0

Frances Zhao

Local Anaesthesia

Course

Frances Zhao

1

Frances Zhao

Contents Part 1: Introduction & Neurophysiology ............................................................................................................................ 12

Methods of inducing LA ....................................................................................................................................................... 12

First LA ................................................................................................................................................................................. 12

Neurons ............................................................................................................................................................................... 13

Nerve structure .................................................................................................................................................................. 14

Neurophysiology ............................................................................................................................................................... 14

Ionic concentrations ......................................................................................................................................................... 15

Electrophysiology of nerve conduction .............................................................................................................................. 15

Electrophysiology of Nerve Conduction ........................................................................................................................ 15

How does a nerve conduct an impulse? ............................................................................................................................ 16

Modes and action of local anaesthetic .............................................................................................................................. 16

Classification of LA substances according to biologica site and mode of action ..................................................... 17

Sequence of mechanism of action of LA ........................................................................................................................... 17

Local anaesthetic molecules ................................................................................................................................................ 17

pKa and pH ............................................................................................................................................................................ 18

Dissociation of LA.................................................................................................................................................................. 18

Actions on nerve membranes .............................................................................................................................................. 18

Membrane action of LA .................................................................................................................................................... 18

Barriers of Diffusion of the Solution ............................................................................................................................... 19

pKa and LA ......................................................................................................................................................................... 19

Why do LA not work well in infected tissues? ............................................................................................................... 19

Induction of Local Anaesthesia ....................................................................................................................................... 20

Blocking process ............................................................................................................................................................ 20

Induction time ............................................................................................................................................................... 20

Factors affecting local anaesthetic action ...................................................................................................................... 21

Recovery from LA Block ................................................................................................................................................... 21

Duration of Anaesthesia ................................................................................................................................................... 21

Part 2 : Pharmacology ........................................................................................................................................................... 22

✓Ester-Type ................................................................................................................................................................... 22

✓Amide-Type ................................................................................................................................................................. 22

Pharmacokinetics of Local Anaesthetics ........................................................................................................................ 22

Pharmacokinetics of local anaesthetics .............................................................................................................................. 22

2

Frances Zhao

Pharmacokinetics of local anaesthetics .................................................................................. Error! Bookmark not defined.

✓Metabolism (Biotransformation) .................................................................................................................................. 23

✓Metabolism of ESTERS ................................................................................................................................................... 23

✓Metabolism of AMIDES ................................................................................................................................................. 23

✓Excretion .......................................................................................................................................................................... 23

Systemic Effects of LA ........................................................................................................................................................... 24

✓Central Nervous System ............................................................................................................................................ 24

Systemic Effects of LA ............................................................................................................... Error! Bookmark not defined.

Other Systemic Effects of LA .................................................................................................... Error! Bookmark not defined.

Vasoconstrictors .................................................................................................................................................................... 25

Chemical structure ................................................................................................................................................................ 26

Mode of action ...................................................................................................................................................................... 26

Vasoconstrictors commonly used ................................................................................................................................... 27

Overdose ................................................................................................................................................................................ 27

Medical Status of Patient ..................................................................................................................................................... 27

Adrenaline –maximum doses .............................................................................................................................................. 28

LA commonly used in Australia ........................................................................................................................................... 28

Lignocaine 2% with Adrenaline 1:80,000 ....................................................................................................................... 28

Prilocaine 3% with Felypressin (Octapressin) ................................................................................................................ 29

Articaine 4% with Adrenaline 1:100,000 ......................................................................................................................... 29

Mepivacaine 3% ................................................................................................................................................................ 30

Bupivacaine 0.5% with Adrenaline 1:200,000 ................................................................................................................ 30

Variability in LA duration ...................................................................................................................................................... 31

variability in LA duration ...................................................................................................... Error! Bookmark not defined.

Calculation of maximum dose ......................................................................................................................................... 31

Adrenaline - Maximum doses.......................................................................................................................................... 32

Contraindications of Local Anaesthetics ........................................................................................................................ 32

Anaesthetics for Topical Application .............................................................................................................................. 32

What factors should be considered when selecting a local anaesthetic? .................................................................. 32

Part 3 : Armamentarium ....................................................................................................................................................... 33

Types of Syringes .............................................................................................................................................................. 33

Non-disposable Aspirating Syringes .............................................................................................................................. 33

Non-disposable Self-aspirating Syringes ....................................................................................................................... 34

3

Frances Zhao

Non-disposable Pressure Syringes ................................................................................................................................. 34

Non-disposable “Jet Injector” .......................................................................................................................................... 35

Disposable Syringes .......................................................................................................................................................... 35

“Safety Syringes” ............................................................................................................................................................... 35

Computer-controlled LA Delivery ................................................................................................................................... 36

Problems with Syringes .................................................................................................................................................... 36

Needle Parts ....................................................................................................................................................................... 36

Needle Gauge and Length ............................................................................................................................................... 37

Needle Gauge and Length ............................................................................................................................................... 37

Problems with Needles ..................................................................................................................................................... 37

One-handed Scoop Technique ....................................................................................................................................... 38

Recommended Needles ................................................................................................................................................... 38

Discharging needles ......................................................................................................................................................... 39

Components of a Cartridge ............................................................................................................................................. 39

Cartridge Content ............................................................................................................................................................. 39

Care and Handling ............................................................................................................................................................ 39

Additional Armamentarium ............................................................................................................................................. 40

Preparation of Armamentarium ...................................................................................................................................... 41

Syringe Preparation .......................................................................................................................................................... 41

Placing an additional cartridge ....................................................................................................................................... 41

Part 4: Patient Evaluation and Basic Technique ............................................................................................................... 43

Medical History .................................................................................................................................................................. 43

Medical Questionnaire ..................................................................................................................................................... 43

Common Medical Conditions .......................................................................................................................................... 44

Medical Questionnaire (Cardiovascular) ........................................................................................................................ 44

Categorisation of Drugs in Pregnancy ........................................................................................................................... 44

Physical Examination ........................................................................................................................................................ 45

Adult Blood Pressure Guidelines ..................................................................................................................................... 45

ASA Classification and Dental Modifications ................................................................................................................. 46

Physical Examination ........................................................................................................................................................ 46

Stress reduction protocol ................................................................................................................................................. 46

Contra-indications for LA ................................................................................................................................................. 46

Ratings of Drug Interactions ............................................................................................................................................ 47

4

Frances Zhao

Local Anaesthetic Drug Interactions ............................................................................................................................... 47

Vasoconstrictor Drug Interactions .................................................................................................................................. 47

✓ VC and Monoamine-oxidase inhibitors - MAOIs (SR 5) ....................................................................................... 48

✓ VC and non-selective β-adrenoceptor antagonist (βblockers) (SR 1) ................................................................ 48

✓ VC and General Anaesthetic (SR 1) ......................................................................................................................... 48

✓ VC and Cocaine (SR 1) .............................................................................................................................................. 48

✓ VC with antipsychotic or α-adrenoceptor blocker (SR 4)..................................................................................... 48

✓ VC with adrenergic neuronal blocker - phenotiazine (SR 4) ............................................................................... 48

✓ VC (epinephrine) with thyroid hormone - thyroxine (SR 4) ................................................................................. 49

Important Facts related to LA Injections ........................................................................................................................ 49

Basic Injection Technique ................................................................................................................................................. 49

Basic injection technique.................................................................................................................................................. 51

Final Recommendations ................................................................................................................................................... 52

Part 5 : anatomy revision I ................................................................................................................................................... 52

Local Anaesthesia Course: Anatomy Revision I ................................................................................................................. 52

✓ Trigeminal Nerve (V) ..................................................................................................................................................... 52

Trigeminal Nerve - Sensory Root .................................................................................................................................... 53

Trigeminal Nerve - Motor Root ....................................................................................................................................... 53

Intracranial Part ................................................................................................................................................................. 53

✓ Sensory Root .............................................................................................................................................................. 54

✓ Motor Root ................................................................................................................................................................ 54

Ophthalmic Nerve Branches ............................................................................................................................................ 54

Nasociliary Nerve .............................................................................................................................................................. 56

Maxillary Nerve Branches ................................................................................................................................................. 57

Posterior Superior Alveolar Branch ................................................................................................................................. 58

Posterior Superior Alveolar Branch ................................................................................................................................. 58

Posterior Superior Alveolar Branch ................................................................................................................................. 58

Anaesthesia Area ........................................................................................................................................................... 59

Middle Superior Alveolar Nerve ...................................................................................................................................... 60

Anterior Superior Alveolar Nerve .................................................................................................................................... 60

Anterior Superior Alveolar Branch .................................................................................................................................. 60

Infraorbital Nerve - Branches in the Face ...................................................................................................................... 61

Anterior Superior Alveolar ............................................................................................................................................... 61

5

Frances Zhao

Pterygopalatine Nerve ...................................................................................................................................................... 61

Palatine Nerves .................................................................................................................................................................. 62

Greater Palatine Nerve ..................................................................................................................................................... 63

Nasopalatine Nerve .......................................................................................................................................................... 63

Part 6: Anatomy Revision II .................................................................................................................................................. 64

Mandibular Nerve ............................................................................................................................................................. 64

✓ Anterior division ........................................................................................................................................................ 64

✓ Posterior division ....................................................................................................................................................... 64

Anterior Division - Muscular Branches ........................................................................................................................... 64

Anterior Division - (Long) Buccal Nerve ......................................................................................................................... 65

✓ Innervation ................................................................................................................................................................. 65

(Long) Buccal Nerve and Great Auricular Nerve ........................................................................................................... 66

(Long) Buccal Nerve and Great Auricular Nerve ........................................................................................................... 67

Posterior Division .............................................................................................................................................................. 67

Auriculotemporal Nerve ............................................................................................................................................... 67

Inferior Alveolar Nerve ..................................................................................................................................................... 68

✓ Branches in the Infratemporal Fossa ...................................................................................................................... 68

✓ Branches in the Mandibular Canal .......................................................................................................................... 68

Structures around the IAN area ...................................................................................................................................... 68

✓ Medial ......................................................................................................................................................................... 68

✓ Lateral ......................................................................................................................................................................... 68

✓ Posterior ..................................................................................................................................................................... 68

Mylohyoid Nerve ............................................................................................................................................................... 69

Inferior Alveolar Nerve .................................................................................................................................................. 69

✓ Path ............................................................................................................................................................................. 69

✓ Innervation (after mylohyoid nerve) ....................................................................................................................... 69

Mental nerve ...................................................................................................................................................................... 70

Incisive Branches of the IAN ............................................................................................................................................ 71

Lingual Nerve ..................................................................................................................................................................... 71

✓ Path ............................................................................................................................................................................. 71

✓ Innervation ................................................................................................................................................................. 71

Tongue Innervation ........................................................................................................................................................... 72

Overview of Mandibular Nerve ....................................................................................................................................... 73

6

Frances Zhao

Intra-oral Mandibular Innervation Areas – know this by heart!!! ....................................................................... 73

Bones Structures of Relevance ........................................................................................................................................ 73

Part 7: Maxillary Techniques ................................................................................................................................................ 74

Overview of Maxillary Nerve ........................................................................................................................................ 74

Supraperiosteal (Buccal infiltration –most common injection in the maxilla) ........................................................... 75

✓ Indication ................................................................................................................................................................... 75

Where can we use Supraperiosteal? ............................................................................................................................... 76

Where can we use Supraperiosteal? ............................................................................................................................... 76

Supraperiosteal Technique .............................................................................................................................................. 76

Supraperiosteal Technique .............................................................................................................................................. 77

Intraligamental – PDL ....................................................................................................................................................... 77

Intraseptal/Intrapapillary .................................................................................................................................................. 78

Intraosseous ....................................................................................................................................................................... 79

Intrapulpal .......................................................................................................................................................................... 79

✓ Indications .................................................................................................................................................................. 79

✓ Contraindications ...................................................................................................................................................... 79

✓ Advantages ................................................................................................................................................................ 79

✓ Disadvantages ........................................................................................................................................................... 79

Local Infiltrations ............................................................................................................................................................... 80

✓ Indications .................................................................................................................................................................. 80

✓ Technique ................................................................................................................................................................... 80

Anatomy ............................................................................................................................................................................. 80

Maxillary Nerves Anaesthetised ...................................................................................................................................... 81

Maxillary Nerves ................................................................................................................................................................ 81

Posterior Superior Alveolar Nerve .................................................................................................................................. 81

.................................................................. 83

Technique ........................................................................................................................................................................... 83

7

Frances Zhao

Middle Superior Alveolar Nerve ...................................................................................................................................... 84

Anterior Superior Alveolar Nerve .................................................................................................................................... 86

✓ Indications .................................................................................................................................................................. 86

✓ Limitations .................................................................................................................................................................. 86

✓ Alternatives ................................................................................................................................................................ 86

Area anaesthetised ............................................................................................................................................................ 86

✓ Branches on the Face ................................................................................................................................................ 86

Technique 1 - Central Incisor as Reference ............................................................................................................... 87

Technique 2 - Vertical using the 1PM as Reference ................................................................................................. 88

Greater Palatine Nerve ..................................................................................................................................................... 89

Technique ....................................................................................................................................................................... 90

Nasopalatine Nerve .......................................................................................................................................................... 91

Maxillary Nerve .................................................................................................................................................................. 91

...................................................................................................................... 93

It didn’t work!!! .................................................................................................................................................................. 93

Part 8: Mandibular Techniques ............................................................................................................................................ 93

Mandibular Nerves Anaesthetised .................................................................................................................................. 94

Anatomy REMEMBER THIS DIAGRAM!!!! ....................................................................................................................... 94

Inferior alveolar nerve block ............................................................................................................................................ 94

✓ Branches ..................................................................................................................................................................... 95

Inferior Alveolar Nerve Block ........................................................................................................................................... 95

✓ Nerves anesthetised.................................................................................................................................................. 96

✓ Areas anesthetized .................................................................................................................................................... 96

8

Frances Zhao

✓ Advantages ................................................................................................................................................................ 96

✓ Disadvantages ........................................................................................................................................................... 96

✓ Complications / Errors ........................................................................................................................................... 99

✓ Facial Nerve Paralysis in IAN Block (too posterior/deep) .................................................................................... 99

Inferior Alveolar Nerve / Lingual Nerve ......................................................................................................................... 99

Mental Nerve ................................................................................................................................................................... 100

Mental Nerve Block ............................................................................................................... Error! Bookmark not defined.

✓ Advantages/Indication ........................................................................................................................................... 101

✓ Disadvantages ......................................................................................................................................................... 101

Incisive Branches of the IAN .......................................................................................................................................... 102

Anatomy ....................................................................................................................................................................... 102

Alternative Technique - Supraperiosteal ...................................................................................................................... 103

Lingual Nerve ................................................................................................................................................................... 103

Technique 1 –with IAN block ......................................................................................................................................... 104

Technique 2 –floor of the mouth .................................................................................................................................. 104

✓ Buccal Nerve ................................................................................................................................................................ 105

✓ Indications/Advantages .............................................................................................................................................. 105

✓ Disadvantages ............................................................................................................................................................. 105

Technique ......................................................................................................................................................................... 106

(Long) Buccal Nerve and Great Auricular Nerve ......................................................................................................... 106

Gow-Gates Mandibular block ........................................................................................................................................ 107

✓ Target area ................................................................................................................................................................... 107

✓ Reference landmarks-maxillary second molar ........................................................................................................ 107

Vazirani-Akinosi Block .................................................................................................................................................... 108

✓ Indications .................................................................................................................................................................... 108

✓ Technique ..................................................................................................................................................................... 108

✓ Indication ..................................................................................................................................................................... 109

✓ Area Anaesthetised ..................................................................................................................................................... 109

Part 9: Complications .......................................................................................................................................................... 109

Needle breakage and injuries ........................................................................................................................................ 110

Injury to Patient and Administrator .............................................................................................................................. 110

Nerve Injuries ................................................................................................................................................................... 111

✓ Causes ....................................................................................................................................................................... 111

9

Frances Zhao

✓ Management ........................................................................................................................................................... 111

Facial nerve paralysis ...................................................................................................................................................... 111

....................................................................... 112

Facial nerve paralysis ...................................................................................................................................................... 112

Orbital nerves paralysis .................................................................................................................................................. 112

Trismus ............................................................................................................................................................................. 113

✓ Causes ....................................................................................................................................................................... 113

✓ Prevention ................................................................................................................................................................ 113

✓ Management ........................................................................................................................................................... 113

Soft tissue injury .............................................................................................................................................................. 113

✓ Causes ....................................................................................................................................................................... 113

✓ Prevention ................................................................................................................................................................ 113

✓ Management ........................................................................................................................................................... 113

Hematoma ....................................................................................................................................................................... 114

✓ Cause ........................................................................................................................................................................ 114

✓ Management ........................................................................................................................................................... 114

Pain on Injection .............................................................................................................................................................. 114

✓ Pain on insertion ..................................................................................................................................................... 114

✓ Pain on withdrawal .................................................................................................................................................. 114

Burning on Injection ....................................................................................................................................................... 114

✓Causes ........................................................................................................................................................................ 114

✓ Management ........................................................................................................................................................... 114

Infection and Edema ....................................................................................................................................................... 114

✓ Infection ................................................................................................................................................................... 114

10

Frances Zhao

✓ Edema ....................................................................................................................................................................... 114

Tissue Vascular Necrosis ................................................................................................................................................ 115

✓ Causes ....................................................................................................................................................................... 115

✓ Management ........................................................................................................................................................... 115

Systemic effects of LA ..................................................................................................................................................... 115

Classification of Adverse Effects .................................................................................................................................... 115

Overdose - Causes .......................................................................................................................................................... 115

✓ Normal ...................................................................................................................................................................... 115

✓ Liver disfunction ...................................................................................................................................................... 115

✓ Large dose (normal liver) ....................................................................................................................................... 115

✓ Intravascular Injection ............................................................................................................................................. 115

Overdose - Predisposing Factors .............................................................................................................................. 115

Dosage of local anaesthetics ...................................................................................................................................... 116

Adrenaline - Maximum doses .................................................................................................................................... 116

✓ Healthy Patients (ASA I) Maximum dose - 200 micrograms ........................................................................ 116

✓ Sick patients (ASA III and IV) Maximum dose - 40 micrograms ................................................................... 117

LA Overdose - Central Nervous System ....................................................................................................................... 117

LA Overdose - CVS and Respiratory ............................................................................................................................. 117

✓ CVS ............................................................................................................................................................................ 117

✓ Respiratory ............................................................................................................................................................... 117

Management of LA Overdose ....................................................................................................................................... 117

✓ Mild overdose .......................................................................................................................................................... 117

Management of LA Overdose ....................................................................................................................................... 117

✓ Severe overdose ...................................................................................................................................................... 117

Epinephrine Overdose .................................................................................................................................................... 118

Management of Epinephrine Overdose ................................................................................................................... 118

Overdose summary ......................................................................................................................................................... 118

Allergy ............................................................................................................................................................................... 119

Causes of Allergy ......................................................................................................................................................... 119

Prevention of Allergic reactions ................................................................................................................................ 119

Types of allergic reactions.......................................................................................................................................... 119

Progression of Anaphylactic Reaction ........................................................................................................................... 119

Management of patients with alleged LA allergy .............................................................................................................. 119

Management of patients with allergic reactions .............................................................................................................. 120

11

Frances Zhao

✓ Delayed skin reactions ............................................................................................................................................... 120

✓ Immediate skin reactions .......................................................................................................................................... 120

Management of patients with allergic reactions......................................................................................................... 120

✓ Respiratory Reactions Bronchospasm (Asthma) ....................................................................................................... 120

✓ Anaphylactic Reactions Laryngeal edema ................................................................................................................. 120

Emergency Drugs and Equipment ................................................................................................................................ 120

Emergency Plan ............................................................................................................................................................... 121

Minimum Requirements ................................................................................................................................................. 121

Emergency Drugs and Equipment ................................................................................................................................ 121

Medications.................................................................................................................................................................. 121

Emergency Drugs and Equipment ................................................................................................................................ 121

Maxillary Techniques ......................................................................................................................................................... 122

It didn’t work!!! ............................................................................................................................................................. 122

Final Recommendations ................................................................................................................................................. 122

12

Frances Zhao

Part 1: Introduction & Neurophysiology Handbook of local anesthesia fifth edition

Sensation of pressure which comes from a different pathway will not be fully blocked by LA.

You need to be able to identify if the sensation the patient is experiencing is pressure or sharp pain.

Assure the patient that it is just pressure.

Local anaesthesia is defined as a loss of sensation in a circumscribed area of the body caused by a

depression of excitation in nerve endings or an inhibition of the conduction process in peripheral

nerves without a loss of consciousness

Methods of inducing LA Mechanical trauma (server the nerve – we don’t do it! But in some cancer patients the surgeon cut a few

nerves to deal with the pain)

Low temperature

Anoxia (no oxygen)

Chemical irritants

Neurolytic agents such as alcohol and phenol

Chemical agents such as LA

The effect has to be TRANSIENT and COMPLETELY REVERSIBLE.

Desirable properties of a local anaesthetic 1. No local irritation

2. No permanent alternation of nerve structure

3. Low systemic toxicity

4. Effective (complete anesthesia), regardless of whether it is injective or applied locally to mucous

membranes

5. Rapid onset

6. Adequate duration

7. Sufficient potency to give complete anaesthesia without the use of harmful concentrated solutions.

(some drugs have to be used in such high concentrations that it becomes toxic)

8. No allergic reactions (it’s pretty rare to have allergic reactions to LA these days but sometimes you can

have allergic reactions to the stabilizer in the LA)

9. Stable in solution and readily undergo transformation in the body

10. Sterile or capable of being sterilized.

LA history Cocaine – still used by some EMT surgeons

Procaine -- induces a lot of allergic reactions. One of the metabolites is PABA.

Lidocaine – gold standard. Still used today.

Meprivacine

Prilocaine

Bupivacine

Articaine –introduced in Europe in the late 60s. Took a while to become in the rest of the world.

13

Frances Zhao

Neurons

✓Motor Neuron Neuron 1

o motor cortex

Neuron 2

o Brainstem nuclei

o Reaches muscles

✓Sensory Neuron • Unipolar

• Pseudounipolar

✓Interneuron

✓Cell body

• Nucleus + Soma

• Dendrites (synapse with other neurons)

✓Axon

• Myelin sheath

• Node of ranvier

• Terminal bouton (bulbous axon terminal)

✓Peripheral process (Dendrite)

• Connects to receptors

✓Cell body

• Located in the Trigeminal Ganglion

✓Central process (Axon)

• Connects to Neuron 2

Anesthesia works on both motor and sensory neurons.

If you go too deep you can hit the facial nerve and cause facial paralysis on that side of the face.

If you’re talking about LA you want to stop sensory nerves.

Trigeminal ganglion –you’re not actually numbing this but the peripheral nerves.

Cell body Nucleus and soma

Dendrities (synapse with other neurons)

Axons

The nerve is located in the trigeminal ganglion. The peripheral processes will then form the nerve. When we’re

numbing something, we’re actually numbing the axons or peripheral processes of the nerve.

Movement is usually bilateral.

Sensory neurons

1. Neuron 1

Trigeminal ganglion

2. Neuron 2

Brainstem nuclei

14

Frances Zhao

3. Neuron 3

Ntalamus

Reaches sensory cortex

Nerve structure (when you’re talking about nerves, you’re actually talking about collection of axons travelling to

a certain area)

Nerve structure ✓Myelin sheath

• Lipid insulating

• Protein

• Schwann cells nucleus on the outer layer

✓Neuron 2

• Constrictions every 0.5 to 3mm

• Nerve membrane exposed

Myelinated nerves conduct impulses at a much faster rate

Delta nerves are what conduct pain.

Neurophysiology o Two layers of lipid

o Transport proteins

Sodium channels

Potassium channels

o Sodium potassium pump

o Sodium – extracellular (+)

o Potassium – intracellular (-)

o The resting stage –outside of the nerve will be positively charged while inside will be negatively charged.

15

Frances Zhao

Resting state of the neuronal membrane

Ionic concentrations Ion Intracellular Extracellular Ratio

Potassium 110 to 170 3 to 5 27:1

Sodium 5 to 10 140 1:14

Chloride 5 to 10 110 1:11

Electrophysiology of nerve conduction ✓Electrical action potentials

• Increase permeability to Na+

• Delayed increase in perm of K+

✓Types of impulses

• Chemical

• Thermal

• Mechanical

• Electrical Once an impulse is initiated, the amplitude and shape of that impulse remains constant, regardless of changes in the quality or strength of the stimulus.

Electrophysiology of Nerve Conduction ✓Resting potential

• -70mV

• Exterior +; Interior -

✓Slow Depolarization

• -50 to -60mV

• Na+ channels open

✓Rapid Depolarization

• +40mV (complete reversal from negative to positive)

✓Repolariazation

• -60 to -90mV

• K+ channels open

16

Frances Zhao

How does a nerve conduct an impulse? ✓Sequential neuron cell membrane depolarization from:

• Segment to segment: unmyelinated nerves

• Node by node (Saltatory conduction): myelinated nerves

Modes and action of local anaesthetic ✓When? Primary action occurs during the depolarization phase of the action potential

• Decrease, particularly in the phase of slow depolarization. An electrical impulse cannot propagate from that

point onwards. The LA will travel inside the nerve and block the Na channels from the inside so the channels

can’t open up anymore.

NEED TO UNDERSTAND HOW THESE DRUGS WORK

✓Where? LA works by blocking sodium channels, thereby preventing nerve cell depolarization and impulse

propagation

• LA bind to specific receptors on the sodium channel

LA must to be lipophilic—must be able to penetrate the membrane. The more lipophilic the LA is, the stronger it

is.

LA usually has 2 components – cationic and free base components. As soon as you inject the LA into the patient,

they will separate and serve different functions.

17

Frances Zhao

Classification of LA substances according to biologica site and mode of action

Classification Definition Chemical substance

Class A Receptor site on external

surface of membrane

Biotoxins

Class B Receptor site on internal

surface of membrane

Scorpion venom, ammonium

analogues of lidocaine

Class C Receptor independent

mechaniams

Benzocaine

Class D Combination of receptor and

receptor-independent

mechanism

Most clinically used LA

(lidocaine, mepivacine,

articaine, prilocaine)

Sequence of mechanism of action of LA 1. Displacement of calcium ions from the sodium channel receptor site;

2. Binding of the LA molecule to this receptor;

3. Blockade of the sodium channel;

4. Decrease in sodium conductance;

5. Depression of the rate of electrical depolarisation;

6. Failure to achieve threshold potential level; (FULL BLOCKADE AT THIS POINT)

7. Lack of development of propagated action potentials;

8. Conduction blockade

Local anaesthetic molecules ✓LA are tertiary (majority) or secondary amines

✓ Lipophilic part

• Aromatic structure (determine what type of LA you have)

✓Intermediate Chain

• Ester linkage or

• Amide linkage

✓Hydrophilic part

• Amine portion

18

Frances Zhao

EACH ANAESTHETIC HAS TWO PARTS – HYDROPHILIC PART TO TRAVEL TO THE TARGET AND

LIPOPHILIC TO PENETRATE THE MEMBRANE

Lipophilic Hydrophilic

Intrinsic potency Allows diffusion in tissues

Penetrates nerve membrane

Rapid onset

pKa and pH ✓LA are basic compounds - pKa ranges from 7.5 to 10

✓Combined with acids form local anaesthetic salts:

• Soluble in water and stable

• Usually hydrochloride salts, dissolved in water or saline. Need to dissociate for the LA to get into the

membrane and bind to receptor. The pH this happens is called the pKa.

✓LA with vasoconstrictor are acidified to avoid its oxidation

✓Tissues normal pH - 7.4

✓Acidification (inflammatory process) - pH drops to 5 – 6. The separation of the components of the anesthetic

will not work properly. The anaesthetic will not be effective. YOU SHOULD NEVER INJECT LA INTO

INFLAMMED tissue. You have a better chance of hitting a farther nerve that’s not inflamed.

• Decreases local anaesthetic effectiveness

Dissociation of LA ✓pKa is the pH value at which both the Free base (RN) and ionised form (RNH+) are in equilibrium

✓LA salt is dissolved in water or saline and has:

• Free Base form (RN) - uncharged molecules

• Cation form (RNH+) - positively charged molecules

✓Proportion of each varies according to pH of solution or tissues

• Low pH - most LA will be in cationic form - RNH+ > RN + H+

• High pH - most LA will be in base form - RNH+ < RN + H+

Actions on nerve membranes ✓Diffusion of the nerve through the nerve sheath

• RN (free base form) enters the neuron

• RNH+ ions form in excess outside re-equilibrates according to tissue pH and drug pKa - more RN forms

enter until equilibrium the cationic form is the one that will bind to the receptor.

✓Binding at the receptor site (ion channel)

• RN excess in interior re-equilibrates to RNH+ ions

• RNH+ ions enter into the sodium channels, and bind to channel receptor from the interior side.

Membrane action of LA RN (free base form) diffuse through the nerve sheath to reach the interior of the neuron RNH +

(cation form) binds to receptor.

19

Frances Zhao

Takes procaine 18 minutes to work because of its pKa. The more basic the LA is, the more time it takes for it

to work. The pKa determines the speed of onset of action.

You need the free base form to go inside the membrane.

Once you inject LA into a tissue, the LA has to travel through all the barriers of the nerve.

Barriers of Diffusion of the Solution

A lot of tissues to travel through – that’s why you need a lot of free base form and the LA to be

hydrophilic.

pKa and LA

Why do LA not work well in infected tissues? pH of extracellular fluid varies, decreases (more acid) in infection or inflammation

much more RNH+ ions form will be present on the outside, and less free base RN form available

Reduced numbers of RN molecules enter the cell, and the remainder outside will be absorbed faster

(increased vascularity)

20

Frances Zhao

Induction of Local Anaesthesia ✓Diffusion

• LA moves from deposition area towards the nerve

• Penetration occurs when a drug passes through a tissue that restricts free molecular movement

(perineurium and perilemma)

• Depends on the Concentration Gradient

• External fasciculi (mantle bundles) are blocked first, inner (core bundles) later

• Mantle bundles innervate proximal areas (molars), and core bundles smore distal areas (incisives)

You want to be as close to the nerve as possible. Articaine has a very good diffusion properties so you can

deviate a little. Lidocaine is a little more technique sensitive.

COMPLETE BLOCKADE REQUIRES ADEQUATE VOLUME AND CONENTRATION OF THE LA.

The fibers to be anaesthetized will be the nerves on the periphery. Especially thick nerves e.g. inferior alveolar

nerve. The ones in the middle are further away. The area of the third molar will get numb faster than the ones in

the lip. If the patient starts to get numb in the lip it probably signifies that the LA has reached the entire nerve.

The reverse is the same—third molar loses numbness first.

Whenever you’re injecting LA into an area where there are too many blood vessels, it will not work as well as it

will be irrigated quickly.

Blocking process Solution diffuses in all directions and concentration increases within the nerve as diffusion progress

The part that diffuses away will be:

o Absorbed by other tissues

o Diluted by interstitial fluid

o Removed by capillaries and lymphatics

o Hydrolyzed (ester-type only)

Induction time Time between injection and complete blockade

Depends on the concentration of the drug and pH of the LA solution.

Anatomy and diffusion constant can’t be controlled by clinician.

21

Frances Zhao

Factors affecting local anaesthetic action

Articaine is more lipophilic – works faster and is more potent.

Modern anaesthetic always have vasoconstrictors to limit the blood flowing to the area. You can also decrease

the amount of LA needed. Whenever you use an anesthetic that doesn’t have a vasoconstrictor, it will work for a

lot shorter time. You use the vasoconstrictor all the time.

Recovery from LA Block ✓Same diffusion patterns, but with reverse order

✓Extraneural concentration is reduced

• Diffusion, dispersion, uptake of the drug

✓Intraneural continues stable initially

✓When extraneural<intraneural:

• Anaesthetic molecules begin to diffuse out of the nerve

✓Core fasculi recover faster than mantle fasculi**

✓Recovery is slower than induction

• LA is bound to receptor in sodium channel and released slowly

The outside of the nerve will recover much faster than the inside.

Duration of Anaesthesia ✓Protein binding (the more proteins they bind to, the long they will stay there for)

• Long acting LA (Ex: Bupivacaine) are more firmly bound. Bupivacaine can last for up to 10 hours! Not used

much in dentistry but used a lot in surgery where you want patients to stay number for longer.

• Shorter action LA (Ex: Lidocaine) not so firmly bound

✓Vascularity of the Region

• Anaesthetic duration is increased in areas with decreased Vascularity

✓Use of Vasoconstrictors

• Addition of vasopressor decreases tissue perfusion, thus increasing duration of block

There are areas where you don’t want to use vasoconstrictors – extremities of the limb – IT’S GOING TO KILL

YOUR BLOOD SUPPLY AFTER A FEW HOURS!!!

It can only be done in areas where it is supplied with blood very well. If you inject too much solution for a greater

palatine block, you can cause necrosis of the tissue.

22

Frances Zhao

Part 2: Pharmacology Esters Amides

Procaine Lidocaine

Cocaine Prilocaine

Benzocaine Articaine

Tetracaine Etidocaine

Mepivacine

Bupivacaine

✓Ester-Type • Procaine (2-4%)

‣ Vasodilating effect

‣ Not used today

• Tetracaine

‣ Topical use only

‣ High potency (6-8x cocaine)

‣ High toxicity

✓Amide-Type • Lidocaine

• Prilocaine

• Articaine

• Mepivacaine

• Bupivacaine

Pharmacokinetics of Local Anaesthetics ✓Uptake (Absorption)

• Most LA are vasodilators, except Cocaine

• This causes increase in rate of absorption, decreasing duration and quality of pain control

• Poorly absorbed orally (if at all)

• Topical Route - better in tracheal mucosa, less in oral mucosa, skin only if damaged

• Injection - IV can reach dangerous toxic concentrations

THESE SOLUTIONS ARE NOT TO BE INJECTED INTO BLOOD VESSELS. BEFORE YOU INJECT LA YOU NEED

TO ASPIRATE AND MAKE SURE YOU’RE NOT INJECTING INTO BLOOD VESSELS.

Pharmacokinetics of local anaesthetics ✓Distribution

• All body tissues (once in blood) including blood-brain barrier and placenta

• Highly perfused have initial high levels: brain, liver, lungs

• Skeletal muscle contains greatest percentage of LA (largest mass)

• Elimination half-time varies:

23

Frances Zhao

Articaine has a shorter half-life so it usually has to be in higher concentrations.

✓Metabolism (Biotransformation) • Primary process through which clinical actions of LA cease

• Relates directly to toxicity (balance between absorption X removal from blood)

✓Metabolism of ESTERS • Hydrolyzed in PLASMA (pseudocholinesterase)

‣1 in 2800 persons have an atypical form of this enzyme, and this prolongs its excretion

• Transformed into PABA (paraaminobenzoic acid)

‣ The PABA can cause allergies

✓Metabolism of AMIDES • More complex, bio-transformed in the LIVER

• Patients with liver dysfunction or heart failure (ASA IV to V) have relative contra-indication.

• Articaine has shorter half-life because part is hydrolysed (cholinesterase) in plasma. Part of its metabolites will

be processed like the ester group (processed in the plasma)

• Prilocaine (large doses) produces orthotoluidine that can induce METHEMOGLOBINEMIA. Can’t tolerate this

metabolite very well and very often need to be hospitalized.

✓Excretion • Is mostly done via the KIDNEYS

• Procaine is hydrolysed and PABA (90% appears in urine)

• Small percentage excreted unchanged

‣ 3% lidoc, 2% procaine, 1% mepivacaine

• Patients with significant renal disease (ASA IV/V), including patients undergoing renal dialysis represent a

relative contraindication

If you have very sick patients that have significant renal problems, they have difficulties excreting these drugs.

Will not come across patients like these very often because most of the time they will be in the hospital.

24

Frances Zhao

Systemic Effects of LA

✓Central Nervous System

• Depress the CNS (IMPORTANT IN OVERDOSES or you accidentally inject into the bloodstream

• Low levels - no action

• Used IV – anticonvulsant properties

‣ Decrease excitability of neurons

• Toxic levels (increasing)

1. Excitation

It starts to depress the areas of your brain that control you usually. Works like alcohol. Patients start

becoming more agitated and more talkative than usual.

2. Sedation (rarely)

3. Tonic-clonic seizure

✓Cardiovascular Effects More resistant to adverse effects than CNS

1. 1 - Direct action on myocardium - depression, decrease electrical excitability

‣ Used for ventricular disritmias (PVC and ventricular tachycardia)

2. 2 - Peripheral Vasculature – dilate blood vessels

‣ Hypotension, only in high levels

‣ Lethal levels - cardiovascular collapse

Because we usually use vasoconstrictors so these effects are evened out by the vasoconstrictors.

25

Frances Zhao

✓Local tissue toxicity • Skeletal muscle damage - “trismus”. Will not be able to open the mouth well because it will damage the

muscle.

✓Respiratory system • Unaffected, but in overdose can produce respiratory arrest

✓Drug interactions • CNS depressants - potentiation of effects

• Succinylcholine (muscle relaxant used in GA) - compete for pseudocholinesterase, can cause prolonged

apnea

• Barbiturates - induce production of hepatic microsomal enzymes which will increase rate of metabolism

of the LA

If your patient is already on drugs that depress the CNS, be careful.

If you use LA on top of these drugs it can cause prolonged paralysis and numbness.

Vasoconstrictors ✓LA are vasodilators (except cocaine)

✓Plain LA are resorbed from the injection site rapidly, resulting in:

• Poor anaesthetic depth

• Short duration of anaesthesia

• Higher LA plasma levels

• Increased bleeding

✓Positive actions • Oppose vasodilatory effects of LA

• Constrict blood vessels, decreasing perfusion

• Slower absorption of both the LA and epinephrine in the CVS

• Lower LA blood levels

• Longer durations of anaesthesia

26

Frances Zhao

• More profound anaesthesia

• Reduce bleeding

Reduction in plasmatic peak levels with epinephrine 1:200,000

Chemical structure

✓Catecholamines • Epinephrine (Adrenalin)

• Norepinephrine

• Levonordefrin

• Dopamine

✓Non-cathecholamines • Amphetamine

• Ephedrine

• Phenylephrine

✓Felypressin (synthetic analogue of vasopressin)

Mode of action

✓Adrenergic Receptors • Alpha - contraction of smooth muscles (vasoconstriction in skin and mucosas). Ideal vasoconstrictors will only

constrict blood vessels but adrenaline will have other effects as well.

‣Alpha 1 - excitatory post synaptic

‣Alpha 2 - inhibitory post-synaptic

• Beta - relaxation of smooth muscles

‣Beta 1 - heart and small intestines (cardiac stimulation and lipolysis)

‣Beta 2 - bronchi, vascular beds, uterus (vasodilation and bronchodilation)

Increased heart rate.

Increased blood pressure.

Dilate lungs and bronchi.

Increase motility in uterus.

27

Frances Zhao

Vasoconstrictors commonly used

✓Adrenaline • Synthetic, but same effect as endogenous adrenaline

• 1:80,000 to 1:300,000

• Vasoconstriction of vessels (α-receptors), pupil dilation, bronchial dilation, skin vessel contraction, ↑ syst

BP, ↑ beat frequency

• Affected by light - store cartridges in cool and dark place (but use at room temperature, or even warm)

• Interactions - should not be used in patients taking MAOIs as they can adversely interact

Maximal dose (ASA I) is 0.2mg which is 20 ml in a 1:100.000 solution

Patients with significant CV diseases (III/IV) is 0.04mg (4 ml)

✓Felypressin • Synthetic analogue of antidiuretic hormone vasopressin

• Dose - 0.03 international units/ml

• Acts more in veins than in arteries - not recommended when hemostasis is required

• No central nervous system effects

• No myocardium effects (beta)

• Has oxytocic actions - do not use in pregnancy

Overdose

✓Adrenaline • CNS stimulation: fear and anxiety, tension, restlessness, throbbing headache, tremor, weakness, dizziness,

pallor, respiratory difficulty, palpitation

• Cardiac effects: dysrhythmias (ventricular)

• Dramatic increase in blood pressure (300 syst; 200 diast mmHg)

• Angina in patients with coronary insufficiency

• Stimulatory phase of the (toxic) overdose is brief (usually assure the patient that it is okay will help)

✓Felypressin • Minimal incidence of systemic reactions

• Oxytoxic actions, contraindicating its use in pregnant patients

Medical Status of Patient

✓Adrenaline ASA I – healthy

ASA II –has a condition but is managed well

ASA III –has a condition but is poorly managed

ASA IV –very sick and should be in hospital

• Heart diseases (ASA IV) ‣Unstable angina pectoris

‣Recent myocardial infarction

‣Recent by-pass surgery (coronary art)

‣Refractory arrhythmia

‣Paroxysmal tachycardia

‣Highly frequent absolute arrhythmia

28

Frances Zhao

‣Untreated or uncontrolled serious hypertension

‣Decompensated cardiac insufficiency

Once impaired medical status is improved (ASA IV becomes III), routine LA with vasoconstrictors can be

used

• Thyroid dysfunction, diabetis (ASA IV)

• MAO inhibitors + tricyclic antidepressants

✓Felypressin

• Pregnancy (can result in contraction of the uterus)

• Coronary artery constriction in high doses

Adrenaline –maximum doses

✓Healthy Patients (ASA I)

• Maximum dose - 200 micrograms

• 1:80,000 (12.5 micrograms/ml x 2.2 ml = 27.5 per cartridge)

‣ Maximum - approx 7cartridges

• 1:100,000 (10 micrograms/ml) x 2.2 ml = 22 per cartridge)

‣ Maximum - approx 9 cartridges

✓Sick patients (ASA III and IV)

• Maximum dose - 40 micrograms

• 1:80,000 - Maximum - approx 2 cartridges

• 1:100,000 - Maximum - approx 2 cartridges

LA commonly used in Australia ✓Lignocaine with adrenaline

✓Articaine with adrenalin

✓Mepivacaine

✓Mepivacaine with adrenaline

✓Bupivacaine with adrenaline (not often available to buy as cartridges but can buy as vials)

✓Prilocaine with felipressin (octapressin)* --comes as American volume

Lignocaine 2% with Adrenaline 1:80,000 ✓Most commonly used

✓Good for blocks and infiltrations-very versatile

✓Rare allergies

✓Commercial names

29

Frances Zhao

• Lignospan 2% special (Septodont)

• ATO Lidocaine 2% (ATO)

• Xylestesin - A (Espe)

• Xylocaine (Dentsply)

Should have an idea of the onset and how long it will last (pupal anaesthesia)

and the maximum dose.

Don’t have to remember pKa.

2% = 2mg/mL

Prilocaine 3% with Felypressin (Octapressin) ✓Equipotent to lignocaine, but less toxic

✓Felypressin has less beta effects / cardiac. Will not affect the heart as well.

✓NOT to be used in pregnancy

✓Can produce cyanosis and metahaemoglobinemia at high doses (> 600 mg)

✓Commercial Names

• Citanest with Octapressin (Dentsply) - 1.8 ml!

Articaine 4% with Adrenaline 1:100,000 ✓Suitable for use only in patients 4 years and older

✓May be an association with neurotoxicity - should not be used in blocks. Has a very high affinity for nerve and

gets into nerve very quickly. Therefore, don’t inject too close to the nerve itself so they don’t prefer giving blocks

30

Frances Zhao

with articaine. Can use for infiltrations but DON’T USE FOR BLOCKS. Also gives a false sensation of effectiveness

so it is less technique sensitive than lignocaine. Try to work with lignocaine more.

✓Good for infiltrations, higher lipid solubility and protein binding rate, becoming popular

✓Commercial names

• Septanest 4% (Septodont) –DOUBLE THE CONCENTRATION OF LIGNOCAINE

• Ubistesin 1/200,000 (Espe)

Same maximum dose as lignocaine. For patients with same weight, you can only use half of what you use

for lignocaine as it is twice the concentration.

Mepivacaine 3% ✓Short-acting LA

✓Less vasodilation than others, can be used without VC. The reason why it can used by itself is that it is not as

vasodilatory as the rest.

✓Used when vasoconstrictors are contra-indicated

✓Suitable for use only in patients 3 years or older

✓Offered with adrenalin as well (with 2%). Only option without vasoconstrictor.

✓Commercial names

• Scandonest 3% Plain (Septodont)

• Scandonest 2% Special (Septodont) - with adrenaline 1;100,000

• ATO Mepivacaine 3% (ATO)

• Mepivastesin (3M)

Bupivacaine 0.5% with Adrenaline 1:200,000 ✓Long-acting LA, but also long onset time

✓Used for post-op analgesia as well

✓Suitable for use only in patients 12 years or older

✓Commercial name

31

Frances Zhao

• Marcaine with adrenaline (Dentsply)

Not sold in Australia! Used for anaesthetic for the spine because it lasts very long.

It’s 8 times as potent as the others.

Variability in LA duration ✓Normal variation from patient to patient

✓Accuracy of injection technique

✓Status of the tissue at injection site

• pH

• Vascularity

✓Anatomical variation

✓Type of injection administered

• Block – HARDER TO DO

• Infiltration

✓Normal variation from patient to patient

✓Accuracy of injection technique

✓Status of the tissue at injection site

• pH

• Vascularity

✓Anatomical variation

✓Type of injection administered

• Block

• Infiltration

Calculation of maximum dose ✓Lidocaine 2% + Adr 1:80,000 - Adult with 70 Kg

• 20mg/ml x 2.2 ml = 44mg per cartridge

• Max dose = 7.0 mg/Kg x 70 Kg = 490 mg

• 490 mg / 44 mg per cartridge = approx 11 cartridges

✓Lidocaine 2% + Adr 1:80,000 - Child with 20 Kg

• 20mg/ml x 2.2 ml = 44mg per cartridge

• Max dose = 7.0 mg/Kg x 20 Kg = 140 mg

• 140 mg / 44 mg per cartridge = 3 cartridges

Consider physical status of the patient and also the duration of time over which the

drug is administered.

32

Frances Zhao

MUST KNOW THIS TABLE

Adrenaline - Maximum doses ✓Healthy Patients (ASA I)

• Maximum dose - 200 micrograms

• 1:80,000 (12.5 micrograms/ml x 2.2 ml = 27.5 per cartridge)

‣ Maximum - approx 7cartridges

• 1:100,000 (10 micrograms/ml) x 2.2 ml = 22 per cartridge)

‣ Maximum - approx 9 cartridges

✓Sick patients (ASA III and IV)

• Maximum dose - 40 micrograms

• 1:80,000 - Maximum - approx 2 cartridges

• 1:100,000 - Maximum - approx 2 cartridges

Contraindications of Local Anaesthetics ✓Hypersensitivity to the substances very rare. Used to be common in the ester group which we don’t use

anymore.

• LA allergy, documented (more in esters), amide usually safe

• Bisulfite allergy - LA containing vasoconstrictors - do not use VC

✓Serious intraventricular conduction defects (AV block)

✓Decompensated patients (ASA III-IV) with liver, renal and cardiovascular disease - relative contraindication.

✓Severe hypotension - relative contraindication

✓Limited plasma cholinesterase activity (articaine only) articaine is partially metabolized in the plasma.

✓Methemoglobinemia, idiopatic or congenital (prilocaine only)

Anaesthetics for Topical Application ✓Lidocaine - 2% to 5%

• Can be combined with cetrimide, prilocaine

✓Benzocaine - 0.6% to 20%

• Can be combined with tetracaine

✓Cocaine Hydrochloride

✓Tetracaine - 0.2% to 1%

What factors should be considered when selecting a local anaesthetic? ✓Duration of the planned treatment

33

Frances Zhao

✓Need for post-treatment pain control

✓Possibility of self-mutilation post-treatment

✓Any medical contraindications (absolute or relative)

✓Possible need for hemostasis

Part 3: Armamentarium

Types of Syringes ✓Nondisposable syringes

• Aspirating

• Self-aspirating

• Pressure syringe for PDL injection

• Jet injector (“needless”)

✓Disposable syringe

✓“Safety” syringes

✓Computer controlled systems

Non-disposable Aspirating Syringes ✓Advantages

• Autoclavable

• Visible cartridge

• Aspiration with one hand

• Long lasting with proper mainteinance

✓Disadvantages

• Weight

• Several mechanisms for aspirating, check if it works for you!

‣Some require a new needle each time to ensure proper aspiration

Positive aspiration can be as high as 10-15%!

34

Frances Zhao

Non-disposable Self-aspirating Syringes ✓Advantages

• Introduced to ease aspiration

• Use the elasticity of the rubber diaphragm of the cartridge

• Pressure on the thumb disk produces positive pressure, when released, negative pressure permits

aspiration

• Easy to aspirate with small hands

✓Disadvantages

• Aspiration is not as reliable

• Finger must be moved from thumb ring to thumb disk to aspirate

Non-disposable Pressure Syringes ✓Advantages

• Designed for Intraligamentary injections (PDL) injection

• Can be used instead of block

‣Careful, can damage PDL

‣Should be used only in extractions to compliment if needed

✓Disadvantages

• Cost - PDL injection also works with conventional syringe

• Easy to inject too fast

2 places where you feel pain – mucosa and bone. Always make sure the bevel is facing the bone.

Short needles are what we usually use. Long needles (more than 3cm) are used for the blocks. For inferior

alveolar block, infraorbital block, posterior superior alveolar block.

35

Frances Zhao

Non-disposable “Jet Injector” ✓Advantages

• Does not require needle

• High pressure (2000 psi)

• Small volumes (0.01 to 0.2 ml)

• Used for topical anaesthesia or palate

✓Disadvantages

• Expensive

• Easy to inject too fast

Disposable Syringes ✓Advantages

• Disposable, single use

• Sterile until opened

• Lightweight

✓Disadvantages

• Does not accept pre-filled dental cartridges

• Aspiration requires two hands

• Not commonly used in Dentistry

Use 2-3 ml syringes with 25 gauge needles

“Safety Syringes” ✓Advantages

• Disposable, single use

• Sterile until opened

• Lightweight

• Less risk of needle-stick injuries

✓Disadvantages

• Cost

• May feel awkward to a first time user

36

Frances Zhao

Computer-controlled LA Delivery ✓Advantages

• Precise control of flow rate and pressure - more comfort

• Some handpieces are lightweight - increased tactile feeling

• Automatic aspiration

• Injects LA slowly –less painful

• Known for being pain-free injection –main reason is speed.

✓Disadvantages

• Cost

• Requires additional armamentarium

Problems with Syringes ✓Leakage during injection

• Off-centre perforations of the rubber diaphragm when reloading

✓Broken cartridge

• Old syringes, bent harpoon

• Plastic ones are cheaper but won’t slide as well as glass

✓Bent harpoon / aspiration device

• Must be sharp and straight

✓Disengagement of the harpoon from the plunger during aspiration

✓Surface deposits

• Ultrasonic (cleaning should usually get rid of this)

Needle Parts ✓Bevel – always make sure the bevel is facing the bone. If you don’t do that you might touch periosteum

when you touch bone.

✓Shaft

✓Hub

✓Syringe adaptor

✓Cartridge penetration

37

Frances Zhao

What should you do to ensure minimal pain?

Don’t change needle direction

Don’t bend needle

Avoid 30 gauge needles

Pain on withdrawal –needle forced to bone producing “fishhook” barbs on tips. When the needle hits the

bone it can bend slightly and when you withdraw it can tear tissues.

Avoid recapping needles, if needed use “one-handed scoop technique”

Needle Gauge and Length ✓Gauge = internal (lumen) diameter

• 30 gauge: thin (<aspiration, > deflection)

• 27 gauge: medium

• 25 gauge: thick

(>aspiration)

Thinner needles = less painful but easier to break for longer needles

The one we have = 27 gauge

Bi-rotational insertion technique (BRIT) minimises needle deflection.

Needle Gauge and Length ✓Length

• Extra short: 10-16 mm

• Short: 21-25 mm - routine use (what we use daily)

• Long: 30-41 mm - used for blocks (IAN, PSA)

Needles should not be inserted into tissues to their hubs unless it is absolutely

necessary for the success of the injection - THEY CAN BREAK!

Problems with Needles ✓Pain on insertion

• Use topic anaesthesia before

• Use good brand/sharp needles

• Not sharp enough

✓Breakage

38

Frances Zhao

• Do not bend needle, no dental technique requires this!

• Do not change needle direction while embedded in tissues

• Avoid 30 gauge needles (59 out of 60 breakage - Malamed, 2004)

✓Pain on withdrawal

• Needle forced to bone producing “fishhook” barbs on tip

✓Injury to Patient and Administrator

• Avoid recapping needles, if needed use “one-handed scoop technique”

One-handed Scoop Technique 1. Place needle on flat surface

2. Hold syringe with dominant hand

3. Scoop the needle cap onto the needle

4. Tip syringe vertically to slide cover over needle

5. Secure needle cap by grasping it near the hub

Non dominant hand should be distant! DO NOT hold

onto needle cap with this hand while scooping Recommended Needles ✓27 gauge - Short

• Most LA injections

✓25/27 gauge - Long

• Inferior alveolar

• Gow-gates mandibular

• Akinosi mandibular

• Infraorbital

• Maxillary nerve block

39

Frances Zhao

Discharging needles ✓Recap needle using scoop technique

✓Remove needle

✓Check that you did not remove the metal adaptor from the syringe

✓Place needle into sharps container

Components of a Cartridge ✓Glass tube (some are plastic)

• US - 1.8 ml

• UK, Australia - 2.2 ml

• Colour code varies by country ✓Stopper (plunger)

• Check if design fits your LA syringe for proper aspiration ✓Aluminium cap

✓Diaphragm

Cartridge Content ✓Plain

• Local Anaesthetic: blocks nerve conduction

• Sterile water: volume

• Sodium chloride: isotonicity of the solution ✓With vasoconstrictor

• Vasopressor: > depth and duration; < absorption ‣More acidic pH - slower onset of action and more “burning” on injection

• Sodium (meta) bisulfite: antioxidant ‣Allergies and pain in injection as it oxidises when it gets “older”

Shelf life for plain LA = 36 months. With vasoconstrictor = 18 months

Care and Handling ✓Blister packs - not sterile, but “very clean”

• Glass cartridges should not be autoclaved ✓Store in original package at room temperature (21oC) and in dark place

• Light accelerates deterioration of the vasopressor) ✓Diaphragm can be wiped with gauzes moistened with 70% ethyl alcohol, but should NOT be immersed in it

40

Frances Zhao

✓Bubble in cartridge

• Small bubble with nitrogen is normal

• Large bubbles caused by freezing - do NOT use, sterility not assured

✓Extruded stopper

• If bubble, caused by freezing

• If not, caused by prolonged storage in disinfectant diffused into cartridge (such as alcohol) - do NOT use,

alcohol is neurotoxic and can cause long term anaesthesia ✓Leakage during injection

• Incorrect needle/cartridge preparation

• Excessive force in PDL injections (more in plastic cart) ✓Burning on injection

• Normal response to pH of the drug

• Cartridge with sterilising solution

• Overheated or too cold cartridge

• Cartridge with vasopressor ✓Sticky stopper - more with plastic cartridges

✓Corroded cap - if immersed in disinfectants

✓Rust on cap - from the container if there is a leaking cartridge

✓Broken cartridge

• Storage, cracked glass, bent harpoons, extruded plungers

Additional Armamentarium ✓Topical Antiseptic (optional)

• Optional

• Povidone-iodine or Chlorhexidine ✓Topical Anaesthetic

• Dry mucosa, apply for 1 minute

• Gel better than spray

• Benzocaine (ester - allergy)

• Lidocaine/Prilocaine (amide)

• Mai contain methylparaben as preservative – allergy

✓Applicator sticks

• Cotton swabs for topic application

• Can be used to compress palatal mucosa ✓Cotton gauze

• Used to dry mucosa for topic LA

• Aid in tissue retraction ✓Haemostat

• Not essential, but should be readily available to remove broken needles from tissue

41

Frances Zhao

Preparation of Armamentarium

Syringe Preparation ✓Retract piston fully

• Some models are loaded sideways, retracting the piston creates space for the cartridge

• Others are loaded by folding the syringe after retracting the piston

✓Insert cartridge

• Side loading - while piston is fully retracted, rubber plunger first

• Back loading - insert the cartridge, aluminium end first

✓Engage harpoon

• Gentle push - do not hit, may break glass

• In twisted harpoon system, twist clock-wise 1/2 turn

✓Attach needle to syringe

• Remove small protective cap

• Screw needle onto syringe ✓Remove cover and expel a few drops of solution

Placing an additional cartridge ✓Recap needle using scoop technique

✓Remove needle

✓Retract the piston

✓Remove used cartridge

✓Insert new cartridge

✓Embed harpoon

✓Reattach needle

42

Frances Zhao

Some dentists replace the cartridge without removing the needle.

This option can only be used if the system they are using still

permits aspiration.

43

Frances Zhao

Part 4: Patient Evaluation and Basic Technique Medical History ✓ Read the medical history form that patients fill in

✓ Dialogue with patient confirming, checking all relevant information

✓ Record significant medical history in patients electronic or paper file

✓ Update the medical history on a regular basis, at least every 6 months

• Has there been any changes in your health since last visit?

• Are you now taking any drugs or medications?

Medical Questionnaire 1. Are you having pain or discomfort at this time?

2. Do you feel very nervous about having dental treatment?

3. Have you ever had a bad experience in the dental office?

4. Have you been in the hospital during the past 2 years?

5. Have you been under the care of a medical doctor during the past 2 years?

6. Have you taken any medicine or drugs during the last 2 years?

7. Are you allergic (e.g.itching, rash, swelling of hands or eyes) to penicillin, aspirin, codeine or any

medications?

8. Have you ever had excessive bleeding requiring treatment?

9. What medical condition you have had or have at present?

10. When you walk up stairs or take a walk, do you get very tired or have to stop because of pain in your

chest?

11. Do your ankles swell during the day?

12. Do you use more than 2 pillows to sleep?

13. Have you lost or gained more than 5 Kg in the past year?

14. Do you ever wake up from sleep short of breath

15. Are you on a special diet?

44

Frances Zhao

16. Has your medical doctor ever said you have a cancer or tumour?

17. Do you have any disease, condition or problem not listed?

18. WOMEN: Are you pregnant now? Are you practicing birth control? Do you anticipate becoming

pregnant?

Relative contraindication for LA

Avoid treatment in 1st and 3rd trimesters

Do NOT use Felypressin

Common Medical Conditions ✓ Heart failure

✓ Heart attack

✓ Angina pectoris

✓ High blood pressure

✓ Heart murmur, rheumatic fever, congenital heart

lesions

✓ Artificial heart valve

✓ Heart pacemaker

✓ Implant cardioverter/defibrillator

✓ Heart operation

✓ Anaemia

✓ Stroke

✓ Kidney trouble

✓ Asthma, hay fever, sinus trouble, allergies

✓ Diabetes

✓ HIV, Hep B, Hep C, liver disease, jaundice, drug

addition, haemophilia

✓ Thyroid disease

✓ Pain in jaw or joints

✓ Epilepsy or seizures

✓ Fainting, dizzy spells,

nervousness

✓ Psychiatric Treatment ✓ Bruise easily

Medical Questionnaire (Cardiovascular)

Categorisation of Drugs in Pregnancy

45

Frances Zhao

Physical Examination ✓ Visual inspection

✓ Vital signs

• Blood pressure

• Pulse

• Respiratory rate

• Temperature

• * Weight/height

✓ E/O Exam

✓ I/O Exam

Adult Blood Pressure Guidelines

46

Frances Zhao

ASA Classification and Dental Modifications

Physical Examination ✓ Determination of Medical Risk

• Can the patient tolerate both physiologically and psychologically the stresses involved in the proposed

treatment?

• Does the patient have a greater risk (morbidity/mortality) than normal?

• If patient has increased risk, what modifications are necessary in the planned treatment to minimise this

risk?

• Is the risk too great for the patient to be managed safely in the dental office?

Stress reduction protocol 1. Sedation: evening before (E.g. Valium 5mg) Benzodiazepine 5mg

2. Sedation: intra-operative. (can only be done in hospital setting)

3. Effective pain control

4. Morning appointment

5. Time factor: do not exceed patient’s tolerance. Don’t try to do too many things in one appointment.

6. Avoid hot, humid weather

7. Postoperative prescriptions. Call them the following day and make sure they’re happy.

8. Postoperative phone call

Contra-indications for LA ✓ Relative

• Malignant hyperthermia or malignant hyperpyrexia

• Atypical plasma cholinesterase particularly if you’re using articaine. Don’t use it. Use lignocaine instead.

• Idiopathic or congenital Methemoglobinemia. Use prilocaine.

✓ Absolute

• Allergy. If patient told you they had a crisis after an injection last time and had to be hospitalized don’t do

it.

47

Frances Zhao

Ratings of Drug Interactions

Local Anaesthetic Drug Interactions ✓ Combination of Local Anaesthetics (Significance Rating 1) e.g. mixing lignocaine and articaine. It’s additive!

• Toxicity is additive, check maximum recommended doses

✓ Opioid sedation (SR 1) the sedative effects of all the drugs that are sedative will be enhanced by LA.

• Increases risk of LA overdose, significant in children

✓ Amide LA with H2- receptor blockers (SR 5)

• Cimetidine modifies biotransformation of lidocaine by competing with it for binding to hepatic oxidative

enzymes. These drugs will decrease the function of the liver and make the metabolism of lignocaine

harder.

• In ASA III + congestive heart failure - increased risk of LA overdose

✓ Sulfonamides and Esters (SR 5)

• Procaine and others may inhibit bacteriostatic action of sulphonamides.

✓ LA induced Methaemoglobinemia (SR 4)

• May result from high doses of prilocaine, not likely in normal doses

• Prilocaine should not be given to patients with congenital MH since it can lead to significant MH, < oxygen

blood levels

• Clinical signs - lethargic, respiratory distress, cyanotic nails, skin pale gray

• Treatment - slow IV administ of 1% methylene blue, or ascorbic acid

Vasoconstrictor Drug Interactions ✓ VC and Tryciclic antidepressants (SR 1)

• These drugs enhance cardiovascular actions of the VC

• There might be some exacerbation of the vasoconstricting effects of the LA –more tachycardia etc

• More significant in nor-epinephrine, less with adrenalin, but max dose should be reduced to approx 2

cartridges only

48

Frances Zhao

✓ VC and Monoamine-oxidase inhibitors - MAOIs (SR 5) • Used for major depression, phobic-anxiety states and obsessivcompulsive disorders

• Potentiate actions of VC by inhibiting their biodegradation by the enzyme monoamine oxidase (MAO)

• Historically was a contra-indication with VC

• Today only phenylephrine remains a contra-indication

• Have a chat with the GP and ask for his opinion.

✓ VC and non-selective β-adrenoceptor antagonist (βblockers) (SR 1) • Increases likelihood of serious elevation of BP

• Monitor vital signs, BP/pulse, check before and 5-10min after LA β-adrenoceptor Antagonists (β-blockers)

• Might trigger a serious crisis of high blood pressure

✓ VC and General Anaesthetic (SR 1) • Halogenated gases used in GA can cause cardia dysrhythmias if they receive epinephrine - discuss with

anaesthetist before!

• Sometimes you would inject LA to patients already on GA (because you want to limit the bleeding –just

want the effects of the adrenaline)

✓ VC and Cocaine (SR 1) • Cocaine stimulates norepinephrine release and inhibits reuptake, producing catecholamine hypersensitivity

• This patient will be very sensitive to adrenaline—effects will be obvious

• Potentially myocardial ischaemia, lethal dysrhythmias, anginal pain, myocardial infarction or cardiac arrest

• Postpone treatment if patient had cocaine within 24 hrs

• Do NOT use gingival retraction cord impregnated in epinephrine.

✓ VC with antipsychotic or α-adrenoceptor blocker (SR 4) • Hypotension as a result of antipsychotic overdose may be intensified, use VC with caution

✓ VC with adrenergic neuronal blocker - phenotiazine (SR 4) • Used for serious psychiatric disorder

• Sympathomimetic effects may be enhanced, if IV injection can cause hypotension. Not contraindicated, but

use small volumes

49

Frances Zhao

✓ VC (epinephrine) with thyroid hormone - thyroxine (SR 4) • Summation effects, use with caution if signs and symptoms of hyperthyroidism are present

• Thyroxine will have similar effects to adrenaline.

Important Facts related to LA Injections • 54.9% of emergency situations happen during or in the first 5 minutes after LA (Japan)

• Over half of the emergencies in America were vasodepressor syncopes (common faint), usually associated

with LA injections. More related to anxiety and stress.

• LA administration becomes increasingly traumatic to patient the longer the dentist has been out of school

• LA should not be painful

• Empathy is the most important skill a dentist must have

• USE LESS VASOCONSTRICTOR IF YOU’RE NOT SURE

Basic Injection Technique 1. Use sterile sharp needle

• Check for fishhook-type barb (rare): draw needle back over gauze. If it’s not going in smoothly you can

already feel that something is wrong.

• Change needle after 3-4 penetrations. If you touch bone get another one because it’s going to be bent.

• Patients cannot differentiate between 25-27-30 gauge (23 too thick). 27 is what we usually use.

2. Check the flow of LA solution

• After harpoon is embedded, expel a few drops

• Self-aspirating systems are not as reliable.

3. Determine whether or not to warm cartridge or syringe

• No need to warm if kept at room temperature (21-22oC)

• Metal can be warmed by holding in hand for 30s before injection

4. Position the patient

• Supine position if possible (head and heart parallel to the floor) with feet elevated slightly. Horizontal

position will be more comfortable for the patient.

• Prevents vasodepressor syncope (common faint)

5. Dry the tissue

50

Frances Zhao

• Use sterile gauze to dry saliva

• Sterile gauze can also be used for retraction

6. Apply topical anaesthetic

• Small quantity

• Only 2-3mm deep

• Ideally 3 minutes

• will not numb deeper tissues

(Therapeutic Guidelines), minimum 1 minute

7. Establish a firm hand rest

• Patient’s face, chin

• Hard tissues such as teeth, palate

• Never have a loose hand on the end.

• Patient’s chest (caution females)

Do NOT rest on arm or shoulders as they may move and cause injuries

8. Make the tissue taut

• Stretch tissues, needle will cut with low resistance

• The injection is much less painful if the mucosa is really stretched.

• Provides better visibility and atraumatic needle insertion

• Americas/Europe - fingers

• Australia - dental mirror is recommended

9. Keep the syringe out of the patient’s line of sight

• Behind patient’s head OR

• In front, but below line of sight

10. Insert the needle into the mucosa (watch and communicate with patient)

• Make sure the bevel of the needle is oriented toward bone

• Insert gently but firmly

• Watch and communicate with patient

• “I don’t expect you to feel this”

• Avoid “This will not hurt”

• Should have the arrow pointing towards the bone. If not you’ll lacerate the periosteum if you

push too hard.

11. Inject several drops of LA solution (optional)

12. Slowly advance the needle toward the target

• In patients apprehensive about injections, continue injecting a few drops of LA, wait 2-3 seconds

advance the needle and repeat

51

Frances Zhao

• This is NOT needed in most patients as they do not feel pain between the mucosa and the periosteum

usually

13.Deposit several drops of LA solution before reaching the periosteum

• Controversial. You might inject into blood vessels.

• Periosteum is richly innervated.

• Develop you tactile sense, some techniques require bone contact

14.Aspirate

• Mandatory before injecting large volumes of LA

• Blood in the cartridge is a positive aspiration

• If positive, remove syringe and change cartridge.

• If you hit an artery you’ll usually feel it very quickly. If there’s a drop of blood there’s not too much

problem – just reposition the needle. But if there’s too much blood throw out the cartridge because blood

is irritating to connective tissues.

15.Slowly deposit the LA solution

• Communicate with the patient

• Slow = no pain = 1ml/min

• 1 cartridge = 2 minutes

• More realistic: 1 cartridge/minute

• It’s easy to move your hand if it’s a huge injection so the best way is to stop midway and reaspirate.

• Every time you’re in an area of lots of connective tissues the injection should go quite easily (lots of

fatty tissues) e.g. IAN block. For others, if you’re injecting into the hard palate it’s going to be

harder to inject and you need to go really SLOWLY.

At least 1 aspiration during injection - if positive:

• Only small volume was injected

• Reposition needle, aspirate twice and continue

16. Slowly withdraw the syringe

• Discard or recap immediately

• When you’re injecting it’s easy to bend the needle you can slowly rotate the needle.

• If recapping - “One handed scoop technique”

• If you hit the nerve (especially when you’re doing the blocks) withdraw the needle immediately.

Assure the patient.

• Nowadays there is no need to place the cartridge in the sharps container, just the needle.

Basic injection technique 1. Observe the patient

• Most adverse reactions occur in the first 5-10 minutes after a LA injection

• Patients should never be left unattended after a LA

52

Frances Zhao

2. Record the injection on the patient’s chart/notes

• LA name, dose, VC used, needle used, injection given, patient reaction

• Volume of LA used –ideally put it in ml rather than number of cartridges.

• Ex: R-IANB, 25-long, 2% ligno + 1:80,000 adr, 44mg. Tolerated well

Final Recommendations ✓ Good History/Examination

✓ Know the anatomy!

✓ Aspiration

✓ Inject slowly

✓ Observe the patient’s reaction

✓ Dosage as low as possible

✓ Use anaesthetics with low toxicity

✓ Be prepared for emergencies - equipment and knowledge

Part 5 : Anatomy Revision I ✓ Trigeminal Nerve (V)

• Ophthalmic

• Maxillary

• Mandibular

Most of the patient's face is innervated by the trigeminal nerve. It has both sensory and motor functions.

Huge nerve. Leaves the brain near the pons. The motor component of this nerve will travel with mandibular

nerve only.

53

Frances Zhao

Trigeminal Nerve - Sensory Root ✓ Stereoceptive

• Face, nasal cavity, oral cavity, paranasal sinuses, eye bulb, meninges

✓ Proprioceptive

• TMJ, teeth, PDL, palate,

Proprioceptive nerve usually work very fast and it's unconscious. They are not well anaesthetized.

Trigeminal Nerve - Motor Root ✓ Masticatory muscles

• Masseter

• Temporalis

• Medial pterygoid

• Lateral pterygoid

✓ Other muscles

• Anterior belly digastric (whenever you're doing a block you're paralysing this. otherwise we're not usually

blocking these nerves)

• Tensor tympani

• Tensor palate

Intracranial Part ✓ Origin from CNS

• Pons (laterally)

✓ Two nerves

54

Frances Zhao

• Sensory root (thick)

• Motor root (thin)

✓ Sensory Root

• Trigeminal ganglion

• Ophthalmic Nerve

o ‣Superior orbital fissure

• Maxillary Nerve

o ‣Foramen rotundum

• Mandibular Nerve

o ‣Foramen ovalis

✓ Motor Root

• No connections to the ganglion

• Joins the Mandibular Nerve (Mixed)

Ophthalmic Nerve Branches • Meningeal branch

This branch goes back into the meninges and innervate the dura mater - any pain you have inside your head is

usually because of this nerve.

✓ Lacrimal Nerve (lateral nerve)

✓ Frontal Nerve (intermediate nerve)

✓ Nasociliary Nerve (medial nerve)

Lacrimal Nerve

✓ Branch

55

Frances Zhao

• Communicant with zygomatic nerve

✓ Innervation

• Skin/mucosa around the lacrimal gland (lateral part of upper eyelid)

• Gland innervation is provided by Facial nerve (VII)

Frontal Nerve (travels all through the orbit and innervates the skin around the frontal region.)

✓ Branches

• Supraorbital

• Suprathrochlear

✓ Innervation

• Skin in frontal area

• Upper eyelid skin and conjunctiva

• Frontal sinus

• Frontal bone

56

Frances Zhao

Nasociliary Nerve Nasocillary nerves that will innervate the eye. Pain around the eye area comes from this nerve. Optic nerve only

innervates the retina.

✓ Branches

• Communicans with cilliary ganglion

• Long and short cilliary

• Posterior and anterior etmoidal

‣Internal and external nasal

• Infratroclear

✓ Innervation

• Eye globe

• Medial area of eyelid

• Nose bridge/tip

• Etmoidal sinuses

• Superior/anterior area of nasal cavity

Nasocillary nerve innervates all the anterior portion of the nose

57

Frances Zhao

Maxillary Nerve Branches • Meningeal branch also innervates the dura mater

✓ Zygomatic Nerve (lateral)

✓ Infraorbital Nerve and Post Sup Alveolar (intermediate nerves) and its branches which will be all the alveolar

nerves

✓ Pterigopalatine Nerve (medial nerves)

Zygomatic Nerve exits through pterygopalatine fossa

✓ Branches

• Zygomaticotemporal

• Zygomaticofacial

✓ Innervation

• Skin over zygoma, side of forehead and anterior part of temporal fossa

58

Frances Zhao

Posterior Superior Alveolar Branch Travels inside the maxilla until it reaches teeth - innervates all upper molars except MB root. Teeth, pulp, soft

tissues, bone are innervated by these nerves. Palate and palatal gingiva are NOT innervated by these nerves.

• Direct branch from the Maxillary nerve in the pterygopalatine fossa before the nerve enters the orbit

✓ Innervation

• Teeth 8 to 6 (not MB root)

• Adjacent buccal mucosa and gingiva

• Maxillary bone in this area

• Mucous membrane of maxillary sinus

Posterior Superior Alveolar Branch

Posterior Superior Alveolar Branch Avoid injecting too posterior risk of damaging pterygoid venous plexus

Infratemporal fossa - covered by connective tissues, fat and this mass of blood vessels. In this region there's a

high risk of injecting into blood vessels.

In Australia, dentists tend to only do buccal infiltrations - buccal infiltrations only works well with buccal roots.

PSA blocks work better as it will anaesthetize all the roots

59

Frances Zhao

Anaesthesia Area

Infraorbital Nerve ✓ Branches in the Infraorbital canal

Changes name to infraorbital nerve after getting into the orbit. hit the face via the infraorbital foramen. While

travelling on the floor of the orbit it branches into 2 more branches - MSA and ASA. MSA - premolars and mesial

roots. ASA - canines and central incisors.

60

Frances Zhao

Middle Superior Alveolar Nerve • Variable, leave the infraorbital nerve within the infraorbital canal helping to form the superior dental plexus

It can be absent in some people. Teeth, bone buccal soft tissue, maxiallry sinus except palatal side

✓ Innervation • Teeth 4, 5 and MB of 6

• Adjacent buccal mucosa and gingiva

• Maxillary bone in this area

• Mucous membrane of maxillary sinus

Anterior Superior Alveolar Nerve • Leaves the Infraorbital Nerve while in the canal, approx 6-10mm before the foramen

✓ Innervation

• Teeth 3, 2, 1

• Adjacent buccal mucosa and gingiva

• Maxillary bone in this area

• Mucous membrane of nasal cavity and sinus

Anterior Superior Alveolar Branch

61

Frances Zhao

Infraorbital Nerve - Branches in the Face ✓ Innervation

• Inferior Palpebral lower eyelid skin and conjunctiva

• Lateral Nasal lateral skin of nose

• Superior Labial upper lip, skin and mucosa

Anterior Superior Alveolar Infraorbital Nerve - Branches in the Face

Pterygopalatine Nerve • Short nerve located in the pterygopalatine fossa immediately attaches to a ganglion - pterygopalatine ganglion

and then divide into several branches.

✓ Branches

62

Frances Zhao

• Orbital, Pharyngeal

• Palatine Nerve

‣Greater palatine nerve

‣Lesser palatine nerve

• Sphenopalatine Nerve

‣Posterior nasal branches

‣Nasopalatine nerve

Palatine Nerves

Divides into 2 nerves - greater palatine nerve and lesser palatine nerve. One goes into the soft palate and other

goes into the hard palate. We're numbing the greater but because they're close together we're essentially

numbing both nerves. Patient will feel uncomfortable - they can't feel air flowing through and they might

complain there's something at the throat—that’s their tonsils.

✓ Greater Palatine

• Innervation mucosa of hard palate and gingiva from teeth 8 to 4

✓ Lesser Palatine

• Innervation mucosa of soft palate

63

Frances Zhao

Greater Palatine Nerve

Nasopalatine Nerve

✓ Path • Sphenopalatine foramen nasal septum – nasopalatine foramen - hard palate

Incisive canal and then gets to the mouth and innervates the anterior part of the palate

✓ Innervation • Nasal septum

• Mucosa of anterior hard palate and palatal gingiva from teeth 3 to 1

64

Frances Zhao

Part 6: Anatomy Revision II Mandibular Nerve Mixed nerve-has both sensory and motor functions

✓ Anterior division • Muscular branches

• Buccal nerve (is sensory)

• Mostly motor nerves

• Branches forward immediately after foramen ovale

✓ Posterior division • Auriculotemporal (lateral)

• Inferior Alveolar (intermediate)

• Lingual nerve (medial)

• Mainly sensory but there is one branch that is motor

Anterior Division - Muscular Branches ✓ Branches and Innervation

• Medial pteygoid nerve (direct from the mandibular nerve)

• Masseteric nerve

• Deep temporal nerves

• Lateral pterygoid nerves

We usually don’t numb as high as the foramen so don’t expect these muscles to be paralyzed.

Facial nerve innervates the buccinator.

65

Frances Zhao

Anterior Division - (Long) Buccal Nerve Provide sensation over a little part of the cheek but mainly sensation of the inner mucosa of the cheek.

✓ Innervation • Skin of cheek

• Mucosa of cheek

• Buccal gingiva of lower molars (need to numb before you do extractions of the lower molars)

The motor innervation of the buccinator muscle is provided by the Facial Nerve (VII )

Crosses the anterior border of the mandible (you can feel that in some people)

66

Frances Zhao

Yellow line – where the nerve travels. Over the anterior border of the ramus

Great auricular nerve –comes from the cervical plexus. (might need some local infiltrations to cover that nerve)

(Long) Buccal Nerve and Great Auricular Nerve ✓Buccal nerve area can overlap with the great auricular nerve area

✓Therefore usually additional injections are needed for the mandibular buccal soft tissues

67

Frances Zhao

(Long) Buccal Nerve and Great Auricular Nerve

Posterior Division • Meningeal Branch (supplying dura mater)

✓ Auriculotemporal (lateral nerve)

✓ Inferior Alveolar to teeth and jaw (intermediate nerve)

✓ Lingual (medial nerve)

Auriculotemporal Nerve

✓ Path

Goes posteriorly – contours mandibular neck - parotid bed - zygomatic arch preauricular area - temporal

region

Supplies innervation to TMJ (any pain related to TMJ will be from this nerve)

Travels posteriorly after the foramen –goes behind the TMJ and behind the ear and goes up to the

temporalis region. Travels through the parotid gland. Rare to have to anaesthetize it. Need to do an

external injection to numb this nerve.

✓ Innervation

• TMJ, parotid area (sensory), meatus, tympanic membrane and temporal region skin

The secretory innervation of the parotid gland is provided by the Glossopharyngeal Nerve (IX)

68

Frances Zhao

Inferior Alveolar Nerve

✓ Branches in the Infratemporal Fossa • Mylohyoid nerve (anterior belly of the diagastric and the geniohyoid muscle)

✓ Branches in the Mandibular Canal Dental branches

Osseous branches

Mental nerve

Incisive nerve

Base and of the skull and the point where it enters the mandible –you can only anaesthetize it in this region.

Once it reaches the mandible, it travels below teeth and will supply bone, PDL and pulp.

Mentalis nerve –when it exists the mandible.

Structures around the IAN area The needle stays behind the mandible and medial pterygoid muscle and not too close to the muscle (will

cause trismus).

✓ Medial • Medial pterygoid muscle

✓ Lateral • Mandibular ramus

✓ Posterior • Parotid gland

• External carotid artery

• Retromandibular vein

• Facial Nerve (VII)

69

Frances Zhao

If you go too far back, the needle will enter the parotid gland and you’ll enter up with facial paralysis.

Mylohyoid Nerve ✓ Path

• Leaves the IAN before it enters the mandibular canal

✓ Innervation

• Motor for anterior belly of diagastric

• Motor for geniohyoid muscle

• ?? Pulp mesial root lower 6

• Skin under mental protuberance

Inferior Alveolar Nerve

✓ Path • Enters mandibular canal and divides into mental nerve and incisive nerve in the 4-5 area

✓ Innervation (after mylohyoid nerve) • Bone branches - mandibular bone

• Teeth branches - all inferior teeth

70

Frances Zhao

• Mental nerve - skin and mucosa of lower lip and mental area

• Incisive branch - Teeth 4 to1, bone and buccal gingiva from 4-1

Mental nerve

71

Frances Zhao

Incisive Branches of the IAN

Lingual Nerve

✓ Path • Infratemporal fossa - anterior to IAN - over mylohyoid muscle flor of mouth - tongue

✓ Innervation • Sensory anterior 2/3 tongue

• Floor of mouth

• Soft tissues/gingiva on lingual side of teeth 8-1

The Lingual Nerve carries secretory fibres to the submandibular and sublingual glands, as well as

gustatory fibres from the anterior 2/3 of the tongue - All from the chorda tympani branch of the Facial

Nerve (VII)

72

Frances Zhao

Tongue Innervation

73

Frances Zhao

Overview of Mandibular Nerve

Intra-oral Mandibular Innervation Areas – know this by heart!!!

Bones Structures of Relevance ✓ Remember the differences in bone thickness around each tooth

• Buccal

• Palatal/lingual

74

Frances Zhao

• Apical

✓ Correlate skull, particularly maxilla and mandible to the nerves studied

• Foramen

• Fissures

• Grooves

• Canals

• Fossae

Part 7: Maxillary Techniques Overview of Maxillary Nerve

75

Frances Zhao

Terminal injections

Supraperiosteal (Buccal infiltration –most common injection in the maxilla) Aiming at the apex of the tooth or slightly higher than the apex of the tooth.

✓ Indications • Pulpal and buccal tissues

• Mostly used in maxilla

✓ Contraindications • Infection

• Dense bone over apices

76

Frances Zhao

• For extractions need palatal/ lingual complement

• Only numbs the buccal soft tissues and the pulp but NOT the palatal soft tissues

Need a very thin buccal plate and the roots of the tooth to be close to the buccal. Palatal roots of the first

molar –buccal infiltration might not work.

Where can we use Supraperiosteal? Superior Incisors/Canines

YES

Superior Premolars

YES

Superior Molars

YES for Buccal Roots

Palatal roots NO

Where can we use Supraperiosteal? Not generally in mandible…

Inferior Incisors / Canines → YES

Inferior Premolars → NO (cortex too thick)

Inferior Molars → NO (cortex too thick)

Supraperiosteal Technique Introduce the needle parallel to the long axis of the tooth into the area where the buccal mucosa folds.

Don’t have to touch periosteum. Technique doesn’t require the needle to touch bone. Works well in the maxilla

apart from the central and lateral incisors –not much space to expand into.

77

Frances Zhao

Supraperiosteal Technique

Needle 27 short

Entry point Mucobuccal fold above apex

Target area Apical region of the tooth, close to the bone

Technique Syringe parallel to tooth long axis

Depth Usually a few millimetres

Volume 1/3 of cartridge over 20 secs

Risks Pain if touches bone, withdraw

Anaesthetised area Pulp, root area(bone), buccal soft tissue

Intraligamental – PDL –very painful!! Not used routinely.

✓ Indications • Extractions (compliment) when other techniques fail

• Avoid using for other procedures, supraperiosteal is better

• If blocks should not be given

• Can damage PDL

✓ Contraindications • Infection

• Painful, do not use as main injection

• Primary teeth (can damage permanent tooth)

78

Frances Zhao

Needle 27 short or 30 extra-short

Entry point PDL, gingival groove

Target area PDL

Technique Syringe parallel to tooth long axis, if available use pressure syringe

Depth Usually a few millimetres

Volume 0.2ml over 20secs

Risks Painful, can damage PDL, needs buccal and lingual infiltrations, solution not

retained

Anaesthetized

area Pulp (not always), root area (bone), soft tissues in the area of injection

Intraseptal/Intrapapillary

✓ Indications • Deciduous teeth or local injection—only when a little gingiva needs to be anaesthetized.

• Applied on the mesial and distal papillae of the selected tooth

• Same injection from buccal to palatal, slowly inserting deeper

• More painful than supraperiosteal

✓ Contraindications • Infection

Needle 27 short

Entry point Centre of interdental papilla

Target area PDL

Technique Needle 90 degrees to gingival (45 to tooth)

Depth Usually a few millimetres

Volume 0.2-0.4mL over 20s –ischemia noticeable, resistance of injection

Risks More painful than supraperiosteal, short duration

Anaesthetized

area Soft tissues and bone in the area of injection

79

Frances Zhao

Intraosseous

✓ Indications • Rarely used, only if other techniques have failed

• Can be used in posterior mandible

✓ Technique • Mucosal anaesthesia

• Bone drilled towards apex of tooth with slow speed

• Needle inserted in the trabecular bone area

• Injects directly into bone. Creates a hole using a bur in the bone and then inject the anaesthesia.

Intrapulpal

✓ Indications • Radical Root Canal Therapy

• Tooth sectioning in extractions

• Provides anaesthesia by LA action and pressure

• Used if other techniques fail

✓ Contraindications • None

• Sometimes only technique

• Very painful so do it very quickly

✓ Advantages • Lack of lip/tongue anaesthesia

• Immediate onset of action

✓ Disadvantages • Need small opening in chamber

• Traumatic - brief pain

• Bending of needle may be needed

• Could kill the pulp!

80

Frances Zhao

Needle 27 short

Entry point Pulp chamber

Target area Pulp

Technique Deposit under pressure, may leak, may need to bend needle

Depth Usually a few millimetres

Volume 0.2-0.3 ml under pressure, 20s

Risks Solution not retained in tissue –advance needle further into chamber or root canals

Anaesthetized

area Pulp

Local Infiltrations

✓ Indications • Used in areas with mixed innervation

• Can be applied distant from an infected area

• Skin procedures

✓ Technique • Several peripheral injections to numb central area

• Introduce needle trough previously numbed area

• Commonly used in skin

✓ Palatal infiltrations if not using greater palatine block. Can do two small injections

• Can be used in conjunction with supraperiosteal to anaesthetise the palatal soft tissues

Local Infiltrations - Buccal nerve

Buccal side of the lower molars. Local Infiltrations - Buccal nerve

Anatomy • Posterior Superior Alveolar

• Middle Superior Alveolar

• Anterior SA (Infraorbital)

• Greater Palatine

• Nasopalatine

• Maxillary Nerve

81

Frances Zhao

Maxillary Nerves Anaesthetised

Anatomy

Maxillary Nerves

Posterior Superior Alveolar Nerve Travels from pterygopalatine fossa downloads

Done on posterior side of the maxilla

✓ Indications • Treatment in 2+ molars

• Palatal roots (while sometimes buccal infiltration will not)

• If supraperiosteal has failed

✓ Contraindication • If risk of haemorrhage is too high

• Injecting close to the plexus of veins –need to be very efficient with aspiration. Can tear small

blood vessels in that plexus while introducing the needle –a small hematoma will develop

immediately. If this happens, stop immediately. The hematoma will develop in the patient’s face.

✓ Advantages • High success rate (>95%)

• Reduced number of injections

• Minimizes volume of LA

82

Frances Zhao

✓ Disadvantages • Risk of hematoma

• Technique arbitrary - no bony

Avoid injecting too posterior risk of damaging pterygoid venous plexus

• Second injection needed for BL(MB?) root of upper 6 (28% of patients)

✓ Anaesthetised Area • Pulps of upper molars except MB root of upper 6

• Bone and max sinus in the area

• Buccal soft tissue

✓ Complications • Haematoma (too far distally)

• Possibility of numbing maxillary (V2) and Abducent (VI) nerves(too high)

• Possibility of numbing mandibular (V3) nerve (too lateral)

• Too far back –will numb the whole infraorbital nerve

• Too high up –can hit abducens nerve –patient will start to have double vision

83

Frances Zhao

Technique

84

Frances Zhao

Needle 27 short

Entry point Mucobuccal fold above the upper second molar

Target point PSA –posterior, superior and medial to posterior border of maxilla

Technique Mouth semi-opened, syringe 45 inward, 45

Depth Average 15-16mm, close to PSA, no need to touch bone (covex surface of maxilla)

Volume ½ to 1 cartridge over 30-60secs

Risks Haematoma, other nerves anaesthethized such as v/2, v/3, and orbital nerves (VI)

Anaesthetized

area Upper molars except MB root of the 6, buccal bone and soft tissues in the area, maxillary

sinus

Middle Superior Alveolar Nerve

Anatomy ✓ Infraorbital Nerve

• Middle Superior Alveolar

• Anterior Superior Alveolar

• Branches on the Face

‣Superior Labial

‣Lateral Nasal

‣Inferior Palpebral

- Premolars, MB root of the first molar.

- Don’t have a specific technique.

- Injection above the premolar region (like a buccal infiltration)

- MSA starts all the way from the orbit so hard to reach.

85

Frances Zhao

Middle Superior Alveolar Nerve ✓ Present in 28-54%. When MSA is absent, the ASA supplies the area

✓ Indications • Procedures in premolars and to compliment MB of first molar

✓ Contraindications • Infection

✓ Area anaesthetised • Upper premolars and MB root of first molar, buccal bone and soft tissue

• Upper lip may get numb

✓ Technique • Like a supraperiosteal injection above the second premolar, but higher

Needle 27 short

Entry point Mucobuccal fold above the upper second premolar

Target area Bone above apex of 2nd premolar

Technique Like supraperiosteal, syringe parallel to tooth, check bevel (close to bone)

Depth Around 10mm, can touch bone, but should retract to avoid injecting under periosteum

Volume 1/3 to ½ cartridge over 30-40 secs

Risks Haematoma, other nerves anaesthetized such as v/2, v/3 and orbit (VI)

86

Frances Zhao

Anaesthetized

area Upper molars except MB root of the 6, buccal bone and soft tissues in the area maxillary sinus

Anterior Superior Alveolar Nerve Usually buccal infiltrations work well with anterior maxilla but if you want to do procedures in more than

one tooth you can block the ASA.

✓ Indications • Dental procedures in more than 2 maxillary teeth

• When supraperiosteal is ineffective due to dense cortical bone

✓ Limitations • Some dentists are afraid to damage the eye

• Difficult anatomical landmarks

• Very painful –injections close to the nose which is very sensitive

✓ Alternatives • Supraperiosteal

Alternative: Supraperiosteal above the canine area

Area anaesthetised

✓ Branches on the Face Immediately anaesthetised: lower eylid, upper lip, nose laterally

87

Frances Zhao

✓ Anterior Superior Alveolar • Anaesthetised later: because the nerve is located approx. 1 cm deep into the canal - needs massage.

• Midline to premolars (72%) or to canine (28% when MSA present), pulp, bone and buccal soft tissues

ASA - Infraorbital Foramen

Technique 1 - Central Incisor as Reference Mesio-incisal corner to disto-cervical corner of the tooth

88

Frances Zhao

Technique 2 - Vertical using the 1PM as Reference Closer to the lip than to the gingiva –a little more distal

Needle 27/25 long (short in smaller patients)

89

Frances Zhao

Entry point Mucobuccal fold above the upper first premolar, but more towards the lip than in

supraperiosteal

Target area Infraorbital foramen (below IO notch)

Technique Syringe parallel to 1PM, avoid premature bone contact, check bevel, keep finger over

foramen, massage/pressure area for 1-2 minutes after injection.

Depth Average 15-16mm (1/2 long)

Volume ½ cartridge over 30-40 secs, “feel” LA solution beneath finger

Risks Pain if touches bone, “shock sensation”

Anaesthetised area Midline to premolars (canines if MSA), buccal bone and soft tissue, upper lip, lower eyelid,

nose

Greater Palatine Nerve

✓ Areas anaesthetised • Posterior part of hard palate up to premolars

• Palatal gingiva 8-4

✓ Problems • All palatal injections can be painful but a great palatine nerve block done properly is the least

painful of all palatine injections.

• Apply pressure with cotton stick/topic

• Ischemia and necrosis may happen—don’t overdo it.

90

Frances Zhao

Technique

Doesn’t go through the foramen itself – don’t have to touch bone

Needle 27 short

Entry point Mucosa over greater palatine foramen-palpate depression over 2nd molar area, between

gingival border and midline, just in front of soft/hard palate junction

Target area Greater palatine foramen

91

Frances Zhao

Technique After topical, apply pressure with cotton swab over foramen 30sec, needle inserted 90

Depth Less than 10mm

Volume ¼ of a cartridge over 30 secs minimum

Risks Necrosis if too much ischaemia

Anaesthetized area Hard palate and palatal gingival from 8 to 4

Nasopalatine Nerve

Needle 27 short

Entry point Palatal mucosa just lateral to the incisive papilla

Target area Incisive foramen beneath the papilla

Technique Injection 45

Injection straighten needle until bone is touched

Depth Around 5mm

Volume 1/5 to ¼ of a cartridge over 30sec

Risks Painful, injection slowly, risk of ischaemia/necrosis

Anaesthetized area Nasopalatine nerves bilaterally—hard palate and palatal gingival from 14 to 24

*Nasopalatine –numbing both sides as both nerves are joined together at this junction. Sometimes from canine

to canine.

Maxillary Nerve ✓ Technique 1 - High-Tuberosity (like a PSA block but high up to hit the maxillary nerve)

Approach • Via the maxillary tuberosity, similar to a high PSA block

92

Frances Zhao

✓ Technique 2 - Greater Palatine

Approach • Via the greater palatine foramen until the pterigopalatine fossa is reached

• Great risk off damaging GP nerve

✓ Technique 3 - Extra-oral

Approach • Under zygomatic arch, needle aims corner of eye

• Very dangerous, risk of braking needle if patient opens mouth (goes through several masticatory

muscles)

• Should not be used

• Will be going through all the muscles of mastication and can potentially damage them

93

Frances Zhao

It didn’t work!!! ✓ How do I know if it worked?

• Tingling (know your target nerve distribution)

• Using probe (gentle at first)

• Cutting into tooth

✓ Patient will feel touch and pressure, not pain, double check and reassure

✓ Analyse the problem - don’t just re-give

✓ Check anatomy (usual cause of failure)

✓ Check other factors

Part 8: Mandibular Techniques Buccal infiltrations usually work as well as the block.

Buccal side of molars –need to numb the buccal area (buccal nerve)

94

Frances Zhao

Mandibular Nerves Anaesthetised

Anatomy REMEMBER THIS DIAGRAM!!!!

Inferior alveolar nerve block

Height—reference the occlusal plane of the mandible. The nerve lies about a 1cm above the occlusal plane of

the mandible.

Common mistake –inject it too low.

Not a big problem if you inject it too high.

The nerve lies resting on the median pterygoid nerve and lingual nerve.

95

Frances Zhao

You need to puncture the buccinators to reach the area. You don’t want your needle to go through the median

pterygoid muscle. Initially insertion point should not be too medial. If the initial insertion point is too close to the

pharynx. Pterygoid mandibular raphe –marks where the buccinators starts and where the anterior border of the

median pterygoid muscle is.

✓ Branches

• Mylohyoid nerve

• Dental branches

• Osseous branches

• Mental nerve

• Incisive branch

Inferior Alveolar Nerve Block

96

Frances Zhao

✓ Nerves anesthetised • IAN

‣Mylohyoid

‣Incisive

‣Mental

• Lingual

✓ Areas anesthetized • Mandibular teeth

• Body of mandible, inferior part of ramus

• Buccal soft tissues anterior to first molar, lower lip, chin (mental nerve)

• Anterior 2/3 of tongue (lingual nerve)

• Lingual soft tissues and floor of mouth (lingual nerve)

✓ Advantages • One injection, wide area anesthesia

• Can be a disadvantage especially for kids who could accidentally hurt their tongue, cheeks etc

✓ Disadvantages • Wide area of anesthesia

• 15-20% failure

• Intraoral landmarks not consistant

• Positive aspiration (10-15% highest of all IO techniques). There are lots of blood vessels in there as well.

• Tongue and lower lip anesthesia discomfiting for many patients

Check on the OPG where the foramen is particularly the height of the foramen.

Final position of the needle will be in the middle between the mandible and the median pterygoid muscle. If

you’re not hitting the mandible, it can mean that you’re closer to the muscle than to the bone or you’re too far

back.

97

Frances Zhao

98

Frances Zhao

Lateral to the raphe, there’s a depression (where you put the needle in) and go more laterally you’ll feel

the anterior border of the mandible.

Keep the syringe parallel to the lower occlusal plane. You should use at two-thirds of the long needle

before you hit bone. Second, you’re going to put it closer to the canine, more posteriorly.

Ideal position – syringe over inferior premolars

If bone resistance: withdraw slightly and bring syringe over canine-incisive

99

Frances Zhao

✓ Complications / Errors • Early bone contact - withdraw slightly and rest syringe anteriorly over canine/incisive

• Overinsertion, no bone contact - risk of injecting into parotid, facial nerve paralysis

• Needle inserted too medially - risk of perforating the medial pterygoid muscle trismus post-op

• Needle too low - below the foramen willlead to failure of the block - inject higher next time

✓ Facial Nerve Paralysis in IAN Block (too posterior/deep)

Inferior Alveolar Nerve / Lingual Nerve ✓ Because the Lingual Nerve runs anteriorly and very close to the IAN, usually both are anaesthetised at the

same time

2/3 of the needle in and 1/3 of the needle out.

100

Frances Zhao

Needle 25/27 long

Entry point 1cm above occlusal plane, between pterygomandibular raphe and anterior border of ramus

Target area IAN before it enters the mandibular foramen

Technique Wide opened mouth, rest syringe over corner of mouth or lower premolars on opposite side,

bone contact needed

Depth 20-25mm (2/3 to ¾) of long needle

Volume ¾ to 1 cartridge if lingual nerve as well

Risks Aspiration essential

Facial nerve (too deep)

Medial pterygoid (too medial)

Anaesthetized

area IAN: mandibular teeth, mandibular, buccal soft tissues from 5 to 1, lower lip.

Lingual nerve: anterior 2/3 tongues, floor of the mouth, lingual soft tissues/gingiva

Mental Nerve

Mental Nerve Block

✓ Area anaesthetised • Mental nerve - lower lip, chin, buccal mucosa from 5 to 1 (quickly obtained as it leaves the mandible)

• Incisive nerve - premolars,canine and incisives, bone in the area (this branch is anesthetised slowly as the

LA enters the mental canal reaching the mandibular canal)

101

Frances Zhao

✓ Advantages/Indication • Dental procedures in anterior mandible

• When IANB is not indicated

• No lingual anaesthesia

• High success rate

• Up to the first premolar

✓ Disadvantages • Requires injection for lingual soft tissues (need to do a lingual nerve block as well)

• Midline can require complimentary injection

• “Shock” sensation when nerve is touched (if it happens withdraw slightly)

102

Frances Zhao

Incisive Branches of the IAN

Anatomy

103

Frances Zhao

Alternative Technique - Supraperiosteal

Lingual Nerve Can numb anywhere along where the lingual nerve travels –doesn’t have to do it with the IAN.

104

Frances Zhao

Technique 1 –with IAN block

Technique 2 –floor of the mouth

105

Frances Zhao

✓ Buccal Nerve

You need to do a separate injection for the buccal nerve. Very superficial (only need to penetrate 2-3mm.

same angulation as the IAN.

✓ Indications/Advantages • Buccal anaesthesia in lower molars area

• Good success rate, easy

✓ Disadvantages • Potential pain if periosteum touched

• Possible innervation from Greater Auricular Nerve

106

Frances Zhao

Technique

(Long) Buccal Nerve and Great Auricular Nerve ✓Buccal nerve area can overlap with the great auricular nerve area

✓Therefore usually additional injections

Neede 27 short

Entry point Mucous membrane distal and buccal to last molar

Target area Buccal nerve as it crosses an border of ramus

Technique Syringe parallel to occlusal plane but buccal to it

Depth Usually a few mm, just perforate buccinators

Volume 0,3ml over 10s

107

Frances Zhao

Risks Few, haematoma?

Anaesthetized area Buccal soft tissues lower molar area, cheek mucosa

Gow-Gates Mandibular block ✓ Described in 1973 (Australian!)

✓ Supposedly high success rate

✓ Anaesthesia of the entire Mandibular nerve, including the IAN, Lingual N, and Auriculotemporal N

✓ Less positive aspiration (2% over 10-15% with regular block)

✓ Steep learning curve, could be used if block fails

✓ Target area • Neck of condyle

• Below Lateral

✓ Reference landmarks-maxillary second molar • Corner of mouth

• Tragus

• Intertragic notch

108

Frances Zhao

Needle 25/27 long

Entry point Mucous membrane medial to mandibular ramus, just distal to the maxillary second molar, much

higher than in the normal IAN block (10-25mm above mandibular occlusal plane)

Target area Lateral side of condylar neck, below lateral ptergygoid muscle

Technique Syringe parallel to the line from the intertragic notch to the corner of the mouth, resting over PM,

but can go to incisives

Depth Average 25mm, similar to IANB, bone contact needed

Volume 1 cartridge over 60-90 secs

Risks Check bone contact, VII nerve paralysis

Anaesthetized

area Entire mandibular nerve, including auriculotemporal

Vazirani-Akinosi Block Mandibular Block - Extra-oral

✓ Indications • Patients with trismus, since it will also anaesthetise the motor fibres for these muscles

✓ Technique • Under zygomatic arch

• Through masseter and sigmoid notch

109

Frances Zhao

• Aims foramen ovale

✓ NOT used regularly

✓ Described in 1960 (Vazirani) and 1977 (Akinosi)

✓ Indication • Closed mouth, trismus

• Alternative to extra-oral techniques in these cases

✓ Area Anaesthetised • Mandibular nerve, including the IAN, lingual nerve, auriculotemporal nerve and muscular

branches (masticatory muscles)

Needle 25/27 long

Entry point Mucous membrane medial to mandibular ramus, directly adjacent to the maxillary tuberosity,

at the height of the mucogingival junction adjacent to the upper third molar

Target area Soft tissues medial to mandibular ramus (pterygomandibular space), above IANB and below

Gow-gates

Technique Closed mouth, syringe parallel to maxillary occlusal place, bevel away from mandibular ramus

(needle deflects towards the ramus), NO bone contact

Depth Average 25mm, similar to IANB, bone contact needed

Volume ¾ cartridge over 60secs

Risks Same as with Gow-gates

Anaesthetized

area Entire mandibular nerve, including auricolutemporal

Part 9: Complications ✓ Most common complications are related to anatomical ortechnique problems

• Incomplete or failure of LA effect - Example - IANB

✓ Overdose and toxicity usually related to intravascular injections

• Particularly with Vasoconstrictors

110

Frances Zhao

✓ Common faint is the most common systemic complication

✓ Dentists should be able to manage these complications

• Proper equipment

• Staff and personal training

• Needle breakage and injuries

• Persistent anaesthesia or paraesthesia

• Facial and orbital nerves paralysis

• Trismus

• Soft tissue injury

• Hematoma

• Pain and Burning on injection

• Infection and Edema

• Tissue vascular necrosis

Needle breakage and injuries ✓ Breakage

• Do not bend needle, no dental technique requires this!

• Do not change needle direction while embedded in tissues

• Avoid 30 gauge needles (59 out of 60 breakage - Malamed, 2004)

• Do not embed too deep into tissues, you should be able to “grab” it if it breaks - artery forceps

✓ IAN Block

• 33/34 litigation cases with broken needles in the US

Injury to Patient and Administrator ✓ Avoid recapping needles, if needed use “one-handed scoop technique”

1. Place needle on flat surface

2. Hold syringe with dominant hand

3. Scoop the needle cap onto the needle

Non dominant hand should be distant! DO NOT hold onto needle cap with this hand while scooping

4. Tip syringe vertically to slide cover over needle

5. Secure needle cap by grasping it near the hub

111

Frances Zhao

Nerve Injuries ✓ Neuropraxia 10-12 days

✓ Axonotmesis 6 weeks

✓ Neurotmesis unlikely to recover

✓ Causes • Trauma from needle

• Injection with LA contaminated with alcohol

• LA solution: articaine and prilocaine > lidocaine

✓ Hyperesthesia worse

✓ Management Usually recovered in 8 weeks, permanent if severe damage

Reassure patient, examine every 2 weeks

If over 1 year send to Oral surgeon or neurologist

Facial nerve paralysis ✓ Causes

• Injections IANB and Mandibular blocks too deep, posterior, no bone contact

DON’T USE ARTICAINE FOR BLOCKS. Just for buccal or local infiltrations.

112

Frances Zhao

Facial nerve paralysis

✓ Management • Reassure patient, back to normal after LA stops

• Remove contact lenses, cover eye with patch, record incident

Orbital nerves paralysis

113

Frances Zhao

✓ Management • Test eye movement in all directions

• Reassure patient, back to normal after LA stops

Trismus

✓ Causes • Usually injections through thick muscles such as the medial pterygoid

• Intramuscular injections - LA is toxic can cause muscular necrosis

• Haemorrhage and infection - tissue irritation, muscle disfunction

• Excessive volumes of LA

• Medial Pterygoid muscle

• Shouldn’t have trismus after LA (if it happens, that’s usually because you’ve hit the median pterygoid

muscle. the way muscles recover from injury is by contracting –trismus

✓ Prevention • Sharp disposable needles, correct technique, atraumatic insertion

• Avoid repeated injections

• Use minimum effective volumes of LA

✓ Management • Heat therapy (20min/hour), warm saline rinse

• Analgesic/antiinflamatory, Diazepan (as muscle relaxant)

• Physiotherapy (open/close/lateral movements)

• Examine patient

• If more treatment needed with trismus, use Vazirani-Akinosi technique

• Improvements usually within 48-72 hours

• If no improvement in 2-3 days consider infection - antibiotics

• Refer to specialist if it does not improve in 5-7 days

Soft tissue injury

✓ Causes • Bites or injuries on lips, tongue, cheek while still anaesthetised

✓ Prevention • Inform patient, avoid eating and drinking while numb

• Use LA with proper duration

✓ Management • Analgesics, saline rinses, petroleum jelly (lubricant)

114

Frances Zhao

Hematoma ✓ Cause - puncture of vein or artery

✓ Management • Immediately - stop procedure, apply pressure at least 2 minutes

• Subsequent - discharge once bleeding stops, advise of risk of trismus, discoloration of mucosa/skin

• Heat after 24 hours. Lasts for 7-14 days, follow up!

Pain on Injection

✓ Pain on insertion • Use topic anaesthesia before

• Use good brand/sharp needles, inject SLOWLY

✓ Pain on withdrawal • Needle forced to bone producing “fishhook” barbson tip

Burning on Injection

✓Causes • Normal response to pH of the drug (more with VC)

• Normally due to temperature

• Solution injected too fast

• Cartridge with sterilising solution

• Overheated or too cold cartridge

• Neurotoxicity of the LA

✓ Management • Transient effect, reassure patient

Infection and Edema

✓ Infection • Causes - contaminated needles, injecting LA in an area with infection, lack of sterile technique, storage

problems

• Management - treat as for trismus, may require drainage and antibiotics - check oral surgery lectures

• Particularly if you’re going through an area of infection—will bring the infection to the other areas.

✓ Edema • Causes - infection, allergy, haemorrhage

• Management - usually not a problem, BUT: if swelling is due to allergy: angioneurotic edema may

compromise airway, see systemic complications (ABC, adrenalin, corticosteroid, antihistamine)

115

Frances Zhao

Tissue Vascular Necrosis

✓ Causes • Excessive volume / VC

• Occurs usually 2 days after injection - ulcer

• Differentiate from aphtous stomatitis and Herpes simplex

✓ Management • Symptomatic, topic anaesthetics

• Lasts for 7-10 days with or without treatment

• Applying too much pressure and introducing air into the tissue.

Systemic effects of LA ✓ US - 300 million of cartridges a year

✓ LA are safe drugs

✓ Drug Administration:

• Principle 1: No drug ever exerts a single action

• Principle 2: No clinically useful drug is entirely devoid of toxicity

• Principle 3: The potential of toxicity of a drug rests in the hands of the user

Classification of Adverse Effects

Allergy X overdose Allergy Overdose

Dose Non-dose-related Dose-related

Signs and symptoms Similar, regardless of allergen Related to pharmacology of the

drug

Management Similar (epinephrine, histamine

blockers)

Different, specific for drug

administered

Overdose - Causes

✓ Normal • Constant absorption

• Constant removal

✓ Liver disfunction • Constant absorption

• Removal slower

✓ Large dose (normal liver) • Constant absorption

• Liver cannot remove fast enough from CVS

✓ Intravascular Injection • Increased absorption in CVS in very short time

Overdose - Predisposing Factors ✓ Patient Factors

✓ Drug Factors

116

Frances Zhao

• Age

• Vasoactivity

• Weight

• Concentration

• Other drugs

• Dose

• Gender

• Route of administration

• Presence of disease

• Rate of injection

• Genetics

• Vascularity of the injection site

• Mental attitude and environment

• Presence of vasoconstrictors

REMEMBER THE DOSAGES – PARTICULARLY ADRENALINE

Dosage of local anaesthetics –remember

Mg/ml 2.2ml

=1cartidge

Max dose

(mg/kg)

Max 2.2ml

cartridge

(adult)

Max 2.2ml

cart (20kg)

Mepivacaine

3% 30 66mg AUS – NS

US –6.6

AUS – 3

US –6

1-2

Mepivacaine

2% + epi

1:100,000

20 44mg AUS – NS

US –6.6

AUS – 3

US –6

1-2

Lidocaine 2%

+epi

1:80,000

20 44mg 4.4 (2007)

7(2012)

11 3

Articaine 4%

+epi

1:100,000

40 88mg 7 5 1.3

Prilocaine 3%

felypressin 30 66mg 6(2007)

9(2012)

9 2

Bupivicaine

0.5% +epi

1:200,000

5 11mg 1.3 8 8

Adrenaline - Maximum doses

✓ Healthy Patients (ASA I) Maximum dose - 200 micrograms 1:80,000 (12.5 micrograms/ml x 2.2 ml = 27.5 per cartridge)

‣ Maximum - approx 7cartridges

1:100,000 (10 micrograms/ml) x 2.2 ml = 22 per cartridge)

‣ Maximum - approx 9 cartridges

117

Frances Zhao

✓ Sick patients (ASA III and IV) Maximum dose - 40 micrograms 1:80,000 - Maximum - approx 2 cartridges

1:100,000 - Maximum - approx 2 cartridges

LA Overdose - Central Nervous System

LA Overdose - CVS and Respiratory

✓ CVS • Myocardial depression

• Bradycardia

• Peripheral vasodilation

• Hypotension

• CV collapse

• Cardiac Arrest

✓ Respiratory • Respiratory depression

• Respiratory Arrest

Management of LA Overdose

✓ Mild overdose • Position patient comfortably (supine, feet elevated)

• Check ABC if needed

• Reassure patient

• Administer oxygen (nasal cannula)

• Monitor/record vital signs

• IV line (if trained)

• Wait for patients recovery

Management of LA Overdose

✓ Severe overdose • Position patient in supine position, feet elevated

• Check ABC, CPR if needed

118

Frances Zhao

• If convulsions:

• ‣Protect patient’s head, arms, legs

• ‣Request medical emergency assistance

• ‣Continue CPR

• ‣Seizures last usually 1-3 min

• ‣If > 5 min, consider anticonvulsants (IV diazepam 5mg/min, or IM midazolam 5mg) - medical help!

• Post seizure phase - patient drowsy or unconscious, breathing shallow, low BP, low heart Frequency -

may require CPR and epinephrine

Epinephrine Overdose

Management of Epinephrine Overdose ✓ Terminate the procedure, and:

• Position patient comfortably (supine, feet elevated)

• Check ABC if needed

• Reassure patient, anxiety and restlessness are common signs

• Administer oxygen (nasal cannula)

• Monitor/record vital signs

• Wait for patients recovery

Overdose summary

Local anaesthetic Epinephrine

Stop treatment Stop treatment

Place patient supine elevate feet Place patient supine elevate feet

Basic life support –ABCD Basic life support –ABCD

Administer oxygen Administer oxygen if not hyperventilating

Give IV anticonvulsants if trained Reassure patient

Reassure patient

119

Frances Zhao

Allergy

Causes of Allergy ✓ Esters

• Drug itself

• Preservatives (methylparaben)

✓ Amides

• Rare

✓ Vasoconstrictos

• Usually due to antioxidant: Sodium (meta) bisulfite

Positive skin testing to one local anaesthetic does not provide any information about other drugs

Prevention of Allergic reactions ✓ Medical questionnaire

• Known allergies, asthma, serious anaphylactic episodes

• What treatment was given, hospitalisation needed?

• What position was the patient?

- upright LA may have caused vasodepressor syncope, not allergy

• Contact the GP

Types of allergic reactions

Type Mechanism Time of reactions Clinical examples

I Anaphylactic (immediate) Seconds – minutes Anaphylaxis, angioedema,

urticarial, hay fever

II Cytotoxic -- Transfusion reactions,

haemolytic anaemia,

certain drug reactions

III Immune complex 6 to 8 hours Serum sickness, acute viral

hepatitis, lupus nephritis

IV Cell-mediated 48 hours Allergic contact dermatitis,

infectious granulomas (TB),

chronic hepatitis

Progression of Anaphylactic Reaction 1. Early phase - skin reactions

• Feeling sick, itching, flushing, giant hives (urticaria) over face and chest, conjunctivitis, vasomotor rhinitis,

pilomotor erection

2. GI an genitourinary reactions - smooth muscle spasms

• Nausea and vomiting, sever abdominal cramps, diarrhea, fecal and urinary incontinence

3. Respiratory reactions

• Chest pain, cough, wheezing (bronchospasm), dyspnea, cyanosis, possible laryngeal edema

4. Cardiovascular reactions

• Pallor, lightheadedness, palpitations, tachycardia, hypotension, cardia dysrhytmias, unconsciousness

Management of patients with alleged LA allergy ✓ Assume that allergy exists

120

Frances Zhao

✓ Elective care

• Postpone until thorough evaluation of the “allergy”

✓ Emergency dental care

• Option 1 - no invasive treatment, maybe nitrous sedation, send to GP

• Option 2 - send to GA

• Option 3 - if allergy was from ester LA, use amide LA

Management of patients with allergic reactions

✓ Delayed skin reactions • ABC if needed

• Oral histamine blocker (50mg diphenhydramine 6/6hr for 3-4 days)

• Observe for 1 hour before discharge

• If drowsiness from anti-histamine, should not leave unescorted

✓ Immediate skin reactions • ABC if needed

• Administer epinephrine 0.3 mg IM or SC

• Administer IM histamine blocker

• Obtain medical advice (000) before patient leaves

Management of patients with allergic reactions Depends on how soon the allergic reactions develop—if they develop immediately, seek help immediately!!

✓ Respiratory Reactions Bronchospasm (Asthma) • ABC if needed

• Stop treatment

• Oxygen 5-6 L/min

• Administer aerosol inhaler (salbutamol or albuterol)

• Observe for 60 min, consider epinephrine IM or SC

• Medical help (000)

✓ Anaphylactic Reactions Laryngeal edema • ABC - call 000 immediately

• Epinephrine, repeat every 10 min if no improvement

• Oxygen

• Check vital signs

• Histamine blocker IM

• Hydrocortisone

• Maintain airway, cricothyrotomy last resource

Emergency Drugs and Equipment ✓ Dental Practices have a wide range of setups:

• From no equipment ?? to full emergency doctor’s bag

✓ Medical emergencies are uncommon

121

Frances Zhao

• Risk that medications will expire before needed

• Easily overlooked or expensive

✓ All dental practitioners have an obligation to ensure that they are properly trained and are up to date with

emergency management (including staff, DA’s should have at least a basic first aid and CPR certificate)

Emergency Plan ✓ Every practice needs to have an established plan for emergencies

✓ Numbers 000 and next medical facility should be prominently placed

• Consider time to get to your practice

• More time / distance needs more equipment and staff training

✓ Location of equipment known

✓ Training staff and YOU!!!!

Minimum Requirements ✓ Oxygen

• Easily transportable to the patient

• Via a bag, mask or nasal 6-8L/min

✓ Disposable plastic airway (Guedel)

✓ Adrenaline

• Pre-loaded vials (1:1,000 or 1:2,000) for tongue or anterolateral thigh injections

• Enough in the office for at least 2 doses

Dental practitioners should carefully consider their emergency equipment needs and staff training, relevant to

their location, patient population and practice type

Emergency Drugs and Equipment ✓ Second Level of desirable

Medications • Glucose - hypoglicemia

• Glyceryl trinitrate tablet or spray angina crisis

• Salbutamol (bronchodilator) and spacer - asthma crisis

• Aspirin - suspected myocardial infarction

• Hydrocortisone for injection Addisonian crisis and also for management of anaphylactic Reactions

Emergency Drugs and Equipment ✓ Other Equipment

• Blood pressure monitor - assess BP, monitor collapsed patients

• Blood glucose monitor – diabetes patients

• Pulse oximeter - essential if doing IV sedation, desirable for oral sedation

• Laryngeal airways - airway protection, facilitate ventilation

122

Frances Zhao

• Automated external defibrillators – part of any modern ABC protocol, available in our emergency kit for

VF

Maxillary Techniques

It didn’t work!!! ✓ How do I know if it worked?

• Tingling (know your target nerve distribution)

• Using probe (gentle at first)

• Cutting into tooth

✓ Patient will feel touch and pressure, not pain, double check and reassure

✓ Analyse the problem - don’t just re-give

✓ Check anatomy (usual cause of failure)

✓ Check other factors

Final Recommendations ✓ Good anamnesis

✓ Know the anatomy!

✓ Aspiration

✓ Inject slowly

✓ Observe the patient’s reaction

✓ Dosage as low as possible

✓ Use anaesthetics with low toxicity

✓ Be prepared for emergencies - equipment and knowledge