Abstract
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 (TM) DC automix and Clearfil (TM) DC automix core buildup materials and a light-cured nanofilled resin composite; Filtek (TM) Z350 XT were used. Substrate specimens were prepared (n = 12/each substrate material) and stored in artificial saliva at 37 degrees C either for one week or three months. Afterward, all specimens were ground flat, etched using Scotchbond (TM) phosphoric acid etchant and received Single Bond Universal adhesive system according to the manufacturers' instructions. The light-cured nanofilled resin composite (Filtek (TM) 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 mm(2)) were obtained from each specimen (30 sticks/group) for microtensile bond strength (mu TBS) 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 (TM) DC and Clearfil (TM) DC) achieved significantly higher repair mu TBS than the light-cured nanofilled resin composite (Filtek (TM) Z350 XT). However, Clearfil (TM) DC revealed the highest value, then Cosmecore (TM) DC and Filtek (TM) 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. (C) 2015 Production and hosting by Elsevier B.V. on behalf of Cairo University.