| Popis: |
Introduction: Bioactive glass (BAG) has been studied widely and seems to be a very promising biomaterial in regeneration of large bone defects and osteomyelitis treatment, because of its bone bonding and antibacterial properties[1]-[5]. Its high stiffness could potentially also enable mechanical reinforcement of large defects. The loose-granular nature of this material, however, makes it difficult to handle by the surgeon. Moreover, in previous research we found only sub-optimal mechanical properties for pure BAG fillings[6]. Recently a BAG putty was developed that is easier to handle. The aim of the current study is to determine the mechanical properties of this putty and its dependence on composition. Materials and Methods: Five different compositions of S53P4 putty were tested in mechanical confined compression tests, after impaction of the samples (n=5 per group). The putty materials all consist of a synthetic binder (matrix: 20 wt% PEG 400, 40 wt% PEG 1500, 15 wt% PEG 3000 and 25 wt% glycerol), BAG granules (2.0-3.15 mm) and BAG powder (300-500 µm). Impaction was performed with the use of a custom-made impaction device (providing clinical relevant strains)[7]. After the samples were equally confined in PMMA chambers, they were subjected to 900 cycles of loading (40 – 850 N) followed by 300 s of rest. From the recorded displacement – time curves, the Young’s Modulus (elastic behaviour), plastic strains (permanent deformations) and creep strains (viscous behaviour) were determined and compared for the five compositions[7],[8]. Results and discussion: The results for impactability (measure for the height difference before and after impaction), Young’s Moduli, creep and plastic strain are shown in Figure 2. Significant differences between the putty compositions were found only for impactability and plastic strain. With an increasing amount of matrix the impactability decreases significantly. It has to be noted that the overall impactability is low, compared to graft materials such as morsellized cancellous bone or porous titanium[6],[7]. However, these materials are much less mouldable than the putty materials. The Young’s moduli of all putty compositions were found to be in range of the modulus of cancellous bone (100-500 MPa), which is the desired range[9]. Furthermore, creep strains were low, which indicate that viscous behaviour will not likely affect the graft layer stability. The plastic strain increases with larger matrix content. Such plastic strain can threaten the graft stability in load-bearing applications and thus should be kept low. Conclusion: For load bearing sites where the putty can be well confined in the defect, putty compositions with the low amount of matrix could be beneficial since their plastic strains are lowest. In other situations, the compositions with more matrix would be preferred because they are easier to handle. |
