Evidence-based literature reviews can provide foundation skills in research-oriented bibliographic inquiry, with an emphasis on such review and synthesis of applicable literature. Information is gathered by surveying a broad array of multidisciplinary research publications written by scholars and researchers. This book is based on a review of about 2,000 carefully selected articles about hydroxyapatite (HA) materials from about 150 peer-review journals in both engineering and medical areas and presents itself as a typical example of evidence-based learning (EBL). HA is very unique material which has been employed equally in both engineering and medical and dental fields. In addition, the name "apatite" comes from the Greek word απατw, which means to deceive. What is actually happening inside the apatite crystal structure is based on the unique characteristics of ion exchangeability. Because of this, versatility of HA has been recognized in wide ranges, including bone-grafting substitutes, various ways to fabricate HAs, HA-based coating materials, HA-based biocomposites, scaffold materials, and drug-delivery systems. This book covers all these interesting areas involved in HA materials science and technology.