Mechanical testing and in vitro degradation of composite materials for bone tissue engineering
Sindelar, Jan (2022)
2022
Master's Programme in Biomedical Sciences and Engineering
Lääketieteen ja terveysteknologian tiedekunta - Faculty of Medicine and Health Technology
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Hyväksymispäivämäärä
2022-08-17
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202207316131
https://urn.fi/URN:NBN:fi:tuni-202207316131
Tiivistelmä
Mechanical testing is one of the most common and most performed characterization methods when studying scaffolds for tissue engineering. Knowledge of the mechanical properties of tissue engineering scaffolds is important since unsuitable mechanical properties are likely to lead to implant failure and possibly even to the damage of surrounding tissues. This is even more of importance for implants in load bearing applications.
Static mechanical testing is simple to perform and commonly used. However, for many mate rials, it does not provide information about their behaviour under long-term sustained or dynamic loads. Creep-recovery, stress relaxation, and dynamic testing are used to assess such behaviour. However, as it is complicated, it is not commonly performed.
In this thesis, static, dynamic, and creep-recovery testing was performed to assess the com plex mechanical behaviour of two composite materials that are being developed for bone tissue engineering. The composites consist of a biodegradable, thermoplastic polymer matrix and a bioceramic filler. Poly-L-DL-lactide was used as a matrix in both composites and bioactive glass 13-93 was used as a filler in one composite and β-tricalcium phosphate in the other. Tensile and compression mechanical testing was performed. Specimens of porous scaffolds were used for compression testing and compact plates for tensile testing. Mechanical properties were assessed over the course of 12 weeks of in vitro degradation in a TRIS buffer solution. Additionally, ion release from the porous scaffolds was measured.
Strength and mass retention were evaluated for the degradation period. Creep and recovery and dynamic testing confirmed that both materials showed strong viscoelastic behaviour and their mechanical behaviour was changing considerably during cyclic dynamic testing, however, less strongly in the case of the β-tricalcium phosphate containing composite.
Results obtained from mechanical testing can be used for mathematical modelling to perform finite element analysis and create constitutive models. Such models and simulations can then be used to aid the design of the final tissue engineering scaffolds.
Static mechanical testing is simple to perform and commonly used. However, for many mate rials, it does not provide information about their behaviour under long-term sustained or dynamic loads. Creep-recovery, stress relaxation, and dynamic testing are used to assess such behaviour. However, as it is complicated, it is not commonly performed.
In this thesis, static, dynamic, and creep-recovery testing was performed to assess the com plex mechanical behaviour of two composite materials that are being developed for bone tissue engineering. The composites consist of a biodegradable, thermoplastic polymer matrix and a bioceramic filler. Poly-L-DL-lactide was used as a matrix in both composites and bioactive glass 13-93 was used as a filler in one composite and β-tricalcium phosphate in the other. Tensile and compression mechanical testing was performed. Specimens of porous scaffolds were used for compression testing and compact plates for tensile testing. Mechanical properties were assessed over the course of 12 weeks of in vitro degradation in a TRIS buffer solution. Additionally, ion release from the porous scaffolds was measured.
Strength and mass retention were evaluated for the degradation period. Creep and recovery and dynamic testing confirmed that both materials showed strong viscoelastic behaviour and their mechanical behaviour was changing considerably during cyclic dynamic testing, however, less strongly in the case of the β-tricalcium phosphate containing composite.
Results obtained from mechanical testing can be used for mathematical modelling to perform finite element analysis and create constitutive models. Such models and simulations can then be used to aid the design of the final tissue engineering scaffolds.