anesthesia in dentistry

8/6/2019 Anesthesia in Dentistry

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Anesthesia In Dentistry


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Anesthesia In Dentistry

Dentistry was often a painful and even a barbarous

affair . Relieving pain is one of the important subjectin dentistry . Many procedures could not be done

properly unless pain is well controlled ; ex. Fillings

, extraction , periodontal procedures , root canal

treatment , minor or major surgeries , etc ..


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Anesthesia In Dentistry (contd)

Some important definitions

Anesthesia : The loss or abolition of all modalities of

sensations which includes :Pain , touch , temperature , and pressure .

General anesthesia : Achieved when the patient

becomes unconscious .

Local anesthesia : The patient remain conscious but

the anesthesia is localized to one part only .


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Infiltration anesthesia : Deposit of solution in the region to

be anesthetized and permeates through the tissue to affect

fine nerve endings .

Block anesthesia : To anesthetize a region by blocking the

conduction in the nerve trunk supplying the area .

Topical or surface anesthesia : Local anesthetic applied

on an intact mucous membrane to anesthetize the nerveendings .


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Paresthesia : Altered sensation occurred when :

- A damaged sensory nerve is regenerating ;

- Local anesthetic action starting to work or wearing off ;

- Described as tingling sensation or pins and needles .

Relative analgesic : A sedation technique in which the

patient remains conscious but mental relaxation is induced by

inhalation of a mixture of nitrous oxide , oxygen , and air .

L.A. is used as adjacent when necessary .

Sedatives : Produce sedation and relieve anxiety by acting

on the CNS ( e.g. Valium (Diazepam) )


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Neurophysiology

A Desirable properties of local anesthetics;

B Fundamentals of impulse generation and

transmission:

Nerve anatomy;

Physiology of the peripheral nerves;Electrophysiology of nerve conduction;

How local anesthetics work;

Basic concepts of pain.


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A Desirable properties of local

anesthetics ;

Local anesthesia has been defined as a loss of sensation in

a circumscribed area of the body caused by depression of

excitation in nerve endings or an inhibition of the conduction

process in peripheral nerves.

There are many methods of inducing local anesthesia , some

of which follow:

* Mechanical trauma;

* Low temperature;* Anoxia;

* Chemical irritants;

* Neurolytic agents such as alcohol and phenol;

* Chemical agents such as local anesthetics.


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Electrophysiology of nerve conduction (contd)

# In simple terms, local anesthetics act by

preventing this entry of sodium ions and

stopping propagation of electricaltransmission by inhibiting nerve cell

depolarization.


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Pharmacology Of Local

Anesthetics

- Local anesthesia is defined as a loss of sensation in

circumscribed area of the body caused by a depression of

excitation in nerve endings or an inhibition of the

conduction process in peripheral nerves.

Types of local anesthesia

a) Topical

b) Infiltrationc) Regional


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Pharmacology Of Local Anesthetics (contd)

Methods Of Inducing L.A.

a) Mechanical trauma

b) Low temperature

c) Chemical irritants

d) Neurolytic agents such as alcohol or phenole) Chemical agents as in L.A.

- L.A. should prevent the conduction and generation of

nerve impulse.


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Local anesthetic

I Classification of anesthetic agents :

Amides, Esters, constitute the major categories of local

anesthetics;

The Ketone-linkage class of anesthesia has relativelylittle clinical importance and currently consists of a single

topical agents.

The Lipophilic part is the largest portion of the

molecule. Aromatic in structure, it is derived from

benzoic acid or aniline.

The Hydrophilic part is an amino derivative of ethyl

alcohol or acetic acid .


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II Clinical Implications of pH and Local Anesthetic Activity (contd)

Most solutions of local anesthetics without avasoconstrictor have a pH between 5.5 and 7;

Local anesthetic solutions that contain a vasopressor

(e.g., Epinephrine) are acidified by the manufacturer toretard oxidation of the vasoconstrictor, thereby prolonging

the period of the drug effectiveness.

Sodium bisulfite is commonly used, in a concentration

between 0.05 % and 0.1 %;

A 2 % solution of Lidocaine, with a pH of 6.8, is acidified

to 4.2 by the addition of Sodium bisulfite.


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Solution Of Local Anesthetic

L.A. drug

Vasopressor drug ------------preservative for vasopressor

Sodium chloride

Distilled water


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Pharmacology Of

Vasoconstrictors

After injection of local anesthetic ( L.A. )

into the tissue , blood vessels in the areadilate resulting in increased blood flow

to the site ;


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Pharmacology Of Vasoconstrictors (contd)

- This increase perfusion leads to the following reactions :

a) Increased rate of absorption of the L.A. into the C.V.S.

with its turn remove it from the injection site ;

b) Higher plasma level of the L.A. , with increased risk of

toxicity ;

c) Decreased duration of action and decreased depth of

anesthesia ;

d) Increased bleeding at the site of L.A. administration to

increased perfusion .


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Pharmacology Of Vasoconstrictors (contd)

- Vasoconstrictors are highly important additions to a

local anesthetic solution , for the following reasons :

a) By constricting blood vessels ( B.V. ) , the vasoconstrictors( V.C. ) decrease blood flow to the site of injection ;

b) Absorption of the L.A. into C.V.S. is slowed , resulting inlower anesthetic blood level ;c) Lower anesthetic blood level decreases the risk of L.A.toxicity ;

d) Higher volume of the L.A. agent remains around thenerve for longer periods , therefore increase the duration of

action of L.A.

e) Decrease bleeding at the site of administration andsurgical site .


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Types Of Vasoconstrictors

( Sympathomimetic or Adrenergic ) drugs

1) Catecholamines :

- Epinephrine- Nor-Epinephrine

- Dopamine

2) Non-catecholamines

- Amphetamine

- Ephedrine

3) Felypressin ---Synthetic analogue ( anti-diureti c

hormone )


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Adrenergic Receptors

- Adrenergic receptors are found in most tissues of the

body ;

- Ahlquist in 1948 recognized two types of adrenergic

receptors , termed alpha and beta based on the

inhibitory or excitatory actions of catecholamines on smooth

muscle


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Adrenergic Receptors (contd)

1) Alpha [] receptors : Activation of [] receptors by asympathomimetic drug usually produces a response that

includes the contraction of smooth muscle in blood

vessels ( vasoconstriction ) .

* Alpha 1 : Excitatory

* Alpha 2 : Inhibitory


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2) Beta [] receptors : Smooth muscle relaxation ,

vasodilatation , bronchodilatation and cardiac

stimulation .

1 : Found in the heart and small intestines and

responsible forcardiac stimulation and lipolysis

2 : Found in the bronchi , vascular beds , and uterusand produces bronchodilation & vasodilation .


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Dilutions of

VasoconstrictorsConcentration 1 : 1000 means 1 gm / 1000 ml

solution ;

This means 1000 mg / 1000 ml = 1 mg / ml

1 : 10.000 0.1 mg / ml

1 : 100.000 0.01 mg / ml

1 : 80.000 0.0125 mg / ml

1 : 200.000 0.005 mg / ml = 5 micrograms /

ml


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- Epinephrine remains the most effective and most used

vasoconstrictor in medicine and dentistry ;

- Nor-Epinephrine is not recommended , because it

produces intense peripheral vasoconstriction with

possible elevation of blood pressure , with nine times

higher side effects than epinephrine .


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Epinephrine { Adrenalin }

Epinephrine as the acid salt is highly soluble in water ;

Slightly acid solutions are relatively stable if they are protected from

air ;

Sodium bisulfite is usually added to epinephrine solutions to delay

its deterioration ( through oxidation ) ;

Epinephrine is available as a synthetic and is also obtained from the

adrenal medulla of animals ( approximately 80% of adrenal medullarysecretions being epinephrine ) ;

Epinephrine acts directly on both - and -adrenergic receptors ;

effect predominate .


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Epinephrine { Adrenalin } (contd..)

Adrenalin has a number of systemicactions ; adrenaline

affects :

1 ) The heart

Increases the rate and force of contraction of the heart

raising cardiac output ;

Increase in pulse rate ;

Rise in systolic and diastolic blood pressures ( standard

dose has little effect ) ;

Increased myocardial oxygen consumption .

These actions lead to an overall decrease in cardiacefficiency


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2 ) Effect on blood vessels

- Vessels supplying the skin , mucous membranes , and

kidneys contain primarily receptors ( epinephrine produces

constriction in these vessels ) ;

- Blood vessels supplying the skeletal muscles contain both

2 and receptors , with 2 predominating . 2

adrenoreceptor stimulation produces vasodilatation by

activation of Adenylate cyclase resulting in fall in diastolic

pressure .


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The injection of epinephrine directly into surgical sites leads to

high tissue concentrations , a predominant -receptor

stimulation , and hemostasis ;

As epinephrine tissue levels decrease with time the primary

action on blood vessels will revert to vasodilation , as 2

actions predominate . It is not uncommon , therefore , for

some bleeding to be noted at about 6 hours following surgery

.


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3 ) Effect on the lungs

B2 adrenoreceptor stimulation in the lungs leads to

bronchiolar muscle relaxation ; It is important life-

threatening in case of bronchoconstriction (acute asthma ).

4 ) Effect on biological membranes

In animal models , the adrenaline- induced

hyperpolarization ( activation of a membrane-bound Na / K

pump ) , has been shown to induce analgesia .


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5 ) Effect on metabolism

Glucose concentration is increased due to an Alpha

adrenergic inhibition of Insulin release .

6

)E

ffect on wound healing

Interferes with wound healing :

- The catecholamine reduces local tissue

oxygen tension ;

- Produces fibrinolysis .

Sodium bisulfite is usually added to epinephrine

solution to delay its deterioration.


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Clinical applications Epinephrine

Management of acute allergic reactions ;

Management of bronchospasm ;

Treatment of cardiac arrest ;

As a vasoconstrictor , for hemostasis ;

As a vasoconstrictor in local anesthetics , to decrease

absorption into the cardiovascular system ;

As a vasoconstrictor in local anesthetics , to increase duration

of action ;

To produce mydriasis .


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Felypressin ( Octapressin )

- Non-sympathomimetic amine ;

- Pronounced on venous than arteriolar microcirculation ;

- No effect on adrenergic nerve transmission , so safely

given to :

- Hyperthyroid patient ;

- MAO inhibitor ;

- Tricyclic antidepressants .


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Felypressin ( Octapressin ) (contd..)

- Contra-indicated for pregnant women ;( oxytocic actions on

the uterus ) ;

- Available in 0.03 IU / ml + 3 % Prilocaine

# : Few contraindications of Epinephrine ; instead we useFelypressin

Patient with significant cardio-vascular disease ;

Patient with thyroid dysfunction , diabetes , sulfite sensitivity

; Patient receiving MAO inhibitors , tricyclic antidepressant .

anesthesia in dentistry

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