Small herbivore dental disease (Proceedings)
Rabbits, guinea pigs, and chinchillas are all monogastric, hindgut-fermenting herbivores adapted to a course, high-fiber diet. They graze and browse almost continuously, chewing on plant material, gradually wearing their teeth down as a result. To compensate, the teeth (incisors and cheek teeth in these species) continue to erupt throughout life, at up to 2 mm per week. The rates of dental wear and tooth eruption are in equilibrium, and if they fall out of synch, problems occur. The dynamic process of mastication, tooth wear, and tooth growth can be thrown out of balance by improper husbandry, which is why dental disease is among the most common presenting complaints in exotic companion mammal practice.
The possession of "open-rooted" teeth that continue to grow throughout life is the most important peculiarity of rabbits and rodents. This single factor underlies many of the diseases typical of these species, and is the primary reason why dental disease is so frequent as well. Lagomorphs and rodents are herbivorous, with highly specialized nutritional requirements and digestive physiology. This is the primary reason why dental disease is frequently followed by other secondary disease processes, which often actually produce the first clinical signs and symptoms noted by owners and veterinarians alike. As prey species, the small herbivores frequently minimize clinical symptoms, making early detection of dental disease a challenge. Small herbivores are highly dependent on normal dental function. As such, dental disease in rabbits, guinea pigs, and chinchillas often has a tremendous impact on health in general.Etiology
The three main causes proposed for dental disease are congenital, nutritional, and metabolic bone disease. The primary congenital abnormality of teeth is incisor malocclusion, and this occurs mostly in dwarf rabbit breeds. Nutritional causes include insufficient dietary fiber and dental wear (all species), and vitamin C deficiency (guinea pigs). Metabolic bone disease can be due to nutritional deficiency of calcium or vitamin D, insufficient sunlight, or renal secondary hyperthyroidism (rabbits). Of course, dental disease can with any process that disrupts the teeth or bones of the skull (e.g. trauma, infection, or neoplasia).
That portion of a tooth extending above the gum line is the clinical crown; extending below the gum line is the reserve crown. Teeth that continue to erupt throughout life are termed elodont or aradicular. The "root" of an elodont tooth is more accurately termed the apex. Teeth that normally exhibit long clinical crowns are referred to as hypsodont (e.g. incisors and cheek teeth of rabbits, guinea pigs, and chinchillas); those with short crowns are termed brachyodont (e.g. cheek teeth of rat- and squirrel-like rodents). Visually indistinguishable aradicular hypsodont premolar and molar teeth are simply referred to as cheek teeth. The long space separating the incisors from the cheek teeth in rabbits and rodents is the diastema. Dental pathology other than congenital disease is called acquired dental disease (ADD).
Malocclusion of the incisor teeth is the most common clinical presentation of dental disease. While dental disease affecting the cheek teeth is a more frequent clinical diagnosis, diseases affecting the incisors are typically more obvious and apparent to owners.
Animals with dental disease tend to hypersalivate or drool. In mild cases, the animal may still be eating, but only selects certain food items from the previous menu. The animal may chew differently, hold its head at an odd angle, or otherwise indicate problems eating or drinking. It may go to food and show initial interest, but refrain from eating due to difficulty or pain. With advanced disease, dysphagia leads to anorexia. Odor from the mouth may be detected, and pus or blood may be evident in severe cases. Lumps or swellings may be evident on the jaw or skull. Exophthalmos, epiphora, or blepharospasm can also be signs. If asked, owners may report that there are fewer droppings than normal, that droppings are smaller than normal, or softer, etc. Weight loss, lethargy, and unkempt appearance are also common. There may also be vocalization or erratic behavior due to discomfort.