Combining Foaming and Starch Consolidation Methods to Develop Macroporous Hydroxyapatite Implants

Abstract

Hydroxyapatite (HA) is the calcium-phosphate material with composition closest to that of bone, what makes it suitable for osseous implant purposes. This material was used to produce macroporous structures with pores larger than 100 mm, which are believed to be suitable for allowing bone ingrowth. The macroporous structures were generated and consolidated by combining foaming and starch consolidation methods. The porous structures could be tailored according to the final application by varying the proportion of different foaming agents, foam-bath concentrate (FBC) and sodium lauril sulphate (SLS). Playing with these proportions it was also possible to improve foam stability and model the size of pores and pore interconnections in order to reproduce the pore structure of natural bone.

Macroporous Ceramics from Particle‐Stabilized Wet Foams

“…Additives are often used to avoid foam collapse by setting the foam structure shortly after air incorporation. This usually occurs by gelling or cross‐linking organic compounds added to the suspension liquid medium 5–11 . A drawback of these methods is the fact that they cannot avoid rapid bubble growth before the setting reaction takes place, which leads to large average bubble sizes (30 μm–1 mm) and a wide bubble size distribution 3 …”

“…This usually occurs by gelling or cross-linking organic compounds added to the suspension liquid medium. [5][6][7][8][9][10][11] A drawback of these methods is the fact that they cannot avoid rapid bubble growth before the setting reaction takes place, which leads to large average bubble sizes (30 mm-1 mm) and a wide bubble size distribution. 3 We have recently shown 12 that ultra-stable wet foams can be produced by using particles instead of surfactants as foam stabilizers in the direct-foaming method.…”

Modified-starch consolidation of alumina ceramics

“…Compared with the starches used both as a binder and a pore-forming agent for the preparation of porous ceramics [2][3][4][5][6][7][8][9][10][11][12][13][14] , the starch used just as a binder Fig.1 The fl ow chart of the processing route Fig.2 Micrographs of swelling behavior of oxidized tapioca starch globules (×500) in excess water during heating at a temperature rate of 2 ℃ /min in the production of high density ceramics is required to be gelatinized more readily at low temperatures. Therefore, it is necessary to investigate the gelling properties of the starches.…”

“…Recent studies on the processing of various ceramics with starch have been performed [2][3][4][5][6][7][8][9][10][11][12][13][14] . For instance, starch has been used as a pore-forming agent for the production of porous structural ceramics [2][3][4] , porous electronic ceramics [5][6][7][8] and porous bioactive ceramics [9][10][11][12][13][14] . In general, the full density cannot be obtained by this technique because the pores are generated during the burn out of starch granules [1,15] .…”

Porous foams based hydroxyapatite prepared by direct foaming method using egg white as a pore promoter

“…In the research for the better ways of porous ceramics elaboration, some other techniques have been developed such as replica [22,23], sacrificial template [24,25], and direct foaming methods [26,27]. The use of the foaming method had success in producing a porous ceramic with a porosity volume around 80 vol-%, in which the structure of the pores was characterized by spherical interconnected cells [28,29].…”