title: Influence of processing parameters on microstructure and biocompatibility of surface laser sintered hydroxyapatite-SiO2 composites.
abstract: Silica-doped hydroxyapatite (HA) is a promising material concerning biocompatibility to natural bone, bioactivity and osteoconductive characteristics. HA exhibits phase transformations during sintering which are attendant to the change in volume and thermal strain. To avoid cracks during sintering, the exact knowledge of the phase transition temperatures is necessary. The sintering behavior of HA can be improved by adding amorphous silica with a low coefficient of thermal expansion. Therefore, the phase transformations in the system HA-SiO2 were analyzed by using differential scanning calorimetry followed by quantitative phase analysis by X-ray diffraction with the Riedveld method. The maximum sintering temperature without reversible phase transformation was defined as 1265°C. In laser surface sintered (LSS) samples, amorphous SiO2 , HA, and Si-α-TCP (or α-TCP) were detected. By comparison, only crystalline phases, such as cristobalite, HA, β-TCP, and Si-α-TCP (or α-TCP), were determined after furnace sintering. Scanning electron microscopy micrographs of furnace sintered and LSS samples show the differences in the resulting microstructures. Biocompatibility was determined by measuring cell activity of osteoblasts cultivated on four laser-sintered materials in the HA-SiO2 system in comparison to normal cell culture plastic. Cell proliferation was similar on all surfaces. The level of the cell activity on day 8 varied depending on the composition of the material and increased linearly as the amorphous SiO2 content rose. Taken together a laser-based method to develop novel biocompatible HA-SiO2 ceramics with adjustable properties and possible applications as orthopedic bioceramics are discussed.
authors.affiliation: Department of Engineering Ceramics, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Kivitz
authors.forename: R
authors.initials: R
authors.lastname: Görke
authors.forename: A F
authors.initials: AF
authors.lastname: Schilling
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: J G
authors.initials: JG
authors.lastname: Heinrich
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D018786:Bone Substitutes / Q000737:chemistry; D001842:Bone and Bones / Q000378:metabolism; D049109:Cell Proliferation; D002516:Ceramics / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry*; D007834:Lasers; D008422:Materials Testing; D051379:Mice; D008855:Microscopy, Electron, Scanning; D010006:Osteoblasts / Q000187:drug effects; D011208:Powders; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D018786:Bone Substitutes; D011208:Powders; D012822:Silicon Dioxide; D017886:Durapatite