Real‐time curing characteristics of experimental resin composites containing amorphous calcium phosphate

The real‐time polymerization of light‐curable experimental resin composites filled with amorphous calcium phosphate (ACP) was monitored. Experimental composites were based on a 2,2‐bis[4‐(2‐ethoxy‐3‐methacryloyloxy propoxy)phenyl]propane (Bis‐EMA)/triethyleneglycol dimethacrylate (TEGDMA)/2‐hydroxyethyl methacrylate (HEMA) resin photoactivated by a camphorquinone/tertiary amine system. Four ACP composites were prepared, containing 40 wt% ACP and 0/10 wt% reinforcing fillers (barium glass and silica). Additionally, two control composites were prepared which contained only reinforcing fillers (40–50 wt%). The degree of conversion (DC) was monitored in real time using a Fourier‐transform infrared (FTIR) spectrometer with an attenuated total reflectance accessory. During the light curing (1,219 mW cm^?2) for either 20 or 40 s, infrared spectra were collected from the bottom of 2‐mm‐thick composite specimens at the rate of two spectra per second over 5 min. When cured for 40 s, the ACP composites attained a high DC (89.1%–92.4%), while the DC of control composites was significantly lower (53.5%–68.4%). All materials showed a lower DC for the shorter curing time (20 s) and various extents of 5‐min postcure polymerization: 12.9%–21.5% for the ACP composites and 2.7%–5.2% for the control composites. The control composites reached the maximum reaction rate much earlier (4.1–4.3 s) and at lower DC (9.9%–10.4%) than did the ACP composites (17.4–22.0 s and 43.5%–49.3%, respectively).