What can i do to know i need a root canal vs. a filling?

Ask your dentist: Your dentist has been trained to evaluate all of the factors in that decision, together with clinical experience. Barring going to dental school yourself, you will need to trust your dentist with these types of problems.

See a dentist ASAP: Dental caries is the most prevalent chronic disease in the world. If cavities aren't treated with fillings, they can lead to root canals, severe toothache, infection and tooth loss. Although cavities can be fixed by the dentist the prevention of cavities is the best strategy for your oral health. See a dentist ASAP.