Clinically relevant radiation therapy doses and obturation techniques modulate the adhesive performance of a resin-based sealer: interfacial integrity and bond strength analyses

To evaluate the effects of clinically relevant radiation therapy doses and obturation techniques on the adhesive performance of a resin-based endodontic sealer. Sixty human mandibular premolars were allocated to 3 groups according to radiation exposure: non-irradiated (NoRT), 30 Gy (clinically absorbed dose for mandibular premolars during nasopharyngeal cancer radiotherapy), and 70 Gy (tumor-target dose). Irradiation was performed using intensity-modulated radiotherapy with fractionated doses of 2 Gy. Root canals were prepared and obturated using lateral condensation (LC) or Tagger’s hybrid technique (HB) with an epoxy resin-based sealer. Push-out bond strength was evaluated in cervical, middle, and apical thirds. Failure modes were analyzed by stereomicroscopy and scanning electron microscopy (SEM). Sealer-dentin interface characteristics and sealer penetration were assessed using SEM and confocal laser scanning microscopy (CLSM). Data were analyzed using three-way ANOVA test with Bonferroni’s post-hoc test (α = 0.05). Radiation dose significantly affected bond strength (P < .001), with both 30 Gy and 70 Gy groups showing reduced values compared with NoRT. HB demonstrated higher bond strength than LC across all irradiation conditions (P < .05). Root third had no significant effect (P > .05). SEM and CLSM analyses revealed interfacial degradation and reduced sealer penetration in both irradiated groups (30 Gy and 70 Gy), with more pronounced alterations observed at 70 Gy. Cohesive failure within the sealer occurred more frequently than mixed or adhesive failures across all experimental conditions. Clinically absorbed and tumor-target radiation doses adversely affected the adhesive performance of the endodontic sealer to root dentin. Obturation technique remained a critical factor, with Tagger’s hybrid technique promoting improved sealer adaptation and penetration under all irradiation conditions. Radiation therapy doses used in head and neck cancer treatment may impair the adhesion of endodontic sealers to root dentin. Selecting obturation techniques that enhance sealer adaptation and penetration may help optimize adhesive performance in teeth exposed to radiation therapy.