Powder Metallurgical Fabrication of Artificial Tooth Root of Hydroxyapatite/Ti with Bio-mimetic Structure

浆液浸法制备氢磷灰石/钛仿生材料具有良好的成形性能和微观组织控制能力。两种成分的梯度层是根据高温加工过程中产生的热应力减小和最佳生物相容性的最佳组成剖面形成的。通过浆料浸渍成功地形成了这种分级层。结合分散介质、分散剂、粘结剂和原料粉的性能，对浆料的分散、沉降、粘度、流变性和屈服值进行了详细的研究。研究了低粘度和高粘度浆料，以扩大薄膜厚度控制的可能性。对于低粘度料浆，必须抑制分散颗粒的沉降，而对于高粘度料浆，阐明料浆的流动特性对于确定屈服值至关重要，这对于精确控制浸涂层厚度是必要的。高粘度浆料不存在沉降现象，膜厚随粘度和屈服值的变化更容易控制。浸渍涂层的固结过程，包括干燥和脱脂，遵循传统的粉末冶金技术，特别注意与烧结收缩有关的问题，这是成分分级的特征。本研究通过优化工艺条件，得到了具有良好生物相容性的分级层。然而，一般来说，最佳工艺条件取决于被加工对象的材料种类、形状和尺寸，在将现有工艺条件应用于实际牙根生产时，需要进行或多或少的实践和技术研究。

Slurry dipping method was employed for the processing of hydroxiapatite/Ti biomimetic materials because of its capability of shape forming and microstructural control. The graded layers of both constituents were formed according to an optimum composition profile for the thermal stress reduction which will occur during high temperature processing, and for the optimum bio compatibility. Such graded layers were successfully formed by slurry dipping. Dispersion, sedimentation, viscosity, rheology, as well as yield value, of the slurries were investigated in detail in connection with properties of dispersion medium, dispersion reagent, binder and raw powders. Low- and high-viscosity slurries were investigated to enlarge a possibility of film thickness control. For the low-viscosity slurry it is necessary to suppress the sedimentation of dispersion particles, while for the high-viscosity slurry it turned out to be important to clarify the flow characteristics of the slurry for the determination of the yield value, which is needed for the precise control of the dip-coated layer thickness. The high-viscosity slurry was free from sedimentation, and the control of the film thickness with viscosity and yield value was rather easier. The consolidation process of the dip-coated layer, including drying and debinding, followed conventional powder metallurgical techniques, with particular attention on an issue pertaining to the sintering shrinkage which is characteristic to composition grading. In the present investigation the process conditions were optimized to get a sound graded layer for a better bio-compatibility. In general, however, the optimum process condition depends on material species, shape and size of the objects to be processed, and in applying the present process conditions to actual tooth root production a modification will be necessary with more or less practical and technical study.