Sustainable and cost-effective production of gypsum-based plasters for dental applications from used dental products and from local mineral extraction U. Karunarathne 1 , R.M.G. Rajapakse 1 , R.D. Jayasinghe 2 , R.M. Jayasinghe 2 , A.U. Malikaramage 1 , C.A. Tennakoon 1 , M.H.M.A.K. Bandara 1 1 Department of Chemistry, Faculty of Science, University of Peradeniya, Sri Lanka, 2 Faculty of Dental Sciences, University of Peradeniya, Sri Lanka The dental industry generates a significant amount of waste in the form of used dental products, including gypsum-based plaster materials. This waste poses environmental challenges and increases disposal costs. In response to these issues, this research explores a sustainable and cost-effective approach to produce dental plaster materials through recycling used dentures and extracting gypsum from local minerals. Through a combination of chemical and physical processes, used dental products, such as discarded plaster casts and impressions, were reclaimed. Chemical dissolution and purification techniques were employed to extract the desired calcium sulfate compounds, which were then carefully reconstituted into gypsum and hemihydrate plaster suitable for dental applications. Alternatively, slaked lime which is extracted from local minerals, and sulphuric acid were used as basic components for manufacturing gypsum by bottom-up wet chemical method. Purified regenerated acid sulfate sources were introduced instead of pure imported sulphuric acid. By leveraging indigenous calcium-rich minerals like dolomite, and corals, the study promotes regional self-sufficiency by minimizing dependence on external sources. Innovative extraction and processing methods were designed to efficiently convert these local minerals into a sustainable and readily available source of gypsum. The parameters of dental plasters are optimized by adding a mixture of zirconium oxide (ZrO 2 ), and silicon dioxide (SiO 2 ) which is used as an additive to optimize the retention time, and strength of the dental plasters, whereas sodium silicate alone was used as a binder. All those additives are extracted from locally available zircon sand. Furthermore, the characterization of the materials developed were done using Fourier-transformed infrared spectroscopy, thermogravimetric analysis, LASER light scattering-based particle size analysis, and mechanical property measurements which were compared with those of commercial products which show compatible results. In conclusion, the culmination of these efforts is a dual-pronged approach that offers substantial benefits to the dental industry and the environment. The developed methods hold the promise of scalability and commercial viability, paving the way for a more circular and resource-efficient dental sector. Ultimately, this study envisions a paradigm shift in dental material sourcing, characterized by minimized waste, reduced environmental impact, and enhanced economic resilience. References 1. Butscher, A., Bohner, M., Hofmann, S., Gauckler, L., & Müller, R. (2011). Structural and material approaches to bone tissue engineering in powder-based three-dimensional printing.Acta biomaterialia,7(3), 907-920. 2. El‐Shall, H., Rashad, M. M., & Abdel‐Aal, E. A. (2005). Effect of cetyl pyridinium chloride additive on crystallization of gypsum in phosphoric and sulfuric acids medium.Crystal Research and Technology: Journal of Experimental and Industrial Crystallography,40(9), 860-866. 3. Gázquez, M. J., Contreras, M., Pérez-Moreno, S. M., Guerrero, J. L., Casas-Ruiz, M., & Bolívar, J. P. (2021). A Review of the Commercial Uses of Sulphate Minerals from the Titanium Dioxide Pigment Industry: The Case of Huelva (Spain). Minerals,11(6), 575.
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