DEFINITION/OVERVIEW

Caries is the decay of the dental hard tissues (enamel, cementum, and dentin) due to the effects of oral bacteria on fermentable carbohydrates on the tooth surface
Caries is very common in humans in Westernized societies, where diets rich in highly refined carbohydrates are the norm
For various reasons (e.g., diet lower in carbohydrates, higher salivary pH, lower salivary amylase, conical crown shape, different indigenous oral flora), caries is not common in the domestic dog, but it does occur and should be looked for
A study published in the Journal of Veterinary Dentistry in 1998 (see “Suggested Reading”) reported that 5.3% of dogs 1 year of age or older had one or more caries lesions, with 52% having bilaterally symmetrical lesions
- Caries can affect the crown or roots of the teeth and is classified as pit-and-fissure, smooth-surface, or root caries (Figs. 32-1 and 32-2)

Figure 32-1 Clinical appearance of a caries lesion of the mesial cusp of the left lower first molar tooth of a dog.

Figure 32-2 Radiographic appearance of a caries lesion of the mesial cusp of the left lower first molar tooth of a dog. Note how close to the pulp the lesion extends on the radiograph. If this tooth were to be salvaged, it would have required endodontic therapy as well as restorative work.

ETIOLOGY/PATHOPHYSIOLOGY

Dogs
- Caries is caused by oral bacteria fermenting carbohydrates on the tooth surface, leading to the production of acids (acetic, lactic, propionic) that demineralize the enamel and dentin, followed by digestion of the organic matrix of the tooth by oral bacteria and/or leukocytes
- There is a constant exchange of minerals between enamel and oral fluids; if there is a net loss of mineral, caries develops
- Early (incipient) caries may be reversible through remineralization
- Once the protein matrix collapses, the lesion is irreversible
- Any factors that allow prolonged retention of fermentable carbohydrates and bacterial plaque on the tooth surface predispose to the development of caries
- A deep occlusal pit on the maxillary first molar is the most common place for caries to develop (Figs. 32-3, 32-4, 32-5, and 32-6)
- Dental surfaces in close contact with an established caries are at risk of developing a lesion
- Deep occlusal pits and developmental grooves on the crown surface predispose to pit and fissure caries (Figs. 32-7, 32-8, and 32-9)
- Tight interdental contacts predispose to smooth-surface caries (Figs. 32-10, 32-11, 32-12, and 32-13)
- Deep periodontal pockets predispose to root caries
- Animals with poorly mineralized enamel, lower salivary pH, diets high in fermentable carbohydrates, and poor oral hygiene are at risk of developing caries
Cats
- To the author’s knowledge, true carious dental decay has never been described in the domestic cat
- In the past, feline tooth resorptions were erroneously termed “feline caries” but have a totally different etiology and pathogenesis

Figure 32-3 Pink disclosing solution (indicated by arrows) used to highlight deep occlusal pits on the left maxillary first molar tooth of a young dog. These sites have not yet developed decay but are at risk. Filling them with a pit-and-fissure sealant to prevent caries development is indicated.

Figure 32-4 (a) The tooth in has no occlusal pit and is not at risk of developing caries. (b) The tooth has a deep pit on the occlusal table and is at great risk of developing caries as outlined in Figs. 32-5 and 32-6.

Figure 32-5 (Left) Food trapped in occlusal pit and early demineralization of enamel. (Right) Early caries at bottom of pit through enamel and into dentin.