**5. Peri-implantitis related to dental implant surfaces**

by chemical means or by acids applied sequentially or in combination [76, 77]. This technique achieves a surface with micro-roughness, which some authors associate with higher values of

*Alkali treatment* is a procedure in which the Ti implant is immersed in either potassium or sodium hydroxide followed by heat treatment (800°C for 20 min) and subsequent rinsing with distilled water. This technique achieves a nanostructured and bioactive sodium titanate layer on the surface of the dental implant, which provides favorable conditions for bone marrow cell differentiation [69]. The thermal oxidation works by changing the crystal structure of the nanometric oxide layer and thus increases the bioactivity of a biocompatible metal [79].

*Sandblast*, *large grit*, *and acid etching (SLA)* applies a strong acid on the blasted surface for the purposes of abrasion. The procedure starts with large particle blasting, which obtains a rough, irregular surface. Then, the acid etching produces surface uniformity and obtains a macroroughness and micro-pits which are able to improve osseointegration. Kim et al. [80] observed that human osteoblasts grow well on the SLA surface which provides space for cell adhesion

Other procedures such as ion implantation, laser treatment, sputtering, and the combination of some of the techniques already mentioned have also been studied in order to improve the

Ion implantation causes atomic rearrangement. It permits the injection of any element on a nearby surface with a beam of high-energy ions (10 KeV) which impacts on the surface of the metal in a vacuum chamber. On colliding with the ions of the substrate material, the incident ions lose energy and settle on the surface of the nearby metal. This technique is considered an ultra clean process because the concentration and depth of the impurities are easy to control, allowing the creation of a layer of high purity. Furthermore, the adhesion between the implanted surface and the substrate is excellent; the process does not alter the properties of the core and is highly reproducible and controllable [85]. However, some authors warn that the possible modification of the nanoscale features and the creation of stress on the Ti surface

Ultraviolet (UV) photo-functionalization is one of the recent advances in the chemical modi‐

Laser technology is an extremely clean, fast, and accurate method which allows nanostructural micromachining at the implant surface [88]. Laser peening involves striking the metal with high-intensity pulses of a laser light beam which produces a deep, regular honeycomb pattern

The slow rate sputter deposition method achieves a thin layer of Ti oxide (300 pm–6.3 nm). This technique increases the oxygen components without altering the surface topography. These biological activities are correlated with the thickness of the TiO2 coating and the oxygen

fication of implant surfaces which does not alter the bioactive properties.

reverse removal torque than machined surface implants [78] (**Figure 1**B).

and proliferation.

**4.3. Other techniques**

116 Dental Implantology and Biomaterial

with small pores [2].

surface properties of dental implants [81–84].

should be taken into consideration [86, 87].

Peri-implantitis is an infectious disease of an already integrated dental implant that causes inflammation of the surrounding hard and soft tissue, leading to the loss of supporting bone (**Figure 4** and **5**). The sequence of microbial colonization on dental implants and biofilm formation is similar to that of teeth. The bacteria that colonize dental implants include the same species as those present in healthy gums and in locations with gingivitis [89–91]. Several *in vivo* studies show that streptococci and *Actinomyces* species predominate in the initial coloni‐ zation; their presence prepares the environment for colonization by other species such as *Porphyromonas*, *Prevotella*, *Capnocytophaga*, and *Fusobacterium* which cause the peri-implantitis [91] (**Table 1**).

**Figure 4.** Intraoral radiograph taken 8 years after implant placement—sandblasted, large-grit and acid etched (SLA) surface treatment type. Note the bone crater-like defect around the implant revealing a severe peri-implantitis (*Clinical records*, *Dr. Jaume Miranda-Rius*).

**Figure 5.** Peri-implantitis clinical image. Surgical debridement of the granulation tissue around the implant (*Clinical records*, *Dr. Jaume Miranda-Rius*).


**Table 1.** List of bacterial species associated to dental implant biofilm.

The surface characteristics of dental implants—roughness, wettability, surface free energy, and composition—play a crucial role in bacterial adhesion and colonization. The highest adhesion capacity is observed on rough Ti surfaces. Some authors have observed that mean roughness values below 0.088 microns significantly inhibit plaque adhesion and maturation [92]. Furthermore, decreasing the wettability of dental implants favors bacterial colonization. Some authors suggest that autoclave-sterilized Ti presents a higher rate of bacterial colonization, given the loss of surface wettability (**Figure 5**).

Surface free energy is the sum of the forces of cohesion and adhesion that determine whether or not there is impregnation (the dispersion of the liquid over a surface). Decreasing surface free energy inhibits bacterial adhesion and biofilm formation on the surface of dental implants and abutments [93]. Thus, bacterial adherence is correlated with the presence of surface components with nonpolar or hydrophobic characteristics [93–95]. Finally, the type of metal and its composition also has an effect on bacterial adhesion and biofilm formation on its surface. Pure metals, especially Ti, nickel, iron, and vanadium, have some bacteriostatic capacity [96].

Some authors have concluded that ZnO and TiO2 reduce the adhesion of staphylococcal bacteria and increase the adhesion of osteoblasts [97]. The addition of silver compounds to increase antimicrobial action has also been studied [98]. Other authors have analyzed the behavior of Ti surfaces modified with vancomycin attached via covalent bonds and have reported a stable surface with a greater inhibition of bacterial adhesion than with Ti alone [99].

## **6. Conclusion**

In this chapter, we have highlighted the important role of the macro- and micro-design of implants and their composition in the process of osseointegration. We have also stressed the significant influence of the surface characteristics of implants on the peri-implant microbiota. All in all, peri-implantitis is an important area for future research. It is extremely difficult to control the progress of an infection once it is established around an implant. The rough surfaces facilitate osseointegration, but also favor the adhesion of oral biofilm. Because of the multi‐ factorial nature of infectious peri-implant complications, studies should also take into account the influence of the permucosal seal. This biological seal aims to integration the neck of the implant or the abutment with the gingival tissue and thus prevent peri-implant infections. Currently, the challenge in the treatment of implant surfaces is to demonstrate the potential of certain coatings for releasing local antimicrobial agents. Given the clear increase in inflam‐ matory peri-implant diseases, we believe that future research should aim to devise new strategies for obtaining antibacterial biomaterials that can help in the prevention or treatment of peri-implantitis.
