Innervation of the face The nervvous system Nerve transmission Definition of Pain Pain Receptors Pain nerve fibers Reaction to pain Pain Pathway Control of Pain Mode of action of local anesthesia

1. Introduction to Oral & Maxillofacial Surgery - Pain
Introduction to Oral Surgery
and Pain Pathway
Dr. Hesham El-Hawary
Lecturer OMFS
Faculty of Oral & Dental Medicine
Cairo University
www.elhawarydentalclinic.com
ELHAWARY

2. Introduction to Oral & Maxillofacial Surgery - Pain
Oral And Maxillofacial Surgery
It is that branch of dental practice that deals with:
– Diagnosis
– Adjunctive and Surgical treatment of diseases
– Injuries and Defects
of human jaws and associated structures
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3. Introduction to Oral & Maxillofacial Surgery - Pain
Oral Surgery
• Infection control & Aseptic surgical techniques
• Anesthesia & its complications
• Teeth Extraction
– Simple forceps extraction
– Surgical removal of teeth and roots
– Impacted teeth
– Complications
• Oral infection
• Oral tumors
• Cysts of the oral cavity
• Management of patients with systemic diseases
• Oro-Facial pain
• Maxillary sinus affections
• Preprothetic surgery
• Implantology
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4. Introduction to Oral & Maxillofacial Surgery - Pain
Maxillofacial Surgery
• Trauma
• Temporomandibular joint disorders
• Distraction osteogenesis
• Management of cleft patients
• Orthognathic surgery
• Reconstruction
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5. Introduction to Oral & Maxillofacial Surgery - Pain
Innervation of the face
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6. Introduction to Oral & Maxillofacial Surgery - Pain
Nervous system
• The nervous system is
– Network of specialized cells
– Communicate information about human surroundings and
himself
• It processes this information and causes reactions in
other parts of the body
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7. Introduction to Oral & Maxillofacial Surgery - Pain
Nervous system Cont.
• It is composed of neurons (nerve cells)
• The nervous system is divided into two categories:
– Peripheral nervous system
– Central nervous system
• Neurons generate and conduct impulses between
and within the two systems
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8. Introduction to Oral & Maxillofacial Surgery - Pain
Nervous system Cont.
• The peripheral nervous system is composed of
– Grouped sensory neurons
– The neurons that connect them to the spinal cord and brain which
make up the central nervous system
• In response to stimuli:
– Sensory neurons generate and propagate signals
– To the central nervous system which then process and conduct back
signals to the muscles and glands
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9. Introduction to Oral & Maxillofacial Surgery - Pain
Nervous system Cont.
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10. Introduction to Oral & Maxillofacial Surgery - Pain
Neuron
• The structural unit of the N.S.
• Two types
– Sensory neuron (afferent)
– Motor neuron (efferent)
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11. Introduction to Oral & Maxillofacial Surgery - Pain
Neuron Cont.
Sensory neurons (efferent)
• Nerve cells that conduct
impulses (as pain sensation)
• From all parts of the body
• To the CNS centrally
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12. Introduction to Oral & Maxillofacial Surgery - Pain
Neuron Cont.
Sensory neurons
1. Dendritic zone
(free nerve endings):
a. Respond to stimuli
b. Producing an impulse that is
transmitted centrally along the
axon
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13. Introduction to Oral & Maxillofacial Surgery - Pain
Neuron Cont.
Sensory neurons
2. Axon
a. Thin cable like structure
b. Has terminal ending that form
synapses with nuclei in the
CNS
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14. Introduction to Oral & Maxillofacial Surgery - Pain
Neuron Cont.
Sensory neurons
3. Cell body
a. Located at a distance from the
axon or the main pathway of
impulse transmission
b. Not involved in the process of
impulse transmission
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15. Introduction to Oral & Maxillofacial Surgery - Pain
Neuron Cont.
Sensory neurons
Cell body cont.
c. The primary function of the cell
body is to provide the vital
metabolic support to the neuron
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16. Introduction to Oral & Maxillofacial Surgery - Pain
Neuron Cont.
Motor neuron
(efferent)
Conduct impulses from the
CNS peripherally
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17. Introduction to Oral & Maxillofacial Surgery - Pain
Nerve Transmission
• In response to stimuli, sensory neurons generate and
propagate signals (nerve impulses) to the central
nervous system which then process and conduct back
signals to the muscles and glands
• The process by which nerve impulses are conducted
along a nerve is called nerve conduction or transmission
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18. Introduction to Oral & Maxillofacial Surgery - Pain
Nerve Transmission Cont.
• The mechanism of nerve conduction is described in
the following steps:
1. Resting state( Resting potential)
2. Excitation state( Depolarization)
3. Repolarization
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19. Introduction to Oral & Maxillofacial Surgery - Pain
Nerve Transmission Cont.
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20. Introduction to Oral & Maxillofacial Surgery - Pain
1. Resting state( Resting potential)
Resting potential is a
negative electrical
potential exists across
the nerve membrane
i.e., the interior of the
nerve is negative in
relation to the exterior,
(-70 to - 90 mv).
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21. Introduction to Oral & Maxillofacial Surgery - Pain
Resting state( Resting potential) Cont.
The nerve membrane in the
resting state is:
 Permeable to Na+ , which
remains outside the nerve
membrane and prevents influx of
it
 Fairly permeable to K+ which
remains inside the nerve
membrane
 Fairly permeable to CL- which
remains outside the nerve
membrane
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22. Introduction to Oral & Maxillofacial Surgery - Pain
2. Excitation state( Depolarization)
Excitation of a nerve by a
stimulus, which may be
chemical, mechanical or
thermal, leads to increased
permeability of the nerve
membrane to Na+ (Na+
influx)
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23. Introduction to Oral & Maxillofacial Surgery - Pain
Excitation state( Depolarization) Cont.
The rapid influx of Na+ to the interior
of the nerve causes depolarization
of the membrane from its resting state
to the firing threshold
(threshold potential)
i.e. Reversal of the electrical potential
across the nerve membrane, which
means negatively exterior
surface of the membrane in
relation to the interior (+40 mv)
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24. Introduction to Oral & Maxillofacial Surgery - Pain
3. Repolarization :
At the end of the depolarization,
the permeability of the membrane to
Na+ decreases
This is followed by sodium pump
which actively transport Na+ outside
the cell while K+ move passively
in to restoring the resting
membrane potential
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25. Introduction to Oral & Maxillofacial Surgery - Pain
Nerve Transmission Cont.
The rapid sequence of depolarization and
repolarization of the nerve is called the action
potential allowing the propagation of the impulse
from one end of the axon to the other
While the impulse remains constant without losing
strength as it passes along the nerve, and this is
called the all or non- law of nerve conduction
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26. Introduction to Oral & Maxillofacial Surgery - Pain
Trigeminal nerve
• Largest of the cranial nerves
• Its name derives from the fact that
it has three major branches:
– Ophthalmic nerve (V1)
– Maxillary nerve (V2)
– Mandibular nerve (V3)
• The ophthalmic and maxillary
nerves are purely sensory
• The mandibular nerve has both
sensory and motor functions
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27. Introduction to Oral & Maxillofacial Surgery - Pain
Pain
pain is unpleasant sensation
created by noxious stimuli,
usually associated with reflex
withdrawal, which is protective
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28. Introduction to Oral & Maxillofacial Surgery - Pain
Pain receptors
• Pain is received and interpreted in CNS along specific
pathway called pain pathway
• Pain receptors:
– These are unmyelinated nerve endings
– Respond to different stimuli
– Provide pain sensation
• Proprioceptive receptors:
– These are nerve endings
– Respond only to pressure
• Sensation from teeth:
– Pulp: pain sensation
– Investing structures: proprioception
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29. Introduction to Oral & Maxillofacial Surgery - Pain
Peripheral Nerve Fibers
A- A- A-gamma A- B C
alpha beta delta
myelin +++ ++ ++ ++ + -
Diameter( 12-20 5-12 5-12 1-4 1-3 0.5-1
µ)
Velocity 70-120 30-70 30-70 12-30 14 1.2
m/s
function motor Touch, Touch , Pain, temp., Symp Pain,
pressure motor pressure temp.,
pressure
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30. Introduction to Oral & Maxillofacial Surgery - Pain
Pain Nerve Fibers
• These are very thin unmyelinated nerves
• A-delta and C fibers, within the nerve
• More easily blocked by the L.A. solutions
• The thicker and myelinated fibers, such as A-
alpha, beta, gamma and B fibers, transmit other
sensation such as touch and pressure with the
motor fibers
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31. Introduction to Oral & Maxillofacial Surgery - Pain
Reaction to pain
(Pain Threshold)
• Pain threshold is the minimum stimulus which elicits
pain
• Differ between individuals
• Vary in the same individual on different occasions
• Affected by fear, apprehension, age, sex, physical
fitness, race and fatigue
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32. Introduction to Oral & Maxillofacial Surgery - Pain
Pain Pathway
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33. Introduction to Oral & Maxillofacial Surgery - Pain
First Order Neuron
• Stimuli from the oral
cavity
• received by nerve
fibers
• Conducted as impulses
along the three
branches of the 5th
cranial nerve
• Into the gasserian
(semilunar) ganglion
(GG)
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34. Introduction to Oral & Maxillofacial Surgery - Pain
First Order Neuron Cont.
• The nerve cells in GG
are unipolar nerve cells
• Each has an axon
which bifurcate into a Y
or T shaped division
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35. Introduction to Oral & Maxillofacial Surgery - Pain
First Order Neuron Cont.
• The central branches of the
T shaped fibers make up
the sensory root of the
trigeminal nerve
• the peripheral branches of
the T shaped fibers form the
three branches of the 5th
cranial nerve
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36. Introduction to Oral & Maxillofacial Surgery - Pain
First Order Neuron Cont.
• Then from the GG the
impulses are passed by
the central branches of
the unipolar cells into
the pons
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37. Introduction to Oral & Maxillofacial Surgery - Pain
First Order Neuron Cont.
• Some branches end in a
collection of nerve cells in
the pons called the P.S.N.,
responsible for touch
• other branches descends
through the medulla where it
terminates in the A.S.N.
responsible for pain & temp
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38. Introduction to Oral & Maxillofacial Surgery - Pain
Second Order Neuron Cont.
• Originates From A.S.N.
and P.S.N another
nerve fibers
• Crosses the midline
and ascends in a
spinothalamic tract of
the 5th cranial nerve
• Terminates in P.V.N. in
the thalamus
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39. Introduction to Oral & Maxillofacial Surgery - Pain
Third Order Neuron Cont.
• Originates from P.V.N.
in the thalamus
• Carries the pain
impulse to the post-
central convolution of
the cortex where all
sensations are felt
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40. Introduction to Oral & Maxillofacial Surgery - Pain
Control of pain
• Removing the cause
• Raising the pain threshold
• Blocking the pathway of the painful impulses
• Preventing the pain reaction by cortical depression
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41. Introduction to Oral & Maxillofacial Surgery - Pain
Control of pain
• Removing the cause
• Raising the pain threshold
• Blocking the pathway of the painful impulses
• Preventing the pain reaction by cortical depression
ELHAWARY

42. Introduction to Oral & Maxillofacial Surgery - Pain
Anesthesia
• Anesthesia: the condition of having sensation
blocked (including the feeling of pain)
• Analgesia: blocking the conscious sensation of pain
• Hypnosis: produces unconsciousness without
analgesia
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43. Introduction to Oral & Maxillofacial Surgery - Pain
Types of anesthesia
• Local Anesthesia:
Any technique that render part of the body
insensitive to pain without affecting consciousness
• General anesthesia:
Drug-induced loss of consciousness during which
patients are not arousable, even by painful
stimulation
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44. Introduction to Oral & Maxillofacial Surgery - Pain
Mode of Action of Local Anesthesia
• Displacing calcium ions from receptors site
• The mechanical or reversible coagulation theory
• The physiological theory – interference with the
nerve tissue metabolism
• Acetyl Choline and enzyme system theory
• Electrical potential theory
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45. Introduction to Oral & Maxillofacial Surgery - Pain
Thank You
www.elhawarydentalclinic.com
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