Mandibular Local Anaesthesia

Question 1

List the branches of the mandibular division of the trigeminal nerve CN V3:

Answer 1

• incisive nerve: supplies anterior teeth
• mental nerve: supplies sensation to lower lip and soft tissues around teeth
• inferior alveolar nerve: division of long buccal nerve - supplies teeth to mental foramen
• lingual nerve: division of long buccal nerve - towards tongue
• long biccal nerve: travels between two heads of lateral pterygoid muscle

Question 2

Answer 2

Question 3

Answer 3

Question 4

Where does the inferior alveolar nerve enter the mandible?

Where is this structure located?

What structure does the needle go through? the needle needs to be lateral to which structure?

Where should the LA be deposited for an IANB?

Answer 4

Mandibular foramen: approximately half way up ascending ramus, in line with the mandibular occlusal plane, behind lingula

Needle goes through buccinator muscle, and must be lateral to pterygomandibular raphe

Aim to deposit LA close to IAN before it enters the mandible

Question 5

List the boundaries of the pterygomandibular space:

Answer 5

Lateral: ramus of mandible

Medial: medial pterygoid muscle

Posterior: parotid and CN VII nerve

Anterior: buccinator

Superior: lateral pterygoid muscle

Question 6

Answer 6

Question 7

What is needed for a block anaesthesia?

Answer 7

• medical history
• long needle - 35mm
• appropriate anaesthetic e.g. lidocaine

Question 8

Describe the steps to an IANB:

What is the key sign of the LA taking effect?

Answer 8

• open mouth wide to see pterygomandibular raphe
• place supporting thumb in coronoid notch of anterior border of ramus of mandible (infront of ascending ramus)
• identify injection point: half way up thumb and half way between ramus and pterygomandibular raphe
• insert needle until bone is reached ~2.5cm (parallel to mandibular occlusal plane) and syringe should be overlying contralateral premolars
• withdraw needle by 1-2mm then aspirate: if no blood aspirated, slowly start to inject ~1.5-2ml
• wait for diffusion to take place

KEY SIGN: numb lower lip on that side

Question 9

What is the difference between an IANB with a lingual nerve block?

What is the key sign of a lingual nerve block?

Answer 9

• Much more superficial, ~1-1.5 cm in with needle for lingual nerve as opposed to 2.5cm for an IANB
• can be done with same injection as IANB

KEY SIGN: numb tongue

Question 10

Describe the long buccal nerve block

Answer 10

• separate injection to IAN block and lingual nerve block
• access at buccal aspect of coronoid notch, alomost immediately touch mandible so a long or short needle may be used

Question 11

Describe the mental nerve block:

Answer 11

• short needle is sufficient
• aim for LA deposited at mental foramen
• like a deep infiltration between mandibular premolars

Question 12

Why is block anaesthesia not reliable for anterior teeth?

How is this overcome?

Are there any issues with this?

Answer 12

• due to a crossover
• bone is thinner so can give infiltrations, but only ~50% success with 1ml buccal infiltration alone
• splitting dose (0.5ml) for each of buccal and lingual increases success rate to 90%
• lingual inflitrations can take 8-10 minutes to achieve pulpal anaesthesia