Anesthesia and anesthetics
I GENERALITIES:
a) Definition:
The purpose of anesthesia is to temporarily and reversibly suppress the sensitivity of a given territory. It is therefore the blocking of all nerve transmission in a territory.
b) Types of anesthesia:
In odontostomatology two types of anesthesia are practiced: *local anesthesia:
The anesthetic product is carried to the level of the nerve endings. It is called periapical (or paraapical).
*regional anesthesia:
The anesthesia is applied to the level of a nerve trunk. It is truncal. *loco-regional anesthesia.
Association of the two types.
Choosing a good mode of anesthesia depends
-of the patient: age, general condition, allergic history.
-pathological conditions: inflammation…
-nature and duration of the intervention
c) goals:
Anesthesia allows:
-to desensitize the surgical act (clinical silence) -to have surgical comfort
11 0 ) ANESTHETIC PRODUCTS:
Used by infiltration or contact, anesthetics must possess certain characteristics.
I O / PROPERTIES OF AN ANESTHETIC;
-have a reversible action
-not cause tissue irritation or adverse reactions
-not cause an allergic reaction
-have low toxicity
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-the anesthetic effect must appear quickly and last sufficiently
-must be stable in diffusion and easily eliminated
2 0 / COMPOSITION OF AN ANESTHETIC:
An anesthetic solution is composed of
*the anesthetic itself
*preservative: reducing agent intended to prevent oxidation which would inhibit the vasoconstrictor
*the antiseptic that maintains the sterility of the solution
*a vasoconstrictor
3 0 / MODE OF ACTION OF ANESTHETICS:
Local anesthetics are alkaloid bases combined with acids (hydrochloric acid) to form water-soluble salts (Weak base + Strong acid = Stable, water-soluble salts).
Due to the alkalinity of the tissues into which it is injected, the anesthetic salt is hydrolyzed into an alkaloid base and released; it easily penetrates the nerve membrane.
- If the pH is alkaline, the base is released easily.
- If the pH is acidic (in the case of infected tissue): the base is difficult to release = unsatisfactory anesthesia.
This water solubility of anesthetics is necessary for their diffusion through the interstitial fluids to the nerve fiber.
- Small nerve fibers are infiltrated first compared to large fibers.
- Myelin is an obstacle to the anesthetic.
- Apart from cocaine, all local anesthetics produce localised vasodilation at the injection site hence •
- bleeding *rapid absorption
*short action
- Usefulness and interest of associating a vasoconstrictor with the anesthetic product.
4 0 /BIO TRANSFORMATION OF ANESTHETICS:
The injected anesthetic product is captured by the nerve, by the capillary then venous system and carried towards the liver where it will be metabolized then eliminated through the urine.
Catabolism of the anesthetic occurs by hydrolysis •
- Ester-linked anesthetics (the least used) are hydrolyzed by plasma and hepatic cholinesterases.
*amide-bonded anesthetics are hydrolyzed in the liver (be careful if you have liver failure).
- * REMARKS •
The anesthetic crosses the placental barrier (risk for the fetus)
The anesthetic also passes into the mammary glands (avoid breastfeeding after anesthesia)
5 0 /ANESTHETIC PRODUCTS:
Cocaine was the first anesthetic used; abandoned due to its toxicity, it served as the basis for several attempts at synthesis.
Currently two groups of local anesthetics are used:
*ester-linked anesthetics
*amide-linked anesthetics
The composition of a local anesthetic includes: •
The bond between the Intermediate chain and the hydrophilic amine group is either an ester bond or an amide bond, hence Two anesthesia groups:
*ester-linked anesthetics:
o RI
AR- c e O – (CH2) n – N
- Procaine: No longer used in dentistry
- Tetracaine (pantocaine): used in cream form (Mucosan@)
The specialties of this group are:
Low toxicity — vasodilatory property — rapid passage into general circulation — short action — responsible for allergic reactions
*amide bond anesthetics: the most modern
RC NH2 – ( CH2
- Lidocaine (Lignocaine, Xylocaine): powerful, exists in various forms
(gel, spray, solution)
- Mepivacaine: double the duration of action compared to xylo
- Scandicaine: derivative of mepivacaine, certain efficacy.
- Articaine (alphacaine, ubistesin, pressicaine): duration of action approx. 75 min, safe and rapid action. Less cardio-depressant effect.
Generally speaking, the specialties of this group are
More powerful than procaine – fast and longer acting – slow biotransformation in the liver – used in 2% concentration with or without vasoconstrictor. Amide bond anesthetics are the most widely used in dentistry.
6 0 THE VASO CONSTRICTORS:
The vasoconstrictor represents an integral and necessary element of most anesthetics.
*It has certain advantages:
-local vasoconstriction thus reducing the circulatory current in the area concerned
(reduced bleeding, and greater concentration of anesthetic) -reduces the toxicity of the anesthetic by delaying its absorption
-reduction in the amount of anesthetic used
-prolongs the duration of action
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-increases the effectiveness of the anesthetic
a) Adrenaline — Epinephrine:
Exists in the body, released by the adrenal medulla. Added to the anesthetic it gives:
- immediate local vasoconstriction followed by vasodilation.
- contraction of striated muscles
an increase in heart rate
an increase in myocardial contractions
hypertension, hyperglycemia.
All these effects would contraindicate the use of adrenaline in heart patients, hypertensive patients, diabetics, hyperthyroid patients, patients taking MAOIs. Concentration: 1/50,000. 1/200,000
Currently it is believed that this concentration is infra toxic and would be far from giving all these side effects.
b) Nor adrenaline — Nor epinephrine:
Also synthesized by the adrenal gland in smaller quantities than adrenaline.
Effects:
- Sustainable Vconstriction
- no secondary vasodilation
little effect on heart rate
- Hypertensive
Concentration: 1 / 30,000
Contraindication: Hypertension — MAOI
111 0 ANESTHESIA TECHNIQUES:
A/ Surface anesthesia:
1- by contact:
It is obtained by applying an anesthetic substance to a mucous membrane to which it provides short-term insensitivity; it is done by three processes:
* whitewashing:
After drying the affected area with warm air, apply a cotton pad soaked in anesthetic. The product is spread on the mucous membrane. The anesthetic effect takes a long time to be obtained.
Indicated for low volume samples. * Tamponage:
A wick soaked in contact anesthetic is placed on the affected area for a few minutes.
*Spraying:
Consists of projecting an anesthetic solution reduced to droplets onto a mucous membrane.
2-By refrigeration (Cryoanesthesia):
Anesthesia is obtained by direct projection of a highly volatile liquid which will cause a sudden decrease in local temperature, thus blocking the sensory receptors. Among the most used products:
B- Infiltration anesthesia:
consists of bringing the anesthetic solution into contact with the nerve endings using a syringe
) Local anesthesia:
a. 1. Periapical (para apical) anesthesia:
The mirror held in the left hand slightly stretches the cheek or lip mucosa to facilitate the penetration of the needle which must be carried out in the direction of the apical region opposite the tooth concerned or the area to be operated on, at the back of the vestibule, the bevel of the needle facing the bone.
Upon penetration, the injection is done gently until the mucosa whitens (3/4 of the cartridge);
On the lingual or palatal side Insert the needle (bevel always facing the bone) halfway between the neck and the apical region and inject the last quarter gently. Wait 2 to 3 minutes before starting the procedure. This anesthesia will last 30 to 40 minutes.
Indications:
-Extractions of all teeth of the upper jaw
-extraction of the incisor-canine block and lower premolar
a.2 intraligamentary anesthesia:
The syringe is inserted into the mesial and distal interdental ridge, with the bevel against the tooth. The needle is inserted as far as possible into the desmodontal space towards the apex where the anesthetic is then injected.
B- Infiltration anesthesia:
consists of bringing the anesthetic solution into contact with the nerve endings using a syringe
) Local anesthesia:
a. 1. Periapical (para apical) anesthesia:
The mirror held in the left hand slightly stretches the cheek or lip mucosa to facilitate the penetration of the needle which must be carried out in the direction of the apical region opposite the tooth concerned or the area to be operated on, at the back of the vestibule, the bevel of the needle facing the bone.
Upon penetration, the injection is done gently until the mucosa whitens (3/4 of the cartridge);
On the lingual or palatal side Insert the needle (bevel always facing the bone) halfway between the neck and the apical region and inject the last quarter gently. Wait 2 to 3 minutes before starting the procedure. This anesthesia will last 30 to 40 minutes.
Indications:
-Extractions of all teeth of the upper jaw -extraction of the incisor-canine block and lower premolar
a.2 intraligamentary anesthesia:
The syringe is inserted into the mesial and distal interdental ridge, with the bevel against the tooth. The needle is inserted as far as possible into the desmodontal space towards the apex where the anesthetic is then injected.
Advantage :
> Very small quantities are sufficient
> Good results
Disadvantages:
-the ischemia caused is greater, which could lead to complications.
-requires special instrumentation: pressure syringe and fine needle.
A.3 Intraseptal anesthesia
This technique is indicated in cases where periapical surgery is contraindicated or as a complement to it.
The needle is introduced at the level of the desmodontal space but this time pushed towards the spongy bone of the septum
B. truncal or loco-regional anesthesia:
the anesthetic product is brought into contact with a nerve trunk
- In the upper jaw:
However, it may be indicated in certain cases:
- Indications:
- multiple extractions
- extended intervention
-surgical extraction of impacted teeth
-cyst enucleation
-in the case of inflammatory phenomena contraindicating local anesthesia.
.1 anesthesia of the nasopalatine nerve
Is done at the level of the anterior palatine hole (located opposite the retroincisive papilla) The needle is introduced parallel to the bony table on the palatine side up to the bony contact where the product will be injected. There will be immediate anesthesia of the anterior palatine region (cc) mucosa and bone.
2 anesthesia of the upper anterior dental nerves (suborbital hole):
• Is done at the level of the suborbital hole (located 1 cm below the orbital floor on the vertical line passing through the pupil
Two methods are used:
*Skin route:
-locate the suborbital hole: 1 cm from the orbital floor and 1 cm from the wing of the nose with the index finger of the left hand
-insert the needle into the nasolabial fold
-the suborbital canal is reached by trial and error, guided by the index finger of the left hand
– gently insert the needle 1 to 2 cm and inject gently
This anesthesia is obtained in 5 minutes and lasts 45 minutes.
*Endorbuccal route
-place the index finger of the left hand on the skin marker of the suborbital hole and release the upper lip with the thumb of the same hand
Gently push the needle in opposite the apex of the 2nd upper PM.
the tip of the needle is felt by the index finger and the orifice of the canal is reached by groping.
– inject gently
.3 Anesthesia of the anterior palatine nerve
- It is done at the level of the posterior palatine hole located at Icm at a distance from the neck of the 2nd upper molar (depression)
- The needle is inserted at this level, the injection is done slowly
- We will obtain anesthesia of the 2/3 post of the hemi vault of the palate
4 – Anesthesia of the superior posterior dental nerve:
- Is done at the level of the accessory palatine hole located behind the tuberosity
- Anesthesia of molars with their supporting tissues
In the mandible
1. Anesthesia at the level of the inferior dental nerve at the spine of Spix
*Technical
– locate the anterior edge of the ascending branch with the index finger of the left hand
-the direction of needle penetration starts from the canine of the opposite region, 1 cm above the occlusal plane
-the needle is gently inserted until bone contact, then withdraw the needle 1 to 2 mm and inject gently,
- This anesthesia takes 5 to 10 minutes and lasts 1 to 1 hour 30 minutes.
It manifests itself by tingling in the lower half of the lip on the same side and at the tip of the tongue (near the lingual nerve).
- This anesthesia gives insensitivity to the dental pulp of the molars + 2nd premolar located on the same side, and to the mucosa on the lingual side.
The vestibular mucosa innervated by the buccal nerve requires additional vestibular para-apical anesthesia.
*Instructions .
-extraction of lower molars
-surgical intervention on the mandible (posterior part) 2-anesthesia of the mental nerve
- Consists of numbing the inferior dental nerve as it exits at the mental foramen located between the apex of the two premolars
- The technique is the same as the para apical
- Anesthesia of the teeth + vestibular mucosa of the incisor-canine block and 1st premolar
3. lingual nerve anesthesia
- Obtained by infiltration opposite the wisdom tooth in contact with the internal table
- Indications for interventions involving the floor of the mouth
- Anesthesia of the hemitongue, floor, lingual side of the gingiva
Gow-Gates technique
- The aim of this technique is above all to try to resolve problems of nerve replacement by injecting as close as possible to the foramen ovale.
- According to the author, this technique would allow the inferior alveolar, buccal and lingual nerves to be infiltrated at once.
- The patient is in the supine position, in a semi-reclining position in the chair.
- The head is hyperextended and tilted toward the operator. The mouth is wide open.
- The index finger locates the anterior edge of the coronoid process capped by the temporal tendon.
- The general direction of the syringe is oblique upwards and outwards directed towards the neck of the condyle just below the insertion of the lateral pterygoid muscle
AKINOSI
- The technique described by Akinosi has as its main objective to perform a regional mandibular infiltration in patients with limited mouth opening.
Technical:
- The cheeks and chewing muscles should be relaxed.
- The teeth are in contact without effort.
- Spread the cheek with the thumb and index finger
- The needle is placed parallel to the occlusal plane and 2 mm above the neck of the teeth (adult).
- If it is a child, the needle is placed 2 mm below the neck of the teeth.
The needle is directed backwards as close as possible to the temporal muscle, to a depth of approximately 15 to 20 mm. The value of an anesthetic cartridge will be injected slowly
Iv o CONCLUSION
Good knowledge of:
- Anatomical landmarks
- Anesthesia techniques described according to these benchmarks are the only guarantee of the success of your anesthetic procedure .
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