Reprint of “Biomimetic apatite coating on yttria-stabilized tetragonal zirconia utilizing femtosecond laser surface processing”

Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) have been used in orthopedic and dental implants because of their excellent physicochemical properties. In this study, we developed an apatite coating technique with low thermal effects for Y-TZP ceramics based on a biomimetic process using a supersaturated calcium phosphate solution (CP solution) as a coating medium. To achieve this, we performed femtosecond laser processing with low thermal effects as a surface pre-modification tool for Y-TZP ceramics. By changing the laser scanning mode, we fabricated two different submicro-/micro-structures on the Y-TZP sample. Both laser-treated samples showed increased water wettability due to ablation plasma and partly formed an apatite layer on their surfaces in the CP solution within 7 days. To further enhance the apatite-forming ability, we applied an alternate dipping process to the laser-treated sample in order to precoat the sample with apatite precursors. The laser-treated and precursor-precoated sample successfully formed an apatite layer on the entire surface in the CP solution within a shorter time period (24 h). The thus-coated apatite layer adhered to the sample so strongly that the layer remained on the sample even after the tape-detaching test. This strong adhesion may be attributed to the mechanical interlocking effects due to laser-induced surface roughening. Our proposed apatite-coating technique using the laser- and precursor-assisted biomimetic process would be useful for the creation of apatite-coated Y-TZP ceramics for orthopedic and dental applications.