A root canal can look flawless on a radiograph and still hurt like crazy. We dig into a real retreatment case where the “good” root canal is the one failing, and the only way forward is to stop guessing and start measuring what might still be living inside the canal system.

Dr. Ryan Walsh joins me to break down how he approaches access through an existing crown, gutta percha removal, patency confirmation with an apex locator, and why a quick ATP-based indicator test can change the plan. We talk through EndoScore basics, what the 1 to 100 scale is actually reflecting, and the practical thresholds that guide decision-making before obturation. When the first reading comes back high, we use calcium hydroxide and reassess, expecting the score to fall if the canal system is truly disinfected.

Then the twist: the score stays higher than it should, which pushes a deeper look at anatomy. By troughing the mesial groove, we uncover a mid-mesial canal, a common enough variation to matter and a sneaky enough space to keep bacteria protected. Once that canal is shaped and cleaned, the score drops dramatically, giving both clinical confidence and a clear, simple story to share with the patient.

If you want more predictable endodontics, better ways to explain persistent symptoms, and a practical framework for using objective data in root canal retreatment, listen through to the end. Subscribe, share this with a colleague, and leave a review with your biggest takeaway.