knowledge of basic elements of materials science, engineering, chemistry, and physics, as well as clinical orthodontics. The subject has been part of graduate orthodontic education for almost three decades. Besides servicing the orthodontic training programs, the book also: investigates the interactions of orthodontic materials with other dental materials as well as hard tissues in the oral cavity, gives a background to allow for proper material selection for efficient orthodontic mechanics, and treats the issues of biocompatibility, cytotoxicity and mutagenicity of materials.