LA

Question 1

Why do we use LA?

Answer 1

• Pain control
• Control bleeding
• Symptom relief for those with facial pain

Question 2

How does LA work within a nerve cell?

Answer 2

Unionised LA are lipid soluble so can diffuse across the lipid cell membrane.
Once inside the nerve cell, the LA molecule comes ionised due to the pH within the cell being lower and then block the sodium channels.

Question 3

Why might LA affect cells differently?

Answer 3

Type of sodium channel
Myelination or not 
Size of nerve 
Length of each nerve 
Depth of nerve fibre
Distribution of Na+ and K+ channels of each nerve 
Inflamed nerve

Question 4

What is the structure of an LA molecule?

Answer 4

Hydrophobic aromatic ring

Hydrophilic amine group

Question 5

What are the two types of LA and where are they metabolised?

Answer 5

Amides - metabolised by the liver

Esters - metabolised by plasma cholinesterases

Question 6

What is the only type of LA which is an ester?

Answer 6

Benzocaine (used in topical)

Question 7

What affects the speed of action of the LA?

Answer 7

• Tissue pH
• pKa of anesthesia
• Diffusion distance to nerve
• Concentration of LA
• Lipid solubility

Question 8

Why do we add a reducing agent to LA?

Answer 8

Prevent degradation of the vasoconstrictor by reducing the amount of oxygen there is to react with adrenaline

Question 9

Why may some patients need to use prilocaine with felypressin?

Answer 9

• Patients with heart conditions

- Patients who are allergic to other LA types

Question 10

Why is articaine more effective than lidocaine?

Answer 10

It is double the concentration

Question 11

Where is articaine metabolised?

Who is this good for?

Answer 11

Metabolised by plasma esterases in surrounding cells (even tho it is an amine).

Good for those with liver disease where the dose needs to be reduced.

Question 12

Why do we not use articaine for a block?

Answer 12

Higher concentration so said to increase the risk of nerve damage.

Question 13

What do we use an extra short needle for?

Answer 13

Intra-ligamentary injection

Question 14

What nerves does the mandibular nerve go into?

Answer 14

Lingual
Buccal
Inferior alveolar

Question 15

What nerve supplies the maxilla palatal gingiva?

Answer 15

Nasopalatine

Anterior palatine

Question 16

What supplies the buccal gingiva of the maxillary arch?

Answer 16

Buccal nerve 3-8 and infraorbital nerve 3-1

Question 17

What technique of LA uses a supra periosteal injection?

Answer 17

Infiltration

Question 18

Should we bevel our needle towards or away from bone? Why?

Answer 18

Towards - reduce trauma to soft tissue and discomfort for patient

Question 19

What do we need to make sure we have done before injecting with a buccal infiltration?

Answer 19

Hit bone and then retract before injecting

Question 20

When we do an maxillary extraction, how much of the cartrige do we give buccally and how much apaltally?

Answer 20

3/4 buccal and 1/4 palatally

Question 21

Why do we give the palatal infection between the midline raphe and the attached mucosa?

Answer 21

Most fleshy part so is the most comfortable

Question 22

Why do we give interpapillary injections?

Answer 22

To avoid palatal injections (advance needle towards the palate)

Question 23

When do we give an intraligamentary injection?

Answer 23

• When the tooth has periodontal infection

Question 24

Why do we stretch the mucosa before injecting?

Answer 24

Less [painful to penetrate with needle

Question 25

What LA do we use for extraction of a mandibular second molar?

Answer 25

ID block and long buccal block

Question 26

What are the main complications of LA?

Answer 26

- Failed LA - Trismus - Prolonged anaesthesia - Pain on injection - Needle breakage - Infection - Soft tissue injury

Question 27

Why does an abscess affect LA effectiveness?

Answer 27

- Reduced pH of tissue = less dissociation of LA molecules once injected - Less ionised LA molecules to block to Na+ channels - Increase in blood supply during infection to the area causing wash out of the anaesthetic

Question 28

Why it is hard to anaesthetise a tooth with irreversible pulpitis?

Answer 28

- Hyperalgesic pulp (increased pain)

Question 29

What technique can cause prolonged anaesthesia?

Answer 29

- Inferior alveolar nerve block

Question 30

What is the difference between prolonged and persistent anesthesia?

Answer 30

Prolonged anaesthesia = lasts days to months | Persistent anaesthesia = permanent nerve damage resulting in change in sensation to area (numb, tingling or burning)

Question 31

What are some systemic complications of LA?

Answer 31

- Intravascular injection - Allergy - Toxicity - Vasovagal

Question 32

What teeth does buccal infiltration work in mandibular teeth?

Answer 32

up the second premolar

Question 33

If we do an intra papillary injection, what other injection can we avoid?

Answer 33

Palatal injection

Question 34

What question can we ask a patient to see if an ID block has worked?

Answer 34

Is your lip and chin numb?

Question 35

How do we know if we have our needle in a nerve?

Answer 35

Patient will feel sharp electric shock

Question 36

What can we inject into which will give the patient a facial palsy?

Answer 36

Parotid gland (facial nerve running through)

Question 37

What LA do we give for a lower third molar extraction?

Answer 37

ID block & buccal nerve block

Question 38

When do we need to use block anaesthesia?

Answer 38

- When anesthesia is required over a larger area - Where bone is porous and LA cannot diffuse in - If there is an abscess near sight of infection inhibiting a buccal infiltration

Question 39

What two nerves does a mental nerve anathetise?

Answer 39

- Mental nerve | - Incisive nerve

Question 40

What soft tissue does a buccal nerve block anaethetise?

Answer 40

Buccal soft tissues distal to second premolar