There have been known various ceramic shaped products having porous surface which have good affinity to living bodies and comparatively high mechanical strength and hence are mainly used as implant materials, i.e. replacements for various hard tissues in living bodies, such as artificial tooth roots or artificial bones.
However, the known porous ceramic shaped products have small pore diameter and less open cells, and hence, when the porous ceramic shaped products are used as an implant, bone tissue is hardly grown within the cells and further it is difficult to sterilize or clean the cells positioned in the inner region of the products.
There has also been used a porous shaped product having a comparatively large pore size and open cells as an implant material. For example, it is disclosed in Japanese Patent Second Publication (Kokoku) No. 41954/1983 that a clay-like plastic composition comprising granules, an aqueous solution of a binder and naphthalene powder is formed and sintered to form a porous shaped product, and the shaped product is inserted into a dense ceramic tube (outer tube) and sintered by heating to form a ceramic shaped product containing a porous region in inner part thereof. However, the shaped product obtained by this method has a drawback that the binding between each granule and also between the granules and the outer tube is very weak because the binding is effected by sintering at the contact point of the granules. That is, in said product, the binding between the granules and the outer tuber is done at only one point and that between each granule is effected at only 6 to 12 points, and hence, the binding between the granules and the outer tube (substrate), which is effected by sintering, is very weak, and further, the binding between each granule is also insufficient.