The viper fangs: clinical anatomy, principles of physical examination and therapy (a review)

Abstract

The assessment of fangs is a fundamental part of clinical examination of viperid snakes. The long curved venom fang is carried by short, highly mobile maxilla. Short anaesthesia is advised for safe physical examination and radiography of the mouth cavity. The fangs are gently forced outside the fang pocket by passing the bar or forceps on the palato-maxillary arch, and rotating them rostrally shifting the mucosal fold. Functional fangs are periodically shed and several generations of replacement teeth lie behind and beneath each fang. In case of fang fracture, therapy should be limited to flushing with a solution of chlorhexidine or povidone iodine, and topical application of pro-coagulant and antibacterial cream. Therapy of chronic fang inflammation is based on removal of necrotized fang and repeated abundant irrigation of the fang pocket. Treatment of chronic stomatitis consists of flushing with chlorhexidine or povidone iodine, physical removal of the plaques, administration of analgesics and antibiotics (marbofloxacin, enrofloxacin or ceftazidime). Extra-oral surgical approach is the best method for odontogenic abscess removal. A vigorous flushing with sterile saline solution, chlorhexidine and povidone iodine and topical application of antibiotics (antibiotic embedded surgical sponge) is advised. Force feeding of the anorectic patient suffering from fang inflammation is a mandatory part of the standard treatment protocol. Venomous snakes, odontogenic abscess, stomatitisThe structure and dentition of the maxilla is of major importance in natural classification of snakes (Edmund 1969) and broad knowledge of the reptile anatomy is mandatory for veterinarians in clinical practice with reptiles. In the viperids (family Viperidae, subfamilies Crotalinae and Viperinae) the fang is the only teeth present on the maxilla and is covered by a large mucosal fold (fang pocket). When the mouth is closed the fang lies folded backwards in a sheath along the roof of the mouth in area of diastema (O'Malley 2005). The long curved venom fang is carried by a relatively short maxilla, which is highly mobile and allows for a broad rotation of the fang. The fang is arranged transversely on the maxilla (Edmund 1969) and is retracted by muscular action during the bite. Fangs in vipers (Viperinae) and pit vipers (Crotalinae) are highly modified fangs (solenoglyphous), have a smooth surface and host the venom canal (VC). This canal communicates with the outside through two orifices, proximal oval foramen and distal oval foramen (Zahradnicek et al. 2008). Venom passes from the venom gland into the fangs entering the proximal oval foramen and is delivered through the distal foramen into the prey (Jackson 2002;Zahradnicek et al. 2008). The triangular maxilla contacts dorsally the prefrontal bone, caudally the ectopterygoid bone and cranially the septomaxilla. The prefrontal bone articulates with the braincase in a movable saddled joint. The snout shows a high degree of mobility, rotating on its attachment on the braincase in conco...