LA - how and why

Question 1

LA uses

Answer 1

Prevention of pain during treatment
Relief of post-surgical or other acute pain
Localisation of pain for diagnosis
Reduction of surgical haemorrhage (vasoconstrictor)

Question 2

GA

Answer 2

Not permitted in dental practice
Requires intensive-care facilities on site
> risk so avoided if possible
Px starved, accompanied, consent and restricted post-op
Contra-indicated in some pxs with underlying medical problems
Only indicated for some children, unco-operative and extremely anxious pxs

Question 3

Advantages of LA

Answer 3

Safe
Easy to use - single operator, unaccompanied and unstarved px with no post-op restrictions
Economical
Px co-operation, e.g. check occlusion after restoration
Long operating time
Haemostasis
No medical contra-indications

Question 4

LA contra-indications

Answer 4

Unmanageable pxs
Injections into acute infection (regional blocks OK)
Possible risk of bleeding with IA block in haemophilia and other bleeding disorders
Allergy (rare)

Question 5

Types of LA

Answer 5

Surface
Infiltrations
Regional block

Question 6

Surface LA

Answer 6

5% lignocaine ointment
10% lignocaine in flavoured spray
Jet injection
Ethyl chloride

Question 7

Infiltrations

Answer 7

Usually between mucosa and periosteum
Effective with thin alveolar bone and vascular channels
Sub-periosteal - painful
Intra-osseus - rarely used

Question 8

Regional block

Answer 8

Required in mandible due to thick cortical bone with no vascular channels

Question 9

Equipment: syringes

Answer 9

Cartridge
Aspirating types (avoids intravaxular injections - systemic effects)
All disposable needle 'resheathing' types

Question 10

Equipment: cartridges

Answer 10

1.8 or 2.2ml sterile LA in glass or plastic tube
‘Blister packed’, outside sometimes ‘cleaned’ by alcohol wipe
Single px use
Self-aspirating type identified by hole in bung
Some syringes aspirate by depressing diaphragm

Question 11

Equipment: needles

Answer 11

Sterile and single px use (cross-infection) - mounted on syringe with help of nurse, keeping hub/ needle sterile
Flexible stainless steel
-27 gauge (0.4mm OD), long (34mm)
-30 gauge (0.3mm OD), short (19mm)
Double bevel
Don't penetrate to hub
Avoid bending
Handle and dispose with care

Question 12

Fundamentals of needle technique

Answer 12

Px comfortable, relaxed, well-positioned and aware of what to expect
Operator stable with good visibility
Equipment ready and out of sight
Surface anaesthesia
Prep of mucosa - savlodil
Tissues stretched taut
Insert needle during stretch and advance to appropriate position
Aspiration
Inject slowly - approx 1ml/15s infiltration
-approx 2ml/20s, IA block
Test for anaesthesia: -questioning 
-probe/bur on dentine (conservation)
-probe mucosa (surgery)
Avoid injecting into foraminae

Question 13

Innervation in the maxilla

Answer 13

Branches of the maxillary nerve, plexus from

1. Posterior superior alveolar nerve - leaves in pterygomaxillary fissure just before infra-orbital canal
2. Middle superior alveolar nerve - if present (approx 50%)
3. Anterior superior alveolar nerve - leaves within infra-orbital canal

Question 14

Anaesthesia in the maxilla method

Answer 14

Deposit approx 1ml bucally over apex of appropriate tooth

• close to bone but supraperiosteal
• effective <2mins, wait approx 4mins, by 6-8 mins assume failure
• avoid floor of nose anteriorly (painful site)
• avoid malar buttress (thick with no vascular channels)

Question 15

Innervation of the palate

Answer 15

1. Anterior (greater) palatine nerves through palatine canal and palatine foramen to all palate
2. Nasopalatine nerve - along nasal septum and through incisive canal to anterior palate

Question 16

Method, anaesthesia in the palate

Answer 16

Anaesthesia for extractions and palatal surgery
Needle from opposite side, at 90 degrees to tissues
Distract and illuminate with mirror
Tissues tight and injection therefore painful - inject slowly in area of maximum thickness
Not posterior to 2nd molar (avoids lesser palatine)
Nasopalatine block - papilla very sensitive, infiltrate first and avoid canal if possible

Question 17

Posterior superior dental

Answer 17

Regional block - rarely necessary (failure of upper 6/7 infiltration - buttress)
Mouth partly closed, cheek retracted with mirror
Long needle, inserted adjacent to mesial upper 8
Inward, upward, backward approx 45 degrees for 20mm (max)
Aspirate (pterygoid plexus)
Commonest site for haematomas

Question 18

Infra-orbital

Answer 18

Regional block - rarely necessary (major surgery, multiple extractions, infected area)
L/A diffuses into canal anterior and middle superior alveolar nerves
Intra-oral - IO foramen palpated with finger, lip reflected with thumb, inject from sulcus adjacent 2nd PM - depth 1.5-2cm, approx 1ml
Extra-oral

Question 19

Intraligamentary injections

Answer 19

Usually limited to use in children, extractions in adults, or failure of normal technique
Use 30 gauge needles, special syringe - pistol or pen type
Antiseptic to gingival crevice
Insert approx 2mm along PDL of each root
Inject slowly, 0.2ml/30s, max 0.4ml/root (usually 0.2ml) - must feel resistance
Fast onset, high success rate
Only with healthy gingivae - not with infection
Damage to PDL/ pulp (< blood flow)/ unerupted teeth
Good for haemophiliacs
Avoid adjacent injecting adjacent teeth - crestal bone