**Abstract**

Hard tissues are natural nanocomposites comprising collagen nanofibers that are interlocked with hydroxyapatite (HAp) nanocrystallites. This mechanical interlocking at the nanoscale provides the unique properties of hard tissues (bone and teeth). Upon fracture, cements are usually used for treatment of simple fractures or as an adhesive for the treatment of complicated fractures that require the use of metallic implants. Most of the commercially available bone cements are polymerbased, and lack the required bioactivity for a successful cementation. Besides calcium phosphate cements, gypsum is one of the early recognized and used biomaterials as a basi for a self-setting cementation. It is based on the controlled hydration of plaster of Paris at room temperature and its subsequent conversion to a self-setting solid gypsum product. In our work, we have taken this process further towards the development of a set of nanocomposites that have enhanced bioactivity and mechanical properties. This chapter will outline the formation, characterization, and properties of gypsum-based nanocomposites for bone cement applications. These modified cements can be formulated at room temperature and have been shown to possess a high degree of bioactivity, and are considered potential candidates for bone fracture and defect treatment.

**Keywords:** gypsum, bone cement, nanocomposite, biomimetic, apatite-forming ability
