I've read root canals aren't safe, because the canals can never be totally sterilized causing bacteria to stay in the root and can spread. true or no?

No: When properly done they are safe. If worried, see the specialist - the Endodontist. Today the specialists use a microscope to visualize the tooth and canal system while they treat the tooth. Canals are instrumented to remove the debris, create a clean surface and disinfected before filling and sealing. Important to get restoration very soon after completion. Good Luck

The truth: There is no valid, scientific evidence linking root canal-treated teeth and disease elsewhere in the body. A root canal is a safe and effective procedure according to scientific research.