If your mouth or jaw hurt, it could be from a toothache. Toothaches usually indicate a cavity but they can also signal gum disease. In some cases, a toothache is a sign of an abscess or impacted tooth. A toothache should be evaluated by a dentist right away to determine the cause of the problem and prevent the tooth from dying.
Many things can cause these symptoms, which can make it difficult to diagnose. Possible causes include sinus problems, toothache, arthritis, injury, teeth grinding, gingivitis or problems with your jaw like TMJ. Your dentist will conduct a thorough exam, which may include X-rays, to determine the source of the pain. Above article from: MouthHealthy.org
A cracked or broken tooth can happen for a variety of reasons- brittle teeth, teeth grinding, injury. The crack may be invisible to the naked eye and even X-ray, but they can be incredibly painful and create bigger problems if left untreated. If you experience pain when chewing see your dentist. They can diagnose the cause and develop a plan for treatment.