pain pathways in dentistry

1. PRESENTED BY:
KHUSHBOO
M.D.S.final YEAR
DEPARTMENT OF PEDODONTICS AND
PREVENTIVE DENTISTRY

2. CONTENTS
 Introduction
 Definitions
 Benefits of pain sensation
 Classification of pain
 Acute pain
 Chronic pain
 Neuropathic pain
 Herpes zoster
 Trigeminal neuralgia
 Musculoskeletal pain
 Referred pain
 Receptors

3.  Sensory neurons
 Pain pathways
 Neural pain pathways
 Pain theories
 Factors affecting pain
 Pain in orofacial region
 Pain diagnosis
 Assessment of pain
 Pain management
 Conclusion
 References

4. INTRODUCTION
 The word pain is derived from the Latin word Peone and
the Greek word Poine meaning penalty or punishment
 Pain is an intensely subjective experience, and is therefore
difficult to describe.
 Prevention and management of pain is an important aspect
of health care.

5. DEFINITION
 Acc to The International Association for the Study of Pain
says an unpleasant sensory and emotional experience
associated with actual or potential tissue damage, or described
in terms of such damage.
or
 Monheim : “An unpleasant emotional experience usually
initiated by noxious stimulus and transmitted over a specialized
neural network to the CNS where it is interpreted as such.”

6. BENEFITS OF PAIN SENSATION
„
 Pain is an important sensory symptom. Though it is an
unpleasant sensation, it has protective or survival
benefits such as:
 1. Pain gives warning signal about the existence of a
problem or threat. It also creates awareness of injury.
 2. Pain prevents further damage by causing reflex
withdrawal of the body from the source of injury

7.  3. Pain forces the person to rest or to minimize the
activities thus enabling rapid healing of injured part
 4. Pain urges the person to take required treatment to
prevent major damage.

8. CHARACTERSTICS OF PAIN
1. Threshold and Intensity
• If the intensity of the stimulus is below the threshold (sub-
threshold) pain is not felt. As the intensity increases more
and more, pain is felt more and more according to the
Weber-Fechner’s law.
• . Adaptation – Pain receptors show no adaptation and so
the pain continues as long as receptors continue to be
stimulated.

9. 3.Localization of pain -
Pain sensation is somewhat poorly localized. However
superficial pain is comparatively better localized than deep
pain.
4.Influence of the rate of damage on intensity of pain
If the rate of tissue injury (extent of damage per unit time) is
high, intensity of pain is also high.

10. CLASSIFICATION OF PAIN
- Based on source/ location/ referral & duration
ACUTE PAIN / TRAUMATIC PAIN
CHRONIC PAIN
VISCERAL OR SPLANCIC PAIN SOMATIC PAIN
SUPERFICIAL OR CUTANEOUS PAIN
DEEP SOMATIC PAIN

11. CHRONIC PAIN
MALIGNANT PAIN
or CANCER PAIN
NON MALIGNANT or
BENIGN PAIN
MUSCULOSKELETAL PAIN NEUROPATHIC
PAIN

12. ACUTE PAIN
 Acute has a sudden onset, usually subsides quickly and is
characterized by sharp, localized sensations with an
identifiable cause.
 Felt with in 0.1 second after pain stimulus is applied
 Sharp pain, pricking pain, electric pain

13.  Acute pain is usually characterized by increased
autonomic nervous system activity resulting in
 Psychological symptoms such as anxiety
 Tachypnoea
 Tachycardia with hypertension
 Pallor
 Diaphoresis
 Pupil dilation

14. VISCERAL PAIN
 Type of nociceptive pain that comes
from the internal organs
 Unlike somatic pain it is harder to
pinpoint
 Caused by the activation of pain
receptors in the chest, abdomen, or
pelvic areas
 In cancer patients pain is caused by
tumour infiltration, constipation,
radiation & chemotherapy

15. SOMATIC PAIN
 Nociceptors are involved
 Often well localized
 Usuallly described as
throbbing or aching
 Can be superficial (skin,
muscle) or deep
(joints,tendons, bones).

16. SUPERFICIAL PAIN
 It is also known as
cutaneous pain
 It arises from superficial
structures such as skin &
subcutaneous tissues
 It is a sharp, bright pain
with a burning quality and
may be abrupt or slow in
onset
DEEP SOMATIC
PAIN
 It originates in deep body
structures such as
periosteum, muscles,
tendons, joints &
blood vessels
 Radiation of pain from
original site of injury occur

17. CHRONIC PAIN
 Chronic pain is arbitrarily defined as pain lasting longer than 3
to 6 months
 It is persistent or episodic pain of duration or intensity that
adversely affects the function and well being of the patient
 It may be nociceptive, inflammatory, neuropathic or functional
in origin
It varies from unrelenting extremely severe pain to pain of
escalating or non – escalating nature.

19. NEUROPTHIC PAIN
 Neuropathic pain is a result of an injury or malfunction
of the nervous system. It is described as
 Aching
 Throbbing
 Burning
 Shooting
 Stinging
 Tenderness/ sensitivity of skin

21. •Herpes zoster is infection that results when varicella-zoster
virus reactivates from its latent state in a posterior dorsal root
ganglion.
•Symptoms usually begin with pain along the affected
dermatome, followed in 2 to 3 days by a vesicular eruption that
is usually diagnostic.
•Treatment is antiviral drugs given within 72 h after skin lesions
appear.
Herpes zoster

22. Trigeminal Neuralgia (Tic Douloureux)
•chronic pain condition characterized by recurring episodes of
extreme, sporadic, sudden burning or electric shock-like face pain.
•pain typically involves the lower face and jaw, although
sometimes it affects the area around the nose and above the eye.
•In almost all cases, the pain is felt on one side of the face.
Although the pain seldom lasts more than a few seconds or a
minute or two per episode
•It is also called tic douloureux.

23. Symptoms
The pain has been described as:
•Sharp knife slicing
•sharp stabbing
•blowtorch burning
•hot ice pick stabbing
•razor scraping
•knife hammering
•throbbing, piercing, stabbing

24. Treatment-modern treatment has allowed surgeons to intervene,
and in many cases reduce or remove the pain.

25. MUSCULOSKELETAL PAIN
This a type of chronic non cancer pain occurring due to
musculoskeletal disorders such as
 Rheumatoid arthritis
Osteoarthritis
 Fibromyalgia
 Peripheral neuropathies

26. NEUROPATHIC PAIN MUSCULOSKELETAL PAIN

27. BASED ON TRANSMISSION
FAST PAIN
Felt about 0.1 sec after a pain stimulus is applied
 It is described as sharp pain,pricking pain, acute & electric pain
 Fast sharp pain is not felt in most deeper tissues of the body
SLOW PAIN
Usually begins after 1 sec or more and may range from seconds
to minutes
 Described as slow, burning, aching, throbbing, nauseous pain
and chronic pain
 Associated with tissue destruction

28. REFERRED PAIN
 Referred pain is the pain that is perceived at a site adjacent to
or away from the site of origin. Deep pain and some visceral
pain are referred to other areas. But, superficial pain is not
referred.
 „EXAMPLES OF REFERRED PAIN
 1. Cardiac pain is felt at inner part of left arm and left
 shoulder
 3. Pain from testis is felt in abdomen
 4. Pain in diaphragm is referred to shoulder
 5. Pain in gallbladder is referred to epigastric region.

30. SITES OF REFERRED PAIN

31. MECHANISM OF PAIN:-
DERMATOME RULE:
 According to dermatome rule, pain is referred to a
structure, which is developed from the same dermatome
from which the pain producing structure is developed. A
dermatome includes all the structures or parts other body,
which are innervated by afferent nerve fibers of one dorsal
root.
 For example, the heart and inner aspect of left arm originate
from the same dermatome. So, the pain in heart is referred
to left arm.

33. RECEPTORS

34. SENSORY RECEPTORS-according to stimulus source
Exteroceptors Proprioceptors Interoceptors
According to modality
Nociceptors Thermoreceptors Mechanoreceptors

35. PAIN RECEPTORS
 NOCICEPTORS or PAIN RECEPTORS
are sensory receptors that are activated by
noxious insults to peripheral tissues
 The receptive endings of the peripheral
pain fibres are free nerve endings
 These receptive endings are widely
distributed in the
 Skin
 Dental pulp
 Periosteum
 Meninges

36.  1) Mechanosensitive nociceptors (of Aδ fibers), which are
sensitive to intense mechanical stimulation (such as pinching
with pliers) or injury to tissues.
 2) Temperature-sensitive (thermosensitive) nociceptors (of Aδ
fibers), which are sensitive to intense heat and cold.
 3) Polymodal nociceptors (of C fibers), which are sensitive to
noxious stimuli that are mechanical, thermal, or chemical in
nature. Although most nociceptors are sensitive to one
particular type of painful stimulus, some may respond to two or
more types.

37.  Nociception is the reception of noxious sensory
information elicited by tissue injury, which is transmitted to
the CNS by nociceptors.
 Pain is the perception of discomfort or an agonizing
sensation of variable magnitude, evoked by the stimulation
of sensory nerve endings.

39. SENSORY NEURONS
First Order Second Order Third Order
39

40. FIRST ORDER NEURON
• These are the cells in the posterior nerve root ganglia, receive
impulses from pain receptors through dendrites
 These impulses are transmitted through the axons to spinal
cord
 Impulses are transmitted by Aδ fibre or C fibres

43. SECOND ORDER NEURONS
• The neurons of marginal nucleus & substantia gelatinosa
form the II order neurons
• Fibres from these neurons ascend in the form of the lateral
spinothalamic tract
• Fibres of fast pain arise from neurons of the marginal
nucleus
• The fibres of slow pain arise from neurons of substantia
gelatinosa

44. THIRD ORDER NEURONS
• The neurons of pain pathway are the neurons in Thalamic
nucleus, reticular formation, tectum, gray matter around the
aqueduct of sylvius
• Axons from these neurons reach the sensory area of cerebral
cortex or hypothalamus

45. PAIN PATHWAYS
 The ascending pathways that mediate pain consist of three
different tracts:
 the neospinothalamic tract,
 the paleospinothalamic tract and
 the archispinothalamic tract.
The first-order neurons are located in the dorsal root
ganglion (DRG) for all three pathways. Each pain tract
originates in different spinal cord regions and ascends to
terminate in different areas in the CNS.

46. NEOSPINOTHALAMIC TRACT

47.  Aδ fibers transmit mainly mechanical and thermal pain,
terminate in the dorsal horns, cross over to the opposite side
of the cord and continue upwards to the brain as anterolateral
columns.
 Most fibers terminate in the ventrobasal or posterior nuclei
of the thalamus; few fibers terminate in the reticular areas.
Signals are also sent to the somatosensory cortex.
 Glutamate is the neurotransmitter secreted in the spinal cord
at Aδ fibers

48. PALEOSPINOTHALAMIC TRACT

49.  The C fibers which carry slow pain terminate in the substantia
gelatinosa of dorsal horns in spinal cord. They also cross over to
the opposite side and continue as anterolateral ascending tracts.
 The paleospinothalamic tract terminates in brain stem in one of
the following areas:
 1. Reticular nuclei of medulla , pons and mesencephalon.
 2. Tectal area of mesencephalon deep.10-25% of the fibers pass
to the thalamus
 3. Periaqueductal gray region surrounding the aqueduct of
Sylvius.

50. ANALGESIC PATHWAY
Analgesic pathway that
interferes with pain
transmission is often
Considered as
descending pain
pathway, the ascending
pain pathway being the
afferent fibers that
transmit pain sensation
to the brain

51. NEURAL PAIN PATHWAYS
51

52. -Pain sensation involves a series of complex interactions
between peripheral nerves & CNS
-Pain sensation is modulated by excitatory and inhibitory
NTs released in response to stimuli
-Sensation of pain is composed of 4 basic processes
 Transduction
Transmission
 Modulation
 Perception

53. Transduction:
This is the conversion of one form of energy to another. It occurs
at a variety of stages along the nociceptive pathway from:
– Stimulus events to chemical tissue events.
– Chemical tissue and synaptic cleft events to
- Electrical events in neurones.
– Electrical events in neurones to chemical events at synapses.
Transmission:
Electrical events are transmitted along neuronal pathways,
while molecules in the synaptic cleft transmit information from
one cell surface to another.

54. Modulation:
• The adjustment of events, by up- or down regulation. This can
occur at all levels of the nociceptive pathway, from tissue, through
primary (1°) afferent neurone and dorsal horn, to higher brain
centres.
•Thus, the pain pathway as described by Descartes has had to be
adapted with time.
Perception:
3rd order neurons project the nociceptive signal to cerebral cortex
of brain. In the cortex the brain perceive the signal as a pain.

56. PAIN THEORIES
Pain theories are proposed to offer the possible physiologic
mechanisms involved in pain. They are as follows
 Specificity theory
 Pattern theory
Gate control theory

57. SPECIFICITY THEORY
• DESCARTES 1664, MULLER 1840
• Pain occurs due to stimulation of specific pain receptors
(nociceptors) with transmission by nerves directly to the brain
PATTERN THEORY
GOLDSCHEIDER – 1894-- stimulus intensity and central
summation are critical determinants of pain
•Particular patterns of nerve impulses that evoke pain are
produced by summation of sensory input within the dorsal horn
of spinal cord

58. GATE CONTROL MECHANISM
• Proposed by MELZACK & WALL IN 1965
• According to this theory, the pain stimuli transmitted by afferent
pain fibres are blocked by GATE MECHANISM located at the
posterior gray horn of the spinal cord
•If the gate is open pain is felt, and if the gate is closed pain
is suppressed

59. •This theory of pain takes into account the relative in put of
neural impulses along large and small fibers, the small nerve
fibers reach the dorsal horn of spinal cord and relay impulses to
further cells which transmit them to higher levels.
• The large nerve fibers have collateral branches, which carry
impulses to substantia gelatinosa where they stimulate secondary
neurons.

62. FACTORS AFFECTING PAIN
 1) Emotional Status
 2) Fatigue
 3) Age
 4) Race and Nationally characterstics
 5) Sex
 6) Fear and apprehension

63.  Odontogenic pain
 Odontogenic pain refers to pain initiating from the teeth or
their supporting structures, the mucosa, gingivae, maxilla,
mandible or periodontal membrane.
 ‘A toothache, or a violent passion, is not necessarily
diminished by our knowledge of its causes, its character, its
importance or insignificance.’TS Eliot
PAIN IN ORAOFACIAL
REGION

64.  Apical pain can be caused by infection
spreading through the apical foramen of the tooth
into the apical periodontal region causing
inflammation (apical periodontitis) and ultimately
a dental abscess if left untreated

65.  Pericoronitis
 Pain commonly arises from the supporting gingivae
and mucosa when infection arises from an erupting
tooth (teething or pericoronitis). This is the most
common cause for the removal of third molar teeth
(wisdom teeth). The pain may be constant or
intermittent, but is often evoked when biting down
with opposing maxillary teeth.

66. PAIN DIAGNOSIS
Diagnosing a pain complaint consists of these major
steps
• History
• Clinical examination
• Accurately identifying the location of the extractions
from which the pain emanates
• Establishing the correct pain category that is
represented in the condition under investigation

67. Assessment of pain
In the assessment of pain intensity, rating scale techniques
are often used. The most commonly used techniques are:
• Numerical Rating Scale
• Visual Analogue Scale
• McGill Pain Questionnaire
• Behavioral Rating Scale

68. Numerical Rating Scale (NRS):

69. Visual Analogue Scale

70. McGill Pain Questionnaire
 It is also known as McGill pain index, is a scale of rating
pain developed at McGill University by Melzack and
Torgerson in 1971.
 It is a self-report questionnaire that allows individuals to
give their doctor a good description of the quality and
intensity of pain that they are experiencing.
 It is a very widely used questionnaire.

71.  Behavioral rating scale: For patients unable to provide a
self-report of pain, a score from 0 to 10 is assigned based
on clinical observation

72. MANAGEMENT OF PAIN
GOALS OF THERAPY
To decrease the subjective intensity
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

73. NON – PHARMACOLOGICAL
MANAGEMENT
The non – pharmacological management involves the following
approaches
Physiotherapy
Psychological techniques
Stimulation therapies – Acupuncture & Transcutaneous
Electrical Nerve Stimulation (TENS)
Palliative care – involves the alleviation of symptoms
but does not cure the disease

74. SURGICAL PROCEDURE FOR THE RELIEF OF
PAIN
CORDOTOMY: In the thoracic
region , the spinal cord opposite
to the side of pain is partially
cut to interrupt the anterolateral
Pathway
THALAMOTOMY: Involves
cauterization of specific pain
areas in the intra thalamic nuclei
in the thalamus, which often
relieves suffering type of pain

75. SYMPATHECTOMY
Excision of the segment of the sympathetic nerve or one or more
sympathetic ganglia
RHIZOTOMY
Surgical removal of spinal nerve roots for the relief of pain or
spastic paralysis

76. FRONTAL LOBOTOMY
Surgical process involving division of one or more nerve tracts
in a lobe of the cerebrum usually frontal lobe
NEWER APPROACHES- TNS, ACUPUNCTURE

77. Transcutaneous Neural Stimulation (TNS)
•With TNS, cutaneous bipolar surface electrodes are placed in the
painful body regions and low voltage electric currents are passed.
•Best results have been obtained when intense stimulation is
maintained for at least an hour daily for more than 3 weeks.
•TNS portable units are in wider spread use in pain clinics
throughout the world and has been proved most effective against
neuropathic pain.

78. Acupuncture (ACUS = NEEDLE, PUNGERE = STING)
•Method of inhibiting pain impulses.
•Acupuncture theory is based on an invisible system of
communication between various organs of the body that is
distinct from circulatory, nervous and endocrine system.
•Needles are inserted through selected areas of skin and then
twirled.
•After 20-30 minutes, pain is deadened for 6-8 hours

79. PAIN INHIBITING MECHANISM
 it can be:
 ENDOGENOUS
 EXOGENOUS

80. Endogenous method of controlling pain includes
 Removing the cause- It is a desirable methods. It is
imperative that any removal leave no permanent
environmental changes in tissue, since this condition would
then be able to create the impulse, even though the original
causative factor had been eliminated.
 Blocking the pathway of pain impulses- This can be
done by injecting drug possessing local analgesic
property in proximity to the nerve involved.
 Thus preventing those particular fibers from
conducting any impulses centrally beyond that point.

81. 3) Raising the pain threshold :
 Raising pain threshold depends on the pharmacological
activity of drugs possessing analgesic properties.
 These drugs raise pain threshold and therefore alter pain
reaction, conceptually there are two components of pain
(a) Nociceptive
(b) Affective component.
 The path of nociceptive component is spinothalamic tract 
Thalamus. This component is purely physical component of
pain.

82. 4) Affective Component
 It is the psychological component associated with pain. The
path is that some fibers from STT to thalamus terminate in some
intermediate stations in the reticular formation of brain stem and
are called spinoreticular thalamic system.
 Non-narcotic analgesic like aspirin can inhibit the nociceptive
but not the affective component of pain whereas opioid
(Morphine) inhibit affective as well as nociceptive components
of the pain. They act centrally at cortical and sub cortical
centers, to change patient mind and his reaction towards pain

83. 5) Preventing pain reaction by cortical depression
 Eliminating pain by cortical depression is by the use of general
anesthesia.
6) Using Psychosomatic Method
 This method affects both pain perception and pain reaction. It
include audio analgesia

84. PHARMACOLOGICAL
MANAGEMENT

86. CONCLUSION
 Pain is bad but not feeling can be worse.
 Dental pain is multicausative in origin.
 The dentist should use multimodalities to treat the patient.
 Nothing is more satisfying to the clinician than the
successful elimination of pain.
 The most important part of managing pain is understanding
the problem and cause of pain
 It is only through proper diagnosis that appropriate therapy
can be selected.

87. REFERENCES
 Textbook of Medical Physiology 10th edition- Guyton and Hall
 Textbook of medical physiology 7th edition- Sembulingam
 Essentials of Medical Pharmacology 7th edition- KD Tripathi
 Kumar KH, Elavarasi P. Definition of pain and classification of
pain disorders. J Adv Clin Res Insights 2016;3:87-90.
 Tandon OP et al Neurophysiology of pain: insight to orofacial
pain. Indian J Physiol Pharmacol 2003; 47 (3) : 247–269
 Chapter 7: Pain Tracts and sources. Ann textbook for the
neuroscience
 Renton T. Dental (odontogenic) pain. v o l . 5 – n o . 1 – m a r c
h 2 0 1 1
 Gupta R, Mohan V, Mahay P, Yadav PK (2016) Orofacial Pain: A
Review. Dentistry 6: 367. doi:10.4172/2161-1122.1000367