Failure of LA 2 Flashcards
Outline factors that contribute to operator dependent failure of LA
- choice of technique and solution
- poor technique
Outline patient dependent factors of LA failure
- anatomical
- pathological
- psychological
As a general rule, what volume of LA should be deposited for infiltration injections?
1ml
As a general rule, what volume of LA should be deposited for regional block techniques?
1.5ml
What volume of LA should be deposited for palatal and long buccal blocks?
0.2-0.5ml
The effect of plain lignocaine is short lived. Explain why this is
this is because of the absence of adrenaline; thus absence of vasoconstriction. LA leaves site faster
Briefly describe the “direct technique” which can be used to increase success of IANB
- dentist places the thumb intra-orally at the deepest concavity of the anterior ascending ramus
- the index finger is placed at the same height extra-orally on the posterior aspect of the ramus
- the puncture point is half-way between the mid-point of the thumb-nail and the pterygomandibular raphe
- the needle is advanced throug this point being delivered parallel to the occlusal plane from the premolar teeth on the opposite side
- the proper bony end point is reached between 15-25mm of penetration
What are common causes of failure of the direct technique ? State how each of these can be rectified
- touching the bone too soon on the anterior ascending ramus - can be rectified by swinging the syringe across the mandibular teeht on the same side, advancing 1cm and then returning to the original angle of approach
- injecting inferior to the mandibular foramen - can be rectified by injecting at a higher level
What does the Gow-Gates technique rely on?
the deposition of LA adjacent to the head of the mandibular condyle
What is the plane of approach for the Gow-Gates technique?
- patients mouth is wide open
- dentist imagines a line drawn from the angle of the mouth to the inter-tragic notch
Briefly outline how the needles is introduced in the Gow-Gates technique
- needle is introduced across the contralateral manibular canine and directed across the mesiopalatal cusp of the ipsilateral second molar
- the needle is advanced until a bony contact is made; needle is then withdrawn slightly and full cartridge is deposited
The Akinosi technique is also known as…
- vazirani akinosi
- closed mouth technique
How does the Akinosi technique differ from the Gow- gates method?
it does not rely upon a bony end-point
Briefly describe how the needle is introduced with the Akinosi method
- syringe is fitted with a 35mm needle
- needle is advanced parallel to the maxillary occlusal plane at the level of the muco-gingival junction
- the needle is advanced until the hub (of the syringe ?) is level with the distal surface of the maxillary 2nd molar (at this point it has penetrated the mucosa at a higer level than the direct approach with the nerve)
mucogingival junction- transition between mucosa and gingivae
As well as the IAN, the Gow gates and Akinosi methods both block what nerves?
- lingual
- long buccal nerve (this is occasional for the Akinosi technique)
What risk is associated with high blocks ?
needles is inserted closer to the maxillary artery and the pterygoid plexus
Contact with maxillary artery can cause: blanching due to arteriospasm
Contact with pterygoid plexus can cause: alarming haematoma
How can laceration of vessels of the pterygoid plexus be controlled ?
firm pressure
this may produce post-injection trismus which may last for weeks
Briefly describe the technique for a mental nerve block
1.5ml injected in the region of the mental foramen which is usually located between the apices of the lower premolars
- available radiographs can be used to accurately localise the foramen
Intraligamentry and intraosseous techniques both rely on the same mechanism to produce anaesthesia. Briefly outline this mechanism
deposition of solution into the cancellous bone of the alveolus
What limitation is associated with intraligamentary anaesthesia ?
variable duration of action
What type of cartridges are used to deliver intra-ligamentary anaesthesia and why ?
glass cartridges as plastic ones deform under pressure
Briefly describe how the needle is introduced for an intraligamentary injection
needle is inserted in the mesio-buccal aspect of the root and advanced until maximum penetration
What is the recommended size of needle for intraligamentary injection?
12mm
30 gauge
What is an appropriate speed of delivery for an intra-ligamentary injection?
at least 10 seconds to deliver 0.2ml
What can you use as a guide to approximate 0.2ml for intraligamentary delivery?
0.2ml is the approximate volume of the cartridge rubber bung
What is the consequence of rapid injection using the intra-ligamentary method?
tooth extrusion
LA solution entering intraosseously will reach systemic circulation rapidly. True or false
true
When is the usse of intraligamentary injection is contraindicated and why?
use is contraindicated in patients at risk of infective endocarditis due to these types of injections producing bacteraemia
it is contraindicated unless antibiotic prophylaxis has been provided
Intra-osseous anaesthesia is more effective when ____ is used
vasoconstrictor
Specialised equipment for delivering intra-osseous anaesthesia includes …
- a matched perforator
- a needle
What can be used to assist intra-osseous LA injection ?
radiograph of the tooth to locate the best inter-radicular zone for anaesthetic injection
What must you do before undertaking intra-osseous LA injection?
0.1ml Gingival anaesthesia!
Briefly describe the ideal location of perforation for intraosseous LA delivery
- region for perforation is within the attached gingiva, 2mm below the gingival margin of the adjacent teeth in the vertical plance bisecting the interdental papilla
Briefly outline the process of an intraosseous injection
- perforator fitted onto a standard dental hand piece
- perforator is advanced through the buccal cortex until unmistakable drop into cancellous space is experienced
- perforator is removed and small 6mm 30 gauge needle is advanced through the defect into the cancellous bone
- 0.2-0.5ml of solution is then adminsitered slowly
Intra-pulpal anaesthesia is useful in what fields of dentistry?
- endodontics
- oral surgery
Intra-pulpal anaesthesia achieves anaesthesia as a result of…
pressure
(remember saline has been reported to be as effective as anaesthetic solution when injected pulpally)
Briefly outline the process of an intra-pulpal injection
- small access cavity is made
- needle that fits snugly into the pulp should be chosen
- approx. 0.1 ml of solution is injected under pressure
What should you do if the access cavity created to deliver intra-pulpal anaesthesia is too big for a snug fit?
- exposed pulp should be bathed in LA for a minute
- after this, needle should be introduced as far apically as possible into the pulp chamber, injecting under pressure
What is the main nerve supply to the maxillary arch?
superior alveolar nerve
State accessory nerve supplies to the maxillary arch
- greater palatine (posterior teeth)
- nasopalatine (anterior teeth)
How can you counter accessory nerve supplies in the maxillary arch?
palatal block or infiltration
The main nerve supply for the mandibular arch is …
the IAN
How can you counter accessory pulpal nerve supply by the long buccal nerve in the mandibular arch ?
long buccal block or infiltration
How can you counter accessory pulpal nerve supply by the lingual nerve in the mandibular arch ?
lingual block or infiltration
How can you counter accessory pulpal nerve supply by the mylohyoid nerve in the mandibular arch ?
- high block
- lingual infiltration
How can you counter accessory pulpal nerve supply by the auriculotemporal nerve in the mandibular arch ?
high block
How can you counter accessory pulpal nerve supply by the upper cervical nerves in the mandibular arch ?
buccal and lingual infiltrations
The long buccal nerve cannot be affected by what types of anaestetheic injection?
- mental block
- incisive block
Where does the mylohyoid nerve originate from?
leaves the main IAN trunk more than a centimeter above the mandibular foramen
How is the auriculotemporal nerve able to send branches to the pulps of mandibular teeth?
through foramina high in the ramus
Why is it recommended that 0.2ml of LA solution is injected disto-lingual to the third molar prior to extraction?
this is because of the accessory supply to the disto-lingual gingiva which causes it to not be anaesthetised
Explain why structures in the midline may need to be anaesthetised by block anaesthesia
this is because they receive bilateral innervation
anastomosis
What is the most obvious barrier to anaesthetic diffusion?
thick corticalplate of the mandibular alveolus
Suggest ways in which you can overcome anastomosis ?
- incisive nerve block
- buccal infiltration
- intraligamentary or intraosseous injection
State factors which can preclude access to delivery of anaesthesia
- trismus
- anatomical changes because of trauma and surgery
Describe how you can deliver palatal anaesthetic to a patient with trismus
- inject while advancing a needle toward the palate throug the mesial and distal gingival papillae from the buccal side
What is the best way to achieve IAN anaesthesia in a patient with trismus?
Akinosi closed mouth technique
there are extraoral approaches but these are not recommended in practice
Suggest reasons why inflammed pulps are difficult to anaesthetise
- increased H+ ions causes more of the anaesthetic agent to exist in its ionised/protonated form which is unable to diffuse across nerves and have an effect
- “wash out”; inflammation has vasodilatory effects which causes anaesthesia to be “wash-out/away” from the target site
Suggest reasons why non-inflammed pulps in close proximity to an area of inflammation would also be difficult to anaesthetise ?
this is because inflammation causes hyperalgesia of the nerves thus minimal stimulation results in activation of nerve responses
Aside from the sedative effect, what are the additional benefits of using BZDs in anxious patients?
- reduced toxicity of LA
- very useful when multiple injections have been administered
What is the best way to initially manage failed LA?
repeat injections
Why is it easier to palapate bony landmarks on the second attempt of delivering LA?
the needle can be manouvered in the tissues painlessly
What technique has been suggested for patients who have already experienced failed anaesthesia ?
Blunderbuss technique
Briefly outline the blunderbuss technique
- IANB —> IANB —> buccal and lingual infiltrations —> intraligamentry
https://www.codsjod.com/doi/CODS/pdf/10.5005/cods-4-2-20
Give the full details of a technique that can be used to delivery LA to patients who have experienced LA failure in the mandible
- conventional IANB and lingual block with 1.5ml lignocaine, followed by long buccal block with remainder of cartridge
- after subjective soft tissue signs of first block; repeat IANB and lingual block with 3% prilocaine with 0.03 IU/ml felypressin
- buccal and lingual infiltrations adjacent to the tooth of interest with 1ml of lignocaine and adrenaline (to eliminate accessory supply)
- intraligamentary injection of 0.2ml lignocaine with adrenaline per root
a total volume of 6ml is administered here which is acceptable in adults
This paper describes a technique that can be used to achieve anaesthesia in patients who have already experienced LA failure. What is the benefit of changing the active agents in the described technique?
- although it does not increase duration of depth and anaesthesia
- with the combination that is suggested, there is an increase in the amount of LA without increasing the amount of adrenaline administered. This is of particular importance to medically compromised individuals
- there is also some evidence that the combination of lignocaine and prilocaine provides a greater speed of anaesthesia
What LA is suggested to be provided for medically compromised patients who have previously experienced LA failure?
High block technique using 3% prilocaine with felypressin
Ropivacaine has been shown to be equally effective as a plain lidocaine and adrenaline containing solution. True or false
True
Adrenaline free LA solutions are cosnsitently reliable when administered via …
periodontal ligament
