Dyspareunia is not a precursor symptom of cancer.
The cause of bruxism is due to holding the breath and exerting oneself, or not exerting oneself sufficiently, and suddenly exerting oneself too hard. If there are physical symptoms of discomfort or other suspicious symptoms of cancer, you need to go to hospital for examination before diagnosis.
Precursor symptoms of cancer are usually a gradually growing lump found in the body, unexplained fever, anaemia, bleeding, etc.