To explore the osteointegration and osteogenic efficacy of additive manufacturing Ti-6Al-4V (TC4) titanium alloy implants, so as to provide experimental evidence for further clinical application.

A total of 42 healthy male New Zealand rabbits were selected. Implants were divided into three groups, i.e., the original surface, surface-modified TC4 titanium alloy implants and titanium bone implants. The femoral condylar of rabbit bilateral hind leg was used as the implantation area. The experimental rabbits were divided into two large groups, 2 weeks (Group A) and 8 weeks (Group B) , with 21 rabbits in each group. Each large group was divided into three subgroups, namely, group A1, A2, A3, B1, B2 and B3, with 7 rabbits in each group. One TC4 titanium alloy implant with original surface and one TC4 titanium alloy implant with surface modification were implanted in group A1 and B1, respectively. In group A2 and B2, rabbits were implanted with TC4 titanium alloy implant and titanium bone implant with the original surface. In group A3 and B3, rabbits were implanted with surface modified TC4 titanium alloy implant and titanium bone implant, respectively. There were 14 implants for each of the three kinds of implants at 2 and 8 weeks. At 2 and 8 weeks after operation, the implant success rate and osseointegration of the three groups were observed and compared for the following indexes: bone volume fraction (BV/TV) , bone trabecular area density (BS/BV) , bone trabecular thickness (Tb.Th) , bone trabecular number (Tb.N) , and bone trabecular septum (Tb.SP) . Using SPSS 21.0 software package, the data of bone mineral density at implant bone interface of three groups at different times were analyzed by two factor ANOVA to verify the influence of different surfaces and times on osteointegration. Tukey′s Multiple Comparisons Test was used to analyze the statistical differences between the groups.

With the progress of osteointegration, both the amount and density of bone tissue on the surface of implants in the three groups gradually increased. At 2 weeks, the BV/TV and Tb.N of the surface modified TC4 titanium alloy implant group were significantly higher than those of the original surface and the titanium bone group (P<0.05) , while its Tb.Th was significantly higher than that of the titanium bone group (P<0.05) , whereas its BS/BV and Tb.Sp were significantly lower than that of the titanium bone group (P<0.05) . At 8 weeks, the differences in BV/TV, BS/BV, Tb.Th, Tb.N and Tb.Sp among the three groups of implants were not statistically significant (P>0.05) .

More bone tissues can be formed on the surface modified TC4 titanium alloy implants than the other kinds of implants at 2 weeks. The surface-modified TC4 titanium alloy implant could be a promising dental implant due to its strong capacity in osteointegration represented by much dense bone trabecular on the surface.