Caries Causes and Prevention

Caries, also called cavity or tooth decay, is a plaque-caused destruction of the hard tissues of the tooth. It starts as inorganic demineralization of the enamel, the white, compact and very hard substance covering and protecting the dentin. The demineralization occurs when bacteria use fermentable carbohydrates (sugar). The acidic fermentation products demineralize the enamel. Once the enamel has been destroyed, the process extends into the dentin, the hard tissue of the tooth which constitutes most of its bulk. Caries is caused by a combination of genetic susceptibility, the presence of bacteria (usually Streptococcus mutans, but also other Streptococcus species, and Lactobacillus species) and an available source of fermentable carbohydrates. Caries can only develop in areas which can develop plaque and accommodate stagnant food particles.^1,3

Dogs and cats do not have serious problems with caries because most of their teeth are built for shearing and tearing rather than grinding. Unlike humans, they do not usually pack food between their teeth and the grinding surfaces of their molars have few pits and fissures which make it easy for bacteria to cling to the enamel and start a colony. Also, the average pH of the human saliva is 6.5, whereas the cat or dog saliva is 7.5. A pH of 7.5 discourages the growth of caries-causing bacteria which need an acidic environment to survive. Another reason that dogs have few problems with caries is that the urea content of their saliva is significantly higher than that of human saliva, so the teeth are constantly bathed ammonium carbonate, an excellent acid-neutralizing agent. Moreover, Streptococcus mutans is not a common inhabitant of the canine mouth.^1,3

Occasionally, caries occurs on grinding surfaces of the molar teeth and the sides of the teeth that face towards the adjacent teeth. Root surfaces also can develop caries. Caries looks like a dark brown or black spot in the enamel. A small enamel defect covers a large cavern of decaying dentin. Diagnosed caries requires treatment. The options are extraction or referral to a restoration specialist. If the process involves the pulp tissue carrying a tooth's nerve and blood supply a special therapy prior to restoration is required.²

Fluoride treatment will not, of itself, stop caries lesions development. The causative agent, the microbial plaque, has to be removed. Frequent plaque removal, exclusion of easily fermentable carbohydrates (mostly sugar) from a dog's diet and frequent topical application of low concentration fluoride preparations will prevent caries and periodontal disease in most dogs.⁴

In general, dry dog foods are more effective in removing plaque and some calculus than soft food types. Some special diets have been formulated specifically to aid in plaque and calculus control and are helpful in maintaining proper oral hygiene. Daily brushing is invaluable in removing plaque and preventing calculus buildup. The ideal toothbrush for a dog should have soft bristles with rounded tip ends to minimize abrasion of the teeth and injury to the gums.⁵

References:
1. Geriatrics and gerontology of the dog and cat By Johnny D. Hoskins
2. Small animal dentistry By Cecilia Gorrel
3. A Colour Handbook of Small Animal Dental and Oral Maxillofacial Disease By Brook A. Niemiec
4. Nutrition and immunology: principles and practice By M. Eric Gershwin
5. Canine Medicine and Disease Prevention