual Analog scale
• Mc Gill Questionnaire
• Numeric Pain Intensity Scale
• Simple Descriptive Pain Intensity Scale
• Graphic Rating Scale
• Verbal Rating scale
• Pain Faces Scale
• MPI Scale
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35. MANAGEMENT OF PAIN
GOALS OF THERAPY
To decrease the subjective intensity acute pain
To reduce the duration of the pain complaints
To decrease the potential for conversion of acute pain to chronic
persistent pain syndromes
To decrease the physiological, psychological, & socioeconomic
sequelae associated with under treatment of pain
To minimize ADRs, & Dis intolerance to pain management therapies
Improving the patients QOL and the ability to perform activities of daily
living
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36. APPROACHES TO PAIN CONTROL
•Remove or
treat cause
Analgesics
Psychothera-
peutic
approaches
supportive
care
Inhibition of
pain
transmission
Neurological
Palliative
radiotherapy
and
pharmaco-
therapy
Anaesthetics
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PAIN

37. OBSTRUCTION IN MANAGEMENT OF
PAIN.
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38. CONCLUSION
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• Before any attempt is made to control or eliminate
pain by any method the patient should receive the
benefit of a diagnosis as careful as possible.
• No treatment should be prescribed on a “per chance”
basis , since pain is a symptom and should be treated
with a plan

39. REFERENCES
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 Guyton & Hall Textbook Of Medical Physiology 12th Edition
 Bell’s Orofacial Pain: 5th Edition: Jeffrey P Okeson
 Monheim’s Local Anesthesia And Pain Control In Dental
Practice, 7th Ed.
 Malamed- Handbook Of Local Anesthesia, 6th Ed
 Gray’s Anatomy: 38th Edition: Churchill Evingstone
 Grossman’s endodontic practice: 13th edition
 Textbook of physiology: Indu Khurana

40. THANKYOU
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