Fatigue behaviour of root filled teeth: The role of endodontic sealers and restorative techniques

This in vitro study aimed to evaluate the fatigue behaviour of root canal treated teeth, filled with either AH Plus Jet (AHP) or AH Plus Bioceramic Sealer (AHPB) and rehabilitated with either mesio-occlusal-distal (MOD) restorations (direct resin composite) or endocrowns (indirect resin composite). Seventy human upper premolars were prepared and randomly divided into five experimental groups according to the endodontic sealer and type of coronal restoration: AHP-MOD: AHP sealer + MOD restoration; AHP-EC: AHP sealer + endocrown; AHPB-MOD: AHPB sealer + MOD restoration; AHPB-EC: AHPB sealer + endocrown; control group (intact teeth). Monotonic testing was performed to define the fatigue parameters, then a cyclic fatigue test was conducted. Fracture analysis was performed using a stereomicroscope. Fatigue failure loads and the number of cycles to failure were analysed using the Kaplan-Meier and Mantel-Cox (Log Rank) test. Survival rates were calculated for each 'step' of the fatigue test. Fracture types were analysed descriptively. Teeth treated with AHP and restored with endocrowns achieved better results in both load resistance and number of cycles, compared to the AHP-MOD group and teeth filled with AHPB regardless of the restoration used (p < 0.05). However, there was no significant difference when these groups were compared to the control (p > 0.05). Most failures (≥ 50%) were catastrophic (longitudinal fractures). Endodontically treated upper premolars filled with an epoxy resin-based sealer and restored with endocrowns presented a superior fatigue behaviour, suggesting this combination may offer better long-term outcomes compared to MOD restorations or calcium silicate-based sealers.