| ObjectiveTo design study a bioactive implant that its elastic modulus matches with thebone tissue through both in vitro and in vivo tests which are able to evaluate thebiocompatibility and biomechanical compatibility of the implant, as well as themechanical biological reaction of the bone tissue around the implant so as to provide a basicstudy for the clinical application of this kind of implant.MethodsTLM titanium alloy (Ti25Nb3Zr3Mo2Sn) which was approximate to β type wasused as the base material for the implant. Its elastic modulus is about1/2of the puretitanium while the mechanical strength is higher. In order to improve the biologicalactivity of the TLM titanium alloy surface, a biomimetic coating with rough andporous structure compounded with nano-HA was prepared via micro-arc oxidation(MAO) and hydrothermal treatment (Htt). In such a manner, two kinds of bionicimplants (TLM-MAO-Htt and Ti-MAO-Htt) were prepared. The surface morphology,phase structure, roughness and hydrophilicity of the coating were detected to characterize itsphysicochemical properties and the hemolysis experiments, cell toxicity test, acute systemictoxicity test and subcutaneous implantation test were applied to evaluate the biocompatibilityof the implants. We also embedded the TLM-MAO-Htt and Ti-MAO-Htt implants intobeagle dogs’ mandible at bone margin level and analyzed the quality of theosseointegration through Raman spectroscopy, nanoindentation, hard tissue slices analysescompared with both rough (Ti-MAO-Htt) and smooth pure titanium implant(Ti-S) with thesame processing. Delayed loading on the implants which can simulate the intraoral loadingenvironment was further carried on to study the mechanical biological behavior ofosseointegrated bone around the TLM-MAO-Htt and Ti-MAO-Htt implants, especially the osseointegration at the neck position. With multidisciplinary approaches of hard tissuesections analysis, Raman spectroscopy and nanoindentation, we quantitatively studied thebioactive and biomechanical compatible advantages of the low elastic modulus implants(TLM-MAO-Htt) compared to the high elastic modulus implants (Ti-MAO-Htt).Results1. TLM titanium alloy possessed a porous surface comprised of bioactive nanoHA after micro-arc oxidation (MAO) and hot water (Htt) treatment, which wassuccessfully mimicked the natural structure of dentin-cementum complex.2. The surface roughness (Ra) of TLM-MAO-Htt coating, was1.684μm; thecontact angle was13.8±1.7°and the hydrophilicity is enhanced; meanwhile, thecoating structure, roughness, and hydrophilic of Ti-MAO-Htt surface was similar tothe TLM-MAO-Htt coating, with no significant difference.3. The coating of TLM-MAO-Htt and Ti-MAO-Htt implants exhibited goodbiocompatibility and ectopic bone formation ability.4. No significant differences were found in the efficiency and quality ofosseointegration between the TLM-MAO-Htt implants and Ti-MAO-Htt implants inin vivo experiment, but both were significantly higher than the Ti-S implants（P≤0.05）.5. In the delayed loading test, we found that the osseointegration rate, percentageof bone inside the thread (BIT), the hardness and elastic modulus of cortical bonearound implants were much lower in the Ti-MAO-Htt group comparing to theTLM-MAO-Htt group （P≤0.05）. There were significant angular resorption in thecortical bone around neck of Ti-MAO-Htt implants, and the bone remodeling wassignificantly more active than TLM-MAO-Htt group.Conclusions1. By micro-arc oxidation and water heat operation on TLM titanium alloysurface, a rough and porous biomimetic coating with nano-HA can be successfullyconstructed, which is similar to dentin-cementum complex.2. Our TLM-MAO-Htt coating exhibits a favorable hydrophilicity,biocompatibility and bioactivity. 3. The quality of osseointegration of TLM-MAO-Htt implants is similar toTi-MAO-Htt implants and superior to Ti-S implants.4. Compared with high elastic modulus implants (Ti-MAO-Htt), TLM-MAO-Httimplants with low elastic modulus possess a better mechanical compatibility with thesurrounding bone. |
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