The aim of the study is to assess the correlation between pre-obturation bacterial detection using fluorescence amplification and outcome of endodontic treatments. Thus, enabling a suitable detection threshold to predict the likelihood of treatment failure. This has the potential to be used a bench side tool in general dental practice to act as a surrogate endpoint for clinicians performing root canal treatment.

Pre-obturation root canal samples were taken using paper points from patients undergoing primary root treatments. The samples were analyzed using a fluorescent spectrometer and a molecular fluorescent vital dye (Calcein AM).

Pre-operative and 1-year post-operative periapical radiographs and Cone Beam Computed Tomography (CBCT) scans were assessed by two calibrated expert examiners to evaluate the outcome of the root canal treatments.

The use of a chairside bacterial stain can allow the clinician to predict the outcome of treatment with confidence. Sampling the root canal space with endodontic paper points followed by ex-situ fluorescent staining and analysis provides a patient-friendly, simple to use and rapid way of predicting root canal treatment outcome.

Inclusion Criteria:

• Patients with at least one tooth diagnosed with the endodontic disease.
• teeth that were tender to percussion and palpation.
• teeth that had a sinus tract and/ swelling.
• Both primary treatment teeth and teeth which had already been root treated were considered.

Exclusion Criteria:

• Patients were excluded if they were pregnant.
• Immunosuppressed patients.
• Non-restorable teeth.
• Teeth with a periodontal probing depth greater than 3mm.
• Teeth with apical radiolucencies with the longest dimension above 1.2cm.

Patients referred to the endodontic postgraduate unit at Guy's Hospital.