Modified Inorganic Surfaces as a Model for Hydroxyapatite Growth The process by which organisms in Nature create minerals is known as biomineralization a process that involves complex interactions between inorganic ions crystals and organic molecules; resulting in a controlled nucleation and growth of minerals from aqueous solutions. During the last few decades biomineralization has been intensively studied due to its involvement in a wide range of biological events; starting with the formation of bones teeth cartilage shells coral (so called physiological mineralization) and encompassing pathological mineralization i.e. the formation of kidney stones dental calculi osteoporosis arteriosclerosis osteogenesis imperfecta etc. During the same period biomineralization has become a hot topic for world wide research throughout the world due to the growing expectations of a good quality and duration of life by the ever increasing population of the aged. Young people in particular also make increasing demands on the quality and the appearance of the existing implants available on the market. The general goals of research and manufacture are now to create and improve implants for various applications in the human body as well as to prevent diseases leading to the formation of minerals such as hydroxyapatite (implicated for example in osteogenesis kidney stones dental calculi arteriosclerosis – all problems which mainly affect women).The results presented in this book will make a significant contribution to the application of the modified surfaces of widely studied materials as a model system for hydroxyapatite coating to the cultivation of cells on surfaces as well as to the growth of hydroxyapatite by applying new technologies (such as laser liquid solid interaction) that facilitate nucleation and growth. In this way materials and layers having possible applications as implants biosensors etc. can be obtained. The in vitro system described here is universal and can be applied not only to the production of hydroxyapatite coatings for implants but also to investigating the basic mechanisms of mineral formation diseases and thus identify new directions for prophylaxis. This will then make a strong contribution to improving the quality and duration of life of the population. The aims of the work presented in this book are: 1. to obtain modified inorganic materials with chemically and topographically controlled surfaces and to study the influence of: (i) the base material (metal semiconductor insulator) (ii) implanted inorganic ions as nucleation sites on the surface of the base material (iii) surface grown nanostructures (iv) surface grown porous silicon layers and (v) the effect of surface deposited organic materials on the nucleation and growth of hydroxyapatite layers using two approaches (biomimetic and laser liquid solid interaction). The second aim is to develop a universal in vitro system for the study of the process of biomineralization by mimicking in vivo situations.This book will therefore be essential reading not only for researchers and manufacturers in the field of ceramics but also for doctors dentists gerontologists and cosmetologists. Pramatarova and Pecheva (both solid state physics Bulgarian Academy of Sciences Sofia) describe two approaches for growing hydroxyapatite layers on variously modified surfaces from super saturated aqueous inorganic solution. Such growth can facilitate research into biomineralization as it occurs in the formation of kidney stones atherosclerosis and other diseases. It can also help research into designing implants such as synthetic bones and teeth.