CF- Local Anaesthesia

Question 1

Trigeminal nerve (CN V) branches

Answer 1

CN V1 - ophthalmic (sensory)
CN V2 - maxillary (sensory)
CN V3 - mandibular (mixed: sensory >motor)

Question 2

Maxillary nerve (CNV2) branches

Answer 2

superior alveolar nerves
infraorbital nerve
greater palatine nerve
nasopalatine nerve

Question 3

Maxillary nerve branches and what they innervate

Answer 3

Superior alveolar nerve: PSA, MSA, ASA

• interdental papillae
• PDL
• buccal gingiva
• dental pulp

PSA - posterior part of mucous membrane of cheek + molar buccal gingiva

Infraorbital nerve anastomoses w MSA and ASA and supplies: anterior and premolar teeth, gingiva and PDL

Greater palatine (through greater palatine foramen): posterior mucous membrane of hard palate, posterior palatal gingiva

Nasopalatine (incisal canal): anterior mucous membrane of hard palate + anterior palatal gingiva

Question 4

4 main branches of mandibular nerve (CNV3)

And what they supply

Answer 4

IAN
lingual nerve
buccal nerve
mental nerve

IAN - teeth and gingiva of lower jaw
lingual nerve - lingual mucosa tissues of md + posterior branch gives small branches to lingual gingiva of molars
sublingual nerve is a branch of lingual - lingual gingiva of anteriors, mucosa of fom
buccal nerve: buccal gingiva of molars
mental: lower ants and premolars, buccal gingiva between midline and 2nd premolar, skin of lower lip and chin

Question 5

Describe path of mandibular nerve

Answer 5

• foramen ovale to infratemporal fossa
• motor branches for mm of mastication leave trunk in infratemporal fossa
• IAN enters ramus of md in mandibular foramen behind lingula
• lingual nerve passes downwards w IAN but doesnt enter md foramen and travels medially towards tongue
• mental nerve exits md at mental foramen between lower premolars
• buccal nerve passes along medial side of ramus of md anterior to IAN then cross anterior border of ramus and ramifies

Question 6

Structures passing through infratemporal fossa (inf and medial to zygomatic arch)

Answer 6

temporalis muscle
lateral pterygoid
medial pterygoid
pterygoid venous plexus 
md nerve 
PSA nerve 
chorda tympani 
otic ganglion
lesser petrosal nerve

Question 7

Explain peripheral nerve physiology

Answer 7

• block voltage gated Na+ channels because they physically plug the transmembrane pore, preventing the normal influx of Na+ (depolarisation) responsible for AP generation which is needed for signalling/conductance

( Na channel is most susceptible to LA binding in the open state, so frequently stimulated nerves tend to be blocked more easily - what is the relevance?)

Question 8

2 basic classes of local anaesthetics. Give examples.

Answer 8

amino-amides - amide link between intermediate chain and aromatic end
(lidocaine, articaine, mepivacaine, prilocaine, bupivicaine)

amino-esters - ester link between immediate chain and aromatic end
(procaine, benzocaine, cocaine)

context:
aromatic region: gives LA lipid solubility (to get into membrane) + basic amine side chain: binds to ion channel, these two elements of LA is joined together by ester or amide (procaine - amide)

Question 9

For lidocaine, articaine, mepivacaine:
%
vasoconstrictor conc
brand name
max dose

Answer 9

lidocaine (lignocaine HCl) 2%, 1:80,000 adrenaline, max 7mg/kg - 11 cartridges
articaine (septonest) 4%, 1:100,000 adrenaline, max 7mg/kg - 5.5 cartridges
mepivacaine (scandonest) 3%, 0 adrenaline, adult max 6.6ml- 2-3 cartridges