Comparison of the biological activities of high-density porous polyethylene implants and oxidized regenerated cellulose-wrapped diced cartilage grafts

The use of alloplastic materials in plastic surgery has become more extensive with advancement of autogenous-tissue reconstruction techniques for the repair of defects, tissue augmentation, and the stabilization of bones. An ideal alloplastic material should be nonallergenic, noncarcinogenic, sterilizable, and easy to shape and should not cause rejection. Alloplastic material used for tissue augmentation should have a low rate of resorption and distortion. High-density porous polyethylene implants (Medpor) have been used widely and successfully for tissue augmentation. The Turkish Delight is a material composed of diced cartilage grafts wrapped in oxidized regenerated cellulose (Surgicel). Its indications are similar to those of the Medpor implant, and an additional donor site is usually not needed. Both materials are used in the same anatomical locations, especially for augmentation. Therefore, the authors evaluated the long-term stability of and suitable anatomical sites for these materials. Medpor implants or Turkish Delights were placed subperiosteally or subfascially in 10 young rabbits, and the resultant changes were evaluated 16 weeks after the operation by macroscopy and histopathology. Changes in projections were measured with an ocular micrometer. Medpor implants were neither resorbed nor distorted when placed subperiosteally or subfascially, and were highly stabilized by the surrounding tissues. Turkish Delight also enabled tissue augmentation, but had a significantly higher rate of resorption compared with the Medpor implant and was loosely bound to the surrounding tissue. The Turkish Delight was less resorbed and better fixed to adjacent tissues when placed subperiosteally than when placed subfascially.     

Proliferation rate of human osteoblast-like cells on alloplastic biomaterials and their clinical application for the transnasal duraplasty procedure

The possibility of transmission of slow virus infection (HIV) and Creutzfeld-Jakob disease by cadaveric dura implants makes it necessary to find synthetic, absorbable materials for the reconstruction of the dura mater. Various procedures with autologous or alloplastic material are described. Four commercially available biomaterials were choosen to study the proliferation rate and the biocompatibility of human osteoblast-like cells (HOB-like cells) on 2- dimensional material by biochemical analysis. With a proliferation assay, the viability and the proliferation capacity of osteoblast-like cells were evaluated. A clinical trial was added to study resorbable fleece as one of the previously tested biomaterial in a small patient group (8 patients) to close anterior cranial fossa dura defects. The results of the proliferation assay showed the highest proliferation rate of HOB-like cells on resorbable fleece. All patients in our clinical trial with anterior cranial fossa dura defects were successfully treated with resorbable fleece. There was no evidence for persisting cerebrospinal fluid rhinorrhea or foreign body reaction after the period of wound healing. The present study demonstrated an excellent biocompatibility of resorbable fleece. The vicryl fleece is an alternative alloplastic material for endonasal closure of defined substantial defects of the dura with cerebrospinal fluid.     

SiC Multilayer Structures as Light Controlled Photonic Active Filters

Tunable wavelength division multiplexing converters based on amorphous SiC multilayer photonic active filters are analyzed. The configuration includes two stacked p-i-n structures (p(a-SiC:H)-í'(a-SiC:H)-n(a-SiC:H)-p(a-SiC:H)-i(a-Si:H)-n(a-Si:H)) sandwiched between two transparent contacts. The manipulation of the magnitude is achieved through appropriated front and back backgrounds. Transfer function characteristics are studied both theoretically and experimentally. An algorithm to decode the multiplex signal is established. An optoelectronic model supports the optoelectronic logic architecture. Results show that the light-activated device combines the demultiplexing operation with the simultaneous photodetection and self-amplification of an optical signal. The output waveform presents a nonlinear amplitude-dependent response to the wavelengths of the input channels. Depending on the wavelength of the external background and irradiation side, it acts either as a short- or a long-pass band filter or as a band-stop filter. A two-stage active circuit is presented and gives insight into the physics of the device.     

Biological Characteristics of the MG-63 Human Osteosarcoma Cells on Composite Tantalum Carbide/Amorphous Carbon Films

Tantalum (Ta) is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC) and TaC/amorphous carbon (a-C) coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C), was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics.     

Engineered cartilage covered ear implants for auricular cartilage reconstruction

Cartilage tissues are often required for auricular tissue reconstruction. Currently, alloplastic ear-shaped medical implants composed of silicon and polyethylene are being used clinically. However, the use of these implants is often associated with complications, including inflammation, infection, erosion, and dislodgement. To overcome these limitations, we propose a system in which tissue-engineered cartilage serves as a shell that entirely covers the alloplastic implants. This study investigated whether cartilage tissue, engineered with chondrocytes and a fibrin hydrogel, would provide adequate coverage of a commercially used medical implant. To demonstrate the in vivo stability of cell-fibrin constructs, we tested variations of fibrinogen and thrombin concentration as well as cell density. After implantation, the retrieved engineered cartilage tissue was evaluated by histo- and immunohistochemical, biochemical, and mechanical analyses. Histomorphological evaluations consistently showed cartilage formation over the medical implants with the maintenance of dimensional stability. An initial cell density was determined that is critical for the production of matrix components such as glycosaminoglycans (GAG), elastin, type II collagen, and for mechanical strength. This study shows that engineered cartilage tissues are able to serve as a shell that entirely covers the medical implant, which may minimize the morbidity associated with implant dislodgement.     

The use of Teflon in orbital floor reconstruction following blunt facial trauma: a 20-year experience

A myriad of materials have been used for reestablishing continuity of the orbital floor following blunt facial trauma. Traditionally, autogenous grafts have been the material of choice for orbital floor reconstruction; however, alloplastic materials have gained popularity because of their availability and ease of use. A large clinical experience with long-term treatment results has never been reported for any substance used in orbital floor reconstruction. The purpose of this study was to review our long-term treatment results using Teflon for orbital floor reconstruction following blunt trauma, with emphasis on the incidence of infection, extrusion, and implant displacement. This report presents a 20-year review of 230 Teflon implants for reconstruction of traumatic orbital floor defects. With a mean follow-up period of 30 months, there was only one implant infection and no complications of extrusion or implant displacement. These findings support the use of Teflon as a safe and effective material for the reconstruction of orbital floor defects following blunt facial trauma.     

Histological Evaluation of the Biocompatibility of Polyurea Crosslinked Silica Aerogel Implants in a Rat Model: A Pilot Study

Background

Aerogels are a versatile group of nanostructured/nanoporous materials with physical and chemical properties that can be adjusted to suit the application of interest. In terms of biomedical applications, aerogels are particularly suitable for implants such as membranes, tissue growth scaffolds, and nerve regeneration and guidance inserts. The mesoporous nature of aerogels can also be used for diffusion based release of drugs that are loaded during the drying stage of the material. From the variety of aerogels polyurea crosslinked silica aerogels have the most potential for future biomedical applications and are explored here.

Methodology

This study assessed the short and long term biocompatibility of polyurea crosslinked silica aerogel implants in a Sprague-Dawley rat model. Implants were inserted at two different locations a) subcutaneously (SC), at the dorsum and b) intramuscularly (IM), between the gluteus maximus and biceps femoris of the left hind extremity. Nearby muscle and other internal organs were evaluated histologically for inflammation, tissue damage, fibrosis and movement (travel) of implant.

Conclusion/Significance

In general polyurea crosslinked silica aerogel (PCSA) was well tolerated as a subcutaneous and an intramuscular implant in the Sprague-Dawley rat with a maximum incubation time of twenty months. In some cases a thin fibrous capsule surrounded the aerogel implant and was interpreted as a normal response to foreign material. No noticeable toxicity was found in the tissues surrounding the implants nor in distant organs. Comparison was made with control rats without any implants inserted, and animals with suture material present. No obvious or noticeable changes were sustained by the implants at either location. Careful necropsy and tissue histology showed age-related changes only. An effective sterilization technique for PCSA implants as well as staining and sectioning protocol has been established. These studies further support the notion that silica-based aerogels could be useful as biomaterials.     

Effect of heparin and alendronate coating on titanium surfaces on inhibition of osteoclast and enhancement of osteoblast function

The failure of orthopedic and dental implants has been attributed mainly to loosening of the implant from host bone, which may be due to weak bonding of the implant material to bone tissue. Titanium (Ti) is used in the field of orthopedic and dental implants because of its excellent biocompatibility and outstanding mechanical properties. Therefore, in the field of materials science and tissue engineering, there has been extensive research to immobilize bioactive molecules on the surface of implant materials in order to provide the implants with improved adhesion to the host bone tissue.In this study, chemically active functional groups were introduced on the surface of Ti by a grafting reaction with heparin and then the Ti was functionalized by immobilizing alendronate onto the heparin-grafted surface. In the MC3T3-E1 cell osteogenic differentiation study, the alendronate-immobilized Ti substrates significantly enhanced alkaline phosphatase activity (ALP) and calcium content. Additionally, nuclear factor kappa B ligand (RANKL)-induced osteoclast differentiation of RAW264.7 cells was inhibited with the alendronate-immobilized Ti as confirmed by TRAP analysis. Real time PCR analysis showed that mRNA expressions of osteocalcin and osteopontin, which are markers for osteogenesis, were upregulated in MC3T3-E1 cells cultured on alendronate-immobilized Ti. The mRNA expressions of TRAP and Cathepsin K, markers for osteoclastogenesis, in RAW264.7 cells cultured on alendronate-immobilized Ti were down-regulated. Our study suggests that alendronate-immobilized Ti may be a bioactive implant with dual functions to enhance osteoblast differentiation and to inhibit osteoclast differentiation simultaneously.     

Long-term results of MISTI gold breast implants: a retrospective study

MISTI Gold breast implants (Bioplasty, St. Paul, Minn.) filled with polyvinylpyrrolidone-hydrogel were developed as a promising alternative to silicone-filled implants. Some studies have reported on the positive effects of the implant, such as improved radiolucency and biocompatibility of the gel; however, there are also reports that such implants increased in volume and were subject to capsular contracture in the human body, resulting in demands for their removal. The purpose of this retrospective study was to analyze the long-term results of a series of patients with MISTI Gold breast implants. Between 1991 and 1993, the authors inserted 83 MISTI Gold implants in 61 patients with an average age of 46 years (range, 16 to 69). The authors were able to follow up 48 patients with 71 MISTI Gold implants. The average follow-up was 68 months (range, 10 to 108 months). The retrospective study found that 59 percent of all MISTI Gold implants were removed after an average period of 4.14 years. The main reason for implant removal was an increase in volume of 38 percent, followed by capsular contracture in 14 percent of all 71 MISTI Gold implants. The average increase in volume of all removed MISTI Gold implants was 43 percent. Capsular contracture was graded as Baker I and II in 63 percent and as Baker III and IV in 37 percent. In conclusion, the authors believe that MISTI Gold implants do not fulfill the criteria of safe breast implants, and they agree with the December of 2000 opinion of the Medical Devices Agency of the Department of Health in London that the hydrogel-filled breast implants should not be used until more information about the filler material and its metabolic fate is available.     

Improving aesthetic outcomes after alloplastic chin augmentation

A novel approach to increase chin projection with alloplastic material is presented. Key aspects of the technique include the consideration of anthropometric normal values in preoperative assessment and planning, a submental approach with wide subperiosteal exposure of the area to be augmented, the use of two-piece porous polyethylene implants for augmentation, and screw fixation of the implant to the mandible. Screw fixation improves the predictability and precision of reconstruction by preventing implant displacement, by obliterating gaps between the implant and the facial skeleton, and by facilitating final implant contouring. In a series of 46 patients (24 primary and 22 secondary) operated on over a 6-year period, this approach allowed anatomically correct, stable chin contours to be created. Iatrogenic problems with macrogenia, mentalis dysfunction, and soft-tissue distortion resulting from implant migration and capsular contracture have been avoided. There have been no infections. Two patients who had had multiple previous chin operations requested revisional surgery to refine contour.     

石墨化炭/ 炭复合材料+ 羟基磷灰石涂层(C/C+HA) 复合骨植入材料研究

目的:通过建立兔股骨缺损的动物实验模型,对采用等温化学气相沉积法和等离子喷涂技术所制备的石墨化炭/炭复合材料+羟基磷灰石涂层(C/C+HA)复合骨植入材料进行骨植入实验的的生物相容性进行评价,探索该复合材料作为植入机体骨组织的可行性依据.方法:采用骨科钻在实验动物股骨髁上钻孔的方法建立骨缺损的动物实验模型,将待研究比较的实验材料分别植入实验动物的股骨髁内,持续观察8周,在术后第2、4、8周时应用X线照片、组织学染色和扫描电镜技术,分别观察所研究材料在机体内对骨缺损愈合及其对机体的影响,进行组间比较和相关性分析.结果:石墨化炭/炭复合材料+羟基磷灰石涂层(C/C+HA)复合骨植入材料的骨植入实验生物相容性良好,材料与骨组织结合牢固,界面中成骨细胞生长明显,且炭颗粒脱落现象少,未见炎症细胞浸润.植入动物体内的材料在植入期未引起机体局部的炎症浸润反应且表面脱落的碳颗粒在机体组织中也未引起局部严重的炎症反应.在实验动物植入材料后的连续8周观察期中,组织学观察显示:表面涂有HA的炭/炭复合材料对骨组织形态改建上表现良好,其与骨组织接界处所形成的纤维结缔组织膜层厚度明显比未涂HA的材料要小,与骨组织结合更为紧密和牢固;碳颗粒出现脱落游离的现象明显减少.结论:在炭/炭复合材料表面涂以HA生物涂层对骨的形态改建和促进骨小梁生长等方面具有良好的作用,是一种具有发展潜力的骨修复材料.     

Carbon fiber reinforced polysulfone--a new implant material

Carbon fibre reinforced polysulfone is a composite material which contains two materials of well known biocompatibility. In comparison to metals this composite material has some advantages which makes it favourable particularly for implants in tumor surgery. The custom made arrangement of fibres in the composite allows the development of implants with special mechanical properties. The radiolucency of the material avoids problems caused by the reflection of x-rays, using metal implants. This special property allows the exact calculation of postoperative radiation doses of tumor patients. Simultaneously the structures behind the implants are not hidden. All implants can be machined during the operation to adapt them to the individual anatomical situation. Animal experimental and clinical applications of plates, screws and spinal segmental replacement implants made of this composite material have shown good results so far.     

To reduce the maximum stress and the stress shielding effect around a dental implant–bone interface using radial functionally graded biomaterials

In a dental implant system, the value of stress and its distribution plays a pivotal role on the strength, durability and life of the implant–bone system. A typical implant consists of a Titanium core and a thin layer of biocompatible material such as the hydroxyapatite. This coating has a wide range of clinical applications in orthopedics and dentistry due to its biocompatibility and bioactivity characteristics. Low bonding strength and sudden variation of mechanical properties between the coating and the metallic layers are the main disadvantages of such common implants. To overcome these problems, a radial distributed functionally graded biomaterial (FGBM) was proposed in this paper and the effect of material property on the stress distribution around the dental implant–bone interface was studied. A three-dimensional finite element simulation was used to illustrate how the use of radial FGBM dental implant can reduce the maximum von Mises stress and, also the stress shielding effect in both the cortical and cancellous bones. The results, of course, give anybody an idea about optimized behaviors that can be achieved using such materials. The finite element solver was validated by familiar methods and the results were compared to previous works in the literature.     

Variability in the properties of silicone gel breast implants.

Several generations of silicone gel breast implants have been produced by implant manufacturers. The primary material usually viewed as the base material in the manufacture of implants is polydimethylsiloxane. Polymeric reactions are notorious for their variability and nonuniformity. The elastomer used in different types of implants can have vastly different properties. Furthermore, the material properties associated with a particular type of implant can vary considerably from one lot to the next. Considering the various designs, styles, and manufacturing techniques associated with silicone gel implants, knowledge of the original properties of the implants before implantation is important in determining the effects of aging in vivo. This study was conducted to investigate differences in key mechanical and chemical properties of silicone gel breast implant materials. The two types of implants chosen for analysis were Silastic I and Silastic II control implants. Material property data were determined for both types of controls and significant differences were found in their values. Lot-to-lot variability was also investigated and found to be significant.     

Biomaterials

Biomaterials--materials used for the elaboration of systems designed for human implantation or organ substitutes--can be classified as metals and alloys, ceramics and polymers. Their uses are largely diversified, for soft and hard tissues replacement. Interactions rise between biological environment and implants, the mechanisms of them not always known: inflammatory response, corrosion and degradation of materials leading to leaching of some constituents possibly toxic and alteration of their mechanical properties. Blood interfacing materials introduce some particular problems of hemocompatibility. The matching of implant to biological medium, in other words, its biocompatibility has to be a priori evaluated, but until now no in vitro or in vivo evaluation method is fully reliable.     

Self-reported symptoms among women after cosmetic breast implant and breast reduction surgery

A retrospective cohort study was performed in Sweden to evaluate the possibility that an individual symptom or constellation of illness symptoms related to silicone occurs in women after breast implant surgery. A random sample (n = 2500) of all women in the Swedish national implant registry who underwent breast augmentation surgery with alloplastic breast implants during the years 1965 through 1993 was compared with a sample (n = 3500) of women who underwent breast reduction surgery during the same period, frequency matched to the implant patients for age and calendar year at the time of surgery. In total, 65 percent of the breast implant patients (n = 1546) and 72 percent of the breast reduction patients (n = 2496) completed a self-administered questionnaire covering 28 rheumatologic and other symptoms and lifestyle and demographic factors. Practically all of the 28 symptoms inquired about were reported more often by women in the breast implant cohort, with 16 (57 percent) significantly more common in breast implant recipients. In contrast, few significant differences or consistent patterns were observed in the length of time since the implant and in the type (silicone or saline) or volume of the implant. Although women with breast implants report a multitude of symptoms more often than women who have breast reduction surgery, the lack of specificity and absence of dose-response relationships suggest that the excess of reported symptoms is not causally related to cosmetic implants.     

Biomedical application of commercial polymers and novel polyisobutylene-based thermoplastic elastomers for soft tissue replacement

Novel polyisobutylene-based thermoplastic elastomers are introduced as prospective implant materials for soft tissue replacement and reconstruction. In comparison, poly(ethylene terephthalate) (PET), poly(tetrafluoroethylene) (PTFE), polypropylene (PP), polyurethanes (PU), and silicones are outlined from well-established implant history as being relatively inert and biocompatible biomaterials for soft tissue replacement, especially in vascular grafts and breast implants. Some general considerations for the design and development of polymers for soft tissue replacement are reviewed from the viewpoint of material science and engineering, with special attention to synthetic materials used in vascular grafts and breast implants.