Introduction

Abstract

The 2004 global dental implant market was estimated to be E 1.2 10 9 and is expected to grow 15% to 18% annually, resulting in market duplication within 4 to 5 years. The main factors contributing to this expected growth include the simplification of implantation methods and the aging of the population. The estimated numbers of implant pillars placed in Europe, the United States, and Japan for 2005-2010 are shown in Table 1.1. Orthopedic implants also constitute a main element in the (bio)medical implant market. Among the orthopedic implants, those used for joint replacement constitute the largest segment, estimated at E 7.6 109 globally in 2004. In Europe alone, this market is estimated at E 1.2 109. The expected annual growth of this market during the next 5 years is 7% to 9%. The number of primary hip implants is around 2 million worldwide, and the number of knee implants is about 1 million. Approximately 10% of these implants (depending on the type) will ultimately fail yearly. The number of revisions is thus about 300,000 each year, which attracts attention owing to the continuous aging of our population and the consequent steep increase in health care costs in relation to the gross domestic product. The final success and lifetime of dental and orthopedic implants is determined by the quality of the bone-implant reaction, which is characterized by a tight bond of the bone with the implant surface without the occurrence of an intervening fibrous tissue layer. In addition to patient-and surgery-related factors, the interfacial bone reaction to medical and dental implants depends on the surface topography and chemistry and the mechanical properties of the implant material used. The best available materials for bone-replacing devices are titanium and calcium phosphate ceramics. Titanium and its alloys are mainly used for their strength, although the thin oxide layer that naturally forms on their surface also acts as a passivating protective barrier, conferring on this metal its known corrosion resistance under physiological conditions. Moreover, titanium oxide is thought to improve the response of bone. Calcium phosphates, however, are chosen for their unrivaled compatibility with human bone: they initiate a rapid biological response, improving adhesion between the bone and the implant and providing a scaffold for bone growth. Apart from living cells and collagenous extracellular matrix (ECM), the main constituent of bones and teeth is a calcium phosphate called hydroxyapatite (HA), or Ca5(PO4)3OH; the ideal surgical implant would thus be made from the same material. However, bulk calcium phosphates are weak and brittle, making them unsuitable for replacing parts of the body, such as teeth, that experience large stress. To eliminate this problem, it was suggested that implants could be improved by coating them with titanium, with calcium phosphate ceramic. This approach would combine the mechanical strength of titanium with the biological properties of calcium phosphate. © 2009 Springer-Verlag New York.