How many diseases can you get in your mouth. close to exact or exact.

This : This is impossible to quantify. You may get diseases from bacteria, viruses, autoimmune diseases, benign and malignant growths, and from systemic manifestations of diseases in other parts of your body.

Too : Too many to count. Prior to modern medicine, not so many. There are so many side effects with the food and drugs we intake and many show themselves in the mouth, wether directly or indirectly. You really want an answer, try webmd and search oral diseases. Like the other dr alluded to: bacterial, viral, fungal are infectious types. Some can be communipical, like herpes, others can be adverse reactions from medicines, like thrush. The most common in the mouth are from tooth decay or periodontal disease. We could only scratch the surface here. If you have a lesion in your mouth that you do not have any idea about, get to you dentist or hospital to have it evaluated. A clinical examination may be all you need to a diagnosis. Usually, we need to test it with a simple scrap to biopsy it. Good luck!