- Recognize the importance of dental pain management.
- Convey important points of pain management and anesthetic safety to clients.
- Alleviate any fears the client may have and remove barriers to proper dental treatment.
- Become familiar with common nerve blocks, the materials needed to perform this procedure, and how to implement them in your practice.
Pathophysiology: When it comes to sensation, the key sensory tissue for the tooth is the pulp and gingival soft tissue with surrounding alveolar bone. Noxious stimuli to the pulp only results in one sensation: pain. The pulp is innervated with alpha (acute pain) and C-delta (chronic pain) fibers that respond to any stimuli with pain. Try placing an ice cube on your tooth for a few minutes, you can’t tell it’s cold, but there will be a pain response. For this reason, many people avoid dental procedures and may also do the same for their pets. If we block that stimuli before it starts, then theoretically, pain management should be much easier.
Common Analgesics Used Perioperatively: Opioids: Morphine, hydromorphone, buprenorphine, fentanyl and others have been advocated for use as a premedication. These medications can be useful for pre, intra and post-operative analgesia. They act peripherally as well as centrally on the central nervous system to help agonize (stimulate) or antagonize (block) certain receptors to produce analgesic effects. Adverse side effects of respiratory depression, hypotension and GI upset may be avoided when used in conjunction with a sedative such as diazepam/midazolam, acepromazine or alpha-2 agonist. These are effective for use when mild to severe pain is anticipated.
Alpha-2 Agonists: Xylazine and medetomidine are occasionally used in conjunction with opioids or other sedatives to help reduce the amount of each needed to produce sedative effects while adding to the analgesic effect. These, like opioids, work both on receptors in the central as well as peripheral nervous system.
NSAIDs: These medications have an anti-inflammatory, analgesic and antipyretic effect and are useful pre-operative as well as intra-operative and post-operative as long as there are no contra-indications and perfusion remains normal throughout the procedure. These medications are useful as an injection, can be given orally and are not controlled substances.
NMDA Antagonists: Ketamine and amantadine are effective medications to prevent the wind-up effect of pain prior to and during the incitement of pain. Ketamine is easy to add to IV fluids as a CRI and can be used in addition to opioids for effective CRI infusion.
Tramadol: Tramadol is a mu-agonist like some opioids and inhibits the re-uptake of serotonin and norepinephrine. It is most useful as an adjunct to other analgesics for post-operative pain rather than used as a sole analgesic agent. Toxicity has been reported in a cat with serotonin syndrome. Recent evidence suggests Tramadol may not be as effective as an analgesic in dogs as once thought.
Gabapentin: Gabapentin was initially developed as an antiseizure medication that may have some analgesic properties, particularly for chronic or neurogenic pain. Gabapentin is likely most effective when combined with other analgesics such as NSAIDs in a multimodal approach.
Maropitant: At least one study found that the neurokinin-1 antagonist, maropitant, improved visceral analgesia in dogs. This medication may also be used pre-operatively to help reduce vomiting in dogs due to other medications.
Local and Regional Nerve Blocks
What you need:
- 1cc syringe with 25 or 27G x 0.5” needle for cats/small dogs
- 3cc syringe with 25G x 1.5” needle for larger dogs
Max dose of bupivacaine (trade name Marcaine):
2-4mg/Kg Dog, 0.5-1.0mg/Kg Cat
Max dose of lidocaine:
2-6mg/Kg Dog, 2-6mg/Kg Cat
0.5% bupivacaine/Marcaine = 5mg/mL
2% lidocaine = 20mg/mL
Infraorbital Nerve Block
The infraorbital nerve block is performed by injecting 0.1-1.0mL (depending on the size of the patient) of the local anesthetic of the clinician’s preference at or around the nerve bundle as it exits the infraorbital canal just dorsal to the distal root of the third maxillary premolar by digitally palpating the infraorbital canal and injecting with a 1cc syringe and 25-27 gauge needle. In dogs, the canal is easy to palpate, but if there is difficulty finding it, the neurovascular bundle can usually be palpated by rolling your finger across the buccal mucosa dorsal to the second/third maxillary premolars. The neurovascular bundle will palpate similar to a tendon beneath the mucosa. By following this caudally to where the bundle goes into the canal, you can find the infraorbital canal. The author’s preference is to inject ventral to the neuromuscular bundle with the bevel of the needle facing the bone until the needle tip reaches the bone, then advancing the tip of the needle to the opening of the foramen. The plunger is always drawn back to ensure the needle tip is not in the infraorbital artery prior to injection. This nerve block should provide regional anesthesia of the buccal mucosa and buccal alveolar bone from the second premolar rostrally to the midline. This should be sufficient for gingival flap surgery in this area, but the deeper infraorbital nerve block is recommended for extraction of these teeth, so the superior alveolar nerves are also included in the desensitization.
Maxillary/Deep Infraorbital Nerve Block
To desensitize the maxillary premolar, canine, and incisor teeth on the same side, the deep infraorbital nerve block can be utilized. Insert the needle into the infraorbital canal until it reaches the medial canthus of the eye. Before injecting the local anesthetic, ensure the needle tip is clear of the infraorbital artery. This block targets the superior alveolar branches of the maxillary/infraorbital nerve, supplying the fourth premolar and rostral teeth. These nerves enter the incisivomaxillary canal at the caudal extent of the infraorbital foramen, right after the infraorbital nerve enters the infraorbital canal. For extended desensitization, the needle can advance slightly in the infraorbital canal, or it can be inserted into the palate mucosa just behind the last molar and advanced 0.5-1.0cm to the level of the maxillary branch of the trigeminal nerve before it enters the infraorbital canal in the sphenopalatine fossa.
Middle Mental Nerve Block
The middle mental nerve originates from the middle mental foramina, located caudal to the mandibular frenulum, ventral to the mesial root of the second premolar, or just behind the apex of the mandibular canine tooth. The foramen can be palpated with firm pressure, feeling like a depression in the bone. This foramen isn’t easily palpable in cats. A study by Krug, et al., found inconsistent desensitization of the mandibular canine tooth/incisors with the middle mental nerve block. Thus, this nerve block is recommended only for soft tissue surgery from the second mandibular premolar rostrally to the midline (gingivectomy, periodontal surgery’s gingival flaps, etc.).
Inferior Alveolar (Mandibular) Nerve Block
Perform the inferior alveolar nerve block by injecting a small amount of local anesthetic at the midpoint of an imaginary line drawn from the angle of the mandible to the distal aspect of the mandibular third molar (last molar). If possible, palpate the foramina intraorally for a better blocking location. Alternatively, use the extraoral approach. Place the index finger on the distal aspect of the last molar and the thumb on the angle of the mandible, forming an imaginary line between them. Insert the needle through the mandible’s ventral surface, advancing its tip to reach the ventral cortical bone. Move the needle off the bone medially until it advances on the medial mandible, to the midway point between the thumb and index finger. Keep the needle close to the mandible and inject the local anesthetic where the mandibular nerve enters the mandibular alveolar foramen. Use caution with this block in cats and dogs not undergoing mandibulectomy or complete mandibular quadrant extractions due to the proximity of the lingual nerve, which could lead to loss of sensation in the tongue’s rostral two-thirds and self-mutilation risks.
Michael Peak, DVM, DAVDC
Dr. Michael Peak graduated with honors from Auburn University’s College of Veterinary Medicine. Following this, he completed a veterinary dentistry residency at the Dallas Dental Service Animal Clinic in 2000. In 2001, he achieved board certification in veterinary dentistry from the American Veterinary Dental College. Dr. Peak’s extensive involvement in the field includes serving as president of the American Veterinary Dental College, chair of its Examination Committee, chair of its Fiscal and Audit Committee, and chair of the Board of Directors. He has also taken on the roles of program chair for the Veterinary Dental Forum—an acclaimed veterinary dentistry continuing education event—and chair of the Veterinary Dental Oversight Group, responsible for supervising the operations of the Veterinary Dental Forum. Dr. Peak is a co-owner of The Pet Dentist at Tampa Bay, LLC.