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Abstract
This study aimed to compare immediate and delayed DC of conventional and bulk-fill resin composites with different consistencies. A total of 64 resin composite specimens were included in the study and divided into four main groups according to the consistency. The groups were further subdivided into two subgroups according to the time of testing whether immediately after curing or after 24h from curing. Soft uncured resin composite was homogenized with spectroscopically pure KBr and mixed in a circular movement using a mortar and pestle. The mixture of uncured resin composite with KBr powder was compressed in a pelleting device under hydraulic pressure to obtain a pellet with standardized dimensions of 10 mm diameter and 2 mm thickness. The composite disc was placed into the FTIR apparatus to test the uncured specimen. The spectra of the uncured sample were scanned in the absorption mode in infrared spectrum from 4000-400 cm-1. The composite pellets were then covered by a transparent matrix strip, and light cured with the curing unit tip applied directly on the sample{u2019}s top surface for 40 sec. The immediately cured composite pellets were then transferred again to the FTIR spectrometer to record the spectra. Then the composite pellets were wrapped in tin foil and placed in a tightly closed plastic container to prevent possible polymerization. They were then stored in an incubator for 24h at 37{u00B0}C to imitate the clinical conditions. After 24h, the pellets were removed from the incubator and transferred to the FTIR spectrometer to record the 24h spectra