WSAVA Nov 2021 Proceedings - Flipbook - Page 46
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DENTAL NERVE BLOCK
The dental nerve block is the most important and effective element in pain
management for canine and feline dental patients. The most efficient and
easiest dental nerve blocks are the infraorbital nerve block and mental
nerve block. This is because the targetted nerves for these two dental
blocks run through the canal of the foramen which is easily located. By
inserting a needle and administering the local anesthetic agent into the
foramen, these nerves will be blocked completely by the spread of the
local anesthetic agent in the canal. To ease the effort of performing dental
nerve blocks among the general practitioners, the author recommends
some landmarks that are easy to recognize and can be applied in the
same way in canine and feline patients. Aspiration should be made before
injection to ensure the local anesthetic agent does not enter the bloodstream, and injection should be smooth to ensure the local anesthetic
solution is not injected into the nerve. The author prefers to use bupivacaine 0.5% because the duration of analgesia of bupivacaine can last up
to 4-6 hours.
INFRAORBITAL NERVE BLOCK
The infraorbital nerve block is the easiest to be performed as the foramen
is relatively larger compared to the mental foramen. The author prefers to
use a 24 G intravenous (IV) catheter to insert into the infraorbital foramen,
as the tip of the catheter is blunt and can reach the caudal end of the infraorbital canal, allowing it to block teeth at the caudal maxillary region. In
dolichocephalic and mesocephalic dog breeds, the infraorbital nerve block
can block the nerve supply to the incisor, canine, and first, second, and
third premolar teeth. In brachycephalic dog breeds and cats, infraorbital
nerve block using an IV catheter can block the nerve supply to all teeth at
the ipsilateral side of the maxilla. The landmark of the infraorbital foramen
is between the smaller maxillary premolar teeth (third premolar teeth) and
the larger maxillary premolar teeth (fourth premolar teeth). The needle
should be directed parallel to the maxilla and inserted at the dorsal onethird of the gum. Once the whole length of 24 G IV catheter is inserted into
the foramen, the foramen should be pressed with a finger during injection
to ensure the local anesthetic solution can spread to the caudal site of the
infraorbital canal.
the nerves supplying to the ipsilateral lower incisor and canine teeth. The
whole length of the 26 G IV catheter should be inserted caudally at the
ventral one-third of the lower gum. The mental nerve block can block the
incisor tooth and canine teeth of the ipsilateral mandible side.
Fig 2: Mental nerve block in dogs: The tip of the lower canine tooth root
(dotted line) points to the mental foramen.
CAUDAL MANDIBULAR NERVE BLOCK
The caudal mandibular nerve block is relatively difficult to locate the nerve
as the nerve is running between the soft tissue/muscle and bone. First,
extra-orally, use a finger to feel the angular process of the mandible (the
ventral angle of the mandible). Then, intraorally, use another finger to feel
the dorsal angle of the mandible, caudal to the last molar teeth. Subsequently, insert a 22 G intravenous catheter stylet (in dogs) or 24 G hypodermic needle (in cats) extra-orally from the angular process (blue cross)
to the dorsal angle(yellow cross) (Fig 3). The needle should be aimed
towards the medial side of the mandible. The target of the block is at the
midpoint of the imaginary line drawn between the angular process and the
dorsal angle. Slowly withdraw the needle back to the angular process from
the dorsal angle of the mandible, and make a line block from the dorsal
angle to the angular process. This nerve block can block all teeth at the
ipsilateral mandibular side.
Fig 3: Caudal mandibular nerve block in dogs: make a line block from the
dorsal angle (yellow cross) to the angular process (blue cross).
POST-OPERATIVE PAIN ASSESSMENT
Fig 1: Infraorbital nerve block in dogs: 24 G IV catheter is inserted into the
infraorbital foramen located dorsal to the intersection between smaller
pre-molar teeth (red outline) and larger pre-molar teeth (purple outline).
MENTAL NERVE BLOCK
The mental nerve block is the second easiest nerve block to be performed. However, the diameter of the mental foramen is much smaller
than the infraorbital foramen. Therefore, the author prefers to insert a
26 G hypodermic needle into the cat’s mental foramen or a 24 G intravenous (IV) catheter into the dog’s mental foramen. The landmark to locate
the mental foramen is to locate the tip of the canine tooth root which is
pointing towards the mental foramen. The mental nerve block can block
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WSAVA GLOBAL COMMUNITY CONGRESS
Post-operatively, pain assessment should be conducted to assess the
adequacy of the pain management. The Feline Grimace Scale is a simple
and practical tool to assess pain in a cat. The assessment of the pain
score is based on five action units of the facial expression of the cat:
ear position, orbital tightening, muzzle tension, whiskers change, and
head position. The assessment has been validated to be used for pain
assessment in cat patients undergoing dental procedures. In dog patients,
Glasglow Composite Pain Scale and Colorado Canine Acute Pain Scales
can be used to assess the patient after the dental procedure. These tools
assess pain based on the changes in the behavior of the dog patient after
the procedure. Good pre-operative and intra-operative pain management
is more effective in treating pain when compared to relying on post-operative pain management alone.
In conclusion, effective pain management for dental patients will provide
better hemodynamic stability during general anesthesia, promote better
appetite after the procedure, and attain smoother recovery.