3. DEFINITION
Local Anaesthesia is defined as a loss of sensation
in a circumscribed area of the body caused by a
depression of excitation in nerve endings or an
inhibition of the conduction process in the peripheral
nerves.(Stanley F. Malamed, Handbook of Local
Anaesthesia 5TH ED)
Local Anaesthetics are drugs which upon topical
application or local injection cause reversible loss of
sensory perception especially of pain in a restricted
area of the body. Not only sensory, but also motor
impulses are interrupted when applied to a mixed
nerve, resulting in muscular paralysis and loss of
autonomic control as well.
4. REQUIREMENTS
Potent to give complete anaesthesia.
Relatively free from producing allergic reactions
Stable in solution form and should undergo
biotransformation in the body readily.
Sterile or capable of being sterilized by heat without
deterioration
Low degree of local toxicity
Shouldn't irritate the tissues.
Shouldn't alter nerve structure permanently
Low systemic toxicity
Versatile.
Rapid onset and sufficient duration of action and
completely reversible.
11. MECHANISM OF ACTION
Altering the basic resting potential of
the nerve membrane
Altering the threshold potential(firing
level)
Decreasing the rate of depolarisation
Prolonging the rate of repolarisation
13. THEORIES OF MECHANISM OF ACTION
Acetylcholine Theory
Calcium Displacement Theory
Surface Charge(repulsion) Theory
Membrane Expansion Theory
Specific Receptor Theory
Now Discredited
16. LA AGENTS
Lidocaine
Amide type.
Onset-Rapid(2-3 min)
Effective topically(5% concentration)
Effective dental concentration-2%
Metabolized in the liver to Monoethylglyceine and Xylidide
Excretion via kidneys.
Allergy is usually non-existant.
Maximum recommended dose-3.2 mg/lb (Lidocaine with epinephrine)
- 4.4mg/lb (Lidocaine w/o epinephrine)
Maximum dose should not exceed 300mg
-
17. Benzocaine
Ester type
Onset-Prolonged; Duration of action-Prolonged
Topical application only
Allergic reactions are rare.
Available as: Aerosols,Gels,Gel patches, Ointments,
Solutions.
Maximum dose- topical 10% mucous membrane gel;
Apply topically to affected area(s) up to 4 times daily
with a cotton swab .
18. THE SYRINGE
Types:
1. Non disposable syringes
a. Breech-loading,metallic,cartridge-type,aspirating
b. Breech-loading,plastic,cartridge-type,aspirating
c. Breech-loading,metallic,cartridge-type,self-aspirating
d. Pressure syringe for PDL injection
e. Jet Injector(“needleless syringe”)
2. Disposable syringes
3. “Safety” syringes
4. Computer controlled local anaesthetic delivery
system
19. DISPOSABLE SYRINGE
These syringes contain a Luer-Lok screw-on needle
attachment but no aspirating tip.
Aspiration can be done by pulling back the plunger
of the syringe before or during injection.
The needle, attached to the syringe must be
inserted into a vial of LA drug and an appropriate
volume of solution is withdrawn
Care should be taken to avoid contaminating the
vial.
2-3 ml syringes with 23-or 25-gauge needles are
recommended.
20. Single use,disposable
Sterile until opened
Lightweight
Doesn’t except prefilled
dental cartridges
Aspiration is difficult
ADVANTAGES DISADVANTAGES
21. COMPUTER CONTROLLED LOCAL
ANAESTHETIC DELIVERY SYSTEM(CCLAD)
Introduced in 1997
The Wand(The Wand/CompuDent)
Improved ergonomics and precision of the dental syringe
Enables a dentist to accurately manipulate needle placement with
fingertip accuracy and deliver LA with a foot-controlled device.
The handpiece is held with a pen like grasp
Flow rate is preprogrammed
22.
23. Precise control of flow
rate and pressure
produces a more
comfortable injection
even in tissues with low
elasticity
Increased tactile
sensation and
ergonomics
Non threatening
Autonomic aspiration
Rotational insertion
technique which
minimizes needle
deflection
Requires additional
armamentarium
Cost
ADVANTAGES DISADVANTAGES
24. THE NEEDLE
Types: Stainless steel
Platinum
Iridium-Platinum Alloy
Ruthenium-Platinum Alloy
Parts:
2 factors considered while selecting the needle-LENGTH and
GAUGE
25. GAUGE OF A NEEDLE
Diameter of the lumen of the needle.
Smaller the number = Greater the diameter of the lumen
Most commonly used-27-gauge long and 30-gauge short
25-gauge needle is most preferred for injections presenting a
higher risk of positive aspiration.
Advantages of a Large-Gauge Needles Over the Small-Gauge Needles
1)Less deflection, as needle advances through the tissues
2)Greater accuracy in injection
3)Less chance of needle breakage
4)Easier aspiration
5)No perceptual differences in patient comfort
28. TYPES OF INJECTION PROCEDURES
1.Nerve block-depositing the LA solution within
close proximity to a main nerve trunk
2).Field block-depositing a in proximity to the larger
nerve branches.
3.Local infiltration-small terminal nerve endings are
anaesthetised.
32. POSTERIOR SUPERIOR ALVEOLAR NERVE BLOCK
(PSA)
Nerves anaesthetized: Posterior superior alveolar nerve and its
branches
Areas anaesthetized: Maxillary 3rd,2nd and 1st molars except the
mesiobuccal root of the maxillary 1st molar.
Landmarks: Mucobuccal fold, Maxillary tuberosity,Zygomatic
process of maxilla
33. For Left PSA nerve block, a right handed administrator should face the patient
from the 10 o’clock;
For Right PSA nerve block a right handed administrator should face the patient
directly from the 8 o’clock position
Technique:
Prepare the tissues at the height of the mucobuccal fold
Orient the bevel towards the bone
Partially open the patient’s mouth; pulling the mandible to the side of
injection,retract the cheek with your fingers and pull the tissue taut.
Insert the needle into the height of the mucobuccal fold over the 2nd molar
Advance the needle in an upward, inward and backward direction(At once)
Slowly advance the needle through the soft tissue
Ensure the needle penetrates 10-14 mm depth.
Aspirate in 2 planes
If both aspirations are negative the deposit 0.9-1.8 ml solution over 30-60
seconds
Withdraw the syringe slowly
Wait for 3-5 minutes before commencing the dental procedure
34.
35. ANTERIOR SUPERIOR ALVEOLAR OR INFRAORBITAL
NERVE BLOCK
(ASA)
Nerves anaesthetized- Anterior superior alveolar
-Middle superior alveolar
-Infraorbital nerve
Areas anaesthetized-
Landmarks: Mucobuccal fold
Infraorbital notch
Infraorbital foramen
36. Assume 10 o’clock position either directly facing the patient or in the same
direction as the patient
Technique-
Position the patient supine or semisupine with the neck extended slightly
37. Prepare the tissue at the injection site
Feel the intraorbital notch,Move the finger inferiorly until a depression is felt.
Here the infraorbital foramen is located
Place the thumb over the infraorbital formen
Retract the lip, pull the tissues in the mucobuccal fold taut
Insert the needle into the height of the mucobuccal fold with the bevel facing
the bone
Orient the needle towards the Infraorbital foramen
The needle should be held parallel with the long axis of the tooth as it is
advanced to avoid premature contact with the bone.
Advance the needle slowly until the bone is contacted
Check the depth of needle penetration,lateral deviation of the needle from the
infraorbital foramen and the orientation of the bevel
Aspirate, then slowly deposit 0.9ml to 1.2ml(30-40 seconds).maintain firm
finger pressure at the injection site
Withdraw the syringe slowly
WAit for 3-5 minutes after the injection before comencing the dental procedure
38. MIDDLE SUPERIOR ALVEOLAR NERVE
BLOCK(MSA)
Nerves anaesthetized: Middle superior alveolar and
terminal branches
Areas anaesthetized:
Landmarks: Mucobuccal fold over the
2nd premolar
39. For Right MSA nerve block, a right handed administrator should face the
patient from the 10 o’clock;
For Left MSA nerve block a right handed administrator should face the patient
directly from the 8 or 9 o’clock position
Prepare the tissue at the injection site
Stretch the patient’s upper lip to make the tissues taut and to gain visibility
Insert the needle into the height of the mucobuccal fold above the 2nd premolar
with the bevel facing the bone
Penetrate the mucous membrane and slowly advance the needle until its tip is
located well above the apex of the 2nd premolar
Aspirate
Slowly deposit 0.9ml-1.2ml in approx. 30-40 seconds
Withdraw the syringe slowly
Wait for 3-5 minutes before commencing the dental treatment
Techniques:
40.
41. GREATER PALATINE NERVE BLOCK
Nerves anaesthetized: Greater Palatine
Areas anaesthetized:
Landmarks: Greater palatine foramen
Junction of maxillary alveolar
process and palatine bone
46. INFERIOR ALVEOLAR NERVE BLOCK/
MANDIBULAR NERVE BLOCK
Nerves anaesthetized: Inferior alveolar nerve
Incisive nerve
Mental nerve
Lingual nerve
Areas anaesthetized: mandibular teeth till the
midline
body of mandible
Inferior portion of
Anterior 2/3rd of the tongue
Floor of the mouth
Lingual soft tissues and
periosteum
47. 3 parameters considered during IANB
1. Height of injection
2. Anteroposterior site of injection
3. Penetration depth
LANDMARKS
Anatomical
Landmarks of Inferior
alveolar nerve block:
Mucobuccal fold.
Anterior border of
Mandibular ramus.
External oblique ridge.
Internal oblique ridge.
Retromolar triangle.
Pterygomandibular
ligament.
Buccal sucking pad.
Pterygomandibular space.
48.
49.
50. BUCCINATOR NERVE BLOCK/LONG
BUCCAL NERVE BLOCK
Nerves anaesthetized: Buccal nerve
Areas anaesthetized:Soft tissues and periosteum,
buccal to mandibular teeth
Landmarks:Mandibular molars,Mucobuccal fold
51.
52. MENTAL NERVE BLOCK
Nerves anaesthetized: Mental nerve
Areas anaesthetized:Soft tissues of the lower lip,
chin and buccal soft tissues anterior to the mental
foramen are anaesthetized
Landmarks:Mandibular premolars,Mucobuccal
fold
53.
54. INFILTRATION ANAESTHESIA
Nerves anaesthetized:Large terminal branches of dental
plexus
Areas anaesthetized: Pulp and root area of the tooth
Buccal periosteum
Connective tissue and mucous
membrane
55. RECENT ADVANCES
Safety Syringes
Computer controlled local
anaesthetic delivery
system
Comfort Control Syringe
Local Anaesthetics with
New Additives
Eutectic mixture of LA
Electronic Dental
Anaesthesia
Vibraject
57. NEEDLE BREAKAGE
Causes:
Primary cause-Bending of the needle that causes
weakening.
Sudden unexpected movement by the patient
Manufacturing defects.
Prevention
Use longer needles for penetration of the tissue beyond
18mm
Use larger-gauge needles
Do not insert the needle upto its hub; rigid and weakest
point
Do not redirect a needle after its insertion into the tissue
58. Management:
a. Remain calm; do not panic.
b. Instruct the patient to not move. Keep the patient’s mouth open or place a
bite block
c. If the fragment is visible then try to remove it with a small hemostat.
d. If the needle is lost and cannot be retrieved easily then do not proceed with
an incision or probing.
e. Inform your insurance company immediately.
f. Refer the patient to an OMFS for consultation.
59. PARAESTHESIA
Persistant anaesthesia (extend well beyond the expected
duration)
Cause:
Trauma to any nerve
Injection of LA solution contaminated by alcohol or a sterilizing
solution near a nerve produces irritation resulting in edema and
increased pressure in the region of the nerve.
Haemorrhage in and around the nerve sheath,which increases the
pressure on the nerve
Problems:
Self-inflicted injury.
Prevention
Strict adherence to injection protocol
Management
Mostly resolves within approximately 8 weeks without treatment.
60. FACIAL NERVE PARALYSIS
Cause:
Administering LA into the capsule of the parotid gland
or place the tip within the parotid gland
Problem
Loss of motor function to the muscles of facial
expression
Management
The situation is transient so one must wait until the
effect of the nerve block wears off.
Remove contact lenses if any
61. TRISMUS
Tetanic spasm of jaw muscles by which the normal mouth opening is
restricted
Causes:
Trauma to muscles or blood muscles in the infratemporal fossa
LA solutions into which alcohol or cold sterilizing solutions have
diffused produce irritation
Haemmorhage
Low-grade infection
Prevention
Use of sharp sterile needle
Practice atraumatic insertion and injection technique
Avoid multiple insertions
Use minimum effective volumes of LA
62. Management
Heat therapy, warm saline rinse analgesics, muscle
relaxants
Physiotherapy consists of opening and closing the
mouth, lateral excursions of the mandible for 5 minutes
every 3-4 hours, using sugarless chewing gum
Antibiotics can also be prescribed for 7 days if the pain
doesn’t subside after 48-72 hours
Refer to an OMFS if there is no improvement in pain or
dysfunction.
63. SOFT TISSUE INJURY
Self-inflicted trauma to lips and tongue is frequently
caused by the patient inadvertently biting or chewing
these tissues while still anaesthetized.
Cause: Trauma
Problem: Swelling and significant pain after the effect of
anaesthesia wears off.
Prevention: Place a cotton roll between lips and teeth if they
are still anaesthetized at the time of discharge.Secure this roll
with dental floss wrapped around the teeth
Warn the patient against eating or drinking hot
foods and biting on the lips or the tongue to test for anaesthesia
64. MANAGEMENT
Analgesics, for pain.
Antibiotics if necessary
Lukewarm saline rinses for decreasing any swelling.
Petroleum jelly to cover lip lesions and minimize
irritation
65. HAEMATOMA
The effusion of blood into the extravascular spaces that can result from
inadvertently nicking a blood vessel during the process of injecting the
local anaesthetic.
Usually results due to the nicking of artery
Cause: Haematomas after IANB are usually visible intraorally whereas
PAS haematomas are visible extraorally.
Problems:Complications are trismus and pain
Prevention:Modify the injection technique slightly as per the
patient’s facial characteristics.
-Minimize the number of needle penetrations into the
tissue.
Management : immediately, apply direct pressure to the site of the
bleeding for 2 mins. In case of IANB pressure is applied to the medial
aspect of the mandibular ramus. In case of ASANB pressure is applied
directly over the infraorbital foramen.
66. Management: immediately, apply direct pressure to the site
of the bleeding for 2 mins. In case of
- IANB pressure is applied to the medial aspect of the
mandibular ramus.
- In case of ASA NB pressure is applied directly over the
infraorbital foramen.
- In case of PSA NB digital pressure can be applied to the
soft tissue in the mucobuccal fold as far distally as can be
tolerated. Apply pressure in the medial and superior
direction and if available apply ice.
- Subsequently after the treatment of hematomas slight
discolouration is likely to be seen. This is due to the
extravasated blood elements which will slowly resorb over
7-14 days. Heat should not be applied immediately though
it can be applied from the 2nd day onwards.
- Avoid any dental treatment until the hematoma resorbs.
67. PAIN ON INJECTION
Causes - Careless injection technique, multiple
injections, rapid deposition of LA solutions
Problems - Patient anxiety leading to sudden
unexpected movements increasing the risk of
needle breakage.
Prevention - Adhere to proper injection techniques,
use sharp needles, use topical anaesthetic before
injecting, use sterile LA solutions, inject LA slowly
68. BURNING ON INJECTION
Cause- pH of the solution, rapid injection of LA,
contamination of LA cartridges, solutions warmed to
normal room temperatures.
Problems- tissue damage may result because of rapid
injection, contaminated tissue injection and overly warmed
LA solution.
Complications- post anaesthetic trismus, oedema,
paraesthesia.
Prevention- slow down the rate of injection to 1 ml per min.
Management- It is a transient phase so management is
usually required for specific complications.
69. INFECTION
Causes - Contamination of needle before
administrating LA, administrating LA into the area of
infection.
Problems- Contamination of needles and solutions.
Prevention- Use sterile disposable needles, handle
needles with care, prepare tissues properly before
injecting LA.
Management- Trismus may be a complication which
must be treated using heat and analgesics and heat.
If there is no improvement the patient should be
started on a 7-10 day antibiotic course.
70. OEDEMA
Causes- trauma during injection, infection, allergy-
angioedema, hemorrhage, injection of irritating solution.
Problems- LA obstruction, pain and dysfunction of the
region, angioneurotic oedema.
Prevention- proper care and handling LA armamentarium,
use atraumatic injection techniques.
Management- prescribe analgesics for pain, antibiotic
therapy if the following persists –
-pain
-mandibular dysfunction
-oedema
-warmth.
71. In case of allergy induced oedema prescribe
intramuscular and oral antihistamine agents if
breathing is not compromised.
If breathing is compromised- P→A→B→C→D
0.15mg epinephrine is injected every 10-15 mins
until respiratory distress resolves.
Histamine blocker is administered either im or iv.
Corticosteroid is administered either im or iv.
Preparations are made for cricothyrotomy if
needed
Thoroughly evaluate the patient before the next
appointment.
72. POST ANAESTHETIC INTRA-ORAL LESIONS
Ulcerations seen 2 days after injection around the
site of the injection and presents with immense
pain.
Recurrent apthous stomatitis on gingival tissues
that are not attached to the underlying bone and the
buccal mucosa.
Herpes simplex seen on tissues attached to
underlying bone. Trauma to tissues by needles, LA
solutions, cotton swab or any other instrument may
activate latent form of diseased processes that
were present in the tissues before injection.
73. Problems- acute sensitivity in ulcerated area.
Prevention- antiviral agents can be used for
extraoral herpes simplex infections.
Management- topical anaesthetic solutions,
mixture of equal amounts of diphenhydramine
and milk of magnesia is rinsed in he mouth.
Ulcerations last for 7-10 days with or without pain.
74. SYSTEMIC COMPLICATIONS
Overdose- results due to:
- biotransformation of drug is unusually slow.
- the unbiotransformed drug is too slowly eliminated
from the body through the kidneys.
- too large a total dose is administered.
- absorption from the injection site is unusually rapid.
- inadvertent intravascular administration occurs.
Management- most of the LA overdose reactions are
self-limiting because the blood level in target organs
continues to decrease as the reaction progresses and
redistribution and biotransformation take place.
Rarely, drugs other than oxygen are necessary.
75. ALLERGY
Allergic responses to LA- dermatitis
- bronchospasm
- systemic anaphylaxis
Of special interest with regard to allergy is the
bacteriostatic agent- methylparaben.
Other causes- sodium bisulfite allergy, epinephrine
allergy, latex allergy, topical anaesthetic allergy.
Prevention- P→A→B→C→D
