**2. Effect of surface roughening techniques on morphology, roughness, composition and oxide type of modified Ti implant surfaces.**

The modification of implant surface in a way to accelerate the osseointegration process is a topic of intense research and competition among implant companies. A variety of surface roughening techniques have been implemented till today including Ti plasma spray (TPS), double acid etching (DAE), sandblasting with large grit and acid etching (SLA), anodization (ANO), machining (MAC) (**Table 1**), laser etching and others [24].


**Table 1.** Dental implants, manufacturer, surface roughening technique and code for commercially available products.

Today, products prepared with the aforementioned techniques are available in dental market as there is no clear evidence for the superiority of one surface modification over the others. The different surface roughening techniques provide characteristic surface patterns on Ti implant surfaces. MAC is characterized by parallel serrations with a rather smooth surface (**Figure 1**). TPS provides surfaces with a random distribution of small granules resemble to solidified droplets probably due to plasma spray process along with a random distribution of surface cracks (**Figure 1**). DAE and SLA depict some similarities due to the final step of acid etching, although SLA illustrates shallow grooves probably due to grit blasting before etching. ANO is characterized by valleys and open craters although the size, the shape and the distribution of these craters are significantly dependent on operational parameters during anodization.

**Figure 1.** Secondary electron images from the root surface of dental implants in 4000 (left) and 24000 (right) nominal magnifications. Parallel serrations are shown on MAC surface due to surface grinding. TPS provides surfaces with a random distribution of small granules along with surface cracks. DAE and SLA illustrate some similarities due to the final step of acid etching although SLA demonstrates shallow grooves associated to grit blasting before etching. ANO is characterized by open craters and valleys.

3D profilometric images (**Figure 2**) provide a better idea for the highest (red) and lowest (blue) areas of each surface. For MAC the highest points are the ridges of serrations while for TPS randomly distributed granular regions. The highest points for SLA are region surrounding valleys while the top of craters constitutes the highest points for ANO. **Table 2** presents representative values for roughness parameters from dental literature. In general, the im‐ plants' surfaces are classified based on Sa (average roughness over the complete 3D surface) in smooth (0.0–0.4 μm), minimally rough (0.5–1.0 μm), moderately rough (1.0–2.0 μm) and rough (>2 μm) [25]. The first category includes the well-polished implant collars while MAC and DAE are classified as minimally rough surfaces. SLA and ANO belong to moderately rough surfaces and TPS to rough ones. Despite this general classification, it must be noted that manufacturers can modify the procedural parameters, and thus commercially available implants might have big differences in their surface roughness even if they are prepared by the same surface roughening technique.

Today, products prepared with the aforementioned techniques are available in dental market as there is no clear evidence for the superiority of one surface modification over the others. The different surface roughening techniques provide characteristic surface patterns on Ti implant surfaces. MAC is characterized by parallel serrations with a rather smooth surface (**Figure 1**). TPS provides surfaces with a random distribution of small granules resemble to solidified droplets probably due to plasma spray process along with a random distribution of surface cracks (**Figure 1**). DAE and SLA depict some similarities due to the final step of acid etching, although SLA illustrates shallow grooves probably due to grit blasting before etching. ANO is characterized by valleys and open craters although the size, the shape and the distribution of these craters are significantly dependent on operational parameters during

**Figure 1.** Secondary electron images from the root surface of dental implants in 4000 (left) and 24000 (right) nominal magnifications. Parallel serrations are shown on MAC surface due to surface grinding. TPS provides surfaces with a random distribution of small granules along with surface cracks. DAE and SLA illustrate some similarities due to the final step of acid etching although SLA demonstrates shallow grooves associated to grit blasting before etching. ANO

anodization.

156 Dental Implantology and Biomaterial

is characterized by open craters and valleys.

From corrosion standpoint, this difference in surface roughness might trigger the crevice corrosion mechanism. In this mechanism, the surface can withstand the corrosive environment but the stagnant solution in the crevice changes the chemistry increasing the aggressiveness of solution.

**Figure 2.** Representative 3D profilometric images from the collar (representative from all implants) and the surfaces of differently modified root surfaces. Red areas are the highest and blue the lowest areas of each surface. Note the differ‐ ence in scale among 3D images.


**Table 2.** Sa (average roughness over the complete 3D surface) and Ra (average roughness along X or Y axes) values for collar and root regions of implants from dental literature.

Implant surfaces are further differentiated in elemental composition as appeared by EDX analysis (**Figure 3**). All spectra showed C and N which should be appended to surface contamination while O should be attributed to surface oxide film. For SLA, Na and Cl were also identified and might be appended to residues of NaCl solution where the implant is placed to avoid atmospheric contamination. P in ANO has been retained from the solution used during anodization.

Although Ti oxide is spontaneously formed when Ti is exposed to atmospheric oxygen, a recent study employing Raman analysis illustrated great differences among the oxide type developed on different surfaces [28]. According to the results of this study, MAC surface contains mainly

**Figure 3.** X-ray EDS spectra from the root surface of dental implants prepared by different surface roughening techni‐ ques. All surfaces illustrated the presence of Ti while C and N should be appended to surface contamination. The pres‐ ence of O is involved with oxide film. Na and Cl were also identified for SLA and might be appended to residues of NaCl solution where the implant is stored. P in ANO has been retained from the solution used during anodization.

amorphous Ti oxide and less anatase, TPS amorphous and less rutile, DAE mainly Ti2O3 and amorphous and less rutile, SLA mainly Brookite and lesser rutile and ANO anatase and less rutile. Given the big differences in all the aforementioned properties, different electrochemical properties are anticipated.
