Regional Anesthesia for Dentistry and Orofacial Surgery in Rhesus Macaques (Macaca mulatta)

Abstract

Regional anesthesia is a commonly used adjunct to orofacial dental and surgical procedures in companion animals and humans. However, appropriate techniques for anesthetizing branches of the mandibular and maxillary nerves have not been described for rhesus monkeys. Skulls of 3 adult rhesus monkeys were examined to identify relevant foramina, establish appropriate landmarks for injection, and estimate injection angles and depth. Cadaver heads of 7 adult rhesus monkeys (4 male, 3 female) were then injected with thiazine dye to demonstrate correct placement of solution to immerse specific branches of the mandibular and maxillary nerves. Different volumes of dye were injected on each side of each head to visualize area of diffusion, and to estimate the minimum volume needed to saturate the area of interest. After injection, the heads were dissected to expose the relevant nerves and skull foramina. We describe techniques for blocking the maxillary nerve as well as its branches: the greater palatine nerve, nasopalatine nerve, and infraorbital nerve. We also describe techniques for blocking branches of the mandibular nerve: inferior alveolar nerve, mental (or incisive) nerve, lingual nerve, and long buccal nerve. Local anesthesia for the mandibular and maxillary nerves can be accomplished in rhesus macaques and is a practical and efficient way to maximize animal welfare during potentially painful orofacial procedures.

Figure 1.

Blocks of the maxillary, greater palatine, and nasopalatine nerves in rhesus macaques. (A) The arrow points to the pterygomaxillary fissure and shows the approximate path of the needle from the mucobuccal fold dorsal to M2. (B) Injection angle to access the maxillary nerve via the pterygomaxillary fissure shown on a cadaver. (C) Arrow points to the greater palatine foramen medial to M3. (D) Injection angle to saturate the greater palatine nerve as it exits the greater palatine foramen shown on a cadaver. (E) Incisive foramina. The dotted line shows ideal placement of local anesthetic between the cranial edge of the canines. (F) Injection lateral to the incisive papilla shown on a cadaver.

Figure 2.

Blocks of the infraorbital and inferior alveolar nerves. (A) Injection angle aimed at the largest infraorbital foramen. (B) Multiple infraorbital foramina. (C) Infraorbital block injection shown on cadaver. The yellow-hubbed needle is inserted into the largest infraorbital foramen for reference. (D) Inferior alveolar injection shown on intact head; yellow-hubbed needles mark the caudal and cranial margins of the vertical mandibular ramus. The red line marks the occlusal plain of the mandibular molars. The X marks the midpoint of the line and approximate location of the mandibular foramen. (E) Medial surface of the mandible showing the mandibular foramen. The red dotted arrow shows path of needle during injection.

Figure 3.

Blocks of the mental, lingual, and long buccal nerves. (A) Mental foramen and injection angle. (B) Mental injection on cadaver. Yellow-hubbed needle is inserted into mental foramen for reference. (C) Cadaver with vertical mandibular ramus removed. The black arrow indicates the inferior alveolar nerve; the white arrow indicates lingual nerve. (D) Lingual nerve shown passing over the mandible at the mandibular notch (green asterisk). The white arrow indicates the lingual nerve; the black arrow indicates the long buccal nerve. (E) Long buccal block injection into the buccal gingiva adjacent to the mandibular molars.