**2.4 Animal experimental and histological evaluation**

The CA films on a Ti screw cylinder for animal experiments were coated by using the abovementioned ethanol solution as follows. The Ti screw cylinders were immersed in the molecular precursor solution for 5 min and taken out from the solution slowly. Subsequently, the precursor films that formed on the Ti screw cylinder were dried at 60°C for 20 min and then heat treated at 600°C for 2 h in air using a furnace. The film thickness was approximately 0.16 μm, and the Ca/P ratio was 1.49 ± 0.20. All implants, CA-coated Ti screw cylinder and uncoated Ti screw cylinder, were sterilized in an autoclave before surgery; the implants were inserted into the trabecular bone of rabbits according to a previously used technique [33, 34]. After the implantation for 2, 4, 8, and 12 weeks, no clinical signs of inflammation or adverse tissue reactions were observed at sacrifice. All implants were still in situ at sacrifice. After implantation for 2 weeks, as has been shown in **Figure 5**, the overall trabecular bone response to the two different implant surfaces was almost identical [35]. With progress of implantation time, as for both implants, new bone and remodeling were observed, and no clear differences in bone responses to the two different implants could be seen (as shown in **Figure 6**). Then, besides a descriptive evaluation, the percentage of bone contact was determined for the 4-, 8-, and 12-week specimens. **Table 3** shows the results of the measured percentage of bone-implant contact. At 4 and 8 weeks, no significant difference existed in bone contact between uncoated and CA-coated implants (P > 0.05). However, after 12 weeks, statistical analysis revealed that the amount of bone contact to the CA-coated implants was significantly higher than the uncoated titanium implant (P < 0.05).

#### **Figure 5.**

*Histological appearances of (a) uncoated Ti screw cylinder and (b) CA-coated Ti screw cylinder 2 weeks after implantation.*

*Fabrication of Apatite Films on Ti Substrates of Simple and Complicated Shapes by Using Stable… DOI: http://dx.doi.org/10.5772/intechopen.80409*

#### **Figure 6.**

*Histological appearances of (a) uncoated Ti screw cylinder and (b) CA-coated Ti screw cylinder 12 weeks after implantation.*


#### **Table 3.**

*Percentage of the measured bone-implant contact.*

Wolke and coworkers suggested that 1-μm-thick heat-treated Ca/P sputter coatings on roughened Ti implants appear to be of sufficient thickness to show bioactive properties under in vivo conditions [36]. Our study demonstrated that a CA coating with a thickness of approximately 0.16 μm, which was also inserted into the trabecular bone of the rabbit, has a beneficial effect on the bone response during the healing phase.

From these results, it was suggested that the MPM is promising as the apatite film formation method. Furthermore, this method is useful to fabricate the apatite films homogeneously on various and complicated shapes, e.g., Ti mesh [37].
