**1. Introduction**

The use of modern materials in biomedical technologies requires detailed knowledge on the impact of the structure and the physicochemical properties of produced systems on their bioactivity. There are a lot of biomaterials, which can be applied in the human body, such as metals, ceramics, synthetic and natural polymers [1–8]. Among them titanium and its alloys have become extremely popular, especially in the implantology [9–15]. Commercially pure titanium (cpTi) is one of the dominant materials used for dental implants [16–20]. Ti6Al4V alloy plays an important role for orthopaedic applications [21–25]. Nickel-titanium alloy (Nitinol, shape memory alloy) has been used in the treatment of cardiovascular implants [26–30]. The combination

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of the high corrosion resistance, the tensile strength, the flexibility, and the biocompatibility, is the reason of widespread and successful application of titianium and its alloys in modern implantology [31–34]. The mentioned outstanding corrosion resistance of Ti and its alloys is a consequence of the passivation oxide layer spontaneous formation. This oxide layer is in fact responsible for the biocompatibility of Ti/Ti alloy. The thickness and the composition of natural oxide coatings, which appear in the presence of air or oxidizing media, and which are based on mainly TiO<sup>2</sup> , Ti<sup>2</sup> O3 or TiO, depend on the environmental conditions [13–15, 35–37]. However, the stoichiometric defects and the low stability of this film can lead, in the case of implants, to their delamination and loosening. The key parameter in the success of bone implants (orthopaedics and dentistry) and the clinical goal is the establishment of a strong and long-lasting connection between the implant surface and peri-implant bone, in other word, achieving the optimal osseointegration [38–43]. Even if Ti and its alloys are biocompatible materials, as they are biostable and biologically inert, the human body recognizes them as foreign ones and tries to isolate them using thin nonmineral, soft tissue layer. Instead, the mechanical interlocking of the titanium surface asperities and the bones pores leads to the formation of the bond between the implant and the bone, that is to the successful osseointegration [44–47]. The mechanical, chemical, and physical methods have been reported to improve the bioactivity of titanium and the bone conductivity (**Table 1**) [12, 48–81].



**Table 1.** Overview of surface modification methods for Ti and Ti alloys.

of the high corrosion resistance, the tensile strength, the flexibility, and the biocompatibility, is the reason of widespread and successful application of titianium and its alloys in modern implantology [31–34]. The mentioned outstanding corrosion resistance of Ti and its alloys is a consequence of the passivation oxide layer spontaneous formation. This oxide layer is in fact responsible for the biocompatibility of Ti/Ti alloy. The thickness and the composition of natural oxide coatings, which appear in the presence of air or oxidizing media, and which are based on

stoichiometric defects and the low stability of this film can lead, in the case of implants, to their delamination and loosening. The key parameter in the success of bone implants (orthopaedics and dentistry) and the clinical goal is the establishment of a strong and long-lasting connection between the implant surface and peri-implant bone, in other word, achieving the optimal osseointegration [38–43]. Even if Ti and its alloys are biocompatible materials, as they are biostable and biologically inert, the human body recognizes them as foreign ones and tries to isolate them using thin nonmineral, soft tissue layer. Instead, the mechanical interlocking of the titanium surface asperities and the bones pores leads to the formation of the bond between the implant and the bone, that is to the successful osseointegration [44–47]. The mechanical, chemical, and physical methods have been reported to improve the bioactivity of titanium and the bone conductivity

**Modification method Modified surface layer The aim of modification Ref.** *Mechanical methods* [12]

Grinding [50–52] Polishing [53]

*Chemical methods* [48]

Acidic treatment <10 nm of surface oxide layer Removal of oxide scales and

Alkaline treatment ~1 μm of titanate gel Improvement of biocompatibility,

treatment ~5 nm of dense inner Improvement of biocompatibility,

and silica

Blasting [50, 51, 54, 55]

or TiO, depend on the environmental conditions [13–15, 35–37]. However, the

Production of the specific surface topography; surface cleaning and roughening, improvement of

bioactivity and bone conductivity

bioactivity and bone conductivity

Improvement of biocompatibility, bioactivity and bone conductivity

Production of the specific surface topography; improvement of biocompatibility, bioactivity and bone conductivity, improvement

Improvement of wear resistance, corrosion resistance, and blood

of corrosion resistance

compatibility

[49]

[56, 57]

[57, 58]

[60–62]

[63–66]

[67–69]

[59]

adhesion in bonding

contamination

mainly TiO<sup>2</sup>

, Ti<sup>2</sup> O3

74 Application of Titanium Dioxide

(**Table 1**) [12, 48–81].

H2 O2

CVD (chemical vapor

deposition)

Machining Rough or smooth surface formed

Sol-gel ~10 μm of thin film, such as

Anodic oxidation ~10 nm to 40 μm of TiO<sup>2</sup>

by subtraction process

calcium phosphate, TiO<sup>2</sup>

electrolyte anions

nanotubular or porous layer, adsorption and incorporation of

~1 μm of TiN, TiC, TiCN, diamond and diamond-like carbon thin films A review of the Ti/Ti alloys surface chemical modification processes, which led to the formation of 1-D titanium dioxide nanostructures and improve the bioactivity of modified titanium materials, is the aim of this chapter. The relationship between the structure and the morphology of titania nanotubes (TNT), titania nanofibres (TNF), and titania nanowires (TNWs) and their bioactivity is discussed in the next subsections. Moreover, it cannot be forgotten that from chemical point of view, described 1D titania nanostructures are in the whole sense of the word, TiO<sup>2</sup> , which is very known semiconducting photocatalyst. So, the aspects associated with the photoactivity of TNT, TNF, and TNW coatings are also discussed. This feature of titania can be treated as additional attribute to use, for example, in the process of implant surface antibacterial disinfection, with the use of UV light. But, the reader should bear in mind the fact that the photoactivity of TiO<sup>2</sup> is strongly dependent on its structure and morphology.
