Jackie in Tampa
08-10-2012, 04:37 PM
Diagnosis and Treatment of Dental Disease in Pet Rodents
V. Capello
Clinica Veterianria S.Siro, Clinica Veterinaria Gran Sasso, Milano, Italy.
TAXONOMY AND DENTAL ANATOMY
Rodents belong to the Order Rodentia, the largest mammalian order. They are grouped into three suborders based on anatomical and functional differences of their jaw muscles, namely the Miomorph (Myomorpha, "rat-like" or "mouse-like"), the Sciuromorph (Sciuromorpha, "squirrel-like"), and the Hystrychomorph (Histrichomorpha, or Caviomorpha, "porcupine-like" or "guinea pig-like") rodents.
Rodents have well-developed incisor teeth. Rodents are monophyodont, with one single set of teeth (no deciduous set), and a single pair of maxillary incisor teeth. Premolar and molar teeth have no anatomical or physiological differences, and are therefore simply called "cheek teeth". Rodents lack canine teeth, and have incisor and cheek teeth separated by a wide edentulous gap called the "diastema".
Porcupine-like rodents (the most common kept as pets are the Guinea Pig, the Chinchilla and the Degu) are true herbivores, with complete elodont (open rooted, growing throughout life) dentition.
Rat-like rodents (the most common kept as pets are the Rat, the Mouse, the Gerbil, the Duprasi and the Hamster, including the Golden or Syrian Hamster and the Russian hamsters) are omnivorous, and have elodont incisor teeth and anelodont (teeth with a limited period of growth) cheek teeth.
A few squirrel-like rodents may be encountered as pets, and include the Prairie Dog, the Chipmunk and the European Citellus, also named "dwarf" prairie dog. Like Miomorphs, Sciuromorphs have elodont incisor teeth, and anelodont cheek teeth.
The dental formula of rodents is presented in Table 1.
Table 1. Dental Formula of Rodents Cheek Teeth INCISORSPREMOLARSMOLARSNumber of Cheek TeethTotal NumberMaxillary/MandibularMaxillary/MandibularMaxillary/MandibularMaxillary/Mandibular 1/11/13/34/4 = 1620Elodont/HypsodontElodont/HypsodontElodont/HypsodontElodont/Hypsodont 1/10/03/33/316Elodont/Hypsodont Anelodont/BrachyodontAnelodont/Brachyodont 1/11-2/13/34-5/4 =16-1820-221/12/13/35/4 = 1822Elodont/HypsodontAnelodont/BrachyodontAnelodont/BrachyodontAnelodont/Brachyodont The cheek teeth of herbivorous species are flat but not smooth, with crests of enamel and grooves in dentine for a proper crushing of food. The anatomy of the cheek teeth of rabbits and porcupine-like rodents is very similar, but guinea pigs show an important structural peculiarity. The mandibular teeth are curved with a pronounced buccal convexity, and the maxillary teeth with a prominent palatal convexity. This results in a 30 degree oblique occlusal plane that slopes from buccal to lingual (lateral to medial) dorsal to ventral (Figure 1).
http://www.ivis.org/images/proceedings/navc/2006/sae/fig616-1_sm.jpg (javascript:fileName='fig616-1.asp';displayFig2()) Figure 1. (javascript:fileName='fig616-1.asp';displayFig2()) To view click on figure
Despite being herbivorous, prairie dogs have brachyodont (short crowned) and anelodont cheek teeth, which are not open rooted and continually growing as is sometimes reported in literature.
The temporomandibular joint and and masticatory muscles of rodent species allow marked rostrocaudal movement, much greater than in lagomorphs. They are able to rostrally subluxate the mandible during gnawing. Unlike lagomorphs, the cheek teeth are in occlusion when the jaw is at rest. This gives the appearance of brachygnathism, as the mandibular diastema is is shorter than the maxillary diastema.
DIAGNOSTICS
The most common clinical signs and symptoms of dental disease in guinea pigs are reduced food intake, anorexia, digestive disturbances and weight loss. Many owners report only chewing difficulties. When compared to rabbits, however, presenting signs and symptoms are usually more severe. Guinea pigs are usually presented for reduced food intake or complete anorexia, which is sometimes reported by owners as sudden onset.
The small size makes safe, effective restraint and oral examination even more difficult in non-anesthetized rodent species than in rabbits. The well-developed buccal skin folds of guinea pigs also complicates introduction of an otoscope cone. Therefore, in most cases, oral examination must be conducted under general anesthesia. Unless the guinea pig is anorexic, the oral cavity normally contains food debris that may impede evaluation of the teeth and soft tissues.
In chinchillas, dental disease often presents as ptyalism and pawing of the mouth. Other common symptoms include chewing and licking of the paws, with resulting dermatitis and other cutaneous lesions. Epiphora and blepharospasm can be symptoms of elongation of the roots of cheek teeth. Dacriocystitis secondary to dental disease can present as nasal discharge and wet fur around the nostrils. The mandibular and maxillary surface should be accurately evaluated. Root elongation may cause cortical bone deformities easily palpable as asymptomatic or painful hard swellings.
Golden hamsters are frequently presented for malocclusion of incisor teeth and for facial swellings, sometimes affecting ocular and periocular structures. Oral inspection of golden hamsters is possible only in calm, properly restrained individuals. Gentle expression of the cheek pouches will help removed stored food that can hinder examination. Inspection of the cheek pouches is an important part of examination of the oral cavity. It can be performed using an otoscope.
Dental fractures of incisor teeth are particularly common in prairie dogs housed indoors. Common causes include falls and chewing on cage bars, especially when cage size is too small. Maxillary teeth are most frequently affected.
Dyspnea, sometimes associated with sneezing or so called "reverse sneezing", can be due to dystrophic change and root deformation of the maxillary incisor teeth (also referred to as pseudo-odontomas) which lead to reduced nasal air passage. Complete intraoral inspection of the conscious prairie dog is not feasible, and should always be performed under general anesthesia. Conscious examination is usually limited to inspection of incisor teeth.
Radiographic examination of the skull and teeth is an essential diagnostic tool in case of suspected dental disease. Due to the tiny size of these species, good to excellent quality skull radiographs are mandatory. They can be obtained with the use of standard radiographic equipment, and screen films. High-resolution mammography x-ray films are particularly advantageous.
Multiple views are necessary for a full evaluation and diagnosis should never be based on any single radiographic image. The five standard radiographic projections are the lateral, the right and left oblique, the ventrodorsal or dorsoventral and the rostrocaudal ("skyline"). Deep sedation or general anesthesia is usually necessary for perfect positioning.
Due to the occlusal angulation of the cheek teeth of the guinea pig, the rosto-caudal and not the lateral projection is the only one that is helpful in viewing the occlusal plane in this species.
Optimal visualization of the oral cavity of rodents is greatly facilitated by endoscopy, especially in smaller patients. The 2.7 mm rigid endoscope and accessories, are ideal for this purpose. Endoscopy becomes even more critical for detection of lesions in rat-like or other small rodents.
The use of computed tomography has been described in the chinchilla. While currently not practical, CT represents a viable future diagnostic option.
Culture and sensitivity tests are important in cases of dental disease-related infection and abscessation. Guinea pigs have long been used as laboratory models for human gingivitis and periodontal disease, and studies indicate anaerobic bacteria play a large role in infections and abscesses. Therefore requests for culture should specify screening for both aerobic and anaerobic organisms. Purulent material from the core of an abscess is usually sterile, which necessitates collection of samples from the abscess capsule wall.
Histopathology can also be useful in selected cases, particularly when bone neoplasia or dental dysplasia are suspected.
V. Capello
Clinica Veterianria S.Siro, Clinica Veterinaria Gran Sasso, Milano, Italy.
TAXONOMY AND DENTAL ANATOMY
Rodents belong to the Order Rodentia, the largest mammalian order. They are grouped into three suborders based on anatomical and functional differences of their jaw muscles, namely the Miomorph (Myomorpha, "rat-like" or "mouse-like"), the Sciuromorph (Sciuromorpha, "squirrel-like"), and the Hystrychomorph (Histrichomorpha, or Caviomorpha, "porcupine-like" or "guinea pig-like") rodents.
Rodents have well-developed incisor teeth. Rodents are monophyodont, with one single set of teeth (no deciduous set), and a single pair of maxillary incisor teeth. Premolar and molar teeth have no anatomical or physiological differences, and are therefore simply called "cheek teeth". Rodents lack canine teeth, and have incisor and cheek teeth separated by a wide edentulous gap called the "diastema".
Porcupine-like rodents (the most common kept as pets are the Guinea Pig, the Chinchilla and the Degu) are true herbivores, with complete elodont (open rooted, growing throughout life) dentition.
Rat-like rodents (the most common kept as pets are the Rat, the Mouse, the Gerbil, the Duprasi and the Hamster, including the Golden or Syrian Hamster and the Russian hamsters) are omnivorous, and have elodont incisor teeth and anelodont (teeth with a limited period of growth) cheek teeth.
A few squirrel-like rodents may be encountered as pets, and include the Prairie Dog, the Chipmunk and the European Citellus, also named "dwarf" prairie dog. Like Miomorphs, Sciuromorphs have elodont incisor teeth, and anelodont cheek teeth.
The dental formula of rodents is presented in Table 1.
Table 1. Dental Formula of Rodents Cheek Teeth INCISORSPREMOLARSMOLARSNumber of Cheek TeethTotal NumberMaxillary/MandibularMaxillary/MandibularMaxillary/MandibularMaxillary/Mandibular 1/11/13/34/4 = 1620Elodont/HypsodontElodont/HypsodontElodont/HypsodontElodont/Hypsodont 1/10/03/33/316Elodont/Hypsodont Anelodont/BrachyodontAnelodont/Brachyodont 1/11-2/13/34-5/4 =16-1820-221/12/13/35/4 = 1822Elodont/HypsodontAnelodont/BrachyodontAnelodont/BrachyodontAnelodont/Brachyodont The cheek teeth of herbivorous species are flat but not smooth, with crests of enamel and grooves in dentine for a proper crushing of food. The anatomy of the cheek teeth of rabbits and porcupine-like rodents is very similar, but guinea pigs show an important structural peculiarity. The mandibular teeth are curved with a pronounced buccal convexity, and the maxillary teeth with a prominent palatal convexity. This results in a 30 degree oblique occlusal plane that slopes from buccal to lingual (lateral to medial) dorsal to ventral (Figure 1).
http://www.ivis.org/images/proceedings/navc/2006/sae/fig616-1_sm.jpg (javascript:fileName='fig616-1.asp';displayFig2()) Figure 1. (javascript:fileName='fig616-1.asp';displayFig2()) To view click on figure
Despite being herbivorous, prairie dogs have brachyodont (short crowned) and anelodont cheek teeth, which are not open rooted and continually growing as is sometimes reported in literature.
The temporomandibular joint and and masticatory muscles of rodent species allow marked rostrocaudal movement, much greater than in lagomorphs. They are able to rostrally subluxate the mandible during gnawing. Unlike lagomorphs, the cheek teeth are in occlusion when the jaw is at rest. This gives the appearance of brachygnathism, as the mandibular diastema is is shorter than the maxillary diastema.
DIAGNOSTICS
The most common clinical signs and symptoms of dental disease in guinea pigs are reduced food intake, anorexia, digestive disturbances and weight loss. Many owners report only chewing difficulties. When compared to rabbits, however, presenting signs and symptoms are usually more severe. Guinea pigs are usually presented for reduced food intake or complete anorexia, which is sometimes reported by owners as sudden onset.
The small size makes safe, effective restraint and oral examination even more difficult in non-anesthetized rodent species than in rabbits. The well-developed buccal skin folds of guinea pigs also complicates introduction of an otoscope cone. Therefore, in most cases, oral examination must be conducted under general anesthesia. Unless the guinea pig is anorexic, the oral cavity normally contains food debris that may impede evaluation of the teeth and soft tissues.
In chinchillas, dental disease often presents as ptyalism and pawing of the mouth. Other common symptoms include chewing and licking of the paws, with resulting dermatitis and other cutaneous lesions. Epiphora and blepharospasm can be symptoms of elongation of the roots of cheek teeth. Dacriocystitis secondary to dental disease can present as nasal discharge and wet fur around the nostrils. The mandibular and maxillary surface should be accurately evaluated. Root elongation may cause cortical bone deformities easily palpable as asymptomatic or painful hard swellings.
Golden hamsters are frequently presented for malocclusion of incisor teeth and for facial swellings, sometimes affecting ocular and periocular structures. Oral inspection of golden hamsters is possible only in calm, properly restrained individuals. Gentle expression of the cheek pouches will help removed stored food that can hinder examination. Inspection of the cheek pouches is an important part of examination of the oral cavity. It can be performed using an otoscope.
Dental fractures of incisor teeth are particularly common in prairie dogs housed indoors. Common causes include falls and chewing on cage bars, especially when cage size is too small. Maxillary teeth are most frequently affected.
Dyspnea, sometimes associated with sneezing or so called "reverse sneezing", can be due to dystrophic change and root deformation of the maxillary incisor teeth (also referred to as pseudo-odontomas) which lead to reduced nasal air passage. Complete intraoral inspection of the conscious prairie dog is not feasible, and should always be performed under general anesthesia. Conscious examination is usually limited to inspection of incisor teeth.
Radiographic examination of the skull and teeth is an essential diagnostic tool in case of suspected dental disease. Due to the tiny size of these species, good to excellent quality skull radiographs are mandatory. They can be obtained with the use of standard radiographic equipment, and screen films. High-resolution mammography x-ray films are particularly advantageous.
Multiple views are necessary for a full evaluation and diagnosis should never be based on any single radiographic image. The five standard radiographic projections are the lateral, the right and left oblique, the ventrodorsal or dorsoventral and the rostrocaudal ("skyline"). Deep sedation or general anesthesia is usually necessary for perfect positioning.
Due to the occlusal angulation of the cheek teeth of the guinea pig, the rosto-caudal and not the lateral projection is the only one that is helpful in viewing the occlusal plane in this species.
Optimal visualization of the oral cavity of rodents is greatly facilitated by endoscopy, especially in smaller patients. The 2.7 mm rigid endoscope and accessories, are ideal for this purpose. Endoscopy becomes even more critical for detection of lesions in rat-like or other small rodents.
The use of computed tomography has been described in the chinchilla. While currently not practical, CT represents a viable future diagnostic option.
Culture and sensitivity tests are important in cases of dental disease-related infection and abscessation. Guinea pigs have long been used as laboratory models for human gingivitis and periodontal disease, and studies indicate anaerobic bacteria play a large role in infections and abscesses. Therefore requests for culture should specify screening for both aerobic and anaerobic organisms. Purulent material from the core of an abscess is usually sterile, which necessitates collection of samples from the abscess capsule wall.
Histopathology can also be useful in selected cases, particularly when bone neoplasia or dental dysplasia are suspected.