Accelerated fatigue resistance and color stability of endodontically treated bleached maxillary incisors restored...

The present study aimed to assess fatigue resistance and color modifications of endodontically treated incisors (ETIs) submitted to internal bleaching and restored using three different techniques.

Forty-five maxillary central incisors received endodontic treatment and were internally bleached. After the completion of bleaching, the ETIs were divided into three groups (n = 15) according to the different restoration procedures: 1) glass-ionomer cement base covered with composite resin (GI); 2) short fiber-reinforced composite resin base with composite resin (SF); 3) composite resin restoration over a fiberglass post (FP). Specimens were subjected to accelerated fatigue testing: frequency of 5 Hz, beginning with a load of 100 N for 5000 cycles and a 25-N load increase applied every 1700 cycles until a load of 1200 N was reached. Samples were loaded until fracture. The Kaplan-Meier survival analysis with the log-rank post hoc test were performed (α = 0.05). Tooth color was measured 4 weeks after the bleaching treatment and again after the final restoration procedure using a spectrophotometer and the Commission Internationale de l'Eclairage (CIE) L*a*b* system. L* values of the specimens were analyzed using the Shapiro-Wilk and paired sample t tests (α = 0.05).

All groups showed similar survival mean cycles until failure (P = 0.332) and presented a major number of nonrestorable failures. The GI group presented the lowest number of nonrepairable fractures (GI = 68%, SF = 79%, FP = 86%) and showed the most stable L* value (P = 0.987).

The fatigue survival of internally bleached ETIs was not affected by the restorative technique utilized. Retaining the glass-ionomer base and covering the surface with composite resin should provide optimal color stability.