Sustainable and cost-effective production of gypsum-based plasters for dental applications from used dental products and from local minerals

U. Karunarathne1*, R.M.G. Rajapakse1, R.D. Jayasinghe2, R.M. Jayasinghe2, A.U. Malikaramage1, C.A. Tennakoon1, M.H.M.A.K. Bandara1

1 Department of Chemistry, Faculty of Science, University of Peradeniya, 2 Faculty of Dental Sciences, University of Peradeniya

Abstract : 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 producing 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 sulphate 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 sulphate 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 (ZrO2), and silicon dioxide (SiO2) 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 (FTIR) spectroscopy, thermogravimetric analysis (TGA), 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.