Zero-value dental mould waste: an innovative pathway for high purity calcium source enabling the production of akermanite ceramics

Abstract

Good bioactivity and tunable mechanical properties of akermanite (Ca₂MgSi₂O₇), as compared to calcium phosphate materials, have garnered increasing attention as a potential bone substitute material. Typically, these Ca-Mg-Si bioceramics are synthesised using commercially available chemicals. In this study, we aimed to transform clinical dental mould waste (DMW) into an alternative calcium source used in synthesising akermanite ceramics. The DMW were initially refined involving alkaline roasting and caustic leaching, resulting in high purity Ca(OH)₂ powder. This Ca(OH)₂ powder was then mixed with MgO and SiO₂ in stoichiometric proportion and subsequently subjected to planetary ball milling, pressed into pellets and sintered at 1200–1250 °C, forming the desired akermanite ceramics. Two calcium sources were investigated: Ca(OH)₂ refined from DMW and chemically available CaO. Comparative analyses between Akr-Ca(OH)₂ and Akr-CaO confirmed that both types of akermanite ceramics exhibited akermanite as the major phase with a minor phase of diopside. Regardless of the calcium source used, the physical and mechanical properties of the akermanite produced improved with increasing sintering temperature. However, Akr-Ca(OH)₂ possess relatively lower mechanical properties than Akr-CaO. These intriguing findings underscored the potential for utilising calcium derived from DMW in producing akermanite ceramics with acceptable mechanical properties. Utilising this sustainable approach to create akermanite ceramics for bone substitutes may indirectly alleviate environmental pollution. This is because dental mould waste (DMW), which contains small amounts of chromium that can leach out and harm soil quality when discarded into landfills, is minimised. Furthermore, this innovative method shows potential for providing an affordable bone substitute option for patients in need.