Monitoring of self-setting apatite cement using near-infrared spectroscopy: time-course evaluation using machine learning

In this study, near-infrared (NIR) spectroscopy, a measurement method not widely used in dentistry, was used to monitor the synthesis of calcium phosphate cement. Tetra calcium phosphate and di calcium phosphate dihydrate were mixed at a Ca/P ratio of 1.67, and water was added dropwise to induce the phase transition to HAp. The reaction conditions were evaluated by measuring NIR spectra every minute for 60 min and every 20 min for 24 h. The obtained NIR spectra were analyzed using singular value decomposition. The synthesized apatite was characterized by measuring XRD, FT-IR, and SEM. In the self-setting apatite cement system, 24-hour monitoring revealed that a phase transition was achieved. NIR monitoring was found to be effective and valuable for evaluating calcium phosphate cements.