Upcycling dental gypsum waste into enhanced plaster of Paris via chemical modification: Mechanical and microstructural study

The primary composition of gypsum products is calcium sulfate dihydrate (CaSO 4 ·2 H 2 O), which is widely used in dentistry to create models, casts, and dies, forming the foundation of dental appliances and prostheses. Meanwhile, the disposal of gypsum materials in dental facilities could lead to environmental pollution without sustainable management. Recycling gypsum materials might provide an opportunity. However, the properties could be compromised by the presence of contaminants during the process. This research explores the sustainable production of Plaster of Paris (POP) using gypsum from waste sources with the aim of enhancing their physical and mechanical properties using CaO, CaCl 2 , MgO, and MgCl 2 at varying amounts to improve the quality of POP produced from waste gypsum. Waste gypsum was thermally converted to produce CaSO 4 ·½H 2 O, followed by additive inclusion to analyze the setting time, compressive strength, diametral tensile strength, and Young’s modulus. Morphological analysis using scanning electron microscopy (SEM) revealed notable improvements in microstructure, with CaO showing the greatest effectiveness in reducing porosity and enhancing strength. Statistical analyses carried out by the ANOVA method indicated that gypsum modified with CaO performed much better with respect to mechanical and morphological properties. These findings demonstrate that oxide-enhanced renewable gypsum could be employed in sustainable dentistry while delivering high-performance upcycled materials.