文献

Cutting test is extensively applied to assess quality of vegetables subjected to the freezing treatment. Particularly, the changes of tissue structures are evaluated on the grounds of maximum cutting force of material. The vegetable material was air frozen by two methods, i.e. at natural convection and by impingement fluidization. The cutting test performed on Brookfield materials testing machine was used to evaluate the influence of freezing method on product texture. The scanning electron microscopic images of tissue were included into the supportive analysis of freezing-mediated damages. It was found that a change in maximum cutting force can not be considered as a fully reliable indicator of material quality evaluation owing to the force value dependence on a mass change of material during its treatment. A complementary attribute that depicts freezing damage size proves to be appropriately defined material elasticity.

Cranioplasty following decompressive craniectomy (DC) has a primary complication when using the autologous bone: aseptic bone resorption (ABR). So far, risk factors such as age, number of fragments, and hydrocephalus have been identified but a thorough understanding of the underlying pathophysiology is still missing. The aim of this osteopathological investigation was to gain a better understanding of the underlying processes. Clinical data of patients who underwent surgical revision due to ABR was collected. Demographics, the time interval between craniectomy and cranioplasty, and endocrine serum parameters affecting bone metabolism were collected. Removed specimens underwent qualitative and quantitative histological examination. Two grafts without ABR were examined as controls. Compared to the controls, the typical layering of the cortical and cancellous bone was largely eliminated in the grafts. Histological investigations revealed the coexistence of osteolytic and osteoblastic activity within the necrosis. Bone appositions were distributed over the entire graft area. Remaining marrow spaces were predominantly fibrotic or necrotic. In areas with marrow cavity fibrosis, hardly any new bone tissue was found in the adjacent bone, while there were increased signs of osteoclastic resorption. Insufficient reintegration of the flap may be due to residual fatty bone marrow contained in the bone flap which seems to act as a barrier for osteogenesis. This may obstruct the reorganization of the bone structure, inducing aseptic bone necrosis. Following a path already taken in orthopedic surgery, thorough lavage of the implant to remove the bone marrow may be a possibility, but will need further investigation.

Statement of problem Although implants containing porous tantalum undergo osseointegration, whether this material significantly alters new bone formation and improves implant stability during healing in comparison to titanium is unclear. Purpose The purpose of this in vivo study was to determine the influence of the inclusion of porous tantalum into a dental implant on the biomechanical properties of the bone-implant interface and peri-implant bone which may contribute to secondary implant stability. Material and methods Threaded titanium implants with a porous tantalum midsection (Trabecular Metal Dental Implant; Zimmer Biomet) or without (Tapered Screw-Vent; Zimmer Biomet) were placed in rabbit tibiae and allowed to heal for 4, 8, or 12 weeks. The implants were evaluated by resonance frequency analysis and removed with surrounding bone for nanoindentation testing. Two-way ANOVA was used to determine the impact of implant type, bone region, and time on the outcomes implant stability quotient (ISQ), hardness, and elastic modulus (α=.05). Results Resonance frequency analysis found no significant difference in ISQ values between implant types at 4, 8, or 12 weeks, and ISQ values did not increase for either implant over time. Nanoindentation showed no significant differences in hardness or elastic modulus in newly formed bone adjacent to either implant type at any time point.

Some biomaterials are osteoinductive, that is, they are able to trigger the osteogenic process by inducing the differentiation of mesenchymal stem cells to the osteogenic lineage. Although the underlying mechanism is still unclear, microporosity and specific surface area (SSA) have been identified as critical factors in material-associated osteoinduction. However, only sintered ceramics, which have a limited range of porosities and SSA, have been analyzed so far. In this work, we were able to extend these ranges to the nanoscale, through the foaming and 3D-printing of biomimetic calcium phosphates, thereby obtaining scaffolds with controlled micro- and nanoporosity and with tailored macropore architectures. Calcium-deficient hydroxyapatite (CDHA) scaffolds were evaluated after 6 and 12 weeks in an ectopic-implantation canine model and compared with two sintered ceramics, biphasic calcium phosphate and β-tricalcium phosphate. Only foams with spherical, concave macropores and not 3D-printed scaffolds with convex, prismatic macropores induced significant ectopic bone formation. Among them, biomimetic nanostructured CDHA produced the highest incidence of ectopic bone and accelerated bone formation when compared with conventional microstructured sintered calcium phosphates with the same macropore architecture. Moreover, they exhibited different bone formation patterns; in CDHA foams, the new ectopic bone progressively replaced the scaffold, whereas in sintered biphasic calcium phosphate scaffolds, bone was deposited on the surface of the material, progressively filling the pore space. In conclusion, this study demonstrates that the high reactivity of nanostructured biomimetic CDHA combined with a spherical, concave macroporosity allows the pushing of the osteoinduction potential beyond the limits of microstructured calcium phosphate ceramics.

This study demonstrates the utility of hydroxyapatite (HA) microspheres as an additive to enhance the radiopaque properties, biocompatibility, and osteoconductivity of poly(methyl methacrylate) (PMMA)-based bone cements. HA microspheres were synthesized using spray drying. They had well-defined spherical shapes, thus allowing for the production of PMMA/HA composites with a very high HA content (20 vol % and 40 vol %). The uniform distribution of these HA microspheres in the PMMA matrix resulted in a remarkable increase in compressive modulus (p < 0.05), while preserving a reasonably high compressive strength. The PMMA/HA bone cements showed much higher radiopacity than PMMA containing BaSO4 as the additive. This was attributed to the high HA content up to 40 vol %. In addition, the biocompatibility and osteoconductivity of PMMA/HA bone cements were significantly enhanced compared to those of PMMA bone cements containing BaSO4, which were assessed using in vitro tests and in vivo animal experiments.