Upcycling Tunisian dental plaster waste into β-tricalcium phosphate: process optimization via Box-Behnken design and characterization.

This research upcycles Tunisian dental plaster waste into β-tricalcium phosphate. The process effectively manages mineral by-products, preventing the accumulation of non-biodegradable dental gypsum waste. An effective Box-Behnken design and response surface methodology was used for optimizing the stoichiometric reaction between dental plaster, CaSO4·2H2O and phosphoric acid. The optimization focused on three critical variables: the solid/liquid (S/L) ratio, sintering temperature, and heating duration. Our results identified the ideal synthesis parameters as an S/L ratio of 3.8, a temperature of 1150 °C, and a 1 hour heating cycle. Comprehensive characterisation, comprising X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and dilatometry, confirmed that the synthesised β-TCP was comparable to a commercial β-TCP. Scanning electron microscopy (SEM) imaging revealed a robust morphology consisting of fused blocks, mimicking bone architecture, and energy-dispersive X-ray spectrometry (EDX) analysis confirmed a Ca/P molar ratio of 1.48.