Innovative micro- and nanostructured coatings for dental and bone implants

Titanium (Ti) and its alloys are extensively used nowadays for dental and orthopaedic implants due to their outstanding mechanical characteristics and acceptable biocompatibility. However, the properties of metal implant/native hard tissue interface can be substantially improved, if titanium is coated by bioactive materials, with the scope to optimise the long-term characteristics of implant, to elicit a required cellular response, and, as a final goal, to provide better performance and increased functionality of the implant. As future implants, Magnesium (Mg) biodegradable alloys are very promising biocompatible materials for biodegradable biomedical implants, such as, for example, orthopaedic fracture fixation pins or screws. They decompose in the conditions of human body, releasing the Mg2+ ion, which has a functional role in many physiological processes. Moreover, Mg alloys have outstanding mechanical properties, similar to that of the natural bone tissue. However, the main problem in using Mg alloys for biomedical implants is their fast degradation in human body conditions, if compared to the native bone tissue growth. This drawback of Mg alloys can be improved by applying protective coatings of ceramic and composite materials, as prospective solution to control the in vitro degradation. Doped (substituted) calcium phosphates and glass-ceramics are perspective materials for coatings on Ti and Mg alloys [1-9]. They provide superficial affinity, functional interface and improved osseointegration. Substituted calcium phosphates can endow coatings with a broad range of particular functional properties, from antibacterial to the magnetic one [1,2,4,5,8,9]. Whereas the focus point of bioactive glass-ceramic materials is their ability to continuously exchange ions with physiological liquids and to release appropriate active trace elements to stimulate cellular response aimed to activate genes responsible for osteogenesis and tissue regeneration [3,6]. In this work, we report the results on deposition of substituted hydroxyapatite (HA) implant coatings, such as Carbonate-HA [1], Fluorine (F)-HA [2], Silicate-HA [4], Iron (Fe)-HA [5], and Zink (Zn)-HA [8]. Furthermore, the results regarding several glass-ceramic composition coatings will be reported [3,6]. The bulk glass-ceramics materials for coating deposition were prepared by sol-gel method. All the coatings were deposited using Pulsed Laser Deposition technique (PLD). It presents several advantages, compared to other deposition techniques, such as the congruent transfer of the target composition to the coating, the possibility to vary film's thickness, degree of crystallinity, adherence, surface morphology and topography, varying the experimental parameters, such as deposition temperature, time, laser pulse length and wavelength. It has been widely used to deposit thin films of ceramic and glass biomaterials onto biocompatible and biodegradable substrates. Films deposited by nanosecond laser sources present micro- and nanostructured morphology favouring the interaction of surface with cells. The properties of coatings were investigated by a number of physico-chemical techniques, such as X-Ray diffraction, FTIR spectroscopy, Raman spectroscopy, atomic force microscopy, scanning electron microscopy (SEM-EDS), and Vickers hardness. In vitro bioactivity and cell tests for the deposited coatings were performed.