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May/June 2014 Today's Veterinary Practice 99 PracTical DenTisTry | Disorders of Dental Hard Tissues in Dogs tvpjournal.com CARIES 1,2,9 Caries (in humans, commonly called "cavities") occur when acid dissolves the hard structures of the teeth. Reports on prevalence vary widely, which may be due to overdiagnosis of discolored surfaces, 18 but caries are fairly rare in dogs and almost unheard of in cats. A study that evaluated dogs seen at a veterinary dental referral facility found a prevalence of 5.3%. 19 Causes & Development Caries lesions begin in areas where food becomes trapped (Table 2); bac- terial digestion of the food produc- es acid, which initiates the lesion. 20 Therefore, home care can help avoid these lesions. Development of caries can ultimately affect the endodontic system. 1. The initial lesion—a surface decalci- fication of the enamel—is caused by a drop in pH . 2. Demineralization follows the direc- tion of the enamel rods. 3. Eventually, caries breaks through the enamel and invades the dentin. Once this occurs, the lesion expands laterally fairly quickly, as dentin is less mineralized than enamel. 4. Once dentin is destroyed, the unsupported enamel will collapse, expanding the lesion. 5. These lesions can progress into the endodontic system, resulting in pain and infection. Clinical Signs & Diagnosis Outwardly, caries appear as a discol- ored tooth defect (Figure 6). Discol- oration is usually brown to black, but can be white very early in develop- ment. Early lesions can mimic wear, and are best diagnosed by tactile feel of the defect with a sharp explorer (Figure 7). Healthy tooth structure is solid, whereas caries is soft and sticky. When penetrating the caries, the explorer will experience "tug back." Prior to therapy, dental radiographs must be exposed to determine the size of the defect and evaluate tooth vital- ity. Caries appear as radiolucent areas (Figure 8). Treatment Options Evidence of endodontic disease: • Root canal therapy is required prior to restoration. • Crowns are recommended since damage is likely significant—creat- ing teeth susceptible to fractures. • Extraction can also be considered. Early to moderately advanced caries: • Removal of all diseased tooth structures is required prior to res- toration. • Composite resin restoration is generally the best choice (Figure 9). • Amalgam , however, is also a valid option. Lesions at or below the gingival margin: • Glass ionomer restoration is most likely the best treatment. 21 DISCOLORED (INTRINSICALLY STAINED) TEETH Intrinsically stained teeth are dis- colored teeth in which the abnormal color stems from inside the tooth, specifically the dentin–pulp complex. Causes & Development 1,2 In dogs, intrinsic staining most often results from blunt trauma of suffi- cient force to cause pulp hemorrhage, but not enough to fracture the tooth. However, in other dogs, there may be no history of trauma and discoloration occurred for other reasons. For exam- Table 2. locations of Dental caries • Occlusal surface of maxillary first molars (most common) • Occlusal surfaces of other molars and maxillary fourth premolars • Deep developmental grooves • sides of tooth, especially contact surfaces (smooth surface caries) • Tooth roots Figure 6. Caries lesion on the occlu- sal surface of the right maxillary first molar (109). Figure 7. Abrasion on the occlusal surface of right maxillary first molar (109); note the dark staining, which mimics a caries. When touched with a sharp explorer, this lesion was hard, in contrast to the sticky feeling with "tug back" expected with caries. Figure 8. Classic radiographic appearance of caries lesion on distal aspect of left mandibular first molar. Figure 9. Composite restoration of left maxillary first molar (209)—(A) Pre-operative picture demonstrating caries, and (B) postoperative picture of composite restoration. A B TVP_2014_0506_PD_HardTissue-Periodontal.indd 99 5/23/2014 6:35:53 PM