Strong pain, swelling, foul breath, and trouble eating can all be symptoms of severe tooth decay and cavities, particularly if the decay reaches the tooth's inner nerve. The severity of the damage will determine the course of treatment; tiny cavities may require filling, larger infections may require root canal therapy, and severely fractured teeth may require extraction. Keep your mouth clean, stay away from extremely hot, cold, or sugary meals until you see a dentist, and only use pain medication as directed by a physician. Severe tooth pain should not be disregarded since an untreated infection can spread to the jaw and gums.