BODY WATCH : Teeth Can Say a Lot About Health : Exams: Regular visits could save your life. Signs of many illnesses, such as AIDS or cancer, show up in the mouth.

Regular dental check-ups can reveal more than just cavities and other toothy problems. Sometimes a dentist can diagnose trouble elsewhere in the body because the first symptoms of many diseases show up in the mouth.

The mouth, doctors say, is like a mirror to the rest of the body.

“The variety of tissues in the oral cavity represent so many similar tissues in parts of the body where it would be hard to readily detect a problem,” says Dr. Alvan Sheath, an oral pathologist and specialist in diseases of the mouth at the University of Texas Health Science Center, San Antonio.

Here’s a guide to what the gums, teeth, bone, tongue, salivary glands and soft tissues can say about your health:

* Dental X-rays not only expose cavities, but may identify bone diseases by showing excessive bone growth or loss.

* X-rays may also reveal secondary growths of breast, lung, colon and prostate cancers, Sheath says. “A tumor within the jawbone may be the first tangible indication of the problem.”

* Non-functioning adrenal glands may cause skin pigmentation changes inside the mouth, and pigmentation changes around the mouth can signal lower gastrointestinal tumors.

* Non-functioning salivary glands, or dry mouth, may be the result of an overly stressful lifestyle, Sheath says. “Salivary glands shut down when people are anxious.”

* In some instances, an undetected heart attack may be felt as pain in the teeth and jaw. When all other dental problems are ruled out, a sharp dentist will consider heart attack as a possibility, Sheath says.

* Pale tissues and gums or a very red tongue can indicate blood disorders.

* An enlarged tongue can suggest thyroid trouble.

* Gum disease may signify diabetes, vitamin C or D deficiency, or infectious viruses. “If we find there’s no other reason for severe gingivitis or lesions in the mouth, we question the patient further and may send them to be tested (for HIV) and then onto an appropriate physician,” says Dr. Chih-Ko Yeh, an assistant professor specializing in infectious diseases/dental diagnostic science at the University of Texas, San Antonio, which has one of the nation’s leading dental schools.

* HIV and AIDS may also manifest themselves as mouth ulcers. Candida infection, tuberculosis, vitamin B deficiency and allergies are also conditions that can produce ulcers.

* And what if you have a toothache? Most times, a toothache is just a toothache.