Eating tobacco and betel nuts causes oral cancers. Decayed teeth form sharp edges which will hurt the oral cavity. Tooth decays are due to chewing tobacco and drinking alcohol in large amounts. If these sharp edges are troubling you for a long period of time then this condition is called mechanical trauma. This mechanical trauma is one of the reasons for oral cancer. If you are facing this problem for a very long time it’s better to visit a dentist and get treatment for this problem in the initial stage or else it may lead to oral cancer. Prevention is better than cure.