Morphometry of the mandibular foramen applied to local anesthesia in hoary fox (Lycalopex vetulus)

Abstract

Great part of the veterinary care in wild carnivores is intended to treat the dental disorders, and oral cavity disorders may generally affect the animal health as a whole. It is factual that knowing the location of the mandibular foramen is vital for local anesthetic block of the inferior alveolar nerve, however, there is still no data on the morphometry of the hoary fox mandibular foramen. The aim was describing morphometry of the mandibular foramen of this species and associating its position with anatomic reference points in the mandible, thus providing support for more effective local anesthetic block of the inferior alveolar nerve in such species. Four adult jaws of Lycalopex vetulus were used. Radiography and biometrics of the hemimandibulas were performed. The rostral third of the jaw body in a lateral view presented three mental foramens, being a rostral, a medium and a caudal. Each hemimandibula presented I3/C1/PM4/M3. The angle of the mandible was marked by the masseteric fossa, the angular incisure, the angular process and the mandibular foramen, and this last one located perpendicularly to the dorsal edge of the angular incisures in medial view. In this view, the crevice to the milohyoid nerve, projected in the caudodorso rostral direction, was also evidenced. The ramus of the mandible was characterized by the presence of the condylar and coronoid processes, and by the dorsal and ventral mandibular incisions. Statistical analyzes did not present significant differences between the antimeres of the studied animals, and the penetration of the needle perpendicularly to the dorsal end of the angular incision on average 8.79mm, overlapped to the medial face of the angle of the mandible could be indicated. Alternatively, the access may also be achieved by inserting the needle in an average of 17.69mm perpendicular to the dorsal end of the angular process, in contact with the medial aspect of the angle of the mandible, and in caudo-rostral projection, also allowing a better anesthetic blockade of the inferior alveolar nerve in L. vetulus. It can also be concluded that the masseteric fossa, the dorsal and ventral mandibular angles, the crevice to the milohyoid nerve, the ramus of the mandible and the mandibular foramen presented differences in their topographic descriptions when compared to the other canids.

Morphometry of the mandibular foramen applied to the local anesthetic block to inferior alveolar nerve in boars (Sus scrofa scrofa Linnaeus, 1758)

“…Here, we observed that the mandibular foramen of this species was positioned in the ramus of the mandible, just as Getty (1986) mentioned for swine and other domestic animals, Souza et al (2013) for the crab-eating fox (Cerdocyon thous), and Souza et al (2016) for the maned wolf (Chrysocyon brachyurus). Yet, Magalhães et al (2019) reported that, in the hoary fox (Lycalopex vetulus), the said structure was located in the region of angle of the mandible, while other authors, such as König & Liebich (2016), and Evans & Lahunta (2017) were less specific, as they had, respectively, indicated only the medial face of the mandible with the anatomic reference in domestic animals and in domestic dogs.…”

“…As far as one can tell, for domestic dogs (Beckman & Legendre, 2002) and cats (Barroso et al, 2009), crab-eating fox (Souza et al, 2013), maned wolf (Souza et al, 2016), and hoary fox (Magalhães et al, 2019), the authors have followed the recommendations of Gross et al (1997) and Egger & Love (2009) to propose the introduction of the needle during the extra-oral technique of the anesthetic block under scrutiny, while using the depression present in the ventral margin of the mandible as a point of reference for the approach of the mandibular foramen. However, in boars, it had been noticed that such osseous accident, addressed by Magalhães et al (2019) as angular incisure, would not be positioned perpendicularly to this foramen, thus leaving it remarkably farther away from the ventral margin of the mandible, which would correlatively increase the space of contact between needle/structure and the risk of local lesions. In addition, in that species, the caudal-ventral-rostral projection of the sulcus for the mylohyoid nerve also renders that form of access unviable, as the nerve would be exposed to the direction of the piercing penetration.…”

“…Next, a single examiner proceeded with the biometry in each of the hemimandibles, using a Starrett  digital electronic pachymeter (capacity of 0-150 mm, resolution of 0.01 mm, and accuracy of ± 0.02 mm). Due to the lack of morphometric information pertinent to the mandibular foramen of swine, the measurements used here were based on and adapted from the studies conducted by Barroso et al (2009), Souza et al (2013Souza et al ( , 2016, Igado (2014), Maximiano (2017), and Magalhães et al (2019), which involved species of yet another order, the Carnivora. Thus, we defined: LAM -the distance between the lateral margin of the condylar process and the root of the lower medial incisive tooth; SAM -the distance between the ventral and alveolar margins of the body of the mandible at the level of the diastema that exists between the fourth lower premolar tooth and the first lower molar tooth; MFVB -the distance between the caudal limit of the ventral margin of the mandibular foramen to the ventral margin of the angle of the mandible in that same level; MFCOND -the distance between the caudal limit of the ventral margin of the mandibular foramen to the medial margin of the condylar process; MFCOR -the distance between the caudal limit of the ventral margin of the mandibular foramen to the dorsal limit of the caudal margin of the coronoid process ( Figure 1).…”

Mandibular morphometry applied to local anaesthetic blockage in the capybara (Hydrochoerus hydrochaeris)

“…The mandibular morphometry has been studied in domestic animals such as Saanen goat (Wang et al, 2021), and in wild animals such as crab-eating fox (Souza Junior et al, 2013), maned wolf (Souza Junior et al, 2016), hoary fox (Magalhães et al, 2019), boars (Paulo et al, 2020) and barking deer and sambar deer (Keneisenuo et al, 2021). The morphometric study of the mandible is important because through it one can know the shape and topography of reference sites used in anaesthetic blocking techniques (Souza Junior et al, 2013).…”

Mandible Size and Shape of the Red Fox (Vulpes vulpes) and Golden Jackal (Canis aureus)

“…Cranial morphometry is crucial for taxonomy and has a major impact on the management and maintenance of the species. Several studies have been conducted regarding the craniometrics of carnivores, including dog (Onar, 1999;Ilgun et al, 2021), wolf (Okarma and Buchalczyk, 1993;Milenković et al, 2010;Khosravi et al, 2012;Gürbüz et al, 2020), fox (Gomes and Valente, 2016;Munkhzull et al, 2018;Magalhães et al, 2019), golden jackal (Monfared, 2013;Rezić et al, 2017) and lynx (Gomerčić et al, 2010;Dayan et al, 2017). Most of these studies include the mandible as the lower part of the facial skeleton.…”