Local Anaesthesia in Dentistry Flashcards
Analgesia
Analgesia: Absenceofsensibilitytopain,particularlythereliefofpainwithoutlossofconsciousness
Anaesthesia:
Anaesthesia: Partialorcompletelossofsensation,withorwithoutlossofconsciousness,aresultofdisease,injury,oradministration ofan anaestheticagent,usuallybyinjectionor inhalation
Local anaesthesia
Local anaesthesia:
A temporary loss of sensation in one small area of the body caused by special drugs calledanaesthetics. The patient is conscious, but without feeling in the area of the body treated with the anaesthetic.
Paraesthesia
Abnormal sensation (not specifically unpleasant), spontaneous or evoked
Dysesthesia
Unpleasant abnormal sensation, spontaneous or evoked
Hypoaesthesia + hyperaesthesia
Hypoaesthesia is a reduced perception of stimulus or decreased sensation
hyperaesthesia is an increased perception of stimulus (need not be pain)
Specific receptor theory
Normally, influx of sodium ions through the voltage gated sodium channels causes nerve depolarisation and action potential propagation.
The principalmechanism of actionof a local anaesthetic is through blockage of voltage-gated sodium channels (VGSCs).
Acts by binding on specific receptors on sodium channel.
Leads to a reversible block ofactionpotential propagation i.e. reversible blocking of nerve conduction.
Specific receptor theory- LA movement across membrane
Unioinised local anaesthetic diffuse across the cell membrane as they are lipophilic. Once the LA has diffused across, it becomes ionised due to the lower intracellular pH. It is the ionised agent that binds to the sodium channel receptors and prevents action potential propagation.
Metabolism of AA and AEst
Amino amides metabolised by the liver
Amino esters metabolised by pseudocholinesterase in the blood to form para-aminobenzoic acid
- can cause an allergic reaction
Excretion of AA and AEst
Excreted via the kidneys
The reason why this is important is because if a patient presents with liver or kidney disease, further advice may need to be sought from the patient’s GP before embarking on treatment involving local anaesthetic.
Ideal Properties of Local Anaesthetic
- Specific and reversible action
- Non irritant, no permanent damage to tissues
- No allergic reaction
- No systemic toxicity
- Rapid onset of action
- Sufficient duration of action for intended procedure
- Potent (high therapeutic ratio)
- Stable in solution
- Not expensive
- Active via topically or by injection
Types of Local Anaesthetics
Esters (cocaine, procaine)
Amides (lidocaine, mepivocaine, prilocaine, bupivacaine, articaine)
- We now most commonly use the amides
Lidocaine 2% plain or with epinephrine 1:80,000 (i.e. 1:80k)
Most common, very effective
Lignospan special, Lignocaine, Xylocaine etc
Prilocaine 4% plain or 3% with felypressin
Similar to lidocaine
Citanest, Citanest with octapressin
Articaine 4% with 1:100,000 or 1:200,00 epinephrine
Better diffusion, fast onset, hydrolysed quickly, not for IDBs (never use articaine when administering an inferior dental blocks as there is a theoretical risk of haematoma).
Septonest