Effect of the timing of primary endodontic treatment and dosage of radiation therapy on the filling material removal

This study investigated the effect of the timing of primary endodontic treatment and dosage of radiotherapy on the remaining filling material (RFM) during endodontic reintervention. 60 single-rooted human mandibular premolars were distributed into five groups (n = 12), according to the timing and dosage of radiation (55Gy or 70Gy): NegativeCG-non-irradiated teeth; Endo-pre-RT_55/70-obturation before irradiation (55Gy or 70Gy); Endo-post-RT_55/70-obturation and reintervention after irradiation (55Gy or 70Gy). Roots were cleaved and analysed under stereomicroscope and Scanning Electron Microscope to quantify (%) the RFM. Experimental groups had a significantly greater amount (p < 0.05) of RFM in the middle and apical thirds than the control group, except for Endo-pre-RT₅₅ in the middle third (p < 0.0001). The apical third had greater amount of RFM (p < 0.05). Radiation therapy, before and after primary endodontic treatment, increased the amount of RFM, regardless of the dose delivered. When necessary, reintervention preferably must be performed before radiation therapy.