Hydroxyapatite (HAp) is a calcium phosphate of chemical formula Ca10(PO4)6(OH)2, with a molar ratio of Ca /P equal to 1.67. This material has a great importance in bioceramics technology, being the main mineral phase constituent in human teeth and bones. It is used as a substitute for damaged hard tissues, coating of orthopedic prostheses and implants and bone tissue repair. However, low mechanical strength and high brittleness makes its use restricted to low mechanic strength areas. One way of improving these properties is to combine HAp with other materials such as zirconia, alumina, mullite, titanium, bioglass and ions in order to join desirable properties of both materials. This review aims to describe the properties resulting from the formation of different ions and materials. It was observed that most of the approaches currently used for mechanical reinforcement are effective in improving fracture toughness and flexural strength and hardness.It was also found that the effect of titanium ions on such the mechanical behavior of HAp composite materials has not been completely elucidated. The improvement of the mechanical behavior due to the addition of reinforcement is dependent on factors such as sintering temperature, amount of reinforcement used, absence of undesirable structural changes, as well as presence of other phases that are deleterious to the ultimate properties of produced materials.
hydroxyapatite; mechanical properties; materials
