Article Text

Download PDFPDF

Quantitative and qualitative assessments of intraoral lesions in 180 small herbivorous mammals
  1. V. Jekl, MVDr, PhD1,
  2. K. Hauptman, MVDr, PhD1 and
  3. Z. Knotek, MVDr, PhD1
  1. 1 Avian and Exotic Animal Clinic, Faculty of Veterinary Medicine, University of Veterinary and Pharmaceutical Sciences Brno, Palackeho 1-3, 612 42 Brno, Czech Republic

Abstract

Between 2002 and 2005 210 rabbits, 257 guinea pigs and 123 chinchillas were examined; oral disease was diagnosed in 38·1 per cent of the rabbits, 23·4 per cent of the guinea pigs and 32·5 per cent of the chinchillas. In the rabbits, the maxillary right P3, mandibular right P3, P4 and M1 and mandibular left P3, P4, and M1 were the teeth most frequently affected; in the guinea pigs, the mandibular right P4 and both the mandibular left incisor and P4 were most often affected; and in the chinchillas the maxillary right P4 and M1 and maxillary left P4 were most often affected. The incisors and first mandibular cheek teeth of the guinea pigs were significantly more often affected than those in the chinchillas or rabbits. Bilateral lesions of the maxillary cheek teeth were significantly more common in the chinchillas. The highest incidence of gingival hyperplasia was recorded in the rabbits. The incidence of gingival erosions and gingivitis were significantly higher in the chinchillas.

View Full Text

Statistics from Altmetric.com

DISEASES of the oral cavity are common in small exotic mammals (Harkness and Wagner 1995, Wiggs and Lobprise 1995, Verstraete and Osofsky 2005). In rabbits, guinea pigs, chinchillas and small rodents, many local and systemic conditions that affect the mouth and oral cavity have been described, including hereditary, infectious, metabolic and traumatic conditions (including foreign bodies), electrical accidents and neoplasms (Lindsey and Fox 1994, Harcourt-Brown 2002, Crossley 2003a, Legendre 2003, Heatley and Smith 2004).

Different forms of congenital, developmental or acquired dental disease induce signs of hypersalivation, anorexia, chewing disturbances, changes in food preferences and poor body condition (Harcourt-Brown 2002, Crossley 2003a). Dental disease can also be accompanied by the development of facial abscesses, wet dermatitis, epiphora, exophthalmia and damage to the temporomandibular joint (Poikela and others 2000, Harcourt-Brown and Baker 2001, Glöckner 2002). Factors that affect the position of the teeth, such as abnormalities in the width, length and height of the jaws, may also result in malocclusion, as may variations in the arrangement of the teeth along the jaw, and the degree of eruption, rotation and tipping of the teeth (Crossley 2003b).

Clinical examination of the oral cavity of small herbivorous mammals needs to be species-specific, owing to differences in their oral anatomy and chewing movements (Popesko and others 1990a, 1990b, Igarashi and others 2000, Crossley 2005). Several methods have been described for close examination of the oral cavity, including endoscopy and computed tomography (Crossley and others 1998, Hernandez-Divers and Murray 2003, Capello and others 2005, Verstraete and others 2005, Jekl 2006).

The aim of this study was to assess qualitatively and quantitatively the incidence and range of oral pathology in three species of small herbivorous mammals examined between 2002 and 2005.

MATERIALS AND METHODS

Between October 2002 and September 2005, 210 rabbits, 257 guinea pigs and 123 chinchillas were examined at the University of Veterinary and Pharmaceutical Sciences Brno; 80 of the rabbits (42 males and 38 females), 60 of the guinea pigs (33 males and 27 females) and 40 of the chinchillas (19 males and 21 females) had dental disease and/or intraoral pathology (Table 1). These animals had been submitted for clinical examination with a history of anorexia, changes in feeding habits (to prefer soft food) and excessive salivation, in some cases coupled with moist dermatitis, swellings of the lower jaw, mild exophthalmia, changes in faecal consistency or malocclusion of the incisors.

History and clinical examination

Each animal's previous intake of food, and signs of bruxism, fur chewing, eating noisily (smacking), and lack of defecation and drinking were recorded. Previous health problems and their treatment were also noted. The animals were then thoroughly examined, ending with an oral examination. The animal's facial symmetry and any abnormal head or jaw movements or vocalisation were recorded, and the jaws, temporomandibular joints and areas around the eyes were palpated. Records were also made of whether the animal showed signs of apathy, general loss of condition, hypothermia, salivation, wet chin, wet fur on the toes of the front legs, cheilitis, poor coat condition, decreased skin elasticity, ectoparasitosis, dyspnoea, rhinitis, epiphora, exophthalmia, meteorism, fluid in the caecum and intestines, small faeces, constipation, diarrhoea or facial abscesses.

Laryngoscopic and endoscopic evaluations

The oral cavity was first examined with a paediatric laryngoscope, and a more thorough examination was then made under general anaesthesia with an endoscope, as described by Jekl and Knotek (2007). Meloxicam and buprenorphine were administered to provide anaesthesia (Flecknell 2001).

Morphological abnormalities of the teeth and details of any soft tissue lesions were recorded, including fractures of the incisors, abnormal elongation of the crowns, pathological occlusion of the incisors, hypodontia, horizontal ridges on the enamel surfaces, and discharges or foreign bodies in the gingival sulcus. The surfaces of the cheek teeth and the intraoral soft tissues, including the tongue, were also examined. Each tooth and gingival sulcus was palpated with a periodontal probe to monitor the movement and depth of the sulcus. In some cases abscesses were also probed. The following pathological changes were recorded for the cheek teeth: widening of interproximal coronal surfaces, coronal elongation, changes in the occlusal surfaces, and the presence of spikes, tooth torsion, tooth movement, tooth fracture, dental caries or hypodontia. The following changes in the soft tissues were recorded: gingival hyperplasia, erosions, gingivitis, food impaction, and any purulent discharge. The data were stored using ScenalyzerLive v 4.0 software; video editing and adjustments were made in Adobe Premiere Pro v 1.5 and Adobe Photoshop v 7.0.

Malocclusion was categorised into four grades on the basis of the endoscopic findings, ranging from minimal to severe pathological changes (Table 2).

Dental nomenclature

The animals' teeth were identified by the Triadan tooth numbering system.

Data analysis

The data were compared using Fisher's exact probability test. All calculations were performed with stat Plus and Microsoft Excel. The a priori significance levels were established as P<0·05 or P<0·01.

RESULTS

Incidence of intraoral pathology

Intraoral pathology was diagnosed in 80 of the 250 rabbits (38·1 per cent), 60 of the 257 guinea pigs (23·4 per cent) and 40 of the 132 chinchillas (32·5 per cent). The incidence of oral cavity disease was significantly higher (P<0·01) in the rabbits than in the guinea pigs. The chinchillas were significantly older (P<0·01) than the guinea pigs or rabbits (Table 1).

History and clinical data

The numbers of animals with various historical and clinical signs of disease are shown in Table 3. The incidences of bruxism and low intake of food were not significantly different in the three species; noisy eating (smacking) was not recorded in the guinea pigs, but was recorded in the chinchillas and rabbits. The incidence of self-mutilation was significantly higher in the chinchillas (P<0·01) than in the guinea pigs or rabbits. More guinea pigs than rabbits showed signs of apathy (P<0·05), and a general loss of condition was observed more often (P<0·01) in the guinea pigs than in the rabbits, but there were no significant differences in terms of apathy and general loss of condition between the chinchillas and the guinea pigs or between the chinchillas and rabbits. Salivation, wet chin and wet fur on the distal parts of the front legs were recorded significantly more often (P<0·01) in the chinchillas than in the guinea pigs and rabbits, and significantly fewer of the guinea pigs (P<0·01) than of the other species were affected by these conditions. Cheilitis was diagnosed only in the guinea pigs. The incidence of reduced skin elasticity was significantly higher in the guinea pigs (P<0·01) than in the rabbits. Ectoparasites were diagnosed in the guinea pigs (Trixacarus caviae, Gyropus ovalis and Gliricola porcelli) and in the rabbits (Cheyletiella species and Psoroptes cuniculi). Dyspnoea was detected most frequently in the guinea pigs and rhinitis was detected most frequently in the rabbits. The incidence of meteorism was significantly higher in the guinea pigs (P<0·01) than in the chinchillas and rabbits, and its incidence in the chinchillas was significantly lower than in the guinea pigs (P<0·01) and rabbits (P<0·05).

Significantly more of the guinea pigs (P<0·01) than chinchillas or rabbits had fluid in the caecum and diarrhoea, and the incidence of constipation was significantly greater (P<0·01) in the chinchillas than in the rabbits and guinea pigs. Significantly more of the rabbits (P<0·01) than guinea pigs or chinchillas had facial abscesses. There were no significant differences between the three species in the incidence of epiphora, exophthalmia, poor coat condition or small faeces.

Quantitative evaluation of tooth pathology

Rabbits

The most affected teeth were maxillary right P3 (107), mandibular right P3, P4, and M1 (407, 408 and 409), and mandibular left P3, P4 and M1 (307, 308 and 309), and the fewest pathological changes were recorded in maxillary right M3 (111), mandibular right M3 (411) and maxillary left M1, M2 and M3 (209, 210 and 211); the differences in frequencies among teeth groups were significant (P<0·01) (Tables 4, 5). Lesions were observed significantly more often (P<0·05) in the lower cheek teeth of both jaws than in the upper cheek teeth (Fig 1).

FIG 1

Three examples of incisor malocclusion in rabbits. (a) Incisor malocclusion due to traumatic fracture and restricted eruption of the left mandibular incisor. (b) Incisor malocclusion due to cheek teeth pathology and suspected metabolic disease (dark enamel staining). (c) Severe incisor and peg teeth overgrowth due to incorrect treatment

Guinea pigs

The most affected teeth (Fig 2) were mandibular right P4 (408), and mandibular left incisor and P4 (301 and 308), and the fewest pathological changes were recorded in all M3 (111, 211, 311 and 411) and both upper M2 (110 and 210); the differences in frequencies among teeth groups were significant (P<0·01) (Tables 4, 5). There weresignificantly more (P<0·01) pathological changes in the lower cheek teeth than in the upper cheek teeth.

FIG 2

Elongated clinical crowns of both mandibular premolars with tongue entrapment in a three-year-old female guinea pig

Chinchillas

The most affected teeth were maxillary right P4 and M1 (108 and 109) and maxillary left P4 (208), and the fewest pathological changes were recorded in all the incisors (101, 201, 301 and 401) and the lower right M3 (411) and lower left M2 and M3 (310 and 311); the differences in frequencies among teeth groups were significant (P<0·01) (Tables 4, 5). There were significantly more (P<0·05) pathological changes in the upper cheek teeth than in the lower cheek teeth.

Interspecies comparison

There were significantly more pathological changes in the upper incisors (101 and 201) of the guinea pigs than of the rabbits and chinchillas (P<0·05). The chinchillas had the highest frequency of pathology of both upper P4 (108 and 208) (P<0·05). The guinea pigs had significantly higher (P<0·01) incidences of pathological changes to the lower incisors (301 and 401) and both lower P4 (308 and 408) than the rabbits or chinchillas. There were significantly fewer pathological changes to the lower cheek teeth of the chinchillas (P<0·01) than to those of the rabbits or guinea pigs.

There were no significant differences between the three species in terms of pathology in the mandibular M1, M2 and M3, in the teeth in the upper jaw, or in the teeth on the left and right side of the mouth.

Qualitative evaluation of tooth pathology

The incidence of selected oral pathologies is presented in Table 6.

Incisors

Significantly more changes in the pattern of wear of the occlusal incisors were observed in the guinea pigs than in the rabbits (Plt;0·05). Horizontal ridges were observed on the labial surface of the incisors of the rabbits significantly more often (P<0·05) than in the guinea pigs and chinchillas. Iatrogenic damage (typical of that seen from clipping) was observed significantly more often (P<0·01) in the guinea pigs than in the chinchillas or rabbits. Pathological changes to the patterns of wear of the occlusal incisor surfaces were observed in all cases of brachygnathia superior in the rabbits. Malocclusion (mainly due to crown elongation) of the peg teeth was observed in 12·5 per cent of the rabbits.

Cheek teeth

Significantly fewer of the guinea pigs had widened interproximal coronal spaces between the upper cheek teeth of both jaws (P<0·01) than of the rabbits (Fig 3) and chinchillas. The rabbits that had this condition in their upper jaws had a significantly higher frequency of it (P<0·05) in their lower jaws than the rabbits without the condition in their upper jaws, and the chinchillas and rabbits with the condition on the right side of the mouth cavity also had the condition significantly more frequently (P<0·01) on the left side. The guinea pigs showed no signs of the condition.

FIG 3

Endoscopic view of the oral cavity of a four-year-old male rabbit, showing elongated clinical crowns of the (a) right and (b) left maxillary P2 and P3 with gingival hyperplasia and widened interproximal coronal spaces between the cheek teeth. Different crown and tooth size is apparent when compared with the periodontal probe.(c) Palpation of the teeth for possible movement and gingival sulcus probing was performed in all cases when observing the oral cavity

Elongated clinical crowns were observed significantly more often in both upper dental arcades of the chinchillas than in the rabbits (P<0·01) or guinea pigs (P<0·05), but in both lower dental arcades the condition was significantly more common (P<0·01) in the guinea pigs than in the rabbits or chinchillas, in which its incidence was minimal, and lower in the chinchillas than in the rabbits. The rabbits and guinea pigs with elongated crowns on the right side of the mouth also had a significantly higher frequency of elongated crowns on the left side (P<0·01). The same pattern was observed in the chinchillas, but with lower significance (P<0·05). In 25 per cent of the guinea pigs with elongated crowns the tongue was completely arched, and in 10 per cent the tongue was almost completely entrapped.

Loose cheek teeth were significantly more common (P<0·01) in the rabbits than in the guinea pigs or chinchillas, and cheek tooth torsion was significantly more often observed (P<0·01) in the rabbits (Fig 4 ) than in the guinea pigs. A significantly higher incidence of tooth decay was recorded in the chinchillas than in the rabbits (P<0·05) or the guinea pigs (P<0·01). Hypodontia of upper right P4 (108) was recorded in one chinchilla, and hypodontia of upper left P2 (206) and both peg teeth was recorded in two rabbits.

FIG 4

Endoscopic view of the oral cavity of a two-year-old male rabbit, showing (a, b) purulent material in the oral cavity together with a necrotic lesion distal to the mandibular right last molar (arrows). (c) Sharp spikes on the mandibular molars cause tongue erosion

Soft tissues

Significantly more gum erosions (P<0·01) were recorded in the chinchillas than in the rabbits or guinea pigs. In the rabbits and chinchillas, there were significantly more erosions (P<0·01) (Fig 5) and gum erosions (P<0·05) in animals with elongated crowns, but this was not the case in the guinea pigs. There were no significant relationships in any of the three species between the occurrence of elongated crowns in the upper and lower jaws.

FIG 5

Endoscopic view of the oral cavity of a three-year-old female chinchilla. (a) Irregular upper cheek teeth size and growth is seen on both upper dental arcades, together with (b, c) spike formation and with wideningof the interproximal coronal spaces

In the chinchillas and guinea pigs there was no significant relationship between a low intake of food and soft tissue (tongue and gum) erosions. However 35 of the 66 rabbits with a low intake of food had soft tissue erosions, compared with none of the 14 rabbits with a normal food intake (P<0·01).

The rabbits had a significantly higher frequency of gum hyperplasia than the guinea pigs (P<0·01) or the chinchillas (P<0·05).

Food impaction was diagnosed significantly more often (P<0·01) in the chinchillas than in the rabbits, and the chinchillas also had a significantly higher incidence (P<0·01) of gingivitis than the guinea pigs and rabbits.

There were no significant differences between the three species in the frequencies of widening of the interproximal coronal spaces between the lower cheek teeth, elongation of the crowns of the lower left cheek teeth, tongue erosions, palate erosions, and changes in the occlusal surface of the cheek teeth, the presence of spikes, incisor fractures and hypodontia.

Grades of malocclusion

The animals' categorisation into the four grades of malocclusion is summarised in Table 7. There were no significant differences between the numbers of animals of the different species in grades 1, 2 and 3, but significantly more guinea pigs than rabbits were placed in grade 4 (P<0·05).

DISCUSSION

There are few publications that provide thorough descriptions of oral disease and of which teeth are affected in small herbivorous mammals (Harcourt-Brown 1995, Crossley 2003a). In the present study, the incidence of dental disease in small herbivorous pets was 30·1 per cent, similar to the incidences reported in other countries (Crossley 2001, Glöckner 2002). However, the results do not include lesions that are mainly detected radiographically, as radiographic assessment was not included in this study, and the true incidence of dental disease will therefore be higher. The incidence of oral cavity diseases, especially periodontal disease and malocclusion, generally increases with increasing age. In this study, the affected animals were, on average, in the second or third part of their life span (Harkness and Wagner 1995).

There are many clinical signs associated with dental disease in small herbivorous mammals (Harcourt-Brown 1996, Wiggs and Lobprise 1997a). One of the main non-specific signs is a reduced intake of food (Harcourt-Brown 2002, Crossley 2003a), and it was the most common reason for the animals to be presented to the authors' clinic (recorded for 95·0 per cent of the chinchillas, 91·7 per cent of the guinea pigs and 95·0 per cent of the rabbits). Crossley (2001) recorded reduced feed consumption in 16 of 56 chinchillas with dental disease. Glöckner (2002) and Harcourt-Brown (1995) described anorexia, in association with malocclusion, in 10 of 21 and in 15 of 40 rabbits. In those studies, the affected animals all had coronal elongations of the cheek teeth with spikes and soft tissue lacerations. In the present study, no similar relationship was observed in the chinchillas and guinea pigs. However, in the rabbits, the incidence of gum erosions was significantly higher in animals with reduced feed consumption. Poor body condition was diagnosed in 53·8 per cent of the rabbits, a significantly smaller proportion than in the guinea pigs (80·0 per cent). Glöckner (2002) recorded poor body condition in nine of 21 rabbits with dental disease. Crossley (2001) recorded poor body condition in association with dental disease in 79·0 per cent of chinchillas, compared with 70·0 per cent in the present study. Poor skin condition and reduced skin elasticity were common signs. Ectoparasitosis was recorded in 20·0 per cent of the guinea pigs (T caviae, G ovalis and G porcelli) and in 15·0 per cent of the rabbits (Cheyletiella species and P cuniculi).

Bruxism is a physiological condition in rabbits, but it can also be associated with painful abdominal stimuli (Flecknell 2001, Jenkins 2001, Crossley and Aiken 2003). Harcourt-Brown (1998), Bradley (2001) and Verstraete and Osofsky (2005) have described teeth-grinding in rabbits and guinea pigs with dental disease. In this study, the average incidence of bruxism was 13·1 per cent. There was no apparent correlation between bruxism and meteorism or between bruxism and dental disease. Bruxism was also recorded in healthy animals.

Bradley (2001) described excessive salivation in guinea pigs with dental disease. In the present study, the lowest incidence of saliva drooling was recorded in the guinea pigs, and it was correlated with the lowest incidence of smacking and wet paws on the forelimbs. Glöckner (2002) recorded excessive salivation in 9·5 per cent of rabbits, but in the present study 32·5 per cent of the rabbits were affected. The highest incidence of excessive salivation (70·0 per cent) with perioral staining (65·0 per cent) was recorded in the chinchillas. In a study of 56 chinchillas with dental disease by Crossley (2001), excessive salivation was observed in 20·0 per cent of the animals and perioral staining in 14·0 per cent.

In chinchillas, fur chewing is a well known behaviour problem in pet and farm animals (Rees 1962, Donnelly 2003). Crossley (2001) described self-mutilation in 21·0 per cent of chinchillas with malocclusion. In the present study 30·0 per cent of the chinchillas were affected, and the problem was correlated with the presence of excessive salivation, perioral staining and wet forelimb paws. Fur chewing in association with dental disease is not a problem in rabbits and guinea pigs (Harcourt-Brown 2002, Hess 2003, Legendre 2003), and no self-mutilation was observed in these species.

The highest incidence of facial abscesses in association with dental disease (27·5 per cent) was diagnosed in the rabbits. Harcourt-Brown (1995) and Glöckner (2002) described this pathology in 35·0 per cent and 46·3 per cent of rabbits, respectively. The abscesses were not examined microbiologically in the present study.

Crossley (2001) described epiphora in 20·0 per cent of chinchillas with dental disease. In the present study, epiphora was recorded in 35·0 per cent of the chinchillas, 18·3 per cent of the guinea pigs and 30·0 per cent of the rabbits. There were no significant differences between the species. Five per cent of the chinchillas, 1·70 per cent of the guinea pigs and 1·30 per cent of the rabbits were diagnosed with mild exophthalmia, but a direct link with the oral disease was observed in only two cases. To confirm whether epiphora is a result of elongation of the apical teeth or other apical pathology, radiographic examination or computed tomography is required (Marini and others 1996, Crossley and others 1998, Verstraete and others 2005). The highest incidence of dyspnoea was recorded in the guinea pigs, and the highest incidence of rhinitis was recorded in the rabbits. Epistaxis was directly linked with oral disease in two cases — a foreign body perforating the hard palate of a rabbit and a maxillary fracture in a chinchilla.

The highest incidence of constipation was observed in the chinchillas. These animals were also apathetic, generally with poor nutrition and reduced skin elasticity. The highest incidence of diarrhoea was observed in the guinea pigs. In the rabbits and guinea pigs with diarrhoea there were also liquid gut contents and meteorism. Harcourt-Brown (1995) observed diarrhoea in 5·0 per cent of rabbits with dental disease. Crossley (2001) observed only one diarrhoeic chinchilla. Secondary gastrointestinal disease in animals with dental disease can be explained by changes in their feeding habits, for example, a preference for soft food, and painful stimuli in the oral cavity. As a result, there is a lower intake of fibre and problems in the formation and ingestion of caecotrophs. According to the species specific feeding habits and gastro intestinal physiology of small herbivorous mammals (Stevens and Hume 1995, Carpenter and Kolmstetter 2000), the above changes could result in aerophagy, gastrointestinal hypomotility, meteorism and enteritis. In this study, the chinchillas appeared to be more sensitive to painful stimuli associated with dental disease than the rabbits and guinea pigs, and they rapidly lost their appetite. The guinea pigs and rabbits preferred softer food, and they suffered a higher incidence of liquid gut contents, meteorism and diarrhoea, probably as a result of dysbiosis.

It is more difficult to evaluate the oral cavity of small herbivorous mammals than those of dogs and cats because their oral cavities are long and narrow (Crossley 1995a, b, Wiggs and Bloom 2003). Suitable methods have been described by Malley (2000), Redrobe (2000), Crossley (2003a) and Capello and others (2005). The optimal method for more detailed examination of the oral cavity is endoscopy (Taylor 1999, Harcourt-Brown 2002, Hernandez-Divers and Murray 2003, Jekl and Knotek 2007).

The guinea pigs had a significantly higher incidence (P<0·01) of pathological changes to all the incisors than the rabbits and chinchillas; there were changes to the occlusal surfaces in 56·7 per cent of the guinea pigs, 55·0 per cent of the chinchillas and 40 per cent of the rabbits. Pathological changes to the pattern of wear of the occlusal surfaces of the incisors were observed in all the cases of brachygnathia superior in the rabbits. Crossley (2001) described an abnormal pattern of wear of the occlusal surfaces of the incisors in 34·0 per cent of chinchillas suffering from dental disease. In the chinchillas in this study, the overall incidence of incisor damage was 20·0 per cent, with the right maxillary incisor teeth being affected more frequently than the others. There was significantly more iatrogenic damage typical of that resulting from tooth clipping (P<0·01) in the guinea pigs (31.7 per cent) than in the chinchillas or rabbits. Loss of occlusion of the incisor teeth, iatrogenic changes to the occlusal surfaces of the incisors and iatrogenic incisor fractures were the most common findings, as also described by Capello and others (2005). Teeth should not be clipped with scissors or pliers because of the possibility of causing damage (Legendre 2002, Crossley 2003a).

In chinchillas, depigmentation of tooth enamel is a physiological condition (Crossley 2003a), and it was observed in 32·5 per cent of the chinchillas. Horizontal folds in the enamel, which are probably caused by abnormal enamel formation due to metabolic disease (Harcourt-Brown 2002), were observed in 12·5 per cent of the rabbits. Malocclusion, mainly due to elongation of the crowns of the peg teeth, was observed in 12·5 per cent of the rabbits.

In the rabbits, the teeth most frequently affected were maxillary right P3 (107), mandibular right P3, P4 and M1 (407, 408 and 409), and mandibular left P3, P4 and M1 (307, 308 and 309). The highest frequency of elongated crowns, the highest frequency of widened interproximal coronal spaces and the highest frequency of gum hyperplasia were observed in both upper dental arcades. The highest incidences of loose cheek teeth and cheek tooth torsion were correlated with the presence of pus in the oral cavity and with periodontitis, abscessed teeth or facial abscesses. In the rabbits there was a positive correlation between low food intake and the presence of soft tissue erosions.

The highest frequency of pathological changes to both the most rostrally (mesially) positioned mandibular premolars (elongated crowns included) were recorded in the guinea pigs. Any elongation of the cheek teeth tends to push the mandible rostrally, so that these teeth, or parts of them, are not worn adequately and become elongated lingually or mesially (Crossley 2005). Sassnau (1994) described perforations of the cheek due to elongation of left mandibular P4 (308). However, in the present study, none of the guinea pigs had perforated cheeks. Bridge-like malocclusion, which is quite common in guinea pigs (Legendre 2003), occurred in 25·0 per cent of the guinea pigs with dental disease, and in 10·0 per cent of them the malocclusions of P4 (308 and 408) were so severe that they caused complete bridge formation and entrapment of the tongue. In all these cases the animals were in poor body condition. In some cases, severe alocclusion with lateral mandibular shift, buccal crown elongations of the distal mandibular cheek teeth (310, 311, 410 and 411) and lingual crown elongations of the distal maxillary teeth (110, 111, 210 and 211) were recorded. In none of the uinea pigs were the interproximal coronal spaces of the cheek teeth widened, probably owing to their distinctive anatomy and the way in which the cheek teeth of guinea pigs erupt (Legendre 2002).

In the chinchillas, the teeth most frequently affected were in the upper jaw (108, 109 and 208). The chinchillas also had significantly higher incidences of gum erosions and gingivitis than the guinea pigs and rabbits, in association with the highest incidence of elongated crowns. Crossley (2001) described spikes on the occlusal surfaces of 7·0 per cent of chinchillas with dental disease, but in the present study they were observed in 80·0 per cent of the animals. The large difference may be due to the different methods used to examine the oral cavity of the animals, by otoscope or rigid endoscope. The chinchillas also had the highest incidences of gingivitis, gum erosions and food impaction, which were probably why they had the highest incidence of excess salivation. A comparison of the damage to each dental arcade in each chinchilla indicated that the changes were mostly bilateral, with the same lesions on both sides.

The development of dental caries requires interactions between the anatomy, physiology, diet and bacterial flora of the host. Chinchillas with dental disease are prone to caries as a result of malocclusion and/or their natural preference for highly energy-dense and easily eaten food (Gutierez and Bozinovic 1998, Wolf and others 2003). The chinchillas in the present study had the highest incidence of dental caries, and in all three species the condition was associated with food impaction in the interproximal spaces or close to the mucosal surface of the cheeks.

Enamel disease is most easily detected by visual and tactile inspection of the teeth (Tholen and Hoyt 1990, Wiggs and Bloom 2003); in the present study it was detected endoscopically. Resorptive lesions of other teeth structures are generally detected by radiography (Wiggs and Lobprise 1997b).

There is a low incidence of intraoral tumours in rabbits, guinea pigs and chinchillas (Harkness and Wagner 1995, Heatley and Smith 2004); hyperplastic mucosal tissue was recorded in only three of the animals in this study, and it was probably caused by long-term gum irritation due to improper mastication.

The incidence of dental disease in these small herbivorous pets was very high, and the three species had specific qualitative and quantitative intraoral pathologies, which will affect the diagnostic procedures applied when individual animals are being examined.

ACKNOWLEDGEMENTS

The authors thank Mrs Frances Harcourt-Brown for critical reading of the manuscript and her valuable comments, and Mr David Crossley for his valuable comments. They also thank Karl Storz Veterinary Endoscopy for technical support, and the technical staff of the Avian and Exotic Animal Clinic, University of Veterinary and Pharmaceutical Science, Brno, for their skilful assistance.

References

View Abstract

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.