Anaesthesia in the mandible

Question 1

IAN anatomy

Answer 1

Branch of mandibular division of trigeminal nerve, initially deep to lateral pterygoid, then in pterygo-mandibular space
-gives off mylohyoid and enters mandibular formamen
Splits in mandibular canal

Question 2

IAN innervates

Answer 2

Inferior alveolar - tooth pulps, perio ligaments and gingivae of posterior teeth
Incisive branch - pulps, perio ligaments and gingivae of first premolar to midline (slight cross-over)
Mental nerve - buccal gingivae, second premolar to midline and lower lip/ chin skin

Question 3

Lingual nerve anatomy

Answer 3

Splits from IAN central central to mandibular foramen, passes downwards and forwards and slightly deeper than IAN
Joined by chorda tympani, passes down by medial side of roots of third molar
Gives branches to submandibular salivary gland
Runs close to submandibular duct and branches into tongue

Question 4

Lingual nerve innervates

Answer 4

Lingual branch of trigeminal - mucous membrane of tongue (anterior to circumvallate papillae), floor of mouth and lingual gingivae
Chorda tympani - mainly taste, secretomotor and vasomotor

Question 5

Long buccal nerve anatomy

Answer 5

Passes between 2 heads of lateral pterygoid, along medial side of mandibular ramus, anterior to IAN, crosses anterior border into cheek

Question 6

Long buccal nerve innervates

Answer 6

Mucosa of cheek and gingivae buccal to premolars and molars

Question 7

Mylohyoid nerve anatomy

Answer 7

Splits from IAN central to mandibular foramen

Question 8

Mylohyoid nerve innervates

Answer 8

Mylohyoid muscle, anterior belly of digastric and skin over chin point
Not usually relevant for dental anaesthesia

Question 9

Infiltration vs regional block mandible

Answer 9

Except for lower incisors, infiltration not satisfactory because of thick cortical plate with few vascular channels, therefore need a regional block
Block in pterygomandibular space, central to mandibular foramen
Regional blocks more uncomfortable for px

Question 10

IAN block - direct method

Answer 10

Method of choice, as needle passes ‘direct’ to injection site
Deposition of LA soln at mandibular foramen
Foramen in ‘undercut’ because of flare of ramus, so needle from opposite side
Approx 5mm medial to midpoint of nail (deepest concavity)
Lateral to pterygomandibular raphe
Aiming for halfway between fingers and thumb
Parallel to occlusal plane
After approx 0.5cm, adjacent to lingual nerve
After approx 2-2.5cm, adjacent to IA nerve
Hit bone, withdraw very slightly and deposit 2/3 of cartridge
Withdraw half way and deposit 1/4 to 1/3 of cartridge for lingual

Question 11

IAN block direct method landmarks

Answer 11

Pterygomandibular raphe (hamulus/ mandible, superior constrictor/ buccinator)
External oblique ridge (coronoid notch) - thumb at deepest concavity
Angle of mandible - little finger
Posterior border of mandible - other fingers
Needle from direction of opposite premolars

Question 12

IAN block positioning

Answer 12

Operator in front, right side, right hand; left side, left hand
Mouth open, mandible parallel with floor
Long needle
When experienced, can use right hand for left blocks and vice versa

Question 13

Factors affecting position - IAN block

Answer 13

Width of ramus (further back if ramus wider)
Angle of ramus and arch
Foramen lower in children

Question 14

Adjustments to position IAN block

Answer 14

If bone struck to soon - withdraw, straighten angle, advance then return to original angle
If bone not struck by 3cm depth - withdraw almost completely, readvance from over opposite molars
Variable onset time - allow 3-4 minutes after initial paraesthesia (usually <1min)
No signs after 3-4 minutes = failure

Question 15

IAN indirect method

Answer 15

Similar entry point, but further lateral
Hit bone, straighten, advance 7mm, return to angle i.e. stays nearer to bone
More manipulation in tissues

Question 16

Bilateral IAN block

Answer 16

Can be done but not recommended routinely
Likely to give bilateral lingual anaesthesia
Proprioceptive supply to tongue
Px discomfort

Question 17

IAN block - Clarke and Holmes

Answer 17

Indirect and solution higher

Question 18

IAN block - Sargenti

Answer 18

Direct but higher

Question 19

IAN block - Vazirani, Akinosi

Answer 19

Mouth closed, along buccal sulcus and higher

Question 20

IAN block - Cow-Gates

Answer 20

Medial to condyle - whole mandibular division

Question 21

IAN block - external approach

Answer 21

If severe ankylosis

Question 22

Mental and incisive nerve block

Answer 22

1-1.5ml LA deposited at mental foramen - diffuses into mandibular canal to block incisive nerve
Usually between apices of premolars - radiograph helpful if available
Mouth partly closed - for retraction
Palpate foramen if possible (often not)
Not always successful

Question 23

Articaine 4%

Answer 23

Because of its bone penetrating ability, articaine has become popular for producing anaesthesia in lower teeth including molars without resorting to mandibular blocks
This may be especially important in pxs with bleeding problems (such as haemophiliacs) where you may wish to avoid a mandibular block
Some studies suggest it may damage nerves

Question 24

Lingual nerve anaesthesia

Answer 24

1. Block at same time as IA nerve
2. 0.5ml submucosally below and behind wisdom tooth
3. Infiltration adjacent to tooth (or surgical site)

Question 25

Long buccal anaesthesia

Answer 25

For molar and premolar extractions and buccal surgery

1. 1/4 of cartridge over external oblique ridge, disto-buccal to third molar (after IA and lingual block)
2. Infiltration immediately disto-buccal to surgical site

Question 26

Never event

Answer 26

Never Events are serious incidents that are entirely preventable because guidance or safety recommendations providing strong systemic protective barriers are available at a national level, and should have been implemented by all healthcare providers
Reported within 48 houts
Preventable