Powder Injection Moulding of Dental Ceramic Brackets Using Water Soluble Binder

Abstract

Powder injection moulding (PIM) is one of mass production and cost effective near net shape processing, especially for small, complex-shaped components for high performance ceramic applications. Alumina has been generally known as one of the most widely used advanced ceramics due to its excellent properties such as high hardness, high strength, as well as its wear resistance and bioinertness. This work investigates PIM technique for a fabrication of alumina and zirconia toughened alumina compounds for dental ceramic brackets application. A water soluble binder system, composed of a major fraction of polyethylene glycol (PEG) and a minor fraction polyvinyl butyral (PVB), has been studied in a preparation of feedstock for PIM. Injection moulding was carried out with a homemade laboratory scale equipment. PEG can be removed rapidly by water leaching. The remaining PVB is removed by subsequent calcination and the samples were then subjected to sintering. The development of feedstock formulations and processing parameters for the powder injection moulding of ceramic brackets has been investigated. The preliminary study showed that the water soluble binder can be used for the fabrication of alumina and zirconia toughened alumina parts by PIM technique. Samples retain their shape after leaching of the PEG in water. The rate of PEG removal is also fast at the initial stage. Density and microstructure of samples depended on feedstock formulars and sintering conditions. The relationship between processing parameters, properties and microstructure of the injection moulded samples were systematically examined.