Optimisation of hardness and setting time of dental zinc phosphate cement using a design of experiments

The main objective of this study is to demonstrate the application of strategy of an experiment design to optimize the compressive strength and setting time of zinc phosphate cement used in the dental application. For this work, the extreme vertices design was chosen. Its factors are components of the mixture forming a ternary system: zinc oxide, aluminum phosphate and orthophosphoric acid (ZnO–AlPO₄–H₃PO₄). The local region of dental cement – in simplex space- explored and limited by upper and lower limits of the three components of the mixture. The optimization of each response and then all together by graphical methods allowed us to obtain the adequate cement.