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Selective laser melting (SLM) is a promising technology capable of producing individual characteristics with a high degree of surface roughness for implants. These surfaces can be modified so as to increase their osseointegration, bone generation and biocompatibility, features which are critical to their clinical success. In this study, we evaluated the effects on preosteoblast proliferation and differentiation of titanium metal (Ti) with a high degree of roughness (Ra = 5.4266 ± 1.282 µm) prepared by SLM (SLM-Ti) that was also subjected to surface bioactive treatment by mixed acid and heat (MAH). The results showed that the MAH treatment further increased the surface roughness, wettability and apatite formation capacity of SLM-Ti, features which are useful for cell attachment and bone bonding. Quantitative measurement of osteogenic-related gene expression by RT-PCR indicated that the MC3T3-E1 cells on the SLM-Ti MAH surface presented a stronger tendency towards osteogenic differentiation at the genetic level through significantly increased expression of Alp, Ocn, Runx2 and Opn. We conclude that bio-activated SLM-Ti enhanced preosteoblast differentiation. These findings suggest that the mixed acid and heat treatment on SLM-Ti is promising method for preparing the next generation of orthopedic and dental implants because of its apatite formation and cell differentiation capability.

Selective laser melting (SLM) titanium alloys require surface modification to achieve early bone-bonding. This study investigated the effects of solution and heat treatment to induce the sustained release of strontium (Sr) ions from SLM Ti6Al4V implants (Sr-S64). The results were compared with a control group comprising an untreated surface [SLM pure titanium (STi) and SLM Ti6Al4V (S64)] and a treated surface to induce the release of calcium (Ca) ions from SLM Ti6Al4V (Ca-S64). The surface-treated materials showed homogenous nanoscale network formation on the original micro-topographical surface and formed bone-like apatite on the surface in a simulated body fluid within 3 days. In vitro evaluation using MC3T3-E1 cells showed that the cells were viable on Sr-S64 surface, and Sr-S64 enhanced cell adhesion-related and osteogenic differentiation-related genes expression. In vivo rabbit tibia model, Sr-S64 provided significantly greater bone-bonding strength and bone-implant contact area than those in controls (STi and S64) in the early phase (2–4 weeks) after implantation; however, there was no statistical difference between Ca-S64 and controls. In conclusion, Sr solution and heat treatment was a safe and effective method to enhance early bone-bonding ability of S-64 by improving the surface characteristics and sustained delivery for Sr.