小动物杂志节选《牙齿的脱落》

Tooth fractures are a risk for very hard dental treats such as antlers, hooves, or nylon bones. The British Veterinary Dental Association notes that “Many veterinary dentists are reporting that they are seeing fractured teeth as a direct result of chewing on antler bars; in par- ticular, the maxillary fourth premolar tooth” (BVDA 2017). Recommendations of techniques that can be utilized to evaluate for excessive treat hardness include being able to dent the treat with a fingernail (Hale 2003).

Additives

Some diets and treats contain antiseptics or additives to retard or inhibit plaque or calculus accumulation. Sodium hexametaphos- phate (HMP) forms soluble complexes with cations (e.g. calcium) and decreases the amount available for forming calculus. (White et al. 2002; Hennet 2007). Adding HMP to a dry diet decreased calculus in dogs by nearly 80% (Stookey et al. 1995), however, tartar is not a major player in the development of gum disease. Studies have shown no difference in plaque or calculus when HMP-coated biscuits were fed to dogs for 3 weeks (Stookey et al. 1996; Logan et al. 2010).

The addition of antiseptics to treats or water additives are an attractive method for treating periodontal disease. However, as pre- viously noted, plaque bacteria have resistance to concentrations of antiseptics up to 500,000 times that which would kill singular bacteria (Elder et al. 1995; Socransky et al., 2002; Quirynen et al. 2006). Therefore, while the substance may have a positive effect on singular bacteria, in most cases at standard concentrations it is beneficial but not when diluted in the drinking water.

Chlorhexidine has been proven to have efficacy as an oral antiseptic which may reduce plaque, especially as a perioperative or pre- prophylaxis rinse (Roudebush et al. 2005) although it may enhance mineralisation of plaque to calculus (Hale 2003). However, suffi- cient contact time is likely not achieved when using as a rinse. In addition, reports of efficacy are variable (for example the addition of chlorhexidine to rawhide chews provided a reduction in plaque but had no effect on the degree of gingivitis) (Rawlings 1998; Brown & McGenity 2005). Along with chlorhexidine, a new chew additive is the anti-plaque agent delmopinol, which has been shown to decrease plaque and calculus (Claydon N et al. 1996), however not as effectively as chlorhexidine (Reddy R 2017).

Enzyme systems may contain glucose oxidase and lactoperoxidase, lysozyme or lactoferrin. These are well studied on the human side and there is even low-grade evidence for efficacy in dogs and cats for oral anti-bacterial effects (Hale 2003).

Water additives

A study on the effects of a xylitol drinking water additive showed reduced plaque and calculus accumulation in cats (Clarke 2006). Concerns about xylitol will limit the use of this ingredient, as at high concentrations it may cause hypoglycaemia. However, in vet- erinary products, the concentration is very low and has been proven to be safe for healthy dogs when used at the recommended dose (Anthony 2011). There are other products in this category without published evidence of efficacy; however, some may have VOHC approval.

Vitamin and mineral deficiencies

Deficiencies in vitaminA, C, D and E and the B vitamins folic acid, niacin, pantothenic acid and riboflavin have been associated with gingival disease (Logan et al. 2010). Diets deficient in calcium may result in nutritional secondary hyperparathyroidism, which can cause periodontal disease (Roudebush et al. 2005). These vitamins and minerals are adequate in diets which meet AAFCO or FEDIAF guidelines but can be deficient in diets which don’t meet those guidelines, such as many homemade diets.

Natural diets and feeding raw bones

Proponents of feeding raw bones have claimed that this improves the cleanliness of teeth in pets. Further claims are sometimes made that feeding commercial pet food contributes to the high prevalence of periodontal disease in domesticated cats and dogs. However, the skulls of 29 African wild dogs eating a “natural diet”, mostly wild antelope, also showed evidence of periodontal disease (41%), teeth wearing (83%) and fractured teeth (48%) (Steenkamp & Gorrel 1999). A study in small feral cats on Marion Island (South Africa) which had been eating a variety of natural foods (mostly birds) showed periodontal disease in 61% of cats, although only 9% had evidence of calculus (Verstraete et al. 1996). In a study in Australia offeral cats eating a mixed natural diet there was less calculus compared to domestic cats fed dry or canned commercial food, although again there was no difference in the prevalence of periodon- tal disease between the two groups (Clarke & Cameron 1998). In a study on eight Beagle dogs fed cortical bone (bovine femur) there was an improvement in dental calculus, although no effect on plaque was reported (Marx et al. 2016).

These studies show that feeding raw bones may aid in cleansing teeth, however, there are currently no published studies that they are beneficial for periodontal disease. There is also the risk of fractured teeth and potentially of the spread of zoonotic disease (LeJeune & Hancock 2001; Lenz et al. 2009, Furtado et al. 2007).

Probiotics

Nitric oxide (NO), an important inflammatory mediator, has been shown to be increased in human periodontitis (Matejka et al. 1998; Lappin et al. 2000; Hirose et al. 2001) and agents blocking the production of NO or its effects might be therapeutically valuable (Paquette & Williams 2000). Lactobacillus brevis (L brevis) is a probiotic bacterium which contains high levels of arginine deiminase. High levels of arginine deiminase inhibit NO generation by competing with nitric oxide synthase for the same arginine substrate. Studies in humans showed topical application of probiotics containingL brevis decreased inflammatory mediators involved in periodontitis (Della Riccia et al. 2007). Studies using probiotics in treatment of periodontal disease in humans have shown improved gingival health, as measured by decreased gum bleeding. The probiotic strains used in these studies include L. reuteri strains, L. brevis (CD2), L. casei Shirota, L. salivarius WB21, and Bacillus subtilis. L. reuteri andL. brevis (Haukioja 2010), Preliminary results of a study of topicalL brevis CD2 in dogs showed a reduction of gingival inflammatory infiltrates.

Conclusions

Homecare is a critical aspect of periodontal therapy, but it is often ignored. Early and consistent client education is the key to com– pliance. There are numerous options available, but tooth brushing remains the gold standard. While the common myth of dry food cleaning the teeth is appealing, standard dry foods do not appear to significantly decrease the risk of periodontitis. Dental diets or treats may confer some benefit and it is recommended to look for products that have published peer reviewed research and/or the VOHC seal of approval, especially for plaque reduction. Products need to clean down to and below the gingival margin. Feeding standard dry foods or raw bones may decrease dental calculus, but there is not much evidence for a decrease in the risk of periodontitis.

Key Points:

• Daily homecare is recommended since plaque accumulates in 24 hours.

• Without homecare, the efficacy of professional periodontal therapy is severely limited.

• Tooth brushing is the gold standard and is most effective on rostral teeth.

• Passive homecare methods may or may not be effective, and any provided benefit will be mainly on the caudal teeth.

• Standard dry dog and cat food is not beneficial for oral health.

• A combination of active and passive methods is likely the best choice.

SECTION 6: DENTAL RADIOLOGY

DENTAL RADIOGRAPHY FOR DOGS AND CATS

Full–mouth dental radiographs are performed as part of the dental patient diagnostic work–up, especially if the animal is presented for the first time, or if the clinical condition has changed significantly since the previous visit. Dental radiographs aid in diagnosis and guide treatment. They are also an important part of the legal record, and can be extremely valuable in client education. Full–mouth dental radiographs will reveal about 40% more pathology than was found on the clinical examination (Verstraete et al. 1998a, b) (see oral pathology section). Due to costs, practitioners are often forced to balance the desire for a full–mouth set of radiographs with their client’s financial constraints. However, at least obtaining dental radiographs ofthe teeth clinically found to be diseased is mandatory.

Equipment and Techniques

Dental radiography requires a dental x–ray unit (e.g., wall–mounted, mobile, hand–held) and a detection system (e.g., conventional intraoral dental films, “direct” digital radiography (DR), or computed radiography (CR)) (Niemiec 2010c, Niemiec et al. 2004a,

Figure 131. Demonstrating the parallel technique for imaging the

mandibular premolar and molar teeth on a model.