Nerve blocks and extractions

Question 1

Pain pathways

Answer 1

Transduction

Transmission

Modulation

Projection

Perception

Question 2

Transduction pain pathway

Answer 2

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

Question 3

Transmission pain pathway

Answer 3

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

Question 4

Modulation pain pathway

Answer 4

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

Question 5

Projection pain pathway

Answer 5

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

Question 6

Perception pain pathway

Answer 6

Subjective exerience of pain within the brain

Question 7

Analgesia for dental patients

Answer 7

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

Question 8

Which nerves supply sensory innervation to the oral cavity?

Answer 8

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

Question 9

Maxillary nerve

Answer 9

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.

Question 10

Pterygopalatine nerve

Answer 10

Supplies the hard and soft palate

Question 11

Infraorbital nerve

Answer 11

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.

Question 12

Mandibular nerve

Answer 12

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.

Question 13

Lingual nerve

Answer 13

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.

Question 14

Alveolar sensory branches

Answer 14

within the mandibular canal

supply the mandibular teeth via foramina in the canal wall.

Question 15

Mental nerves

Answer 15

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.

Question 16

Materials used for dental analgesia

Answer 16

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

Question 17

Drugs used for dental local anaesthesia

Answer 17

Lignocaine

Bupivacaine

Question 18

Lignocaine

Answer 18

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).

Question 19

Bupivacaine

Answer 19

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.

Question 20

Injection technique for dental LA

Answer 20

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.

Question 21

Volumes used for dental LA

Answer 21

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

Question 22

What will and infraorbital block desensitise?

Answer 22

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)

Question 23

Technique for infraorbital block

Answer 23

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.

Question 24

What will a maxillary block desensitise?

Answer 24

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.

Question 25

Technique for maxillary block

Answer 25

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

Question 26

What will mandibular (inferior alveolar) block desensitise?

Answer 26

all ipsilateral mandibular teeth, bone and intraoral soft tissue

Question 27

Technique for mandibular (inferior alveolar) block

Answer 27

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.

Question 28

Intraoral approach to mandibular block in small dogs and cats

Answer 28

○ 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.

Question 29

Intraoral approach to mandibular block in medium and large dogs

Answer 29

○ 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.

Question 30

Extraoral approach to mandibular block

Answer 30

○ 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.

Question 31

Complications of dental local anaesthesia

Answer 31

Transient elevations in blood pressure and heart rate Haematoma formation Risk of LA overdose Ensure aspiration before injection Orbital penetration Neuropraxia Lingual nerve block

Question 32

Infiltration anaesthesia

Answer 32

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

Question 33

Indications for tooth extraction

Answer 33

-Periodontal disease Trauma (fractures, pulpitis) Malocclusions Tooth resorption Oral inflammatory disease (FCGS, CCUS) Persistent deciduous teeth Unerupted teeth Advanced caries

Question 34

Contraindications for tooth extraction

Answer 34

Poor general health – risk of anaesthesia outweighs benefits of treatment Coagulopathy Teeth in an area previously treated with radiation therapy

Question 35

Equipment needed for tooth extraction

Answer 35

Intra-oral radiography equipment Dental machine with high-speed handpiece and range of burs Lighting PPE – gloves, mask, eye protection

Question 36

Closed (non-surgical) extractions

Answer 36

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

Question 37

Open (surgical) extractions

Answer 37

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

Question 38

What do you rinse the oral cavity with before open extractions

Answer 38

0.12% chlorhexidine gluconate solution

Question 39

Envelope flap

Answer 39

Sulcular incision only

Question 40

Triangle flap

Answer 40

single vertical releasing incision

Question 41

Pedicle (trapezoid) flap

Answer 41

Two vertical releasing incisions

Question 42

Sectioning of multi-rooted teeth

Answer 42

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

Question 43

Coronectomy prior to extractions

Answer 43

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

Question 44

Post op care of tooth extractions

Answer 44

Analgesia as appropriate Soft food 7-14 days No access to hard treats or toys Recheck at 7-14 days

Question 45

Complications of tooth extraction

Answer 45

Fractured tooth roots Haemorrhage Mandibular and maxillary fractures Oronasal fistulas Ophthalmic complications

Question 46

Fractured tooth roots

Answer 46

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

Question 47

When would a root tip be left in place?

Answer 47

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

Question 48

Haemorrhage caused by tooth extraction

Answer 48

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

Question 49

Maxillary and mandibular fractures during tooth extraction

Answer 49

Most commonly associated with mandibular canine and first molar NB small dogs Bone loss from periodontal disease

Question 50

Oronasal fistulas (ONF)

Answer 50

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

Question 51

Ophthalmic complications of tooth extraction

Answer 51

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

Question 52

Key points to avoid extraction complications

Answer 52

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