anatomy of L.A

Question 1

the INFRA ORBITAL NERVE BLOCK

• where is the needle deposited

Answer 1

in the vicinity of the infra-orbital foramen

the solution will actually ENTER the foramen to anaesthetise the DISTAL parts of the ION and its branches

Question 2

the INFRA ORBITAL NERVE BLOCK

-what will it anaesthetise

Answer 2

• upper lip (because it affects the terminal branches going to skin of face
• maxillary teeth to canine and their LABIAL gingivae (because affects the ASA)
  Does NOT affect the palatine gingivae of these teeth!

Question 3

the INFRA ORBITAL NERVE BLOCK

-what will it NOT anaesthetise

Answer 3

• the maxillary PALATINE gingivae which are adjacent to the anaesthetised teeth (because they are not supplied by the distal ION branches)
• —>would need nasopalatine block, greater palatine block or local infiltration instead
• the maxillary CENTRAL incisor can receive innervation from both ASA nerves, but wont be affected in the ipsilateral IO block (on one side of face)
• the maxillary pre-molars and their buccal gingivae (because they are innervated by the MSA nerve if its present OR the PSA)

Question 4

the INFRA ORBITAL NERVE BLOCK

-complications if L.A. solution is deposited into the orbit by mistake

Answer 4

muscles which move eye will be temporarily paralysed= uncoordinated eye movement= diplopia (double vision)
teeth will NOT be anaesthetised

Question 5

the PSA NERVE BLOCK

-what will it anaesthetise

Answer 5

• maxillary molars and their buccal gingivae (but not their palatine gingivae)

Question 6

the PSA NERVE BLOCK

• what will it NOT anesthetise

Answer 6

• the maxillary pre-molars and their buccal gingivae (will be innervated by the MSA or ASA nerves)

Question 7

the PSA NERVE BLOCK

its branches run along the posterior surface of the maxilla.
on the posterior surface of maxilla there is also an important venous plexus called…

Answer 7

the pterygoid venous plexus

Question 8

what are the implications of the PSA being close to the pterygoid venous plexus (posterior of maxilla)

Answer 8

can introductive infection into this plexus when giving a PSA block, that infection can travel along the venous communications of the plexus into the CRANIAL CAVITY= can cause an INTRA-CRANIAL INFECTION

Question 9

nerve blocks are used for mandibular L.A’s and local infiltration approach is used in maxilla

why

Answer 9

• cortical bone of mandible is denser than maxilla therefore it is a bigger barrier to infiltrating anaesthetic

Question 10

the IAN block / inferior dental block

-at which point do you want to anaesthetise the IAN

Answer 10

• point it enters the mandibular foramen

Question 11

why is it possible that
—->although the IAN supplying teeth and its terminal branch, incisive nerve, are DISTINCT to the nerves which supply the gingivae on the medial aspects of teeth (the lingual nerve), we can use a SINGLE NERVE BLOCK to anaesthetise BOTH of these sensory supplies simultaneously

Answer 11

the IAN and the LINGUAL NERVE consistently lie close together as they pass superficial to the medial pterygoid muscle in the infra-temporal fossa
therefore if the IAN is anaesthetised, it is NOT UNUSUAL for the lingual nerve to be too

Question 12

the IAN block / inferior dental block

-what will it anaesthetise

Answer 12

• ipsilateral mandibular teeth (aka all mandibular teeth on one side of face- supplied by the IAN and its insicive branch)
• BUCCAL AND LABIAL gingivae of pre-molars, canine, incisors (supplied by the IAN and its mental branch)
• LINGUAL gingivae of these teeth (supplied by the lingual nerve)

Question 13

the IAN block / inferior dental block

• what will it NOT anaesthetise

Answer 13

• the BUCCAL gingivae of MOLARS (supplied by the long buccal nerve)
• –> ONLY a long buccal nerve block can anaesthetise the buccal gingivae of mandibular molars

Question 14

what is the implication of the lower incisors receiving BILATERAL INNERVATION from the incisive nerves

Answer 14

(the lower incisor = both incisive nerves,
the upper incisor= the ASA nerve branches thus also bilateral innervation)

the tooth may retain sensation even when ipsilateral IAN block has worked

Question 15

clinical implications of the IAN block with regards to anatomical relations

Answer 15

1. close to parotid which wraps itself around the posterior border of the ramus. can anaesthetise the facial nerve branches which run through the parotid gland= cause UNILATERAL facial paralysis
2. IAN lies immediately superficial to the medial pteyrgoid muscle in the area L.A. is deposited. damaging the muscle during procedure= discomfort for patient

Question 16

the distal parts of the IAN branches can specifically be blocked by which nerve blocks

Answer 16

the mental nerve block (will block the mental nerve)

the incisive nerve block (will block the mental AND incisive nerve)

both of these nerves do NOT affect the proximal regions of the nerve

Question 17

the MENTAL and INCISIVE NERVE BLOCKS

• where the L.A deposited in these nerve blocks
• how do you ensure the incisive nerve is blocked

Answer 17

• in the vicinity of the mental foramen (which lies between the apices of the mandibular pre-molars)

injecting L.A. near the mental foramen will anaesthetise the mental nerve BUT need to administer a HIGH volume of solution AND apply pressure to soft tissues in the vicinity of mental foramen = encourages solution into the mandible via the mental foramen where it will also anaesthetise the incisive nerve (and the more superficially placed mental nerve)

Question 18

where does the mental foramen lie in mandible

Answer 18

usually between the apices of the FIRST and SECOND PRE-MOLAR ROOTS

Question 19

landmarks when applying IAN block

Answer 19

• external oblique ridge

- coronoid notch