Degree of Conversion at 4mm Depth of Bulk-fill Resin-composite

Objectives: Since bulk-fill (BF) resin-composites should cure efficiently to a depth of 4mm or greater, the aim was to determine the time-dependence of degree of conversion (DC) at that depth.
Methods: Eight representative BF materials were studied [x-tra base (xtb), Venus Bulk Fill (VBF), Tetric EvoCeram Bulk Fill (TECBF), Sonic Fill (SF), Filtek Bulk Fill (FBF), everX Posterior (eXP), Beautifil-Bulk Flowable (BBF), Beautifil-Bulk Restorative (BBR)]. Specimens were fabricated in white Delrin moulds of 4 mm height and 5 mm internal diameter. They were irradiated for 20 s with an Elipar S10 LCU of average tip irradiance of 1200 mW/cm². The specimens were irradiated in situ on a (FTIR) spectrometer with an attenuated total reflectance (ATR) accessory attachment (Nexus, Thermo Nicolet, Madison, USA). Spectra were recorded before irradiation and at intervals of 5, 30 and 60 min and 24 h post irradiation.
Results: The mean and SD of DC of each material at 5 min and 24 h are presented here. (Table 1)
Conclusions: All BF materials were found to exhibit after 24 h a DC between 49.7 % and 71.9 % at 4 mm depth under the stated irradiation conditions.