Titanium dental implant surfaces obtained by anodic spark deposition - From the past to the future

Commercial titanium-based dental implants are obtained applying various methods such as machining, acid etching, anodization, plasma spraying, grit blasting or combination techniques yielding materials with smooth or micro-roughened surfaces. Those techniques are used to optimize the surface properties and to maximize biocompatibility and bioactivity with bone tissue. Present review is focused on the material surfaces obtained by anodic spark deposition (ASD). From the early 1980s till present, the results of numerous studies have shown that anodically oxidized surfaces with different dopants express a positive effect on osteoblasts behavior in vitro and osseointegration in vivo. Those surfaces demonstrated a high biocompatibility and rapid osseointegration in clinical application. This paper provides an overview of the preparation of implant surfaces by employing ASD process. Moreover, reviewed are clinically used ASD implant surfaces (Ticer, TiUnite, Osstem, etc.). The electrolyte variations in ASD process and their influence on surface properties are given herein. Using different electrolytes, anode voltages and temperatures, the above fabrication process can yield various surface morphologies from smooth to rough, porous surfaces. Furthermore, ASD enables thickening of oxide layers and enrichment with different dopands from used electrolyte, which hinder release of potentially toxic titanium ions in surrounding tissue. Particularly exciting results were achieved by calcium and phosphorus doping of the oxide layer (Ticer, ZL Microdent; TiUnite, Nobel Biocare Holding AB) which significantly increased the osteocompatibility. Ticer, a dental implant with anodically oxidized surface and the first among similar materials employed in clinical practice, was found to promote fast osteoblast cell differentiation and mineralization processes. Moreover, Ticer accelerate the integration with the bone, increase the bone/implant contact and improve primary and secondary stability of the implants. Additionally, potential innovations in this field such as fabrication of nanotubes on the implant surfaces as well as novel approaches (e.g. coating with proteins, nanostructured topography; combining implant body and surface derived from titanium and zirconia) are elaborated in this review. Besides, biochemical aspects on implant surface cell/tissue interaction are summarized. From the clinical point of view implant surfaces fabricated by ASD technology possess fast and improved osseointegration, high healing rates and long term prognosis.