Part [1] local anesthesia for dental students

1. 1
Introduction.
Anatomy
Neurohistology.
Pain control.
Chapter 1
Basic local anesthesia.
Dr/Atef fouda
Prof. Oral & Maxillofacial Surgery
Cairo University
Egypt

2. Atef A. Fouda.
Prof of Oral & Maxillofacial Surgery
Cairo University

3. 3
Introduction.

4. ‫سنه‬ ‫أغسطس‬ ‫من‬ ‫التاسع‬ ‫في‬ ‫ولد‬1819‫في‬
‫بأمريكا‬ ‫شارلتون‬ ‫مدينة‬.‫ويعتب‬ ‫أسنان‬ ‫طبيب‬‫ر‬
‫استخدم‬ ‫من‬ ‫أول‬‫مخدرة‬ ‫كماده‬ ‫اإليثير‬
‫عام‬ ‫وذلك‬1846‫الجراحية‬ ‫العمليات‬ ‫في‬.
William Thomas Green Morton
4

5. Local
anesthesia
synthesized
from cocaine.
In 1930
In 1970
The use of local anesthesia by
dentists has been a routine part of
practice.
5

6. Analgesia means block of pain while anesthesia
means block of all sensations which is actually
resulted.
Terminology
6

7. 7
Neurohistology.

8. Cell body
Axon
Dendrites
8
Neuron
Neuron is a cell with its cell
membrane elongated [Axon]and
ended with tree like branches called
dendrites, its terminal part have
receptors.
receptors

9. myelinated Nerve axon
Un
Myelin sheath
Node of ranvier
Cell body
Axon
Dendrites
9
Neuron
Or covered with
interrupted myelin
sheath; myelinated
nerve.
The axon of the neuron
may be uncovered
which called
unmyelinated nerve
axon.
myelinated Nerve axon

10. Ganglion
Neural
bundle
10
Great number of axons travel together
which called neural bundle.
Each axon ends with neural cell.
Aggregation of cells called ganglion.

11. All neurons
aggregated in bundles
to form part of the
nerve trunk.
11

12. The main nerve trunk is composed of :
neural bundles,
blood vessels,
And
Connective Tissue
sheath.
[nerve sheath]
Neuron
Neural
bundle
Blood
vessels
Nerve
sheath
12

13. 1-Unipolar
3-Bipolar
4-Multi polar
2-PseudoUnipolar
13
1234

14. 14
Trigeminal nerve
is a mixed nerve
that contain
sensory, Motor,
pain and
autonomic fibers.

15. Trigeminal nerve
Autonomic neurons :
Myelinated.
Multipolar type.
Trigeminal nerve
Pain neurons :
Unmyelinated.
Unipolar type.
Trigeminal nerve
Motor neurons :
Myelinated.
Multipolar type.
Trigeminal nerve sensory
neurons :
Myelinated.
Pseudounipolar type.
15

16. Neuron function
A-delta fibers.
Myelinated ,Thick
Pseudounipolar
Temperature,
pressure,
proprioception
C -fibers
Unmyelinated, Thin.
Unipolar
pain
B- fibers
Unmyelinated
Unipolar
Sympathetic
A-alpha fibers
Myelinated
Multipolar
Motor
16

17. 17

18. 18
Pain pathway

19. 19
Trigeminal ganglion
Sensory stimuli travel
from receptors to the
pons without rely.

20. 20
After rely in the
pons crosses the
midline and travels
to the contralateral
side in the
thalamus.[Trigemin
al luminescus].
The fibers then
travel to end in the
sensory cortex of
the brain.

21. Specificity theory:
Stat that pain is a specific sensation, with its own sensory apparatus
independent of touch and other senses .
The pain apparatus formed from “C “nerve fibers (thin unmyelinated
fibers).
Pain Pathway
21
Moritz Schiff, in 1876, was first to definitively
formulate the specificity theory of pain when, he
demonstrated that touch and pain sensations traveled
to the brain along separate pathways.
Moritz Schiff

22. First order neuron:
22
Injury site
[pulp of a tooth]
spinal cord
“Substantia
gelatinosa”
Pain Pathway

23. Second order neuron:
Spinal cord Thalamus.
23
Pain Pathway

24. Third order neuron:
Thalamus
Somatosensory cortex.
Spino
thalamic
tract
24
Pain Pathway

25. First order neuron:
“Substantia gelatinosa”
Second order neuron:
Spinal cord Thalamus.
Third order neuron:
Thalamus Somatosensory cortex.
Spino
thalamic
tract
25
Injury site
[pulp of a tooth]
spinal cord
Pain Pathway

26. 26

27. Pain modulation
Gate control theory:
In the thalamus pain modulated
according to activity of sensory
fibers(A delta myelinated fibers) and
activity of pain fibers(C nerve fibers).
Pain is divided into:
pain perception (feeling of pain) and
pain reaction (the response to pain).
Thalamus
27

28. Pain reaction:
Pain reaction depends primarily on the
integration between thalamus and
cerebral cortex. Depressed thalamic
action results in greater tolerance to
pain and subsequently less pain is felt.
28

29. Pain threshold:
Pain threshold is the point along a curve of increasing perception of
a stimulus at which pain begins to be felt. It is an entirely subjective
phenomenon.
The pain reaction threshold is inversely proportional to pain
reaction. A patient who is hypo reactive is considered to have a high
pain threshold, whereas a patient with a low pain reaction threshold
is hyper reactive.
29

30. Control of pain:
•Removing the cause.(eliminate source of pain).
•Blocking the pathway of pain.(Local anesthesia).
•Raising the pain threshold.(use of analgesics).
•Cortical depression to prevent pain reaction
(general anesthesia).
30

31. 31
Neurophysiology.
Pharmacology of L.A.
Properties of local anesthetic agents.
Chapter 2

32. 32
Neurophysiology.

33. Human cell
Cell membrane consists of phospholipids.
The lipid bilayer permits passage of fat soluble
substances.
Other substances enter the cell through protein gates
which propagates along the cell membrane.
33

34. Sodium ions in high concentration outside
the cell.
When gates open a flow of sodium ions
go through gates until equilibrium
between concentration outside and inside
the cell.

35. In resting state of cell
membrane the sodium
molecules concentrated
outside of the cell
membrane, while
potassium concentrates
inside the cell .
With resultant
Relative negative charges
created inside the cell
membrane while positive
charges detected outside.
-70mv
Resting state

36. As a result of external stimulant (pain)the membrane
showed depolarization “the charges reversed on the
membrane sides”
Cell membrane in resting state with positive
charge outside and negative charges inside.
Reversal of polarity

37. Propagation of action potential

38. Na
Na
Na
Na Na Na
Na Na
Na
Na
Na
Na
Na
Na
Na
Na
Na
Na NaNa
Na
K
INSIDE
OUTSIDE
40mv
Depolarization
Stimulus
Gate open

39. Na
Na
Na
Na
Na
Na
Na Na
Na
Aden
osine
Ph
Ph
Ph
Outside
Inside
Repolarization

40. 40
To stop the transmission of pain impulses , the
action potential should be prevented from
propagation.
To prevent the action potential, the influx of
sodium ion through the gates should be
prohibited.
The membrane gates closed by the
action of local anesthetic agents.
Pain control

41. Membrane expansion theory:
This theory postulates that an increased lateral
pressure within the nerve membrane is
produced by local anesthetic agents. The
increased pressure results in constriction of the
gates preventing sodium influx from outside to
inside the neural axon.
Theories of local anesthesia:
Partial expansion of the cell membrane due to
the effect of local anesthetic agent

42. 42
Sodium channel blockers:
The anesthetic agent attached to
special protein found in the gates of
cell membrane preventing sodium
transfer.
Penetration of local anethetic agent into the cell
membrane gate.
Na
Na Na
Na