Thursday, March 19, 2009

Inferior Alveolar Block

There are 3 methods of achieving inferior alveolar block: Direct, Gow-Gates, and Akinosi. I will only cover the Direct method here.

Direct method
Your thumb should be positioned on the coronoid notch of the mandible as shown in the adjacent photo and your first finger should be positioned on the posterior border of the ramus on the patient's jaw.

We anaesthetise the inferior alveolar nerve by inserting the needle about 1 to 1.5 cm above the mandibular occlusal plane and about halfway between the coronoid notch and the pterygomandibular raphe. If the barrel of the syringe is over the contralateral premolars, then the angle will be about right.

Push the needle in until bone is felt (a depth of 2-3 cm usually), then withdraw the needle slightly away from the bone - the end of the needle should now be in the pterygomandibular space. Now aspirate to ensure the needle isn't in the inferior alveolar artery or vein before slowly injecting the local anaesthetic into the pterygomandibular space. We inject here because this is where the inferior alveolar and lingual nerves can be found.

Provided this was done correctly, after a few minutes the entire bone, periodontium, gum and teeth of the side injected will be anaesthetised. A bit of the tongue, the lip and the skin on the chin will also be anaesthetised on that side.

Complications
Never buy pink pills from turban headed indian liquor shop owners. That's the mnemonic to remember the complications of anterior alveolar nerve block.
  • Never - Needle Breakage
  • Buy - Bruising
  • Pink - Pain
  • Pills - Paraesthesia
  • From - Facial paralysis
  • Turban - Trismus
  • Headed - Haematoma formation
  • Indian - Infection
  • Liquor - Lip biting
  • Shop - Sloughing
  • Owners - Oedema
Other complications are transmission of infections, fainting, and methaemoglobinaemia (prilocaine and benzocaine).

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