Stackable modular 3D printed bioactive glass scaffolds with metal screws
Basak, Asha (2023)
Basak, Asha
2023
Bioteknologian ja biolääketieteen tekniikan maisteriohjelma - Master's Programme in Biotechnology and Biomedical Engineering
Lääketieteen ja terveysteknologian tiedekunta - Faculty of Medicine and Health Technology
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Hyväksymispäivämäärä
2023-05-18
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202304264465
https://urn.fi/URN:NBN:fi:tuni-202304264465
Tiivistelmä
Bioactive glass has been widely studied for its potential in various biomedical applications, particularly in the field of tissue engineering and regenerative medicine. The surface of bioactive glass can dissolve and precipitate a hydroxyapatite layer when it comes into contact with body fluids, which mimics the structure of natural bone and promotes bone growth. The main aim of this Master’s Thesis is to develop a new approach to making bone replacement scaffolds which can meet the various demands of large bone scaffolds used to treat large defects usually induced from trauma or bone cancer. For example, mandible replacement is important because with an injured mandible daily essential works such as biting, chewing, speaking become very difficult. However, the replaced part needs mechanical properties shape, size, ability to tailor intraoperatively, bioactivity, perfusion, and ability to add sensors actuators. It is difficult for a single material to have all requisite properties in practice. To address these issues, we 3D printed porous bioactive glass scaffolds, stack them with the stainless steel screws after the sintering process.
As a proof of concept, a structure with modular components including large holes to fit metallic screws was produced, to take the load. The sintered hexagon scaffolds were stacked with stainless steel screws so that it makes them as strong as the trabecular or cortical bone. In order to stack the scaffolds, larger holes must be made in the scaffolds for the screws to fit. The main goal is to incorporate the bioactivity of the bioactive glass and mechanical strength of the stainless steel screws so that the scaffolds are not only bioactive, biocompatible but also have strong mechanical properties like human bone. The background related studies and motivation of the thesis were described in chapter one and chapter two of this thesis.
The B12.5 MgSr borosilicate glass and 25 wt% Pluronic was used for 3D printing of all shape of scaffolds including: hexagon, logpile and ordinary logpile. Two sintered hexagon scaffolds were stacked with the stainless steel screws and one titanium plate was added on the top, and one titanium plate on the bottom. Some small holes were created in the titanium plates to mimic the porous structure. The mechanical properties (load/displacement curves) for these stacked scaffolds analyzed with a mechanical testing stand and compared to scaffolds without metal. The detailed method for making ink, 3D printing and sintering of the scaffolds, stacking the scaffolds and measuring and analyzing the mechanical properties are described in chapter three.
We examined the mechanical properties of the scaffolds in terms of Young’s modulus, maximum compressive strength and compressive strain at maximum compressive strength. The mean Young’s modulus of the single hexagon sample was 2.4±1 MPa and for single logpile scaffolds was 1.5±0.7 MPa. While the stacked hexagon scaffold’s mean Young’s modulus was 122±33 MPa. This means that the stacking and adding metal plates and screws vastly increased the Young’s Modulus. The maximum compressive strength of the logpile scaffolds were very low (0.02 MPa) as they bent into concave shapes after sintering which reduced the contact area of the scaffold and the plates of the Instron Electropuls compression platen. The mean maximum compressive strength of the hexagon scaffolds was 0.2±0.4 MPa where for the stacked hexagon scaffold it was 3.3±2 MPa. The Young’s modulus and the maximum compressive strength of the trabecular bone are 50-500 MPa and 0.1-16 MPa. However, the ordinary logpile scaffolds had better result than stacked scaffolds as their Young’s modulus and maximum compressive strength were 329±216 MPa and 4.8±3 MPa albeit over a smaller strain range. The ordinary scaffolds are less porous, smaller and more uniform than the hexagon and logpile scaffolds that we used. Overall, our results showed the metal screws does help increasing the mechanical properties of the stacked hexagon scaffolds as they have the Young’s Modulus and maximum compressive strength similar to trabecular bone.
As a proof of concept, a structure with modular components including large holes to fit metallic screws was produced, to take the load. The sintered hexagon scaffolds were stacked with stainless steel screws so that it makes them as strong as the trabecular or cortical bone. In order to stack the scaffolds, larger holes must be made in the scaffolds for the screws to fit. The main goal is to incorporate the bioactivity of the bioactive glass and mechanical strength of the stainless steel screws so that the scaffolds are not only bioactive, biocompatible but also have strong mechanical properties like human bone. The background related studies and motivation of the thesis were described in chapter one and chapter two of this thesis.
The B12.5 MgSr borosilicate glass and 25 wt% Pluronic was used for 3D printing of all shape of scaffolds including: hexagon, logpile and ordinary logpile. Two sintered hexagon scaffolds were stacked with the stainless steel screws and one titanium plate was added on the top, and one titanium plate on the bottom. Some small holes were created in the titanium plates to mimic the porous structure. The mechanical properties (load/displacement curves) for these stacked scaffolds analyzed with a mechanical testing stand and compared to scaffolds without metal. The detailed method for making ink, 3D printing and sintering of the scaffolds, stacking the scaffolds and measuring and analyzing the mechanical properties are described in chapter three.
We examined the mechanical properties of the scaffolds in terms of Young’s modulus, maximum compressive strength and compressive strain at maximum compressive strength. The mean Young’s modulus of the single hexagon sample was 2.4±1 MPa and for single logpile scaffolds was 1.5±0.7 MPa. While the stacked hexagon scaffold’s mean Young’s modulus was 122±33 MPa. This means that the stacking and adding metal plates and screws vastly increased the Young’s Modulus. The maximum compressive strength of the logpile scaffolds were very low (0.02 MPa) as they bent into concave shapes after sintering which reduced the contact area of the scaffold and the plates of the Instron Electropuls compression platen. The mean maximum compressive strength of the hexagon scaffolds was 0.2±0.4 MPa where for the stacked hexagon scaffold it was 3.3±2 MPa. The Young’s modulus and the maximum compressive strength of the trabecular bone are 50-500 MPa and 0.1-16 MPa. However, the ordinary logpile scaffolds had better result than stacked scaffolds as their Young’s modulus and maximum compressive strength were 329±216 MPa and 4.8±3 MPa albeit over a smaller strain range. The ordinary scaffolds are less porous, smaller and more uniform than the hexagon and logpile scaffolds that we used. Overall, our results showed the metal screws does help increasing the mechanical properties of the stacked hexagon scaffolds as they have the Young’s Modulus and maximum compressive strength similar to trabecular bone.