What causes endo failures?

From Ian Furst, Coronation Dental Specialty Group

When confronted with a failing endo the big question is, “how is the bacteria getting in?”. Was residual bacteria left during the original endo, is there a vertical root fracture or is there coronal leakage? Dr. Jason Hales, at The Endo Blog, reviews a case of a separated instrument where cleaning and shaping was still completed. Jason’s been posting this blog for years, and it’s a must read for endo.