overview + inferior alveolar nerve block (IANB)

why are mandibular injections more difficult than mx?

b/c md cortical bone is thick and dense, anesthetic cannot diffuse through it well

result: md infiltrations often fail, so nerve blocks are usually needed instead

key mandibular injections

inferior alveolar nerve block

long buccal block

mental block

incisive block

gow-gates block

supraperiosteal injection

periodontal ligament (PDL) injection

what is another name for the inferior alveolar nerve block

mandibular block

what is the purpose of an IANB?

to anesthetize the mandibular teeth and associated periodontium, lingual soft tissue to the midline, and facial soft tissue anterior to the mandibular first molar

which nerves are anesthetized during an IANB

inferior alveolar nerve

incisive nerve

mental nerve

lingual nerve (usually)

which cranial nerve gives rise to the inferior alveolar nerve

CN V3 (md division of the trigeminal nerve)

what sttructures become numb after an IANB

md teeth to the midline

body of the mandible

inferior part of the ramus

buccal mucosa anterior to the mental foramen

anterior 2/3 of the tongue

floor of the mouth

lingual soft tissues and periosteum

when is an IANB indicated

to numb one quadrant

when is an IANB contraindicated

infection or acute inflammation at the injection site

patients likely to bite their lip or tongue afterward (young children and patients unable to understand numbness)

biggest advantage of an IANB

one injection anesthetizes a large area

biggest disadvantages of an IANB

high failure rate

landmarks difficult to locate

highest positive aspiration rate

large area stays numb

patients may bite lip/tongue

cross-innervation or bifid canals can cause incomplete anesthesia

which injection has the highest positive aspiration rate?

IANB

positive aspiration: 10-15%

why is the IANB considered one of the least reliable injections

b/c landmarks vary between patients, anatomy is inconsistent, the inferior alveolar nerve is difficult to reach precisely

why might an IANB fail even if your technique is correct?

cross-innervation

bifid mandibular canal

bifid inferior alveolar nerve

missed landmarks

needle deposited too far from the nerve

what is bifid and why is it important

bifid means split into two branches

a pt may have a bifid inferior alveolar nerve or mandibular canal, meaning there are two nerve pathways instead of one

clinical significance: an IANB may only anesthetize one branch and some teeth may remain sensitive → partial anesthesia or an apparent failed IANB despite correct technique