A small amount of vinegar will be placed at each site with a cotton swab before the probe is placed. The procedure takes about 1-2 minutes at each site. A small sample of tissue from each site, both the normal and abnormal, will be removed. The biopsies done on the normal tissue are done for this study only and are not part of standard care. The samples will be removed either at the time of surgery or under local anesthesia in the clinic. Briefly, the small areas to be biopsied will be numbed with topical anesthesia and an injection of local anesthesia. Then a small amount of tissue, about as big as a pencil eraser, will be removed with sterile surgical instruments. This should cause little discomfort or bleeding. The tissue will be placed in a special fluid and then looked at with a special microscope. The tissue samples will be examined with a microscope by a pathologist to learn if the tissue is cancerous or precancerous. These results will be compared with the pictures that were made of the lining of the mouth.