Head and Neck Anatomy in Relation to LA

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Head and Neck Anatomy inRelation to Local Anaesthesia

Dr Heather Apthorpe

Bdent 2

A preparatory lecture of essentialknowledge prior to Local Anaesthesia

RCA


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Knowing your anatomy is a

pre-requisite for administering LA


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From :Abrahams, Boon, Spratt.2008. Mc Minn’s Clinical Atlas of Human Anatomy 6th Ed


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From:Abrahams,Boon,Spratt.2008

. Mc Minn’sClinical

Atlas ofHuman

Anatomy

6th Ed


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Blood supply to the headCommon carotid artery divides toInternal carotid-supplies brain,eye and carries sympatheticplexus.External carotid gives offbranches-Superior thyroid a.

Lingual a. supplies tongue (2)Facial a. supplies face (includingfacial expression muscles) (3)Occipital a.(runs posteriorly andexits behind mastoid to supplyoccipital area)Maxillary a.(deep to neck of

condyle)Superficial temporal a. (suppliesscalp) (4).


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Venous drainage of the head and

neck

Be aware of theposition of theveins and thedirection of venousdrainage.

Also position of theInferior AlveolarVein in mandibleand Pterygoidplexus -

(in Pterygopalatine fossa)


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Sensory Nerve supply

As dental clinicians you will be mostinvolved in anaesthesia of the teethand oral region.

The cranial nerve that you are aboutto form a life long relationship with,is the Trigemminal Nerve (CNV).

In order to deal with it effectively, itis necessary to know it thoroughly.


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Trigemminal Nerve CNV

Largest cranial nerve, made up of 3 divisions:Ophthalmic,Maxillary,Mandibular

Sensory to the face, scalp, nose, mouth andteeth (via Div 1,2&3)

Small motor component to muscles ofmastication (via Div 3 only)Contains 4 nuclei in the brain:Sensory-

1. spinal nucleus in the medulla2. mesencephalic nucleus in the midbrain3. pontine (chief) sensory nucleus in the pons

Motor-1. motor nucleus in the pons


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Ophthalmic nerve CNV1

Smallest division

Supplies sensory innervation to orbit,lacrimal gland, nose and skin of theeyelids and forehead

Enters orbit through superior orbitalfissure

Divides into lacrimal, frontal,nasociliary branches


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Ophthalmic nerve (CNV1)

Haglund, Evers. Local anaesthesia in dentistry , 5th Ed, 1984, AstraLakemedel


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Maxillary nerve (CNV2)


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Divides into 4 branches:infraorbital, zygomatic, superior alveolar , palatine.

Infraorbital n. enters infraorbital groove and exits at

infraorbital foramen on maxilla. Supplies skin of

lower eyelid, front of cheek, side of the nose.

Zygomatic n. has 2 branches:

zygomaticotemporal :

(supplies skin of the temple) and

zygomaticofacial

(supplies skin over cheekbones)


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Dental and sinus branches

Superior alveolar n. has threebranches: posterior, middle andanterior.

Supply the maxillary teeth and buccalgingiva and buccal vestibule.

supply the maxillary sinus for sensoryinnervation.

Explains ‘tooth pain’ in sinusitis.


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Palatine n. divides into:greater and lessor palatine nerves

nasal branches

enters greater palatine canal in maxilla

nasal branches supply nasal mucosagreater palatine supplies posterior hard

palate and gingiva (to level of canine teeth)

lessor palatine nerves supply soft palate

nasopalatine n. is terminal branch of one ofthe nasal branches. It supplies soft tissue onanterior part of hard palate (13-23)


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Maxillary nerve- another view


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Posterior, middle and anterior superioralveolar branches of maxillary nerve.

•Howe, Whitehead, Local anaesthesia in dentistry 1st Ed, 1972, JohnWright and Sons.


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Anterior, middle and posterior superior

alveolar branches maxillary nerve

•Haglund, Evers. Local anaesthesia in dentistry , 5th Ed, 1984, AstraLakemedel.


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Maxillary Anterior teeth

The anterior superior alveolar nerve innervates– The incisors,– canines,– the buccal gingiva and– the periosteum

Important: The nerves anastomose over the midline

The medial spread of L.A. may be hindered bythe labial frenulum in the midline.

The nasopalatine nerve innervates– The palatal gingiva,– The palatal mucosa and

– The palatal periosteum of the incisors and canine.

– Emerges from the bone through the incisive or nasopalatineforamen.


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Maxillary anterior teeth

The anterior superioralveolar nerveinnervates– The incisors,– canines,– the buccal gingiva and– the periosteum

Important: Thenerves anastomose overthe midline

The medialspread of L.A. may behindered by the labialfrenum in the midline.


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Variations in depth of needle placement in infiltration

anaesthesia

Aim is to position the needlehorizontally adjacent to theapex of the tooth root, toallow the solution to reach thenerve as it leaves the tooth

Deep buccal sulcus meansfairly superficial placement ofneedle tip under mucosa

Shallow buccal sulcus meansthe needle needs to penetratefurther in order to be placedadjacent to the root apex


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Author’s own photo October ‘08


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Maxillary pre-molar teeth

The middle superioralveolar nerve(The superior dental plexusis formed by convergentbranches from theposterior, middle and

anterior superior alveolarnerves. The presence ofthe middle superioralveolar nerve is irregular)Innervates:– The maxillary premolars

– the buccal gingiva and– the periosteum of the

alveolar ridge

Howe, Whitehead, Local anaesthesiain dentistry 1st Ed, 1972, John

Wright and Sons.


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Author’s own photo July ‘08


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Maxillary molar teeth

The Posterior SuperiorAlveolar Nerves:branch off the maxillarynerve down the posteriorsurface of the maxilla,which they enter to

innervate– the upper molars,– the buccal gingiva and– Periosteum over the

buccal surface of alveolarridge.

Howe, Whitehead, Local anaesthesiain dentistry 1st Ed, 1972, JohnWright and Sons.


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Branches of the mandibular nerve in

relation to the mandible.


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Mandibular nerve CNV3Both sensory and motor

Motor to muscles ofmastication, mylohyoid,anterior belly of digastric,tensor tympani, tensor velipalatini.

Sensory to anterior twothirds of tongue, floor ofmouth, buccal mucosa,mandibular teeth, skin oftemporal region, lateralcheek, mandible (not atangle-cervical plexus), chin

and lower lip.

Emerges from cranialcavity through foramenovale into infratemporalfossa, where it branches.


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Mandibular incisor teeth

The incisive nerve– (a distal branch of the

inferior dental nerve)innervates the

– canine and– incisor teeth, and

– the first premolar

– the teeth from 33 to 43can be anaesthetised byinfiltration or bymandibular block.

From; Howe and Whitehead, Local

Anaesthesia in dentistry, 1972, Wright &

Sons Ltd p65


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Mental nerve- branch of IAN

The mental nerveinnervates– the buccal gingiva , the lip

and– the periosteum of themandibular incisors and firstpremolars

Not the lowerincisor teeth.They are innervated by theIAN.The nerve exits through themental foramen.

The mental nerve will also beblocked by the IAN injection.It can be anaesthetised aloneby infiltration next to thenerve as shown at left.


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Mental NerveInnervates thebuccal and labialmucosa from 33 tomidline and from 43to midline. Nocrossover at themidline.Innervates the lowerlip on that side tothe corner of themouth.

Can beanaesthetised at themental foramen orvia IAN block.

You can alsoanaesthetise themandibular premolarteeth by mentalnerve block if the

anaesthetic solutionis placed closeenough to theforamen.

This is very easywhen using ‘Septanest’ LA(Articaine).


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Inferior Alveolar Nerve Block

A nerve block that depositsLA at the opening of themandibular canal on theinside of the mandible inorder to anaesthetise theinferior alveolar nerve.

Area of anaesthesia:

all mandibular teeth on thatside to the midline.lower lip, labial mucosa (tocorner of mouth), labial

gingiva and periosteumover teeth from 1st premolarto central incisor..


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Variations in the mandible topography

The level of themandibular foramenvaries depending onage and degree ofedentulism.For this reason it isoften useful topalpate the anteriorand posterior bordersof the ascendingramus because thetip of the needle is

going to be aimed toend up approximatelymidway between thefinger and thumb

From;Howe and Whitehead, Local Anaesthesia in dentistry, 1972, Wright & Sons Ltd p63


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Inferior Alveolar Nerve Block Horizontal

Angulation

The barrel of the

syringe should

usually lie over the

premolar teeth on

the opposite side.


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Inferior Alveolar Nerve Block

Palpation of coronoid notch on anterior

border of mandible.

Insertion of long needle using ‘safe’

method with mirror to retract tissues.

Red line represents another possible

entry point for the needle.


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Long Buccal Nerve

The long buccal nerve(CNV3) innervates themucosa of the cheek,vestibule and gingivaadjacent to themandibular molar teethas far forward as thesecond pre-molar tooth.A separate injection isrequired whendisturbing the buccalvestibule mucosa egwhen extracting a lower

molar tooth. You caneither inject next totooth or do buccal nerveblock.

IAN

block

buccal

nerve

block


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Lingual nerve

The Lingual nerveinnervates– the lingual gingiva and– periosteum of the

mandibularteeth from 38 to 31 and 48

to 41

Coronal section showing

position for anaesthetisingthe lingual nerve

Pterygomandibular

raphe

U f IAN Bl k f L l


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Uses of IAN Block for Local

Anaesthesia on mandibular teeth

Cavity Preparations and Pulp Surgery(Endodontics)The IAN block is used and no blocking of

the lingual nerve is necessary.

Surgical Procedures – example: exodontia

The IAN block should be supplemented by adeposition of solution at the lingual nerve.

The soft tissues surrounding the molars areanesthetized by blocking the long buccal nerve.

Deep scaling and periodontal procedures

The IAN block should be supplemented bysolution deposition at the lingual and long buccalnerves.


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Thank you for your attention


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Head and Neck Anatomy in Relation to LA

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