Exotic Animals Oral and Dental Diseases

Exotic Animals Oral and Dental Diseases

Roberto Fecchio1, Marco Antonio Gioso2, and Kristin Bannon3

1 Safari Co. – Zoo and Exotic Animals Dental Consultant, São Paulo/SP, Brazil

2 Laboratório de Odontologia Comparada da FMVZ, University of São Paulo, São Paulo, Brazil

3 Veterinary Dentistry and Oral Surgery of New Mexico, LLC, Algodones, NM, USA

22.1 Introduction

The application of veterinary dentistry is a fairly recent endeavor in Zoo and Exotic Animal Medicine. Despite the emergence of zoos during the nineteenth century, the first scientific publications about dental treatments in wild patients were not available until the 1970s [13]. The knowledge of anatomy, physiology, nutrition, and animal behavior can increase the well‐being and longevity of animals in captivity [1, 4]. The examination of the oral cavity to detect and correct early problems must be part of an overall evaluation program of animal health [1, 5]. Animal conditioning for examination has been increasingly used (Figure 22.1), but a detailed evaluation of the oral cavity can only be performed when the animal is chemically restrained [57] and therefore should be part of every physical examination performed when the animal is anesthetized for other procedures [5, 6, 8]. In addition, chemical restraint provides greater protection to both the animal and the professionals involved.

Photo of a man facing a hippopotamus with its mouth wide open. The man is holding the upper lip of the animal with his left hand while holding an object on his right hand.

Figure 22.1 Conditioning for restraint aids in examinations.

However, detection of oral lesions in captive animals often occurs only after the clinical signs of diseases such as anorexia, weight loss, drooling, changes on holding and chewing food, pain, and discomfort are noted. As the severity of the oral disease progresses, changes in attitude, breeding behavior, food selection in the diet, oronasal discharge, bumps, and malodor can be identified [1, 5, 7, 8].

Although some diseases are more prevalent, it is important that the examination of the oral cavity assess both hard tissues: tooth and bone (presence of calculus, caries, fracture, mobility, and demineralization), and the soft tissues: lip, tongue, gums, palate, cheeks, and pharynx (swelling, bleeding, ulceration, and coloring) [1].

Preventing oral health problems preserves the efficiency of the digestive processes, contributing to the maintenance of general health, and by improving their reproductive abilities, increasing their life expectancy and substantially improving the quality of animal life [1, 5, 7].

22.2 Teeth Classification

The wide variety of dentition found among wild animals is closely linked to the evolutionary and adaptive aspects of each species. Therefore, the teeth have different functions such as holding and chewing food, social and sexual interaction, dimorphism, defense and predation, locomotion, phonation, inoculation of venom, as working tools, and instruments for body cleaning [1, 7].

The classification of the various sets of teeth of animals is based on their morphophysiological aspects (see Chapter 1 – Oral Anatomy and Physiology).

  • Anelodont. Animals whose teeth have limited growth and a clear line dividing the crown and root (cementoenamel junction). These teeth undergo rhizogenesis (root development) during which the dental apex forms after full longitudinal tooth development. The neurovascular supply is maintained through a foramen or multiple foramina formed into a delta. This group can be divided into hypsodont (radicular) and brachyodont, described below. Among the anelodonts are carnivores, primates, and some herbivores [3, 5, 9].
  • Brachyodont. A tooth in which the longitudinal length of the crown is smaller than the root and the entire root portion is inside the alveolar bone. The crowns are fully covered with enamel that extends down to the neck of the tooth. Cementum is only found below the gingival margin. The families Felidae, Canidae, Ursidae, and the Primates are included in this group [3, 5, 9].
  • Hypsodont. A tooth in which the longitudinal length of the crown is greater than the root. Enamel extends below the gingiva margin. This category includes the radicular hypsodont tooth (true root) and aradicular hyposodont tooth (open‐rooted) [3, 5, 9].
  • Radicular Hypsodont (subdivision of Hypsodont). Dentition with true roots, sometimes called “closed rooted” teeth. These teeth erupt throughout life, but eventually develop a true closed apex and the subgingival reserve crown is eventually exposed and placed into occlusion. Anatomically, there is an observed clinical crown (extra‐alveolar), reserve crown (intra‐alveolar), and root. Examples belonging to this category are the premolars and molars of equines (zebras, horses) and bovines [3, 5, 9]. The crown/root ratio varies according to family. The equidae have long reserve crowns when young, while the bovidae and camelidae have relatively shorter crowns. The occlusal surface has a pattern interspersed with enamel, cementum, and dentin in different proportions, which maintains the surface texture, and have infundibulas or multilobed molars.
  • Aradicular Hypsodont (subdivision of Hypsodont). Dentition which continually grows throughout the life of the animal with no development of true roots, sometimes called “open rooted” or “open apex.” Previously known as “Elodont.” As the teeth are worn down, new crown becomes exposed from the continuously growing teeth (such as the incisors of rodents and incisors and cheek teeth of lagomorphs) [3, 5, 9]. While the submerged segment of the crown is sometimes referred to as the “clinical root,” it is not a true root structure. The shape of the elodont pulp facilitates a rich blood supply to the pulp tissue and a high activity within the odontoblastic layer sustains continuous growth and often allows for repair to take place on exposure of the pulp chambers. The aradicular hypsodont species groups can be further divided according to the location of these teeth:

    • All teeth such as lagomorphs (rabbits and hares), caviomorph rodents (chinchillas, guinea pigs), and wombat.
    • Only anterior teeth (the premolars and molars are anelodont) such as miomorph rodents (rats, mice, and squirrels), elephants, and hippopotamus.
    • Only posterior teeth such as aardvark and sloths.

  • Heterodont. Animals whose teeth have different morphology, according to appearance, function, and situation; these teeth are typically divided into incisors, canines, premolars, and molars [3, 5, 9]. The dental eruption can be grouped where the teeth erupt laterally (carnivores, primates, herbivores, and ruminants) or sequentially (molar teeth of elephants and kangaroos), where the teeth erupt horizontally.
  • Homodont. Animals whose teeth are morphologically similar throughout the mouth. Considered the most primitive type of dentition. Examples of animals belonging to this group are dolphins, crocodiles, alligators, and sharks [3, 5, 9] (Figure 22.2).
  • Monophyodont. A subdivision of Homodonts without tooth replacement after loss of the first set. This is the typical pattern found in whales and dolphins [3, 5, 9] (Figure 22.3).
  • Polyphyodont. A subdivision of Homodonts with constant tooth substitutions through life. In this group, dental replacement can occur vertically (crocodiles and snakes) or horizontally (sharks) [3, 5, 9]. They are usually classified according to type and position of attachment (Figure 22.4):

    • Pleurodont. Have an eroded lingual side and are attached to a higher sided labial wall, such as snakes and lizards.
    • Acrodont. Found in lizards such as water dragons and chameleons, which have teeth attached to the crest of the bone.
    • Thecodont. The teeth are embedded in a deep bony socket but, unlike in mammals (that also have a thecodont dentition with teeth in alveoli), there is no periodontal ligament. This type is restricted only to crocodiles.

  • Lophodont. Each molar consists of intricate folding of enamel and dentin with a ridge or crest complex of dentine lamellae covered by enamel, with cementum among the ridges. The cusps are joined to form ridges or lophs. This anatomical pattern of teeth allows grinding of a variety of native plants during chewing.
Image described by caption.

Figure 22.2 Homodont dentition (seal).

Image described by caption.

Figure 22.3 Monophyodont dentition (dolphin).

3 Schematics of tooth attachment categories illustrating acrodont (left), pleurodont (middle), and thecodont (right).

Figure 22.4 Tooth attachment categories.

Table 22.1, proposed by Kertesz [9], illustrates many of the classification terms described above, with some terminology updated. Although it does not describe all types of teeth, it is very useful for clinical and treatment purposes for most animals.

Table 22.1 Animal dental classification.

Source: Adapted from reference [9] with updated terminology.

Tree diagram illustrating branching lines connecting labels types of teeth, homodonts, heterodonts, monophyodonts, grouped eruption, anelodonts, aradicular hyspsodent, hypsodonts, brachyodonts, etc.

22.3 Indication for Dental Treatment

The main difficulty of a clinical oral examination in zoo and exotic patients is the detailed inspection. Suspicion of oral diseases is typically based on clinical and behavioral changes [1], such as:

  • Aggressive behavior (caused by pain)
  • Rubbing the head against objects and friction of the legs/paws on the face
  • Changes in drinking or eating behavior
  • Acute reactions after food/water ingestion
  • Dysphagia or anorexia
  • Progressive weight loss
  • Change in selection of food items (softer)
  • Undigested food in feces
  • Oral bleeding.

The most common clinical signs are:

  • Head asymmetries
  • Abnormal salivation
  • Nasal, ocular, dental, or oral discharge
  • Malocclusion
  • Excessive dental growth.

The characteristic movements of lips, tongue, teeth, and cheeks during mastication of each species should be considered. The veterinarian should understand the differences between species and research individual information with handlers and other professionals who have more intimate contact with particular wild species as necessary [1]. Some of the captive zoo and exotic animals carry a risk of zoonotic diseases. Any clinical examination on these animals requires the use of personal protective equipment (PPE) such as cap, mask, goggles, and gloves.

Oral diseases of wild animals have varied etiologies and have been classified by the American Association of Zoo Veterinarians (AAZV) into four categories: (1) developmental and congenital defects, (2) maxillofacial trauma, (3) periodontal disease, and (4) dental trauma. Oral disease results from a wide variety of circumstances and the clinical appearance of the disease process may vary considerably within a single species, and can vary enormously from one species to another. This text will cover the categories, in order of relative importance, of different exotic animal populations.

22.4 Mammals

22.4.1 Primates

Different countries have a large diversity of fauna and flora. Brazil, for instance, has the largest number of species of primates in the world [10]. They are animals that, in most families, have a dental anatomy similar to humans [11]. Dental procedures in primates have many challenges, such as the wide variation in oral morphophysiology and associated zoonoses, and therefore require appropriate knowledge, training, equipment, rapidness, and accuracy.

Due to the evolving proximity between humans and other primates, zoonotic diseases are of fundamental importance to be taken into account during the approach, especially during physical examination and dental treatment when there are released aerosols with the action of the dental handpieces and ultrasound.

The major oral diseases found in primates are as follows. Periodontal Disease

Periodontal disease is the most prevalent disease in captive primates, affecting up to 57% of primates in captivity [12]. Localized periodontal disease is common in all species of primates, but generalized disease has a higher prevalence in the genus Ateles (spider monkeys) [5, 7]. Elderly animals seem to be more predisposed to periodontal disease and usually have more advanced degrees of disease. The difference between the diet offered in captivity and what the animal has access to in the wild seems to predispose to plaque buildup and, consequently, to periodontal disease in captive animals [1, 11].

The pathophysiology of periodontal disease in primates is similar to that observed in humans. Dental anatomical similarities indicate similar predisposing factors, mainly due to the absence of interdental spaces (diastema). Proper treatment of periodontal disease in wild animals include supra and subgingival calculus removal and polishing of the entire tooth surface, and antibiotics as indicated [13]. Endodontic Disorders

Endodontic disease is highly prevalent among oral lesions, reaching a prevalence of 14% in capuchin monkeys (Cebus apella) in captivity [12]. The most common causes of pulp exposure in primates are accidental fractures and the deliberate amputation of the crowns of canine teeth (iatrogenic) [5, 7, 13, 14].

Bacterial invasion of the exposed pulp causes periapical bone loss, infection, and eventually infraorbital (upper) or mandibular (lower) fistula [5, 7, 11]. Similar to treatment of domestic species, endodontic diseases need treatment. Depending on the severity and duration of the lesion, tooth extraction may become the best option, while an endodontic procedure is always an option. Both procedures may require antibiotics [4, 11, 14, 15].

The endodontic treatment technique in primates is analogous to domestic animals. However, primates have a single apical foramen as in humans, not in the form of delta, as in carnivores [15]. The presence of a single apical foramen requires a slightly modified endodontic technique for appropriate cleaning, filing, and obturation of the canal. Caries

By definition, caries is the demineralization of enamel, dentin, or cementum by the action of bacteria and their acid metabolites [5, 11, 13]. Typically the process occurs due to the acid production of bacteria adhered to the teeth in an oral low pH (below 5.5). Caries often occurs in primates kept as pets, in which a poor diet creates conditions conducive to the growth of cariogenic bacteria, such as Streptococcus mutans. Further research is required in order to establish the influence of the immune system for each species on the formation of carious lesions.

Several factors may contribute to the onset of caries in primates, such as dental fractures, dental malocclusion or crowding, abnormal dental anatomy (fossae, enamel scars, deep enamel sulcus), acidic oral pH, and inadequate diets (with high levels of carbohydrates) [12, 13].

Similar to caries in domestic species, treatment consists of debridement of necrotic tissue and restoration of the cleaned defect with materials such as glass ionomer and composite resins. In more advanced cases with pulp involvement, treatment involves endodontic therapy of the tooth or extraction [13].

Carious lesions are not commonly identified. In one study of 85 lemurs (Lemur sp.), only two had lesions [11] and in a study of 42 monkeys (Cebus apella), none had visible caries [12]. Occlusal Abnormalities

Occlusal abnormalities are often associated with a greater number of teeth than normal (supranumerary). The excess number of teeth is rarely more than one tooth for each dental arcade [12, 16].

In primates, the teeth most affected by crowding are the premolars. The prevalence of malocclusion in primates in the wild is above 40% and in captivity this percentage can double [16, 17] (Figure 22.5).

2 Photos displaying hands holding the monkey’s lips exposing its teeth with maxillary incisor malocclusion (left), and monkey’s head in lateral view facing leftwards, with subsequent skull deformity (right).

Figure 22.5 Monkey (Cebus sp.) with a maxillary incisor malocclusion and subsequent skull deformity.

In captivity, nutritional disorders can aggravate the incidence of deformities. Insufficient bone growth results in teeth assuming similar positions to those of other teeth, causing serious irregularities. Spencer points to a relationship between the root surface and the amount of chewing force, in which primates eating harder food items would have greater root surface, probably due to the influence of the anteroposterior force that occurs during mastication.

22.4.2 Carnivores

Dental principles in carnivores are based on those used in dogs and cats, although wild animal morphophysiology and dentition functions differ in comparison to domestic animals. Oral diseases are among the most prevalent diseases in captive carnivores and should be part of all management programs on these species [1]. The major oral diseases found in carnivores are the following. Periodontal Disease

Periodontal disease is the most prevalent oral disease in carnivores [1, 5, 7 1821]. Like in domestic animals, the growth and the multiplication of microorganisms in dental plaque are determining factors for the initiation and development of periodontal disease. However, some factors may predispose to periodontal disease, such as poor diet, dental and periodontal abnormalities, immune disorders, malocclusion, persistence of deciduous teeth, and some systemic diseases [1, 5, 7, 22].

Recent studies indicate an important relationship between the consistency of the diet and the formation of plaque. Artificial and soft diets generally do not have the same composition as the natural foraging and free‐range diets (bones, ligaments, joints, etc.). They also require little masticatory exercise, contributing to the formation of gingivitis and plaque, which organizes as a colony and can mineralize to form dental calculus and potentially cause damage to the periodontal tissues [22].

In more advanced cases, there may be involvement of all periodontal tissues and eventual exfoliation of the tooth. Prevention of periodontal disease is obtained by correcting the diet and regular clinical assessment and treatment.

In addition to local infection, microorganisms can reach the bloodstream through gingival bleeding and may contribute to diseases such as glomerulonephritis, arthritis, endocarditis, and meningitis. The death of a black bear (Ursus americanus) has been reported due to bacterial endocarditis caused by Staphylococcus aureus, with infection of other organs, for which the oral cavity may have been the primary focus of infection [23].

One study [24] was designed to evaluate the major diseases of the oral cavity related to periodontal disease in Panthera onca in captivity as well as free‐ranging animals, in order to determine if environmental conditions could influence oral health. It used a sample of 42 (N = 42) jaguars (Panthera onca) from 18 institutions in captivity in São Paulo and four (N = 4) free‐ranging jaguars (Panthera onca), captured in the wetlands of Mato Grosso do Sul, Pantanal. The results of clinical signs that lead to periodontal disease were as follows for the animals in captivity: plaque (7%), gingivitis (50%), dental calculus (100%), furcation exposure (14.2%), periodontal pockets (33.3%), and gingival recession (14.2%).

The clinical signs are basically the same as those found in domestic animals and the proper treatment for periodontal disease in non‐domestic animals includes mainly removal of subgingival and supragingival calculus, polishing all tooth surfaces, and antibiotics [1, 4, 13]. Dental Trauma and Endodontic Disease

Along with periodontal disease, dental injuries are highly prevalent in wild carnivores, mainly in captive animals [1, 5, 7, 15].

Dental traumas are differentiated by their characteristics and intensity. Attrition is the constant wear between two or more teeth, erosion is destruction of the tooth structure by chemical agents, and abrasion is the destruction of tooth structures from objects. The tooth surface is capable of supporting certain physiological limits of abrasion, attrition, and erosion. If teeth have dysplasia due to injuries or malocclusion, this limit can be overcome and structural damage to the teeth can be seen. This can also occur in fights or frequent contact with hard objects and enclosure fences. This problem is common in large felines and in other carnivores with aggressive habits due to chewing on the steel bars or concrete structures in the enclosures. The tooth surface is capable of supporting certain physiologically limited friction. If this limit is exceeded by malocclusion, injury, or repetition, excessive wear of the teeth occurs that can progress to fracture. In addition to the dental issues, this syndrome is usually associated with behavioral disorders, characterizing situations of stress in animals kept in captivity. When wear occurs slowly, the odontoblasts are capable of producing tertiary dentin in order to repair the tooth and protect the pulp [15]. In a paper on marsupials, it was reported that the genus Didelphis suffers premature wear of the teeth in the wild due to their predatory habits [25].

More intense trauma can also cause tooth fractures, may involve different structures, and are classified in different degrees [26, 27]:

  • Enamel fracture – Fractures involving enamel
  • Uncomplicated crown fracture – Fracture of enamel and dentin
  • Complicated crown fracture – Fracture with pulp exposure
  • Traumatic tooth loss
  • Root fracture.

In cases of pulp exposure or indirect endodontic involvement, there is contamination by pathogenic microorganisms, which can migrate to the root apex and cause a periapical infection [26, 27]. As a result of this infection, mandibular or maxillary fistulae can be observed.

One study from Brazil [24] reported that 73.07% of the captive population of jaguars (Panthera onca) and 58.33% of the population of pumas (Puma concolor) were affected by dental fractures. The predisposing factor to these lesions appears to be traumatic wear of the teeth. Iatrogenic fractures can occur when attempting to physically restrain animals not sedated or in early stages of sedation, while they are still responsive to external stimuli.

In some dental fractures, the pulp chamber of the crown was exposed or compromised (42.3% in P. onca and 12.5% in P. concolor), which often evolves into pulp necrosis (95% in P. onca). The most affected teeth are the canines, with cusp fractures: 31.57% in P. onca and 71% in P. concolor.

Treatment involves endodontics and restorations, as well as prosthodontics and maxillofacial surgery [15, 28, 29]. However, in some cases, extraction is necessary due to extensive periapical alveolar destruction. Caries

Carnivores are virtually free of caries. It has the same pathophysiology seen in primates, but its prevalence is much lower in carnivores. This is due to the non‐cariogenic factors presented by carnivores such as diets with lower carbohydrate content, dental anatomy (large spaces between the teeth and occlusal surface in the form of cusps, reducing food impaction), and higher salivary pH [30].

Caries may cause intense pain and can lead to anorexia, especially if it reaches the dentin–pulp complex. Animals living in human areas tend to have more dental caries due to a higher intake of carbohydrates and sweets in their diet. Clinically, demineralization of dental structures by the action of acid metabolites produced by bacteria is observed (Figure 22.6). These should be distinguished from tooth resorptive lesions.

Image described by caption.

Figure 22.6 Use of dental explorer to show caries in the left lower canine of a lion (Panthera leo).

Source: Photo: Luiz João Rossi Jr.

The treatment is similar to primates, with debridement of necrotic tissue and restoration of the carious lesion using materials of glass ionomer or composites. In more advanced cases with dental pulp involvement, root canal or extraction is necessary. Resorptive Lesions

Resorptive lesions are common in domestic cats [31] and are also reported in captive and wild animals [20, 32], with only a few studies in these species [33]. There are reports involving lions, leopards [32], jaguars, pumas, ocelots [5], and wild cats [20] (Figure 22.7).

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Aug 15, 2020 | Posted by in GENERAL | Comments Off on Exotic Animals Oral and Dental Diseases

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