Oral cancer can reveal itself with red or white lesions on the tongue, the floor of the mouth or the soft tissue at the back of the mouth.
Immunosuppression and viral infections can also show up in the mouth, long before they become visible elsewhere.
If the lining of the mouth is too pale it could be a sign the patient has anemia.
This is a condition where the body is lacking enough red blood cells to circulate oxygen effectively. It is rarely fatal but if severe and left untreated it can be dangerous.
Excessive tooth grinding could be a sign that you are suffering from stress.
Stress can cause high blood pressure, which can cause health problems and even be fatal.
Routine bone scans can show signs that a lack of density might be because of osteoporosis.
The condition itself is not fatal, but a fracture can have fatal outcomes, especially in women.
A dry mouth, receding gums and excessive bleeding could be the early signs of diabetes.
If the dentist spots this they will recommend you should have a blood test with your doctor.