A Bleaching Breakthrough or Breakage? The Impact of Carbamide Peroxide on Tooth Strength– An Ex Vivo Study

Abstract

Background: Intracoronal bleaching is widely employed for managing discoloration in nonvital teeth. However, concerns remain regarding its potential influence on the structural integrity of endodontically treated teeth.

Aim: To evaluate and compare the fracture resistance of endodontically treated teeth subjected to intracoronal bleaching using different concentrations of carbamide peroxide.

Materials and Methods: 60 extracted mandibular first premolars were endodontically treated, restored with a cervical barrier, and randomly divided into four groups (n=15 each). Group 1: endodontically treated teeth (Control group); Group 2: bleaching with 15% carbamide peroxide; Group 3: bleaching with 20% carbamide peroxide; Group 4: bleaching with 35% carbamide peroxide. Samples were incubated for 7 days at 37°C, followed by restoration with glass ionomer cement. Fracture resistance was tested using a Universal Testing Machine (Instron). Data were statistically analyzed.

Results: Teeth bleached with 15% carbamide peroxide demonstrated significantly higher fracture resistance compared with 20% and 35% groups (p < 0.05). A concentration-dependent reduction in fracture resistance was observed.

Conclusion: The findings of this ex vivo study suggest that intracoronal bleaching with higher concentrations of carbamide peroxide diminishes the fracture resistance of endodontically treated teeth. Clinicians should consider using lower concentrations to minimize the risk of structural compromise.