Laboratory of Bone and Implant Sciences, The Weintraub Center for Reconstructive Biotechnology, Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry, UCLA School of Dentistry, Los Angeles, CA 90095-1668, USA.
Int J Nanomedicine. 2012;7:859-73. doi: 10.2147/IJN.S28082. Epub 2012 Feb 17.
The mechanism by which hydroxyapatite (HA)-coated titanium promotes bone-implant integration is largely unknown. Furthermore, refining the fabrication of nano-structured HA to the level applicable to the mass production process for titanium implants is challenging. This study reports successful creation of nanopolymorphic crystalline HA on microroughened titanium surfaces using a combination of flame spray and low-temperature calcination and tests its biological capability to enhance bone-implant integration. Sandblasted microroughened titanium implants and sandblasted + HA-coated titanium implants were subjected to biomechanical and histomorphometric analyses in a rat model. The HA was 55% crystallized and consisted of nanoscale needle-like architectures developed in various diameters, lengths, and orientations, which resulted in a 70% increase in surface area compared to noncoated microroughened surfaces. The HA was free from impurity contaminants, with a calcium/phosphorus ratio of 1.66 being equivalent to that of stoichiometric HA. As compared to microroughened implants, HA-coated implants increased the strength of bone-implant integration consistently at both early and late stages of healing. HA-coated implants showed an increased percentage of bone-implant contact and bone volume within 50 μm proximity of the implant surface, as well as a remarkably reduced percentage of soft tissue intervention between bone and the implant surface. In contrast, bone volume outside the 50 μm border was lower around HA-coated implants. Thus, this study demonstrated that the addition of pure nanopolymorphic crystalline HA to microroughened titanium not only accelerates but also enhances the level of bone-implant integration and identified the specific tissue morphogenesis parameters modulated by HA coating. In particular, the nanocrystalline HA was proven to be drastic in increasing osteoconductivity and inhibiting soft tissue infiltration, but the effect was limited to the immediate microenvironment surrounding the implant.
羟基磷灰石（HA）涂层钛促进骨-植入物整合的机制在很大程度上尚不清楚。此外，将纳米结构 HA 的制造精化到适用于钛植入物大规模生产过程的水平具有挑战性。本研究报告了使用火焰喷涂和低温煅烧相结合的方法在微粗糙钛表面上成功制备纳米多晶型 HA，并测试了其增强骨-植入物整合的生物学能力。对喷砂微粗糙钛植入物和喷砂+HA 涂层钛植入物进行了生物力学和组织形态计量学分析，以大鼠模型进行了测试。HA 的结晶度为 55%，由纳米级针状结构组成，其直径、长度和方向各不相同，与非涂层微粗糙表面相比，表面积增加了 70%。HA 无杂质污染物，钙/磷比为 1.66，与化学计量的 HA 相当。与微粗糙植入物相比，HA 涂层植入物在愈合的早期和晚期均持续增加骨-植入物整合的强度。HA 涂层植入物增加了植入物表面附近 50 μm 范围内的骨-植入物接触和骨体积的百分比，同时显著降低了骨与植入物表面之间软组织介入的百分比。相比之下，HA 涂层植入物周围 50 μm 边界之外的骨体积较低。因此，本研究表明，将纯纳米多晶型 HA 添加到微粗糙钛中不仅可以加速，而且可以增强骨-植入物整合的水平，并确定了 HA 涂层调节的特定组织形态发生参数。特别是，纳米晶 HA 被证明在增加骨传导性和抑制软组织浸润方面非常有效，但效果仅限于植入物周围的直接微环境。
