contact the american cancer soicety and request information on what mouth cancer is all about. Ask for literature that has photographs of what mouth cancer looks like. Also ask if there are any support groups for people with mouth cancer and see it if they are opened to the public. Take your dad to one and let him see first hand what chewing tobacco does to the mouth and throat. Sometimes drastct measures need to be taken. I'm speaking from experience. I smoked cigarettes for 30 years and talked about quiting. I even had a doctor tell me if I didn't stop smoking that I would die of lung cancer and he had tears in his eyes when he told me that. I have had lupus for almost 21 years and due to the smoking that weakened my lungs the lupus always flares up in my lungs and has given me pulmonary fibrois. I'm on oxygen 24/7. Good luck with your dad.