When you have a deep cavity that is close to the pulp, the pulp may get inflamed if it is infected by bacteria. If you experience, for examples, toothache (sensitive teeth) when drinking either hot or cold drinks, toothache when chewing, or persistent toothache makes you hard to fall asleep. Under these circumstances, a simple filling may not help, you might need a root canal treatment, which removes infected and inflamed pulp. A dentist will have x-ray on your teeth to make sure which teeth requires a root canal treatment. In addition to deep cavity, cracked teeth, serious periodontal disease and tooth injury will all cause toothache that might requires a root canal treatment later. So, if you have a toothache, it’s better for you to consult a dentist at an early stage.