Dental Directions: When considering the teeth, imagine you are facing the ferret, gazing directly at their mouth. The maxillary dental arch is dorsal (or superior), and the mandibular dental arch is ventral (or inferior). The tooth surface you see when the ferret opens its lips, which curves to follow the teeth towards the back of the mouth, and which faces outward, is called the vestibular surface (= labial, buccal). The part facing the tongue (or the inside of the mouth), which also curves to follow the teeth towards the back of the mouth, is called the lingual surface (palatal, if maxillary teeth). The mesial surface is the edge of the teeth that faces towards the 1st incisor (= towards the median sagittal plane). The distal surface is the edge of the teeth that faces towards the back of the mouth (away from the median sagittal plane). The occlusal surface is the part of the tooth that faces the other teeth (the cutting or grinding part). The apex is the tip of the root, so the apical surface is the part of the tooth facing the roots (the bottom of the tooth). The cervical surface is essentially the neck of the tooth, where the root meets the crown, and can extend a short way under the enamel. Dental Shorthand: Teeth are assigned to one of four regions: the Right Maxillary, the Left Maxillary, the Right Mandibular, and the Left Mandibular quadrants. All animal teeth are named by dentition, side, arcade, position, and type of tooth, such as the "permanent right mandibular 2nd incisor". Since this is such a long description, odontological shorthand has developed over the years, (which is definitely NOT standardized! There are nearly as many variants as authors). "R" or "L" means "right" and "left", respectively. Incisors are shorted to "I", canines to "C", premolars to "PM" or "P", and molars shortened to "M". The letters used for tooth types are also used to identify the dentition; lowercase "c" means the tooth is a deciduous canine and uppercase "C" means it is a permanent canine (some shorthand methods use a lowercase "d" to distinguish deciduous teeth; dI, dC, dPM). Individual teeth are numbered, starting at the edge closest to the midline or front of the mouth (= median sagittal plane) and proceeding towards the back of the mouth. The number is placed to the right of the letter, and is subscripted for mandibular teeth and superscripted for maxillary teeth. Thus, "deciduous right maxillary 2nd incisor" is shortened to Ri2/ and "permanent left mandibular 1st molar" becomes LM/1. When using a text program that does not allow sub-or superscripting (like most email), placing a slash under or over the number will indicate jaw position, which is also a good idea when writing out the formula by hand (thus, "2/" is a superscripted 2, and "/2" is subscripted 2). In addition, sometimes a short dash is made over a lowercase letter to insure clarity. When the number is neither sub- or superscripted (C1), it means the tooth is found in both the upper and lower jaws; but this isn't seen as often. Dental Formulae: The dental formula (= natural dentition, complete dentition) can be written in many ways (like dental shorthand, standardization of dental formulae has eluded odontologists). However, all use the standard incisor-canine-premolar-molar sequence, which is the sequence of the teeth in the jaw. The most complicated method lists all teeth in both arcades (illustrated here with the ferret deciduous dentition): pm3 : c1 : i3-4 : i3-4 : c1 : pm3 16 ----------------------------------- = -- = 28-30 pm3 : c1 : i3 : i3 : c1 : pm3 14 You will notice the number of upper incisors indicated by "3-4". This simply means the ferret may have 3 or 4 maxillary deciduous incisors (the "28-30" means the ferret can have between 28 and 30 deciduous teeth). This is a hard formula to write, requiring several passes on the keyboard and subject to becoming a confused mess if the pagination is off a tiny bit, so it often simplified as: pm3/3 : c1/1 : i3-4/3 : i3-4/3 : c1/1 : pm3/3 = 16/14 = 28-30 However, since both sides of the jaw are symmetrical, there is no need to write both down, so the deciduous dental formula for the ferret is simplified: i3-4/3 : c1/1 : pm3/3 = 16/14 = 28-30 Finally, in the last simplification, it is assumed the reader can do simple mathematics, and the numbers are dropped, leaving the most commonly encountered dental formula for the deciduous dentition of the ferret being: i3-4/3 : c1/1 : pm3/3 = 28-30 The dental formula for the ferret's permanent dentition: I3/3 : C1/1 : PM3/3 : M1/2 = 34 Mind you, as earlier indicated, there are a LOT of different ways to write the dental formula of mammals. This method is only one of many, and while used in Colyer's and other comprehensive texts, it should not be considered the best or only method. Prototypic Eutherian Dentition: Mammals are divided into three basic groups, more or less depending on how they give birth. Prototherians (= monotremes) are egg-laying mammals such as the platypus, and they lack teeth in the adult (the platypus dental formula is considered to be 0/5 : 1/1 : 2/2 : 3/3 = 34). Metatherians (= marsupials) are pouched mammals such as the opossum, and they retain a primitive dental formula containing extra incisors and postcanine teeth (the opossum has 50 teeth, including 10 upper and 8 lower incisors). Eutherians (= placental mammals) are mammals that possess a functional placenta, and have a simplified dentition compared to marsupials. The prototypical eutherian permanent dentition (generalized mammalian dentition, ancestral eutherian dentition) is considered to be: I3/3 =96 C1/1 =96 PM4/4 =96 M3/3 = 44 The prototypical eutherian deciduous dentition is: i3/3 =96 c1/1 =96 pm4/4 = 32 Most species have some variant of this formula -- usually a reduction in the number of teeth. The ferret is no exception, lacking an upper and lower premolar, and an upper and two lower molars in the permanent dentition. When numbering, there are rules for considering lost teeth; premolars are lost from the front, and molars are lost from the rear. This means the ferret lacks the maxillary and mandibular 1st premolar, as well as the maxillary 3rd molar, and mandibular 2nd and 3rd molars. This is a developmental loss of teeth, or hypodontia. Humans have likewise lost teeth; the first two premolars are missing, but because of centuries of dental nomenclature prior to the modern understanding of tooth homology, the teeth in the 3rd and 4th position remain the "1st and 2nd deciduous molars", and the "1st and 2nd permanent premolars". Knowing the prototypic eutherian dentition is valuable for understanding extra or missing teeth in a particular set of jaws, and is of great benefit in discovering evolutionary relationships. Gingivitis and Periodontitis: Where gingivitis is -- in essence -- an infection or inflammation of the gums (= gingivia), periodontitis is an infection of the outer tooth and surrounding dental structures as a whole, including the gingivia, alveolar bone, periodontal ligament, and tooth surfaces. Either can be localized or extended, although periodontal disease generally attacks a larger area than gingivitis. Periodontal disease is far more serious because it can result in the loss of the tooth through the destruction of the supporting bone or loss of the periodontal ligament. The exact mechanisms for the shift from gingivitis to periodontitis are still under investigation, especially in the ferret. However, it is clear gingival plaque plays a role, as does the presence of tartar (= dental calculus, calcareous deposit, mineralized plaque). Diet is also a major contributing factor from both the mechanical and compositional aspect. Plaque is a tenacious film composed of bacteria embedded in a food and saliva matrix (roughly 70% is composed of bacteria, and 30% is composed of matrix). It is commonly found on tooth surfaces, between teeth, and -- in the case of an open gingival sulcus due to inflammation -- under the gums adjacent to the bone and other periodontal structures. Plaque often progresses into "materia alba"; the cheesy, white deposit on and between the teeth, consisting of food and skin debris, and significant numbers of bacteria. Over time materia alba will calcify, forming dental calculus, which is a hard concretion typically found adhering to the teeth at the gum line (in ferrets, dental calculi is rich is calcium phosphates, and is often a form of bone-hard hydroxyapatite). In the presence of plaque, materia alba, and/or dental calculus, other mechanisms -- including autoimmune reactions, tobacco products, drug therapy and systemic diseases (especially lymphoma) play a part in the transformation of a simple disease into one which threatens the health of the mouth. Aleutian's Disease may also be a factor in periodontal destruction in ferrets; advanced periodontitis is often associated with the viral disease in ranched American mink. As the disease progresses, causing the gingivia and bone to withdraw, it exposes the root (= long in the tooth). Ultimately, the tooth can lose so much support that it will break or fall out. While this is more common in the incisors and cheek teeth, it is not unheard of in the canines. Most cases are treatable with antibiotics, changes to the ferret's diet, or dental work. Ferrets with loose or discolored teeth, with obvious deposits along the gum lines, or with bad breath which does not resolve in week or so, should be evaluated by a veterinarian. While the loss of teeth and dental structure is the prevailing consequence of the ailment, periodontal disease may promote other bacterial disorders, such as cystitis, kidney infections, or endocarditis. An excellent review of periodontal disease in various wild and captive species can be found in Colyer's Variations and Diseases of the Teeth of Animals (A. E. W. Miles and Caroline Grigson, eds. 1990 Cambridge University Press, revised edition). Miles and Grigson report periodontal disease in wild mustelids has never been found, yet the disease is extremely common in captive and pet mustelids, including American mink, polecats, ferrets, and other species. I have noticed a similar trend; several skulls of polecats once housed in zoos showed extensive periodontal disease, reactive bone and dental calculus, yet skulls from feral ferrets and wild polecats showed very little evidence of the disease. Indeed, the paucity of wild animals displaying evidence of gingival and periodontal disease, compared to the plethora of captive animals suffering from the affliction, suggests the common factor to be a human-designed diet (I consider it to be a triggering mechanism). Modern zoos, which feed their captive predators a more natural "meat and bone" diet, have reported significant reductions of periodontal disease. Historically, soft diets have been associated with periodontal ailments, and an emphasis has been placed on feeding ferrets a hard food as a preventative. However, little attention has been given to the various food components in the diet, or even to the initial definitions of "soft", "semi-moist" and "moist"; were they minced meats or cereal based? Obviously, periodontal disease is a highly complex problem and suggesting any single factor as being the cause would be simplistic. However, even if the exact mechanism for shifting gingivitis towards periodontitis is unproven, there is still a strong correlation of the disease to diet, as well as to deposits of plaque, materia alba and tartar, and reducing such deposits would have benefit. This would include restricting access to soft, sticky fruits and reducing total starchy carbohydrates (especially cereals). Rubbing a tartar-control dentifrice on the teeth on a weekly basis may have value, although I am unaware if the fluoride is a danger or not (I would appreciate veterinarian comments regarding the dangers of ferrets ingesting small amounts of fluoridated toothpaste). Additionally, augmenting the diet with hard or fibrous "chewing" foods, such as hard gelatin products, dog biscuits, or even bone may be of help (in one instance, laboratory ferrets with a high incidence of periodontal disease showed a marked improvement after the addition of beef ribs to the diet). The addition of bone to a ferret's diet is controversial and usually results in comparisons to domestic dogs choking on chicken bones. It is difficult to understand how a report of a dog bolting a chicken bone can be contrasted to a ferret gnawing the end off a chicken femur that can hardly fit into their mouth, but the comparison is common. The ferret's polecat progenitor evolved eating bones of this size, and while the occasional ferret may have a problem, that is insufficient reason to oppose a practice with established positive benefits. On occasion, human infants drown during bathing, but few fuss-budgets suggest mothers stop bathing their children. Rather, extra care is suggested, which is good advice when feeding bone. Far more ferrets have died from being trapped behind furniture, from being accidentally stepped on, or even from chewing electrical cords than have had confirmed deaths from bone. Zoo dietitians routinely feed obligate carnivores a "meat-and-bone" diet, and complications caused from bone ingestion are extremely rare. You just have to be careful, feed bones which must be gnawed rather than bolted, and allow the ferret time to learn how to eat the new food. In terms of risk, eating bone is clearly safer than inoculations. Cooked chicken necks and backs, and beef ribs and vertebrae are excellent treats; they don't splinter like long bones, they cannot be swallowed in large enough chunks to cause blockages, they allow the ferret access to chewable bone, and they are large enough to be easily located for later disposal. Round bones from beef or pork steaks are also good, especially if they still contain marrow. The harder bones are too large and hard for the ferret to chew, but if you leave small amounts of meat on the bone (fibrous connective tissue or gristle is especially good), it will still help clean the ferret's teeth as they pull and tug on the tissue. It is carnivorian dental floss. Nonetheless, if you have questions regarding the feeding of bone to your ferret, consult your veterinarian. Just point out that ferrets are not dogs if those "dog swallowing chicken bone" anecdotes are brought up. Bob C [Posted in FML issue 3505]