Local Anaesthetic

Question 1

Describe the structure of local anaesthetics

Answer 1

Aromatic region (hydrophobic)
Ester or amide bond
Basic amine side chains (hydrophilic - causes pain)

Question 2

Describe the different chemical forms of local anaesthetics

Answer 2

They are presented as a hydrochloride (B.HCl) to render the amine base more water soluble making the injection less painful
LA is partly dissociated, its active in its ionised form but can only cross the membrane in its unionised form

Question 3

What are local anaesthetic preparations composed of?

Answer 3

LA base present as hydrochloride
2-4% solution for dental use
Reducing agent (Sodium Metabisulphide)
Preservatives and fungicide
May have vasoconstrictor - adrenaline or felypressin

Question 4

Give examples of Ester local anaesthetics

Answer 4

Cocaine
Procaine
Benzocaine

Question 5

Give examples of Amide local anaesthetics

Answer 5

Lignocaine (lidocaine)
Prilocaine
Articaine
Bupivicane

Question 6

What does the IANB give anaesthesia to?

Answer 6

Mandibular teeth on one side (inferior alveolar nerve)
Lower lip and chin on one side (mental nerve)
Parts of the tongue and lingual gingival tissue on one side (lingual nerve)

Question 7

What area does an IANB not give anaesthesia to?

Answer 7

The buccal gingivae - can be done with a buccal block

Question 8

Where is the non-dominant thumb placed for the IANB

Answer 8

Intra-orally in the retro-molar region of the mandible

Question 9

Where is the non-dominant index or middle finger placed for the IANB?

Answer 9

Extra-orally at the posterior border of the ramus

Question 10

In what position does the needle enter the mouth for an IANB?

Answer 10

Needle is advanced from the premolar region of the opposite wide, with the syringe held parallel to the mandibular occlusal plane

Question 11

Where is the needle inserted for an IANB?

Answer 11

Through the mucosa in the mandibular retro-molar region lateral to the pterygomandibular raphe, midway between the raphe and the anterior border of the ascending ramus of the mandible, aiming for a point halfway between the operator’s thumb and index finger
About 5mm above the mandibular occlusal plane

Question 12

How far is the needle inserted for an IANB?

Answer 12

Until the medial border of the mandible is reached

Once bone has been touched, the needle is withdrawn slightly until it is supra-periosteal

Question 13

How much local anaesthetic is deposited in an IANB?

Answer 13

1.5ml, then withdraw halfway and deposit the remaining 0.5ml

Question 14

How is the lingual nerve anaesthetised in an IANB?

Answer 14

By withdrawing the needle halfway, aspirating again and depositing most of the remaining solution