Dentistry encompasses conditions of all structures of the oral cavity, namely teeth (hard tissues and periodontium), oral mucosa, salivary glands, etc. Veterinary dentistry and human dentistry have many similarities but also differ greatly in many respects.

Recognition of Disease, Examination, Diagnosis and Treatment

In human dentistry the patient can tell the dentist what their symptoms are and they can respond to queries when pathology is identified. Our dogs and cats cannot communicate directly with us in this way. Instead, they rely on owners picking up on an abnormality and seeking help for them. Several variables (i.e., how good is the animal at showing that something is wrong, how good the owner is at picking up on these signs and interpreting them correctly) come into play. In fact, disease is often advanced before obvious clinical signs are present. Even then, an owner may not notice!

In human dentistry, examination, radiography, diagnosis and treatment are performed in the conscious patient. In veterinary dentistry, all dentistry and oral surgery must be performed under general anaesthesia. Conscious examination of an amenable dog or cat may identify gross abnormalities but only the complete examination will give the information required to diagnose and plan optimal treatment. The complete examination of an anaesthetized animal invariably detects more pathology than thought based on conscious oral examination.

Oral conditions and diseases are a diagnostic challenge. Several disease conditions are generally present simultaneously. The great majority of dogs and cats will have gingivitis and or periodontitis as well as other problems. Moreover, clinical signs are rarely specific; i.e., malodour, changing in eating patterns, and dysphagia are indications that there is a problem in the oral cavity, but they are not necessarily specific for a particular disease. Finally, manifestations of disease are often discrete and are often not detected on conscious clinical examination. Even if they are detected on conscious examination, general anaesthesia is required to evaluate the extent of pathology. The importance of a full oral exam under general anaesthesia (definitive examination) cannot be underestimated.

Treatment strategies

 All pathology identified should be addressed

 May require several GA's

 Animal proofing

 Home care to detect problems early

 Regular checks

Anatomical and Functional Differences

The basic structure of teeth and their periodontal support is similar between man and dogs and cats. The main differences are:

 Tooth number and type. Human dentition is 32 teeth if all molars are present. The human dental formula is: 2 x 2(I), 1(C), 2(PM), 3(M)/2(I), 1(C), 2(PM), 3(M).

 Feline dentition is 30 teeth and the dental formula is: 2 x 3(I), 1(C), 3(PM), 1(M)/3(I), 1(C), 2(PM), 1(M). Canine dentition is 42 teeth with the following dental formula: 2 x 3(I), 1(C), 4(PM), 2(M)/3(I), 1(C), 4(PM), 3(M).

 Tooth shape and contact points. Canine and feline teeth do not have the tight contact between teeth that we have in man. Moreover, occlusal surfaces differ - the dog has much fewer chewing surfaces than man and the cat has no true chewing surfaces.

 Thinner enamel. Canine and feline enamel is dramatically thinner than in man.

 Pulp system closer to the occlusal surface in dogs and cats as compared to man. Consequently, tooth fracture in our pets often results in pulpal exposure and consequent endodontic pathology.

 Bone to tooth ratio different. The relatively reduced amount of bone as compared to man is the main reason why traditional fracture repair is not suitable in dogs and cats.

 Dogs and cats have a predominant open/close jaw action, which is very different from the human jaw movement which allows open/close as well as large lateral deviations. Also, the biting forces are greater in the dog as compared to man.

Aesthetic Considerations

Aesthetics/cosmetics is a big part of human dentistry. In veterinary dentistry, aesthetics is at best a secondary consideration. The goal of veterinary dentistry in the broadest sense is a functional and pain-free oral cavity. While the animal itself is unconcerned about appearance, there are many breeders and owners, especially in the dog show world who are extremely concerned about malocclusion and aesthetics. Malocclusion occurs in breeds with all head shapes (dolicho-, meso- and brachycephalic). Often the breed standards are 'unrealistic'. The aetiopathogenesis of malocclusion is not fully understood.

Occlusion is the term used to describe the 'bite'; i.e., the relationship of teeth in the same jaw as well as the relationship of teeth in opposing jaws. Occlusion is determined by shape of the head, jaw length and width and of course the position of the teeth. By definition, malocclusion is an abnormality in the position of the teeth. Malocclusion is common in dogs, but it also occurs in cats. The clinical significance of malocclusion is that it may cause discomfort and sometimes pain to the affected animal. In some cases, it may be the direct cause of severe oral pathology. It is consequently important to diagnose malocclusion early in the life of the animal so that preventative measures can be taken.

Malocclusion can result from jaw length and/or width discrepancy (skeletal malocclusion), from tooth malpositioning (dental malocclusion) or a combination of both. The development of the occlusion is determined by both genetic and environmental factors. It is known that jaw length, tooth bud position and tooth size are inherited (Stockard 1941). It is also known that the development of the upper jaw, mandible and teeth are independently regulated genetically (Stockard 1941). Disharmony in the regulation of these structures results in malocclusion. Alteration of jaw growth by hormonal disorder, trauma or functional modification may result in skeletal malocclusion (Hennet, Harvey 1992a). Although tooth bud position is inherited, various events during development and growth may alter the definitive tooth position.

It is claimed that at least 50% of malocclusions are acquired and have no genetic cause (Beard 1989; Shipp, Fahrenkrug 1992). There are no data to support such a claim in dogs or cats. Not much research has been done and there are no large epidemiological studies available. Specific genetic mechanisms regulating malocclusion are unknown. A polygenic mechanism, however, is likely and explains why not all siblings in successive generations are affected by malocclusion to the same degree, if affected at all. With a polygenic mechanism, the severity of clinical signs is linked to the number of defective genes.

The most reasonable approach suggested (Hennet, Harvey 1992b; Hennet 1995) to evaluate whether malocclusion is hereditary or acquired is as follows:

 Skeletal malocclusion is considered inherited unless a developmental cause can be reliably identified.

 Pure dental malocclusion, unless known to have breed or family predisposition, should be given the benefit of a doubt and not be considered inherited.

References

1.  Hennet PR. Orthodontics in small carnivores. In: Crossley DA, Penman S, eds. BSAVA Manual of Small Animal Dentistry. Cheltenham, UK: British Small Animal Veterinary Association; 1995:182–192.

2.  Hennet PR, Harvey CE. Craniofacial development and growth in the dog. J Vet Dent. 1992a;9(2):11–18.

3.  Hennet PR, Harvey CE. Diagnostic approach to malocclusions in dogs. J Vet Dent. 1992b;9(2):23–26.

4.  Shipp AD, Fahrenkrug P. Practitioner's Guide to Veterinary Dentistry. Beverley Hills, CA: Dr Shipp's Laboratories. 1992:117–147.

5.  Stockard CR. The genetic and endocrinic basis for differences in form and behaviour. In: The American Anatomical Memoirs No. 19. Philadelphia, PA: The Wistar Institute of Anatomy and Biology; 1941.