Repair bond strength of dual-cured resin composite core buildup materials

The reparability of dual-cured resin composite core buildup materials using a light-cured one following one week or three months storage,prior to repair was evaluated. two different dual-cured resin composites; cosmecore™ dc automix and clearfil™ dc automix core buildup materials and a light-cured nanofilled resin composite; filtek™ z350 xt were used. substrate specimens were prepared (n = 12/each substrate material) and stored in artificial saliva at 37 °c either for one week or three months. afterward,all specimens were ground flat,etched using scotchbond™ phosphoric acid etchant and received single bond universal adhesive system according to the manufacturers' instructions. the light-cured nanofilled resin composite (filtek™ z350 xt) was used as a repair material buildup. to determine the cohesive strength of each solid substrate material,additional specimens from each core material (n = 12) were prepared and stored for the same periods. five sticks (0.8 ± 0.01 mm2) were obtained from each specimen (30 sticks/group) for microtensile bond strength (μtbs) testing. modes of failure were also determined. two-way anova revealed a significant effect for the core materials but not for the storage periods or their interaction. after one week,dual-cured resin composite core buildup materials (cosmecore™ dc and clearfil™ dc) achieved significantly higher repair μtbs than the light-cured nanofilled resin composite (filtek™ z350 xt). however,clearfil™ dc revealed the highest value,then cosmecore™ dc and filtek™ z350 xt,following storage for 3-month. repair strength values recovered 64-86% of the cohesive strengths of solid substrate materials. the predominant mode of failure was the mixed type. dual-cured resin composite core buildup materials revealed acceptable repair bond strength values even after 3-month storage. © 2015.