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SA Dentistry > Nerve blocks and extractions > Flashcards

Nerve blocks and extractions Flashcards

1
Q

Pain pathways

A

Transduction

Transmission

Modulation

Projection

Perception

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2
Q

Transduction pain pathway

A

nociceptors are stimulated by tissue injury (mechanical, thermal or chemical) and produce electrical impulses

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3
Q

Transmission pain pathway

A

the electrical impulses travel to the dorsal horn of the spinal cord via fast myelinated A-delta fibres or slower unmyelinated C fibres

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4
Q

Modulation pain pathway

A

input from both ascending and descending pathways may decrease or amplify the impulses within the dorsal horn (wind-up pain)

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5
Q

Projection pain pathway

A

pain impulses are sent from dorsal horn to higher centres of conscious perception

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6
Q

Perception pain pathway

A

Subjective exerience of pain within the brain

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7
Q

Analgesia for dental patients

A

Opioids
- usually with pre-med
- can affect all levels of pain pathway

NSAIDs
- with pre-med, during, or after procedure
- can affect both transduction and transmission

Local anaesthetics
- local or regional nerve blocks
- can affect both transduction and transmission

Alpha-2 agonists
- may be used in pre-med
- can affect both modulation and perception

Ketamine
- affects modulation and perception

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8
Q

Which nerves supply sensory innervation to the oral cavity?

A

Two branches of the trigeminal nerve
- Maxillary nerve
- Mandibular nerve

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9
Q

Maxillary nerve

A

Originates from the round foramen.

At the pterygopalatine fossa it gives rise to the zygomatic and pterygopalatine nerves and continues via the maxillary foramen into the infraorbital canal as the infraorbital nerve.

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10
Q

Pterygopalatine nerve

A

Supplies the hard and soft palate

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11
Q

Infraorbital nerve

A

Gives rise the the caudal superior alveolar nerve immediately before entering the infraorbital canal - this innervates the first and second molar teeth

Within the infraorbital canal it gives rise to the middle and rostral superior alveolar nerves which supply the premolars and canines/incisors.

Exits the infraorbital foramen and splits into the external and internal nasal nerves and the superior labial nerves.

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12
Q

Mandibular nerve

A

Oginated from the round foramen.

It runs rostrally around the TMJ and gives rise to the buccal, masseteric and auriculotemporal nerves.

Mandibular nerve continues rostrally over the medial surface of the caudal mandible where it enters the mandibular canal via the mandibular foramen and continues as the inferior alveolar nerve.

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13
Q

Lingual nerve

A

arises from the mandibular nerve just caudal to the mandibular foramen and supplies sensory innervation to the rostral 2/3 of the tongue and sublingual mucosa.

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14
Q

Alveolar sensory branches

A

within the mandibular canal

supply the mandibular teeth via foramina in the canal wall.

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15
Q

Mental nerves

A

Branches of the mandibular nerve
- caudal
- middle
- rostral

exit via the respective foramina and supply the lower lip and rostral 1/3 of the intermandibular area.

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16
Q

Materials used for dental analgesia

A

23-27 gauge needles, 5/8” to 1.5” depending on site and size of patient.

Dental aspirating syringes are helpful, but bupivacaine cartridges not available

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17
Q

Drugs used for dental local anaesthesia

A

Lignocaine

Bupivacaine

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18
Q

Lignocaine

A

usually used as 2% solution with or without adrenaline.

Rapid onset of action (30-120 seconds) but limited duration (30minutes to 2 hours).

Maximum total dose 4mg/kg (need to be careful in small dogs and cats).

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19
Q

Bupivacaine

A

available in various strengths from 0.25 to 0.75%.

Slower onset (6-10 minutes) but longer duration (6-8 hours, some studies suggest may last 24-48 hour in some patients).

The addition of buprenorphine may extend the duration to up to four days.

Maximum total dose 2mg/kg.

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20
Q

Injection technique for dental LA

A

Use a fresh needle for each injection site.

Insert needle gently with bevel orientated parallel to the nerve to reduce the risk of transection.

Avoid side to side movement.

Ideally needle is placed in close proximity to target nerve without penetrating the nerve sheath.

Aspirate to ensure no vascular penetration, then rotate and re-aspirate in case bevel was against vessel wall.

Apply digital pressure immediately post injection to reduce risk of haematoma formation and encourage diffusion of the medication.

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21
Q

Volumes used for dental LA

A

Cats and small dogs: 0.1-0.15ml per site

Medium dogs: 0.2-0.3ml per site

Large dogs: 0.3-0.4ml per site

22
Q

What will and infraorbital block desensitise?

A

Ipsilateral teeth, bone, and intraoral soft tissues

Teeth affected depend on depth of needle insertion:
○ Incisors and canine if close to infraorbital foramen (rostral superior alveolar nerve)
○ Premolars 1-4 if deeper (middle superior alveolar nerve)
○ Blocking molars requires insertion of needle beyond the maxillary foramen into the pterygopalatine fossa (caudal superior alveolar nerve)

23
Q

Technique for infraorbital block

A

Palpate submucosal neurovascular bundle dorsal to maxillary premolars and trace back to infraorbital foramen (situated dorsal to third premolar).

Insert needle rostral to foramen directed in rostrocaudal direction.

Keep needle parallel to dental arcade to reduce risk of globe penetration.

NB Infraorbital canal is very short in cats and brachycephalic dogs.

24
Q

What will a maxillary block desensitise?

A

Will desensitise whole quadrant including teeth, alveolar bone, gingiva, mucosa and mucosa of the hard palate.

Will also block some of the extra-oral soft tissue on nose upper lip and haired skin of the rostral muzzle.

Agents are placed into the pterygopalatine fossa and includes blockade of the major palatine nerve.

Bilateral injection can also block the structures of the caudal nasal cavity.

25
Q

Technique for maxillary block

A

Lateral approach:
○ Needle is inserted at rostro-ventral border of zygomatic arch caudal and dorsal to last molar and directed either perpendicular to the mucosa or rostrally towards the opposite nostril.
○ Needle should remain parallel to palate as it approaches the caudal opening of the infraorbital canal.

Ventral approach
○ Hold mouth wide open, insert needle into soft tissue caudal to last molar with needle directed dorsally
○ Needle tip should not need to advance more than 1-3mm into the mucosa

Infraorbital approach

26
Q

What will mandibular (inferior alveolar) block desensitise?

A

all ipsilateral mandibular teeth, bone and intraoral soft tissue

27
Q

Technique for mandibular (inferior alveolar) block

A

The mandibular foramen is located on the medial mandible halfway along a line drawn from the last molar to the angular process.

The foramen can usually be palpated intraorally in medium to large dogs – follow the neurovascular bundle as it enters the canal.

Agents are deposited over the foramen.

NB deposition of drugs too caudally or medially or in too large a volume can cause anaesthesia of the lingual nerve, which increased the risk of post-operative self-trauma.

28
Q

Intraoral approach to mandibular block in small dogs and cats

A

○ Place index finger onto angular process

○ Insert needle just caudal to last molar pointing towards angular process

○ Advance needle along the medial surface of the ramus to the level of the mandibular foramen.

29
Q

Intraoral approach to mandibular block in medium and large dogs

A

○ Palpate neurovascular bundle as it enters the mandibular foramen.

○ Insert needle just caudal to last molar and advance towards neurovascular bundle until you can palpate the needle tip under your finger.

30
Q

Extraoral approach to mandibular block

A

○ Palpate ventral notch of mandible just rostral to angular process.

○ Insert needle through skin at the midpoint of the notch on the lingual surface of the mandible.

○ Advance the needle along the medial surface of the ramus to the level of the mandibular foramen (usually 0.5-1cm dorsal to the ventral cortex).

○ Place digital pressure intraorally to reduce haematoma formation.

31
Q

Complications of dental local anaesthesia

A

Transient elevations in blood pressure and heart rate

Haematoma formation

Risk of LA overdose

Ensure aspiration before injection

Orbital penetration

Neuropraxia

Lingual nerve block

32
Q

Infiltration anaesthesia

A

Avoids the risk of iatrogenic nerve damage

Technically easier to perform.

Small bleb of local injected into gingiva and alveolar periosteum in the region of the apex of the tooth to be treated, ideally on both the buccal and lingual/palatal aspects.

Local diffuses into the tissue.

Can be used for all areas apart from caudal mandibular teeth (more dense cortical bone in this area inhibits diffusion).

? Evidence for efficacy…

Likely reduced effect in inflamed tissues due to lower pH

33
Q

Indications for tooth extraction

A

-Periodontal disease

Trauma (fractures, pulpitis)

Malocclusions

Tooth resorption

Oral inflammatory disease (FCGS, CCUS)

Persistent deciduous teeth

Unerupted teeth

Advanced caries

34
Q

Contraindications for tooth extraction

A

Poor general health – risk of anaesthesia outweighs benefits of treatment

Coagulopathy

Teeth in an area previously treated with radiation therapy

35
Q

Equipment needed for tooth extraction

A

Intra-oral radiography equipment

Dental machine with high-speed handpiece and range of burs

Lighting

PPE – gloves, mask, eye protection

36
Q

Closed (non-surgical) extractions

A

Extraction is completed without raising a flap

Small single rooted teeth

Teeth with significant attachment loss

Multi-rooted teeth must be sectioned before extraction
- Each single-rooted segment is then treated like a single-rooted tooth

37
Q

Open (surgical) extractions

A

Elevation of muco-periosteal flap
○ Improved visibility
○ Easier sectioning of multi-rooted teeth
○ Enables removal of buccal (or lingual) alveolar bone (alveolectomy)
○ Protects soft tissues from iatrogenic damage
○ Allows tension-free primary closure of soft tissues

Consider open technique for all but the simplest extractions

38
Q

What do you rinse the oral cavity with before open extractions

A

0.12% chlorhexidine gluconate solution

39
Q

Envelope flap

A

Sulcular incision only

40
Q

Triangle flap

A

single vertical releasing incision

41
Q

Pedicle (trapezoid) flap

A

Two vertical releasing incisions

42
Q

Sectioning of multi-rooted teeth

A

Multi-rooted teeth should be sectioned so that each root can be treated like a single-rooted tooth

Always section from furcation in coronal direction

Check radiograph for abnormal root number or morphology

43
Q

Coronectomy prior to extractions

A

Crown amputation (coronectomy) can be used as an alternative to sectioning before extracting the roots individually

○ Better visualisation of periodontal ligament all around the roots

○ Better access to roots, particularly in three-rooted upper 4th premolars

○ Enables buccal alveolectomy with cross-cut fissure (straight) bur

44
Q

Post op care of tooth extractions

A

Analgesia as appropriate

Soft food 7-14 days

No access to hard treats or toys

Recheck at 7-14 days

45
Q

Complications of tooth extraction

A

Fractured tooth roots

Haemorrhage

Mandibular and maxillary fractures

Oronasal fistulas

Ophthalmic complications

46
Q

Fractured tooth roots

A

Failure to remove sufficient alveolar bone

Using extraction forceps too early and with too much force

?less likely after coronectomy

Look for bulbous or curved roots

47
Q

When would a root tip be left in place?

A

if the risks or removing them outweigh the benefits

Fragment must be small and deep within alveolus

No sign of endodontic disease

Must not leave in Feline Chronic Gingivostomatitis (FCGS) cases

48
Q

Haemorrhage caused by tooth extraction

A

Usually results from slipping with dental instruments

Trauma to neurovascular structures, sublingual region etc

Control via ligation, direct pressure or absorbable haemostatic agents

Avoid by employing short finger stop and using controlled force

49
Q

Maxillary and mandibular fractures during tooth extraction

A

Most commonly associated with mandibular canine and first molar

NB small dogs

Bone loss from periodontal disease

50
Q

Oronasal fistulas (ONF)

A

Dachshunds

Ensure flap raised and closed without tension even if tooth very loose

Once formed will not heal without surgical intervention (have healed as far as body is concerned)

Require surgical debridement and closure

Hole in bone bigger than visible hole in mucosa

Single layer closure often sufficient

First attempt is most likely to be successful

51
Q

Ophthalmic complications of tooth extraction

A

Thin shelf of bone between orbit and roots of maxillary PM4 and molars

Orbital (or even brain) penetration if possible if instruments slip

Use short finger stop and controlled force

52
Q

Key points to avoid extraction complications

A

Use radiographs to be prepared for difficult extractions

Make large flaps and close without tension

Remove plenty of buccal bone

Use luxators / elevators correctly to break down periodontal ligament before using forceps

Use controlled force with short finger stop

SA Dentistry (3 decks)

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