## 4 Conclusions  
* Directionally solidified eutectics in the W-TCP and MgO-MSZ systems with good comprehensive properties and controlled microstructure have been grown by the LFZ technique. Microstructure characteristics at different solidification rate were investigated.
* W-TCP eutectic composition. Microstructure was strongly dependent on processing rate, obtaining crystalline eutectics, glass-ceramics, or glasses when increased the growth rate. At slow rate of 20 mm/h phases of apatite and pseudo-wollastonite were observed. At moderate rates of 100 mm/h crystalline phases of apatite in a glass matrix of calcium silicate were formed. At rates above 200 mm/h the eutectic rods grew amorphous. Crystalline cylinders were subjected to a superficial laser melting process, generating a glassy layer that improved their flexural strength, from 73.8 MPa to 129 MPa.
* MgO-MgSZ eutectic composition. The microstructure changed from fibrillar/lamellar to colonies and cells with increasing growth rate in the range from 50 to 750 mm/h. Correspondingly, the phase spacing decreased gradually. The relationship between eutectic phase spacing with solidification rate can be summarized as \(\lambda=8.24\)V\({}^{-1/2}\). Hardness and the fracture toughness of 11 GPa and 1.5 MPam\({}^{1/2}\), respectively, were obtained for rods grown at 750 mm/h. Flexural strength of 900 MPa was obtained.
* A simple and useful strategy to prepare rapidly solidified MgO-MgSZ nanoeutectic ceramic rods by laser surface remelting is proposed. After laser remelting, the lamellar spacing was refined sharply, without the need of high temperature preheating to avoid crack generation.
* After soaking in SBF, the MgO phase of the eutectic dissolves, leaving a zirconia skeleton on the surface in contact with the liquid. Pores of around 0.2 \(\upmu\)m with approximately the same size as the structural elements (zirconia phase) are homogeneously distributed on the ceramic surface.
* The limited bioactivity of the MgO-MgSZ eutectic can be improved by the use of W-TCP eutectic as a bioactive cladding. The combination of dip coating and laser surface melting was able to meet the requirements in terms of coating thickness, homogeneity, and adhesion to the substrate. No coating spallation from the substrate was observed that could result in adverse clinical response.  
Methodology, all authors; validation, all authors; investigation, all authors; writing--original draft preparation, J.I.P.; writing--review, all authors; funding acquisition, all authors. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Departamento de Ciencia, Universidad y Sociedad del Conocimiento del Gobiermo de Aragon through the financial support to the Research Group T02-20R. [PERSON] wants to acknowledge the support of the China Scholarship Council during his sabbatical stay in Zaragoza. [PERSON] thanks the PIT2 program of the University of Murcia's own research plan.  
Authors acknowledge the use of Servicio de Microscopia Electronica (Servicios de Apoyo a la Investigacion), Universidad de Zaragoza.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.