Distribution of cells in soft tissue and fluid space around hollow and solid implants in the rat

The development of the tissue surrounding an implanted material is anticipated to be regulated by the biological factors in the interface as well as the physicochemical properties of the implant material. In the present study light microscopic morphometry and transmission electron microscopy were used to evaluate the distribution of cells adjacent to the implant surface of different implant designs (hollow and solid implants) and materials (titanium and polytetrafluoroethylene). An increased number of leukocytes, predominantly PMN, was retrieved from the exudate inside hollow implants 1 and 9 days after surgery. In contrast, the increased cellularity in the soft tissue around the hollow implants was mainly due to an increased number of monocytes/macrophages and fibroblasts. The presence of a fluid space around both hollow and solid implants was revealed by the use of an electropolishing technique and ground sections. In the fluid space around solid titanium the concentration of leukocytes and the proportion of PMN decreased between 1 and 7 days. After 1 day the majority of leukocytes were freely suspended in the fluid and were rarely directly apposed to the implant surface. A majority of the monocytes/macrophages present in the fluid space after 7 days were attached to the fibrin matrix at the border between the fluid space and the reorganized tissue. Our studies demonstrate that hollow implants promote the influx and a persistence of PMN in the interior of the implant in comparison with the tissue surrounding the hollow and solid implants. Furthermore, during the first week after implantation inflammatory cells are not preferentially distributed directly on the titanium implant surface.     

Degenerative mineralization in the fibrous capsule of silicone breast implants

The formation of a fibrous capsule made of long collagen fibers surrounding breast implants represents an unavoidable phenomenon as the patients reaction to the presence of a foreign body. Depending upon the size and shape of the implants and the chemicals percolating through the shell, this fibrous capsule is continuously remodeled. The compaction of the foreign debris in the vicinity of the silicone shell is followed by the loss of cellular activity, shrinkage and necrosis. Calcification is the ultimate step. These phenomena were illustrated in the analysis of 18 explanted breast prostheses after 20 or more years of implantation. The degenerative mineralization was shown in scanning electron microscopy and light microscopy. The minerals proved to be bone-like hydroxyapatite by X-ray diffraction and Solid State NMR analysis. Whatever the characteristics of any sophisticated new model of breast implant, phenomenon of mineralization might be minimized but it is very unlikely that it would be totally eliminated.     

Three-dimensional modeling of removal torque and fracture progression around implants

In the present study, a model for simulations of removal torque experiments was developed using finite element method. The interfacial retention and fracturing of the surrounding material caused by the surface features during torque was analyzed. It was hypothesized that the progression of removal torque and the phases identified in the torque response plot represents sequential fractures at the interface. The 3-dimensional finite element model fairly accurately predicts the torque required to break the fixation of acid-etched implants, and also provides insight to how sequential fractures progress downwards along the implant side.     

Molecular mobility of polymeric implants and acute inflammatory response: An experimental study in mice

An overlooked factor in biomaterial research is the surface molecular flexibility for polymer based implants. The mobility of the polymer chains provides a way for the surface to adapt itself to the environment. This is relevant when the implant comes in contact with a biological fluid and its constituents. By changing the length of the alkyl side chain of poly(alkyl methacrylates) (PAMAs) an interesting opportunity is provided where it is possible to study the surface molecular mobility without changing the surface hydrophobicity, nor does it introduce any additives or any changes in the degree of polymer cross-linking. Four variants of PAMAs were implanted in the peritoneum of Balb/c mice using a well described setup. End points were taken after 18 h and estimations of inflammatory cell recruitment and implant-associated cells were studied. Relationship between surface molecular mobility and inflammatory cell recruitment as well as surface-associated cells was noted.     

Retrieval and analysis of surgical implants in Brazil: The need for proper regulation

This paper summarizes several cases of metallurgical failure analysis of surgical implants conducted at the Laboratory of Failure Analysis of IPT, in Brazil. Investigation revealed that most of the samples were not in accordance with ISO standards and presented evidence of corrosion assisted fracture. Additionally, some components were found to contain fabrication/processing defects that contributed to premature failure. The implant of nonbiocompatible materials results in immeasurable damage to patients as well as losses for the public investment. It is proposed that local sanitary regulation agencies create mechanisms to avoid commercialization of surgical implants that are not in accordance with standards and adopt the practice of retrieval analysis of failed implants. This would protect the public health by identifying and preventing the main causes of failure in surgical implants.     

Effect of polyglycolic acid membrane on bone regeneration around titanium implants inserted in bone sockets

An experimental animal model was used to evaluate the value of resorbable, non-permeable polyglycolic acid (PGA) membranes in relation to fixtures implanted into simulated extraction sockets. Brånemark fixtures (length 7.0 mm, diameter 3.75 mm) were implanted into edentulous areas of maxillary bone in six sheep. Five fixtures were covered with 0.15-mm-thick PGA membrane (Biofix^®) held in place with a cover screw (PGA group) and five were implanted without membrane (control group). The animals were killed after 4 months and undecalcified mesiodistal sections were prepared from resected jaw specimens. Histomorphometry was used to measure the distance from the shoulder of the fixture to the level of intimate bone contact (SB distance). SB distance was found to be greater in the PGA than in the control group in relation both to the mesial (1.44 ± 0.88 mm versus 0.96 ± 0.47 mm) and distal (1.13 ± 0.80 mm versus 0.77 ± 0.63 mm) aspects of implants. This statistically not significant difference in bone regeneration between the two groups is related to the physical properties of the PGA membrane used.     

Analysis of the inflammatory response to titanium and PTFE implants in soft tissue by macrophage phenotype quantification

Implants of commercially pure titanium and polytetrafluoroethylene (PTFE) were inserted in the rat abdominal wall for 1, 6 or 12 wk. The foreign body reaction was evaluated by immunohistochemical quantification of monocytes/macrophages and by the thickness of the foreign-body capsule. At all time intervals, the majority of interfacial cells were ED1-positive while ED2-positive cells were localized deeper in the tissue. Neither titanium nor PTFE displayed a significant change in capsule thickness over time. The total cell numbers decreased overtime for both types of material. At 12 wk the PTFE implants, compared to titanium, were surrounded by a significantly thicker reactive capsule with larger total cell numbers. No significant differences were seen in the macrophage subset response between the two types of implants. Thus, the present study showed differences between titanium and PTFE at 12 wk but not at earlier time points.     

膨胀机轴承烧坏事故分析及处理

介绍了5种膨胀机轴承烧坏事故,分析了原因,阐述了解决方法。     

Determination of low molecular weight silicones in plasma and blood of women after exposure to silicone breast implants by GC/MS

A sensitive, one-step sample preparation method for detection of volatile, low molecular weight (LMW) cyclic silicones hexamethylcyclotrisiloxane (D3), octamethyl-cyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in plasma and blood using gas chromatography coupled with mass spectrometry (GC/MS, SIM mode) is presented. In spiked experiments, extraction efficiencies for these siloxanes (100-20 000 ng/mL) were approximately 90% for plasma and approximately 80% for blood; only in the case of D3 was the recovery very low. Plasma and blood of women who are or were exposed to silicone gel-filled implants and of control subjects were analyzed for low molecular weight silicones. D3-D6 were not detectable in control plasma or blood. Although the investigated numbers of patients samples are very limited, and thus, no statistical analysis is possible, our data clearly show a general increase in the amount of LMW cyclic siloxanes in the bodies of women with silicone implants. In particular, several years after ruptured silicone implants were removed, siloxanes could still be found in blood samples from several women. Siloxane compound D3 varied between 6 and 12 ng/mL (plasma) and between 20 and 28 ng/mL (blood), whereas the concentration range of D4 was 14-50 ng/mL (plasma) and 79-92 ng/mL (blood). D5 and D6, with one exception, could not be detected.     

三起增压透平膨胀机故障的分析及处理

KDON-3200/6500型空分设备配套的增压透平膨胀机在运行过程中转速突然下降,制冷量明显减少;检修完毕试车过程中转速超高,各个运行参数达不到工艺要求;气动薄膜调节阀顶部漏气,阀门开不到位。分析以上三起故障的原因并提出了解决方法。     

Bone remodelling in the pores and around load bearing transchondral isoelastic porous-coated glassy carbon implants: Experimental study in rabbits

Cylinders of porous-coated glassy carbon were implanted into drill holes made through the articular surface of the medial condyle of both tibiae of ten rabbits for six and 12 weeks. Bone ingrowth and remodelling was examined by radiographic, histologic, oxytetracycline-fluorescence and microradiographic methods. Bone ingrowth into pores and load bearing implants was seen by all examination methods. Bone ingrowth occurred earlier when the pores were facing cancellous bone than cortical bone. Appositional bone formation occurred on the trabeculae a few millimetres from the interface during the early phase of remodelling at six weeks. At 12 weeks resorptive remodelling had occurred both in the surroundings and in those pores that face cancellous bone, whereas the amount of bone still increased in the pores facing cortical bone. In its porous-coated form glassy carbon functions well as a frame for ingrowing bone and it shows good osteoconductivity. Its mechanical properties are suitable for functioning as a structural bone substitute in places where the loads are mainly compressive. The difference between findings at six and 12 weeks indicated physiologic stress distribution and the adverse effects of stiff materials on bone remodelling were avoided by using this isoelastic material.     

Comparison of a xenogeneic and an alloplastic material used in dental implants in terms of physico-chemical characteristics and in vivo inflammatory response

Two commercial bone grafts used in dentistry (Osteobiol Gen-Os®, a xenograft of porcine origin, and Bonelike®, a hydroxyapatite based synthetic material), in the form of granules, were characterized and evaluated in vivo regarding the intensity of the tissue inflammatory response. These biomaterials were characterized in terms of morphology, particle size distribution, porosity and pore size, specific surface area and density. The chemical composition and structure of the materials were accessed by Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD). The graft materials were implanted in the gluteus maximus muscles of Wistar rats and the inflammatory response was evaluated through histological analysis, after one week of implantation.The results showed that the two grafts have quite different characteristics in practically all the evaluated properties. While Osteobiol® exhibits a structure and composition similar to the natural bone, Bonelike® is constituted by a main crystalline phase of hydroxyapatite and two secondary phases of α- and β-tricalcium phosphate. Osteobiol® granules, besides being larger, are irregular, and exhibit sharp-edged tips, while those of Bonelike® are approximately cylindrical, with round contours, and more uniform in size. The in vivo response evaluated from the inflammatory infiltrates revealed that although both implants did not cause severe inflammation, Bonelike® granules elicit a consistently more intense inflammatory reaction than that triggered by the granules of Osteobiol®, particularly in terms of collagen production and formation of fibrous capsule. This reaction was partly explained in terms of the characteristics evaluated for the granules of this material.     

Association between depression and inflammatory/anti‐inflammatory cytokines in chronic kidney disease and end‐stage renal disease patients: A review of literature

Depression is a common psychiatric disorder in patients with advanced chronic kidney diseases (CKDs). Strong correlation has been reported between depression and patients' morbidity and mortality among dialysis patients. On the contrary, chronic inflammation may be a major contributor to morbidity and mortality in these patients. Elevated plasma levels of proinflammatory cytokines, especially C‐reactive protein and interleukin (IL)‐6, have been correlated with cardiovascular events, hospitalization, and all‐cause and cardiovascular‐associated mortality in dialysis patients. Studies suggested that inflammation‐mediated atherosclerotic cardiovascular diseases are the possible reasons for depression‐induced mortality among patients without renal diseases. Several studies found significant elevations in circulating levels of proinflammatory cytokines, particularly IL‐6 and tumor necrosis factor‐α, in patients with major depression. Furthermore, depressive mood and behaviors, including sadness and suicidal ideation, were observed in patients who received repeated injections of recombinant cytokines. A thorough literature review indicates that while depressive symptoms and elevated inflammatory cytokine levels coexist in CKD and dialysis patients, their association is uncertain. Depression seems to be more associated with elevated serum levels of IL‐6 than other cytokines in these patients. Further studies are needed to clarify the possibility of a causal relationship between inflammation and depressive symptoms in CKD and dialysis patients.     

Propagation loss and birefringence properties around 1.55 μm of polymeric optical waveguides fabricated with cross-linked silicone

We newly synthesized cross-linked silicone from methyl and deuterated phenyl (d-phenyl) groups in various amounts and used the resultant polymers to fabricate single-mode optical waveguides. We measured the losses and birefringence of the waveguides by the cutback method and Senalmont ellipsometry, respectively. The propagation loss decreased as we increased the d-phenyl content. The propagation loss was 0.23 dB/cm at 1.55 μm for a waveguide fabricated using cross-linked silicone with a 95-mol.% d-phenyl content. In contrast, the birefringence increased with increasing d-phenyl content. This indicates that the increase in phenyl content influences the orientation of optically anisotropic phenyl groups in the film, resulting in a birefringence increase. The birefringence value was 2.0×10⁻⁴ for a waveguide fabricated from cross-linked silicone with a 27-mol.% d-phenyl content.     

Role of body temperature variations in bat immune response to viral infections

The ability of bats to coexist with viruses without being harmed is an interesting issue that is still under investigation. Here we use a mathematical model to show that the pattern of body temperature variations observed in bats between day and night is responsible for their ability to keep viruses in check. From the dynamical systems point of view, our model displays an intriguing quasi-periodic behaviour that might be relevant in making the system robust by avoiding viral escape due to perturbations in the body temperature cycle.     

Up-regulation of T lymphocyte and antibody production by inflammatory cytokines released by macrophage exposure to multi-walled carbon nanotubes

Our data demonstrate that multi-walled carbon nanotubes (MWCNTs) are internalized by macrophages, subsequently activating them to produce interleukin (IL)-12 (IL-12). This cytokine induced the proliferative response of T lymphocytes to a nonspecific mitogen and to ovalbumin (OVA). This increase in the proliferative response was accompanied by an increase in the expression of pro-inflammatory cytokines, such as interferon-gamma (IFNγ), tumor necrosis factor-alpha (TNFα) and IL-6, in mice inoculated with MWCNTs, whether or not they had been immunized with OVA. A decrease in the expression of transforming growth factor-beta (TGFβ) was observed in the mice treated with MWCNTs, whereas the suppression of the expression of both TGFβ and IL-10 was observed in mice that had been both treated and immunized. The activation of the T lymphocyte response by the pro-inflammatory cytokines leads to an increase in antibody production to OVA, suggesting the important immunostimulatory effect of carbon nanotubes.     

Morphometrical analysis of multinucleated giant cells in subdermal implants of poly-lactic acid in rats

The use of bioabsorbable polymers in (bio)medical applications has increased greatly in recent years, mainly because of their good bioreabsorption and biocompatibility. In this work, we examined the development of foreign body giant cells in intimate contact with porous membranes of poly L–lactic acid containing 7% of plasticizer triethylcitrate implanted in the backs of rats. The membranes were removed 2, 7, 14, 21, 28, 60, 90 and 180 days after implantation, along with a portion of the tissue around the implant. Histological analysis of the implant and tissue revealed the formation of a fibrous capsule from the seventh day of implantation onwards. Foreign body giant cells appeared from the seventh day and increased in number up to the twenty-eighth day and then up to the ninetieth day of implantation, remaining constant up to the end of the study onwards, and increased in number up to the ninetieth day after implantation and then remained constant. The number of nuclei in these cells increased from the seventh day of implantation up to the ninetieth day and then up to the end of the study.     

Total platinum concentration and platinum oxidation states in body fluids, tissue, and explants from women exposed to silicone and saline breast implants by IC-ICPMS

Ion chromatography-inductively coupled plasma-mass spectrometry was used to determine the total platinum concentration and platinum oxidation states in samples from women exposed to silicone and saline breast implants. Samples included the following: whole blood, urine, hair, nails, sweat, brain tissue, breast milk, and explants. Mean Pt concentration in samples from women exposed to silicone breast implants were as follows: whole blood, 568.1 +/- 74.77 pmol/L (n = 9); urine, 1.77 +/- 0.847 mug/g of creatinine (n = 10); hair, 2.13 +/- 2.984 ng/g (n = 9); nails, 0.88 +/- 0.335 ng/g (n = 9); sweat, 1.90 +/- 1.691 ng/g (n = 9); breast milk, 1.09 +/- 0.316 mug/L (n = 6). Pt in explanted silicone breast implant gel (n = 9) occurred mainly in the +2, +4, and +6 oxidation states. Pt in whole blood (n = 7) and breast milk samples (n = 6) from women exposed to silicone breast implants occurred mainly in the +2 and +4 oxidation states. Saline breast implant fluid (n = 2) did not contain detectable levels of Pt. This is the most comprehensive report, to date, to show that women exposed to silicone breast implants have Pt levels that exceed that of the general population, and the first report, to date, to document the various Pt oxidation states present in samples from women exposed to silicone breast implants.     

Stress analysis in bone tissue around single implants with different diameters and veneering materials: A 3-D finite element study

The aim of this study was to evaluate the stress distribution on bone tissue with a single prosthesis supported by implants of large and conventional diameter and presenting different veneering materials using the 3-D finite element method. Sixteen models were fabricated to reproduce a bone block with implants, using two diameters (3.75 × 10 mm and 5.00 × 10 mm), four different veneering materials (composite resin, acrylic resin, porcelain, and NiCr crown), and two loads (axial (200 N) and oblique (100 N)). For data analysis, the maximum principal stress and von Mises criterion were used. For the axial load, the cortical bone in all models did not exhibit significant differences, and the trabecular bone presented higher tensile stress with reduced implant diameter. For the oblique load, the cortical bone presented a significant increase in tensile stress on the same side as the loading for smaller implant diameters. The trabecular bone showed a similar but more discreet trend. There was no difference in bone tissue with different veneering materials. The veneering material did not influence the stress distribution in the supporting tissues of single implant-supported prostheses. The large-diameter implants improved the transference of occlusal loads to bone tissue and decreased stress mainly under oblique loads. Oblique loading was more detrimental to distribution stresses than axial loading.