The effect of internal bleaching procedures on root fracture resistance of simulated immature teeth

Objectives: To compare the fracture resistance of simulated immature mandibular incisor teeth exposed to single-visit revascularization procedures after intracoronal bleaching with sodium perborate mixed with 37% carbamide peroxide gel.
Methods: Sixty extracted mandibular incisor teeth were divided into four experimental groups (G1– G4)(Figure 1) and one control (G5; n=12). Access cavities were prepared and root canal preparation was done in experimental groups. A divergent open apex was prepared by retrograde apical preparation with F3 ProTaper rotary file inserted to the length of the cutting blade in all samples. The canals were irrigated with 5.25% NaOCl solution and 17% EDTA. Following groups were assigned as follows G1: pulp chamber was filled with wMTA (ProRoot MTA; Dentsply Tulsa Dental, TN)/bleached intracoronally with sodium perborate mixed with 37% carbamide peroxide gel; G2: pulp chamber was filled with wMTA/no bleaching; G3: pulp chamber was filled with Biodentine (Septodont, Saint Maur des Fosses, France)/ bleached intracoronally with sodium perborate mixed with 37% carbamide peroxide gel; G4: pulp chamber was filled with Biodentine/no bleaching. Bleaching sessions were performed regularly twice a week for 2 weeks. Final restoration was completed with composite resin following bleaching procedure. Each sample was then subjected to fracture testing using a universal testing machine. The peak load to fracture and the fracture resistance were recorded, and the data were analyzed statistically with Kruskal Wallis and post-hoc Dunn test at p =0.05.
Results: No differences in fracture resistance were observed between the experimental groups (p > 0.05). However, all experimental groups presented statistically significant lower fracture resistance values than the control group (p < 0.05) (Table 1).
Conclusions: Conclusion: Neither calcium silicate cements nor bleaching procedure have impact on fracture resistance values. Opening access cavity was the most detrimental factor that affected fracture resistance values.