Uses of local anaesthesia
-Diagnostic: to isolate a source of pain
-Therapeutic: to reduce or abolish the pain
of pathological condition
-Perioperative: to achieve comfort during
operative procedures
-Postoperative: to reduce postoperative
pain
Diagnostic use
Administration of local anaesthetic
can be a useful way of finding the
source of a patient's pain. An
example of this is the pain of a
pulpitis, which can be very difficult
for both the patient and the dentist
to isolate because of its tendency
to be referred to other parts of the
mouth or face
Therapeutic use
Local anaesthetics can, in themselves, constitute
part of a treatment regimen for painful surgical
conditions. The ability of the dentist to abolish pain
for a patient. The use of a block technique to
eliminate the pain of dry socket (localised osteitis)
can be immensely helpful to the management of
this very painful condition, particularly in the first
few days. Inferior dental blocks of long-acting local
anaesthetics such as bupivacaine can give total
comfort for several hours, allowing patients to catch
up on lost sleep and perhaps reduce the use of
systemic analgesics to avoid overuse.
Perioperative use
• It reduces the arrhythmias, which are
noted on electrocardiogram (ECG) during
the surgery when significant afferent
stimulation is taking place. This can be
seen, for example, when a tooth is being
elevated.
It also provides local haemostasis to the
operative site and provides immediate
postoperative analgesia.
Postoperative use
After surgery with either local or
general anaesthesia, the continuing
effect of the anaesthetic is a most
beneficial way of reducing patient
discomfort. It helps to reduce or even
eliminate the need for stronger (often
narcotic) systemic analgesics.
Basic Techniques of Local
Anesthesia
The various types of techniques used for
deposition of these agents, in dentistry are
as follows:
(1) Surface or topical anesthesia,
(2) Infiltration anesthesia,
(3) Field block, and
(4) Nerve block or conduction anesthesia .
Surface or Topical Anesthesia
By this method small terminal
nerves in the surface area of the
intact mucosa or the skin up to the
depth of about 2 mm are
anesthetised by application of a
local anesthetic agent directly to the
area .
-Nerves Anesthetised
Superficial nerve endings.
-Indications
i .Prior to the infiltration injection techniques
or nerve blocks for making the insertion of
the needle painless
ii. Prior to carrying out incision and drainage
of abscesses
iii. Prior to removal of sutures .
Spray
I .The active in gradient is a suitable local anesthetic agent,
such as 10% or 15% lignocaine hydrochloride in water
base .
II. Ethyl chloride spray: It produces anesthesia by
refrigeration. When sprayed onto either mucous membrane
or skin, it gets volatilised rapidly, and produces rapid
anesthesia.
Ointment
It is used for similar purposes as spray. The active in
gredient is a suitable local anesthetic agent, such as 5%
lignocaine hydrochloride.
Emulsion
The active in gredient is a suitable local anesthetic agent,
such as 2% lignocaine hydrochloride.
Jet Injection
Method: It is a technique by which a small amount of local
anesthetic solution is expelled as a jet into submucosa
without the use of a hypodermic needle. Specialised
syringes are used for this technique.
Infiltration Anesthesia or Local
Infiltration
This method is also known as
terminal or peripheral
anesthesia, as the induction of
anesthesia is by the action of
anesthetic agents on the
terminal nerve fibers .
Maxilla
The maxilla has thin labial/buccal cortical plate;
and moreover shows areas of porosity, and the
compact bone presents numerous foramina which
aid in absorption of local anesthetic solution.
These factors, therefore, make the maxilla more
favorable for infiltration anesthesia techniques .
Mandible
The bone is generally dense and has thicker
cortical plates than maxilla, particularly in
posterior region, more so in the region of external
oblique ridge. Only the anterior part of mandible
presents sufficient porosity, which is favorable for
infiltration techniques.
Advantages
Easy and simple injection
Very high success rate, and
Good control of bleeding.
Disadvantages
The action is limited to a small
area; hence considerable amount
of solution has to be injected with
multiple penetrations when large
field is to be anesthetised.
Indications
This method is used when only the
mucous membrane and the
underlying connective tissues are
to be anesthetised.
Contraindications
Presence of acute inflammation or
infection at the site of injection.
Applications
Infiltration anesthesia helps in anesthetising (1)
teeth as it affects dental nerves before they
enter apical foramina; and (2) periodontal
tissues .
Other Applications
Infiltration anesthesia is often used in
conjunction with general anesthesia to reduce
bleeding at the site of surgery; when
vasoconstrictor is added to local anesthetic
solution.
Technique
Needle: The recommended gauge is 25, 27 or 30; and the
recommended length is 25 mm .
Bevel of the needle: The bevel should be facing the bone .
Point of insertion: It is in the middle of the area to be
operated .
Depth of penetration: It is beneath the mucous membrane into
the connective tissue .
This technique may require more than one needle insertions
depending upon the extent of area to be anesthetised .
Care should be taken to avoid injury to the tissues in the
following ways :
Avoid injecting the solution too rapidly. And cold solutions
Avoid injecting too large a volume of the local anesthetic
solution.
Avoid injecting too superficially. And subperiostealy
These situations will result in injury to the tissues in the form
of pain at the time of injection, or persistent post-injection pain
or sloughing of the overlying soft tissues .
Types of Infiltration Anesthesia
Submucosal or subcutaneous anesthesia
Paraperiosteal or supraperiosteal anesthesia
Subperiosteal anesthesia
Intraligamentary (Periodontal ligament)
anesthesia
Intrapulpal anesthesia
Intraosseous anesthesia
Intraseptal anesthesia
Palatal infiltration
Technique: The local anesthetic
solution is deposited in the
immediate submucosal tissue
layers. The solution diffuses
through the interstitial tissues
and reaches the terminal fibers
of the nerve in the area of
deposition of the local
anesthetic solution .
Procedure: The needle is
inserted beneath the mucosal
layers. Care should be
exercised to avoid injecting too
superficially. Excessive amounts
injected superficially may lead to
sloughing of the overlying
tissues. Usually 0.25-0.5 ml of
the local anesthetic solution is
deposited.
Submucosal
Injection
Paraperiosteal or Supraperiosteal Injection
It is commonly called the local infiltration and is
the most frequently used local anesthetic
technique. The paraperiosteal injection is
commonly used injection technique for
obtaining anesthesia in the region of all
maxillary teeth and mandibular anterior teeth
because of thin cortical plates and abundant
cancellous bone .
Site of insertion: The needle is inserted through
the mucosa, and the solution is deposited in
close proximity to the periosteum or along the
periosteum, in the vicinity of the apex of the
tooth to be treated, as close to the bone as
possible.
Indications: This method is used for procedures in the
entire maxilla and anterior mandible. In these areas,
the cortical plates are thin, and there is abundant
cancellous bone. The local anesthetic solution
penetrates bone through Haversian canals. These
canals are numerous near the apices of teeth near the
surfaces.
Pulpal anesthesia when treatment is limited to one or
two teeth in maxilla, and anterior mandible.
Soft tissue anesthesia for surgical procedures in a
circumscribed area.
Children and young adults. In children, this technique
can be used in the posterior mandible to anesthetise
deciduous molars as the cortical bone is thin in this
region.
Contraindications:
Presence of acute inflammation or infection in the area of
injection .
Presence of dense bone covering the apices of teeth, as in
maxillary first molar, because of overlying buttress of
zygoma.
Advantages:
.High success rate
.Technically easy injection
.Usually atraumatic
Disadvantages:
The technique is not recommended for large areas because
of: (i) need for multiple penetrations, (ii) the necessity to
administer larger volumes of anesthetic solution, and (iii)
satisfactory anesthesia cannot be always produced.
Technique
Needle: A 25 or 27 gauge short needle is
recommended .
Point of insertion: It is at the height of mucobuccal
fold in the vicinity of the tooth to be anesthetised .
Target area: The apical region or above the apex of
the tooth to be anesthetised.
Depth of insertion: Few millimeters.
Bevel: The position of the bevel of the needle
should be facing the bone.
Landmarks:
- Mucobuccal fold in the region of the tooth to be
anesthetised.
- Crown of the tooth.
- Root contour of the tooth.
-Position
Procedure
of the patient:
The occlusal plane of maxillary teeth should be at an angle of 45° to the
floor .
-Position of the operator :
i .For maxillary injections, for the right side, the operator stands by the side
of the patient; and for the left side, the operator stands in front of the
patient .
ii. For mandibular injections, the operator stands by the side of the patient
for the left side; and in front of the patient for the right side .
-Preparation of the tissues at the site of injection with an antiseptic .
-Application of topical anesthetic at the site of injection .
-Retract the lip/cheek, pulling the tissues taut .
-Take a preloaded syringe. Initially, hold it at an angle of 45° to the long
axis of the tooth to be anesthetised, with the bevel of the needle facing the
bone. Insert the needle at the height of mucobuccal fold, or a few
millimeters away from the labial cortex .
-Aspirate, if negative, deposit approximately 0.5 ml of the solution slowly
over 20 seconds .
-Depth of insertion: few millimeters .
-Withdraw the syringe slowly .
-Cover the needle .
-Wait for 2-3 minutes, check for the signs and symptoms of anesthesia,
and start the procedure.