**2. Biomaterials for dental implants**

Currently, the main materials used in the composition of dental implants are commercially pure titanium (cp Ti), Ti alloys, and ceramic compounds.

#### **2.1. Alloys**

*Titanium* (Ti) is a silver-gray, biologically inert transition metal with a high corrosion resist‐ ance due to the spontaneous formation of a surface oxide film (3–10 nm thick) which insu‐ lates it from the environment [11, 12]. Thanks to its composition and thickness, this oxide layer makes Ti biocompatible. Ti has four grades of purity which are related to the corrosion resistance, ductility, and strength. Grade 1 Ti is the purest and most ductile and has the highest corrosion resistance, but it is also the weakest. Grade 4 Ti is the strongest and has moderate plasticity and is therefore the grade most frequently used in dental implants [13].

*Titanium alloys.* Manufacturers of dental implants use a specifically designed alloy which has the following composition: 6% aluminum, 4% vanadium, up to 0.25% iron, up to 0.2% oxygen, and 90% Ti [14]. This alloy has a greater corrosion resistance, high resistance to fatigue, and low elastic modulus [11]. Due to the strict mechanical demands on dental implants during chewing, especially in the posterior areas, Ti alloys are preferred to cp Ti [2].

### **2.2. Ceramic compounds**

Proper integration of the surface of a dental implant with the surrounding bone is essential to ensure the longevity and function of the prosthesis supported by the implant [2]. The cell adhesion between the bone interface and the implant surface is considered the most biologi‐ cally important stage in the process. This structural and functional integration is influenced

Some implant surfaces may influence the differentiation and proliferation of osteoblasts and may affect the regulation of the transcription factors responsible for the expression of the genes associated with the formation of the bone matrix. Their use may even shorten the implant

The treatment of a surface can be classified according to mechanical, chemical, and physical processes. In dental implants, the modifications of the outer surface are designed to modify the topography and surface energy. This improves wettability and increases cell growth and

The biocompatibility and roughness of the materials are the key features in the interaction between the tissue and osseointegration [8]. In addition, the surface of dental implants can be significantly increased using suitable modification procedures such as additive or subtractive

Currently, the main materials used in the composition of dental implants are commercially

*Titanium* (Ti) is a silver-gray, biologically inert transition metal with a high corrosion resist‐ ance due to the spontaneous formation of a surface oxide film (3–10 nm thick) which insu‐ lates it from the environment [11, 12]. Thanks to its composition and thickness, this oxide layer makes Ti biocompatible. Ti has four grades of purity which are related to the corrosion resistance, ductility, and strength. Grade 1 Ti is the purest and most ductile and has the highest corrosion resistance, but it is also the weakest. Grade 4 Ti is the strongest and has moderate plasticity and is therefore the grade most frequently used in dental implants [13].

*Titanium alloys.* Manufacturers of dental implants use a specifically designed alloy which has the following composition: 6% aluminum, 4% vanadium, up to 0.25% iron, up to 0.2% oxygen, and 90% Ti [14]. This alloy has a greater corrosion resistance, high resistance to fatigue, and low elastic modulus [11]. Due to the strict mechanical demands on dental implants during chewing, especially in the posterior areas, Ti alloys are preferred to cp

by the activity of adjacent cells and by the properties of the implant surface itself.

proliferation, which eventually accelerates the process of osseointegration [4–7].

integration period [3].

110 Dental Implantology and Biomaterial

techniques [9, 10].

**2.1. Alloys**

Ti [2].

**2. Biomaterials for dental implants**

pure titanium (cp Ti), Ti alloys, and ceramic compounds.

*Zirconia* is a highly biocompatible ceramic compound with osseointegration capacity [15, 16]. It possesses ideal physical properties as a biomaterial, with good values of resistance to flexion, hardness, and corrosion resistance. Some authors have reported that zirconia has similar biocompatibility and osseointegration values to Ti [17]. However, other comparisons of the two biomaterials have reported lower osseointegration values for zirconia implants and have attributed these differences to the treatment of the surfaces rather than to the material itself [18].

Zirconia implants, as a substitute for metals, are indicated in the restoration of anterior teeth with aesthetic aims. However, more prospective studies of their survival and long-term stability are required; indeed, some authors still recommend caution with regard to consider‐ ing zirconia implants [19].

*Hydroxyapatite* (HA) is a bioceramic used as a surface coating on Ti implants, incorporating calcium phosphates to facilitate prompt osseointegration. HA has excellent biocompatibility, osseoconductive capacity, and satisfactory mechanical properties which make it a good surface biomaterial [20].

Implants with HA coating have demonstrated a faster reduction in early mobility and other potential advantages such as its short-term osseoconductive capacity. However, the rate of long-term survival of these implants is still controversial [21–25].
