SIMULATION AND OPTIMIZATION OF POROUS BONE-LIKE MICROSTRUCTURES WITH SPECIFIC MECHANICAL PROPERTIES

Bone trabecular structure can be characterized as a connected network of mineral bars and plates with unique mechanical properties. Standard methods of producing bone-like structures based on periodic structures or foams have same limitations. The organization of the trabecular bone (meso scale) is adapted to the values of stresses and strains affecting the skeletal system. To simulate bone-like structure, the methodology of generating stochastic structure based on hyperuniform spatial points distribution is proposed. Statistical analysis of generated structure shows the possibility to generate clouds of points in wide range of random close packing density, up to 59.52%. Points connected by Voronoi tessellation produce to unique porous topology with no closed-cells and with wide range of connectivity. Manufacturing of a generated structure is only limited by used technique. The proposed algorithm was developed regardless of the manufacturing technique, however, same examples of the structure were printed using 3D addictive technology. The mechanical properties of developed structure are strongly dependent on the material from which they are made, but the modification of the structure allows to change the strength in specific and controlled way

Desing of the algorithm, print and analysis of porous structures with modifiable parameters

The purpose of this paper was to create an algorithm able to creating a porous structure with variable properties, print and analyze them. The basic concepts related to it were introduced and the process of creating an algorithm in Rhinoceros software was described. Having a suitable test group of porous structures, it was shown that it is possible to modify their porosity. In the next step, the structures were presented for printing and its effect. The obtained physical models were examined by microtomography. The resulting cross-sections were processed in ImageJ software. Having cross-sections of the original bone and printed structures, it was possible to compare their porosity and the average diameter of the trabeculae in the structure. With this procedure, it is possible to deduce whether it is possible to print accurate structures that will serve as porous bone implants. The resulting differential porosity comparison was 2.0–7.5 %, while the thickness was about 18–35 %

Desing of the algorithm, print and analysis of porous structures with modifiable parameters

The purpose of this paper was to create an algorithm able to creating a porous structure with variable properties, print and analyze them. The basic concepts related to it were introduced and the process of creating an algorithm in Rhinoceros software was described. Having a suitable test group of porous structures, it was shown that it is possible to modify their porosity. In the next step, the structures were presented for printing and its effect. The obtained physical models were examined by microtomography. The resulting cross-sections were processed in ImageJ software. Having cross-sections of the original bone and printed structures, it was possible to compare their porosity and the average diameter of the trabeculae in the structure. With this procedure, it is possible to deduce whether it is possible to print accurate structures that will serve as porous bone implants. The resulting differential porosity comparison was 2.0–7.5 %, while the thickness was about 18–35 %

Micro-CT study of the dehiscences of the tympanic segment of the facial canal

PURPOSE: To depict the anatomy of the tympanic segment of the facial canal using a 3D visualization technique, to detect dehiscences, and to evaluate their frequency, location, shape, and size. METHODS: Research included 36 human temporal bones (18 infant and 18 adult samples) which were scanned using a Nanotom 180N device. The final resolution of the reconstructed object was 18 µm. Obtained micro-CT data were subsequently processed by the volume rendering software. RESULTS: The micro-CT study allowed for the 3D visualization of the tympanic segment of the facial canal and detects dehiscences in the studied material in both infants and adults. Most of the dehiscences (66.7 %) involved the inferior wall of the tympanic segment in infants as well as in adults, and were located above and backward to the oval window. The most frequent dehiscence shape was elliptic (66.7 % in infants; 50 % in adults). Furthermore, we observed dehiscences of fusiform and trapezoidal shape in infants. Length of the dehiscences in most cases ranged from 0.5 to 1.4 mm (50 % in infants; 75 % in adults). CONCLUSIONS: Volumetric reconstructions demonstrated the course of the tympanic segment of the facial canal and its relationship with the tympanic cavity. Knowledge about the size and location of any dehiscence within the tympanic segment of the facial canal is necessary due to the surgical significance of this region. If a dehiscence occurs, there is an increased risk of injury to the facial nerve during the operations or spread of inflammation from the middle ear

INFLUENCE OF PRINTING AND LOADING DIRECTION ON MECHANICAL RESPONSE IN 3D PRINTED MODELS OF HUMAN TRABECULAR BONE

The paper deals with investigation on directional variations of mechanical response in 3D printed models of human trabecular bone. Sample of trabecular bone tissue was resected from human donor and 3D model was obtained by X-ray computed tomography. Then a series of cubical samples was prepared by additive manufacturing technique and tested by uniaxial compression loading mode. Mechanical response was compared in nine different combinations of direction of 3D printing and loading direction. The results show neglectible influence on the deformation response in elastic region (stiffness) and significant changes of the behaviour in plastic region (stress and strain at yield point, strain at full collapse)

How to obtain the maximum properties flexibility of 3d printed ketoprofen tablets using only one drug-loaded filament?

The flexibility of dose and dosage forms makes 3D printing a very interesting tool for personalized medicine, with fused deposition modeling being the most promising and intensively developed method. In our research, we analyzed how various types of disintegrants and drug loading in poly(vinyl alcohol)-based filaments affect their mechanical properties and printability. We also assessed the effect of drug dosage and tablet spatial structure on the dissolution profiles. Given that the development of a method that allows the production of dosage forms with different properties from a single drug-loaded filament is desirable, we developed a method of printing ketoprofen tablets with different dose and dissolution profiles from a single feedstock filament. We optimized the filament preparation by hot-melt extrusion and characterized them. Then, we printed single, bi-, and tri-layer tablets varying with dose, infill density, internal structure, and composition. We analyzed the reproducibility of a spatial structure, phase, and degree of molecular order of ketoprofen in the tablets, and the dissolution profiles. We have printed tablets with immediateand sustained-release characteristics using one drug-loaded filament, which demonstrates that a single filament can serve as a versatile source for the manufacturing of tablets exhibiting various release characteristics