The shear bond strength of freshly added composite resin to a repaired chemically bleached composite.

Abstract

Objective: This in-vitro study was done to evaluate the shear bond strength (SBS) of a repaired chemically bleached composite using a freshly added composite material. Materials and Methods:Forty composite disk specimens were prepared using a (8X3mm) Teflon mold. All specimens were immersed in saline solution for 2 months. Afterwards, the specimens were equally divided into four groups (10 each) depending on the instance of new composite addition. A Teflon mold (5X3mm) was used for adding the new composite disk by packing of the new composite to the previously cured disk. Group A (the control group) new composite was added to non-bleached composite samples. While group B fresh composite was added immediately after bleaching, group C it was added 1 week after bleaching, and group D it was added 2 weeks after bleaching. Bleaching was done utilizing chemical bleaching technique. The SBS between the two composite disks was measured using Instron universal testing machine.Results: A highly statistically significant difference was revealed by using of ANOVA test between the four groups (p<0.001), with the highest mean shear stress values noted in group A followed by D then group C, while the lowest recorded in group B. A High statistically significant difference between group B vs. A and D (p<0.001*) was shown by using of Pairwise Posthok test, denoting the lower shear bond stress values of group B versus both these groups. Furthermore, a significant statistical difference was noted between groups A & B versus C. While, non-significant differences were recorded between groups A&C versus group D. Conclusions:Teeth bleaching significantly decreases SBS in composite repair procedures, despite using ethanol based adhesives. In addition, postponing the composite repair after bleaching procedure has a major role in regaining the desired SBS.