An introduction to Local Anaesthetic contents, instruments, basic pharmacology and mechanism of action, methods of delivery and complications

1. LOCAL ANAESTHESIA IN DENTAL
PRACTICE
Dr. Christis Isseyegh

2. What is a local anaesthetic?
 A local anaesthetic is a drug used to reversibly
prevent the transmission of nerve impulses in the area
where it is applied, without affecting consciousness.

3. How do local anaesthetics work?
 Induce loss of sensation hence locally
preventing pain in a well-defined area of the
body.
 When propagation of a nerve impulse is
prevented, then there can be no
sensation/impulse reaching the CNS/brain.
 Local anaesthetics-LAs- are eliciting their
conduction-blocking effects by reversibly
blocking the movement of sodium inside the
nerve axon required for action potentials.

5. Some more details
 Local anaesthetics reversibly block the
movement of sodium in and out of the cell at the
region where they are applied.
 Without sodium, there can be no nerve
depolarisation hence no action potentials
propagate.
 Lack of action potentials/impulses implies LOSS
OF SENSATION which includes the absence of
PAINFUL sensations.

6. No action potentials = No impulses
http://esciencecentral.org/ebooks/minimally-invasive/images/anesthesia-cosmetic-procedures-image-2.jpg

7. Types of Local Anaesthetics:
 There are two main types of local
anaesthetics: AMIDES & ESTERS.
 All made up of three main components:
 A lipophilic/hydrophobic aromatic
compound.
 An intermediate chain/linage which can be
either an ester or an amide [This is the part which allows
the distinction between the esters and the amides].
 A hydrophilic amine.

8. Amide vs. Ester
http://media.dentalcare.com/images/en-US/education/ce449/fig03.jpg

9. Amide vs. Ester
 Esters are easily broken down by pseudocholinesterase
in the plasma therefore they have a much shorter
duration of action.
 Amides are stable in plasma and they are only broken
down in the liver. Have lower potential to produce
allergic reactions than esters.
AMIDES ESTERS
Lignocaine / Lidocaine Procaine [Novacaine]
Bupivacaine Benzocaine [Topical 20%]
Prilocaine Cocaine [Rarely employed these
days]
Articaine Amethocaine [Skin topical]
Mepivicaine --

10. Contents of an LA cartridge:
 Local anaesthetic drug.
 Vasoconstrictor +/-.
 Reducing agent: Used to
stabilize the vasoconstrictor so
it doesn’t get oxidised.
 Preservatives.
 Fungicide.
 Isotonic solution: Modified
Ringer’s solution.
http://media.dentalcare.com/images/en-US/education/ce364/fig01.jpg

11. Lidocaine 2% [20mg/ml]:
 Most common.
 Gold Standard – Used for over
50 years in dentistry.
 Lignospan/xylocaine.
 1:80,000 adrenaline as a
vasoconstrictor.
 Max. Dose = 500mg or 11x2.2ml
cartridges for a 70kg man.
 Pulpal anaesthesia: 45 minutes.
 Soft tissues: 2-3 hours.
 Half life: 90 minutes.
 Topical preparations exist.
http://www.septodont.co.uk/sites/default/files/Lignospan-Special-photo.jpg

12. Prilocaine 3%:
 Citanest.
 Contains felypressin
[octapressin] as a
vasoconstrictor.
 Latex-free bung.
 Max. Dose=400mg.
 4% solution exists which is
useful in vasoconstrictor-free
anaesthesia.
 Half Life: 90 minutes
 EMLA topical gel: Prilocaine
2.5% + Lidocaine 2.5%.
http://www.nextdental.com/systhumbs/images/thumbs/
productvariantdetailmain-0003617_1000.jpeg

13. Articaine 4%
 Available with either 1:100,000 or 1:200,000
adrenaline.
 More effective than lidocaine 2% when used as
buccal infiltration to anaesthetise the lower 6’s
and lower incisors.
 MUST NOT be used for nerve blocks because it
can cause temporary or permanent
paraesthesia.
 Can penetrate bone more than other LA
agents, hence given buccally in patients with
coagulation defects to avoid ID blocks.

14. Articaine 4%
 Metabolised more quickly
than other dental LA agents.
 Metabolised partially by
plasma.
 Half-life: 20 minutes.
 Advantage in relation to
reduced toxicity if repeated
injections are required for a
long procedure.
 Max. Dose = 500mg, hence
about 5 cartridges.
http://www.dimensionsofdentalhygiene.com/uploadedImages/
DDH/Magazine/2012/03_March/Features/ppx06.jpg

15. Mepivicaine
 Two types of
formulation available
in UK.
 2% [20mg/ml] with
1:100,000 adrenaline
[Scandonest].
 3% [30mg/ml] plain
solution useful if
vasoconstrictor-free
LA is required. http://www.septodont.co.uk/sites/default/files/Scandonest2-Special.jpg

16. Vasoconstrictors
Adrenaline:
 Naturally occurring hormone.
 Gives more profound
anaesthesia.
 Improves control of
haemorrhage, especially in
infiltration type anaesthesia.
 Reduces systemic absorption
hence:
 Prolongs the duration of pulpal
anaesthesia.
 Reduces the toxicity [hence we
can probably inject more].
http://thumbs.dreamstime.com/z/structure-adrenaline-29160062.jpg

17. Vasoconstrictors
Felypressin:
 A synthetic octapeptide.
 Similar to the pituitary
hormone vasopressin.
 In dental LA added as
0.03IU/ml to 3%
Prilocaine=Citanest.
 Not as effective as
adrenaline hence poorer
haemorrhage control.
 Does not have the
unwanted effects of
adrenaline i.e. palpitations.
http://www.polypeptide.com/web/upload/products/big/141087184054183220aff5d.png

18. Complications with vasoconstrictors:
 Adrenaline can induce tachycardia/fainting.
 Adrenaline is contraindicated in patients with
unstable hypertension and unstable angina.
 Adrenaline is contraindicated in patients
taking Monoamine Oxidase Inhibitors-
MAOIs.
 Felypressin is contra-indicated in the late
pregnancy stages.

19. Needle Choice:
 Needle length has to be enough to reach the
area required depth before its complete depth
has entered the tissues:
 Short needle 25mm for infiltration.
 Long needle 35mm for ID block.
 Needle gauge gives a measure of needle
thickness:
 30 is thinner and is used for infiltration LA.
 25-27 is thicker and is used for an inferior alveolar
nerve block, because it deflects less within the
tissues.

20. Cartridge check:
 Made-up of a cap, cylinder and plunger.
 Check if it’s the correct medication.
 Check the expiry date and any visible
damage.
 Check for air bubbles in the solution.
 Check for cloudiness as this may indicate a
bacterial infection.
http://media.dentalcare.com/images/en-US/education/ce364/fig01.jpg

21. Trigeminal Nerve Anatomy CN-V
http://www.frca.co.uk/images/trigeminal_nerve_general.jpg

22. CN-V2 Maxillary Division
http://www.frca.co.uk/images/maxillary_branch.jpg

23. CN-V3 Mandibular Division
http://www.frca.co.uk/images/mandibular_branch.jpg

24. Innervation of teeth and
soft tissues

25. Choice of anaesthesia
 Depends on the tooth that needs to be
anaesthetised.
 Maxillary [Infiltration].
 Mandibular [Nerve Block].
 Depends on the type of treatment you are going
to carry out.
 Extractions: All nerves in the area need to be
anaesthetised. Main supply plus accessory nerves!
 Restorative / Perio: Usually sufficient to block main
nerve supply.

26. Infiltration vs. Nerve Block
Infiltration Nerve Block

27. Infiltration Anaesthesia
 Act locally to provide good LA.
 Effective on local soft tissues.
 Act on teeth where bone is reasonably thin.
 Used for upper teeth mainly and lower
anterior teeth.
 Anaesthetic diffuses through alveolar bone to
root apex.
 Not as effective on posterior mandibular
teeth due to the thick cortical bone.

28. Buccal Infiltration
http://pocketdentistry.com/wp-content/uploads/285/QE06_Meechan_fig041b.jpg
Injected deep into vestibular fold

29. Palatal Infiltration
http://www.nysora.com/files/2013/oral-maxillofacial-regional-anesthesia/16.jpg

30. Nerve Block Anaesthesia
 Anaesthetic delivered to major nerve.
 Blocks all sensation downstream of the injection
site.
 The more proximal the block, the greater the
area affected.
 Commonly used nerve blocks in dentistry:
 Inferior alveolar nerve block.
 Mental nerve block.
 Lingual nerve Block.
 Long buccal nerve block.
 Greater Palatine nerve block.
 Nasopalatine nerve block.

31. Inferior alveolar nerve block
Nerves Affected:
 Inferior alveolar nerve.
 Mental Nerve [ & incisive nerve].
Target Area:
 Mandibular foramen [within the pterygoid
space].
Tissues Anaesthetised:
 All mandibular teeth; skin of chin; labial mucosa
and lower lip. Left or right depending on side of
injection.

32. Anatomical Landmarks:
 Coronoid notch.
 Pterygomandibular raphe.
 Occlusal plane for mandibular posteriors.
DirectTechnique:
 Palpate and identify injection site.
 Advance needle from contralateral premolars,
horizontally 1cm above the occlusal plane.
 Needle goes in 2-2.5cm, hit bone, retract needle
1mm, aspirate, inject slowly.
Inferior alveolar nerve block

33. Inferior alveolar nerve block
http://www.jcda.ca/uploads/c127/fig1.jpg
http://www.pitt.edu/~regional/Dental%20Blocks/Image93.jpg

34. Inferior alveolar nerve block
https://cchungdentalis.files.wordpress.com/2013/04/mandibular-nerves-block-1.jpg

35. Mental Nerve Block
Nerves Affected:
 Mental Nerve and
incisive nerve.
Injection site:
 Mental Foramen.
Tissues Anaesthetised:
 Mandibular incisors
and canine; labial
gingiva; skin of chin. https://cchungdentalis.files.wordpress.com/2013/04/mandibular-nerves-block-3.jpg

36. Lingual Nerve Block
Nerves Affected:
 Lingual nerve.
Injection site:
 Anterior to inferior alveolar site. Similar
technique.
Tissues Anaesthetised:
 Mucosa of anterior 2/3 of tongue.
 Lingual alveolar mucosa and lingual gingivae
of all teeth ipsilateral to the injection side.

37. Long Buccal Nerve Block
Nerves Affected:
 Long buccal nerve.
Injection site:
 Retromolar fossa.
Tissues Anaesthetised:
 Skin and mucus
membrane of cheek.
 Buccal alveolar mucosa.
 Gingivae of molars.
 Ipsilateral to injection side. https://cchungdentalis.files.wordpress.com/2013/04/mandibular-nerves-block-2.jpg

38. Greater Palatine Nerve Block
Nerves Affected:
 Greater Palatine Nerve.
Injection site:
 Greater Palatine
Foramen [can be
palpated].
Tissues Anaesthetised:
 All hard palatal mucosa
and gingiva posterior to
maxillary canines.
 Ipsilateral to injection
side.
https://cchungdentalis.files.wordpress.com/2013/02/maxillary-local-anesthesia-5.jpg

39. Nasopalatine Nerve Block
Nerves Affected:
 Nasopalatine Nerve.
Injection site:
 Mouth of incisive foramen
[posterior to incisive
papilla].
Tissues Anaesthetised:
 Palatal mucosa and
gingiva anterior to
maxillary canines.
 Bilateral
https://cchungdentalis.files.wordpress.com/2013/02/maxillary-local-anesthesia-6.jpg

40. Complications of LA
 Pain, swelling [LA into muscle].
 Spread of acute infection.
 Facial Nerve Palsy [LA into parotid gland].
 Bleeding.
 Allergy [very rare].
 Trauma to anaesthetised tissues.