**Author details**

The rougher surface promoted a greater osteogenic response than the smooth surface in terms

The biological responses induced in MC3T3 cells, a widely diffused osteoblast model, were correlated with the surface roughness, even in this case. The effect of roughness on osteoblast adhesion has been mainly attributed to an increased surface-to-volume ratio that may provide more sites for cell attachment [118]. Consistently, the rougher surface tested (Si3N4–TiN\_A) could promote better cell viability, higher density of focal adhesions and more pronounced calcium deposition than the smoother one (Si3N4–TiN\_B). Taken together, these data confirmed the biocompatibility of silicon nitride–titanium nitride composites in accordance with the literature, which has indeed so far explored preferably the pristine Si3N4 material [93, 94, 99, 119]. The possible application of surfaces directly obtained by EDM to Si3N4–TiN is therefore noteworthy. Further research should be oriented at investigating the in vivo effects of such surface finishing, as well as the importance of the texture in the pattern recognition operated

As stated in previous sections, even though titanium and titanium alloys are the material of choice for dental implants, they are not without drawbacks. Among the possible issues, for instance, the hypersensitivity in allergic patients and some aesthetic concerns deserve atten‐ tion. To address these problems, ceramics have been introduced to the market in the last decades. Y-TZP was first proposed owing to its biocompatibility, white *root-like* color and low plaque affinity. More recently, oxidic composites containing variable amounts of zirconium oxide such as zirconia-toughened alumina (ZTA) and especially alumina-toughened zirconia (AZT) were recently considered an improved alternative to Y-TZP. These implants seem very suitable to replace the anterior teeth to avoid the formation of dark shimmer in the presence of thin gingival biotype. However, one-piece ceramic implants may be more difficult to place

Nevertheless, the demand of non-metallic materials endowed with high mechanical features is prompting research and industry to explore also ceramics such as silicon nitride. This non-oxidic material, whose use is almost completely limited to orthopedics in the biomedi‐ cal field, possesses really promising quality even for dental application. The possibility to dope silicon nitride with titanium nitride, thus rendering it electroconductive, enables a range of manufacturing processes like the electro discharge machining. This opens compel‐ ling perspectives in the future as biomaterials are supposed to be increasingly customizable, maneuverable, and adaptable to the particular necessity of the single case, possibly entering

than two-pieces titanium implants if angulated abutments are required.

of calcium deposition (**Figure 10B**).

78 Dental Implantology and Biomaterial

by cells.

**5. Concluding remarks**

the digital *work-flow*.

Federico Mussano1\*, Tullio Genova1,2, Luca Munaron1,2, Maria Giulia Faga3 and Stefano Carossa1

