Abstract
To find out the optimal porosity and pore size of porous titanium (Ti) regarding the cytocompatibility and osteogenic differentiation. Six groups of porous Ti samples with different porosities and pore sizes were fabricated by the powder metallurgy process. The microstructure and compressive mechanical properties were characterized. The cytocompatibility was examined by a series of biological tests as protein absorption with BCA assay kit, cell attachment with laser scanning confocal microscopy and vinculin expression, cell proliferation with CCK-8 assay. Cell differentiation and calcification were detected by qPCR and Alizarin Red S dying respectively. Pores distributed homogeneously throughout the porous Ti samples. The compressive test results showed that Young’s modulus ranged from 2.80 ± 0.03 GPa to 5.43 ± 0.34 GPa and the compressive strength increased from 112.4 ± 3.6 MPa to 231.1 ± 9.4 MPa. Porous Ti with high porosity (53.3 ± 1.2%) and small pore size (191.6 ± 3.7 μm) adsorbed more proteins. More MC3T3-E1 cells adhered onto dense Ti samples than onto any other porous ones already after culture and no difference was identified within the porous groups. The porous structure of porous Ti with a porosity of 53.3 ± 1.2% and an average pore size of 191.6 ± 3.7 μm facilitated cell differentiation and calcification. Small pores were not beneficial to the osteo-initiation at the very beginning. Porous Ti with a porosity of 53.3 ± 1.2% and an average pore size of 191.6 ± 3.7 μm fabricated by powder metallurgy process showed the expected mechanical property and improved osseointegration as implants in dental treatment.
Highlights
Titanium (Ti) possesses unique biocompatibility and has been widely used as an implant in dental treatment in the last few decades
It has been reported that porosity of 66.1% showed best bone contact [5], whereas in another study porosity of 30–40% was suggested to have a positive effect on osteogenic differentiation and bone ingrowth [6]
Six types of porous Ti samples with different porosities and pore sizes as Group AI to AIII and BI to BIII were fabricated by powder metallurgy process and sintered using conventional method [18]
Summary
Titanium (Ti) possesses unique biocompatibility and has been widely used as an implant in dental treatment in the last few decades. Commercial Ti implants are mostly dense, with Young’s modulus (114 GPa) much higher than that of cancellous and cortical bone [1]. High modulus of the implant is known to cause stress-shielding at the bone-implant interface [2], and a dense superficial layer prevents the bone from ingrowing and forming interlock between the surrounding bone tissues, subsequently resulting in implant loosening. Porous structure was introduced to lower elastic modulus so as to match well with bone tissues, restrain bone atrophy and improve bone remodeling [3, 4]. It is well known that higher porosity facilitates bone ingrowth, and weakens mechanical properties of the implant such as hardness, compressive strength, and elastic modulus at the same time [7]
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