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No she doesn't
Research has proven that 85% of dogs over 3 yrs of age have some degree of periodontal disease. When tissues in the mouth are broken down by bacteria, sulfur is released, resulting in a foul smell.
Often, diagnostics for periodontal disease detection can only be done under anesthesia, and many dogs will hide their disease quite well. Dental x-rays, and probing of the periodontal pockets, just as in a human mouth, are essential for determining the location and severity of the problem.
Now, if a full periodontal evaluation under anesthesia doesn't reveal or fix the problem, the next possible source of the halitosis is disease of the esophagus or stomach. An ulcer or irritation can collect bacteria and produce a foul smell. Endoscopy is usually required for such a diagnosis.