Plastic Implants Research Articles

Particle tracking, recognition and LET evaluation of out-of-field proton therapy delivered to a phantom with implants

Objective. This study aims to assess the composition of scattered particles generated in proton therapy for tumors situated proximal to some titanium (Ti) dental implants. The investigation involves decomposing the mixed field and recording Linear Energy Transfer (LET) spectra to quantify the influence of metallic dental inserts located behind the tumor. Approach. A therapeutic conformal proton beam was used to deliver the treatment plan to an anthropomorphic head phantom with two types of implants inserted in the target volume (made of Ti and plastic, respectively). The scattered radiation resulted during the irradiation was detected by a hybrid semiconductor pixel detector MiniPIX Timepix3 that was placed distal to the Spread-out Bragg peak. Visualization and field decomposition of stray radiation were generated using algorithms trained in particle recognition based on artificial intelligence neural networks (AI NN). Spectral sensitive aspects of the scattered radiation were collected using two angular positions of the detector relative to the beam direction: 0° and 60°. Results. Using AI NN, 3 classes of particles were identified: protons, electrons & photons, and ions & fast neutrons. Placing a Ti implant in the beam’s path resulted in predominantly electrons and photons, contributing 52.2% of the total number of detected particles, whereas for plastic implants, the contribution was 65.4%. Scattered protons comprised 45.5% and 31.9% with and without metal inserts, respectively. The LET spectra were derived for each group of particles identified, with values ranging from 0.01 to 7.5 keV μm−1 for Ti implants/plastic implants. The low-LET component was primarily composed of electrons and photons, while the high-LET component corresponded to protons and ions. Significance. This method, complemented by directional maps, holds the potential for evaluating and validating treatment plans involving stray radiation near organs at risk, offering precise discrimination of the mixed field, and enhancing in this way the LET calculation.

Comparison of Titanium and PEEK Medical Plastic Implant Materials for Their Bacterial Biofilm Formation Properties.

This study investigated two of the most commonly used CAD–CAM materials for patient-specific reconstruction in craniomaxillofacial surgery. The aim of this study was to access the biofilm formation of Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis, and Escherichia coli on titanium and PEEK medical implant materials. Two titanium specimens (titanium grade 2 tooled with a Planmeca CAD–CAM milling device and titanium grade 5 tooled with a computer-aided design direct metal laser sintering device (CAD-DMLS)) and one PEEK specimen tooled with a Planmeca CAD–CAM milling device were studied. Bacterial adhesion on implants was evaluated in two groups (saliva-treated group and non-saliva-treated group) to imitate intraoral and extraoral surgical routes for implant placement. The PEEK medical implant material showed higher bacterial adhesion by S. aureus, S. mutans, and E. coli than titanium grade 2 and titanium grade 5, whereas E. faecalis showed higher adhesion to titanium as compared to PEEK. Saliva contamination of implants also effected bacterial attachment. Salivary coating enhanced biofilm formation by S. aureus, S. mutans, and E. faecalis. In conclusion, our findings imply that regardless of the implant material type or tooling techniques used, salivary coating plays a vital role in bacterial adhesion. In addition, the majority of the bacterial strains showed higher adhesion to PEEK than titanium.

The Anti-Infectious Role of Sphingosine in Microbial Diseases.

Sphingolipids are important structural membrane components and, together with cholesterol, are often organized in lipid rafts, where they act as signaling molecules in many cellular functions. They play crucial roles in regulating pathobiological processes, such as cancer, inflammation, and infectious diseases. The bioactive metabolites ceramide, sphingosine-1-phosphate, and sphingosine have been shown to be involved in the pathogenesis of several microbes. In contrast to ceramide, which often promotes bacterial and viral infections (for instance, by mediating adhesion and internalization), sphingosine, which is released from ceramide by the activity of ceramidases, kills many bacterial, viral, and fungal pathogens. In particular, sphingosine is an important natural component of the defense against bacterial pathogens in the respiratory tract. Pathologically reduced sphingosine levels in cystic fibrosis airway epithelial cells are normalized by inhalation of sphingosine, and coating plastic implants with sphingosine prevents bacterial infections. Pretreatment of cells with exogenous sphingosine also prevents the viral spike protein of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) from interacting with host cell receptors and inhibits the propagation of herpes simplex virus type 1 (HSV-1) in macrophages. Recent examinations reveal that the bactericidal effect of sphingosine might be due to bacterial membrane permeabilization and the subsequent death of the bacteria.

Effectiveness of the Sequential Use of Plastic and Titanium Implants for Experimental Replacement of the Mandibular Defect in Animals Using Preliminary Digital Design.

Using the templates preliminarily made by 3D design and prototyping methods, defects in the lateral area of the lower jaw of sheep were created using the piezosurgical technique. The defects were replaced by plastic implants obtained by the method of layer-by-layer fusion of the FDM printing-fusing deposition modeling and fixation with titanium screws to the jaw body. In the time interval, plastic implants are replaced by titanium implants obtained by selective laser sintering (SLS) using a 3D printer. To study the processes of reparative osteogenesis, microsamples of tissues of the preimplantation zone were analyzed. As a result, signs of osteo- and fibro-osseointegration were identified. The obtained data are regarded as a prerequisite for further clinical trials of the developed protocols for the sequential replacement of jaw defects using 3D printing.

An antibacterial coated polymer prevents biofilm formation and implant-associated infection

To prevent infections associated with medical implants, various antimicrobial silver-coated implant materials have been developed. However, these materials do not always provide consistent antibacterial effects in vivo despite having dramatic antibacterial effects in vitro, probably because the antibacterial effects involve silver-ion-mediated reactive oxygen species generation. Additionally, the silver application process often requires extremely high temperatures, which damage non-metal implant materials. We recently developed a bacteria-resistant coating consisting of hydroxyapatite film on which ionic silver is immobilized via inositol hexaphosphate chelation, using a series of immersion and drying steps performed at low heat. Here we applied this coating to a polymer, polyetheretherketone (PEEK), and analyzed the properties and antibacterial activity of the coated polymer in vitro and in vivo. The ionic silver coating demonstrated significant bactericidal activity and prevented bacterial biofilm formation in vitro. Bio-imaging of a soft tissue infection mouse model in which a silver-coated PEEK plate was implanted revealed a dramatic absence of bacterial signals 10 days after inoculation. These animals also showed a strong reduction in histological features of infection, compared to the control animals. This innovative coating can be applied to complex structures for clinical use, and could prevent infections associated with a variety of plastic implants.

Morphological assessment of osseointegration during replacement of mandible defect with implants that made using additive technologies. Experimental research

According to the pre-made patterns of 3D-design and prototyping patterns during the experiment, defects of the lateral portion of the ram's lower jaw were created using the piezosurgical technique. The defects were replaced by plastic implants obtained by the method of layer-by-layer melting of FDM-printing (fusing deposition modeling, FDM) and fixing titanium screws to the jaw body. In the time interval, plastic implants are replaced by titanium ones, obtained using SLS technology -selective laser sintering using a 3D-printer. In order to study the processes of reparative osteogenesis, microsamples of tissues of the periimplantation zone were analyzed. As a result, signs of osteo- and fibro-osseointegration were identified. The data obtained are regarded as a prerequisite for further clinical trials of the developed protocols for the sequential replacement of defects of the jaws using 3D-printing.

Bioactive Glasses and Glass-Ceramics for Healthcare Applications in Bone Regeneration and Tissue Engineering.

The discovery of bioactive glasses (BGs) in the late 1960s by Larry Hench et al. was driven by the need for implant materials with an ability to bond to living tissues, which were intended to replace inert metal and plastic implants that were not well tolerated by the body. Among a number of tested compositions, the one that later became designated by the well-known trademark of 45S5 Bioglass® excelled in its ability to bond to bone and soft tissues. Bonding to living tissues was mediated through the formation of an interfacial bone-like hydroxyapatite layer when the bioglass was put in contact with biological fluids in vivo. This feature represented a remarkable milestone, and has inspired many other investigations aiming at further exploring the in vitro and in vivo performances of this and other related BG compositions. This paradigmatic example of a target-oriented research is certainly one of the most valuable contributions that one can learn from Larry Hench. Such a goal-oriented approach needs to be continuously stimulated, aiming at finding out better performing materials to overcome the limitations of the existing ones, including the 45S5 Bioglass®. Its well-known that its main limitations include: (i) the high pH environment that is created by its high sodium content could turn it cytotoxic; (ii) and the poor sintering ability makes the fabrication of porous three-dimensional (3D) scaffolds difficult. All of these relevant features strongly depend on a number of interrelated factors that need to be well compromised. The selected chemical composition strongly determines the glass structure, the biocompatibility, the degradation rate, and the ease of processing (scaffolds fabrication and sintering). This manuscript presents a first general appraisal of the scientific output in the interrelated areas of bioactive glasses and glass-ceramics, scaffolds, implant coatings, and tissue engineering. Then, it gives an overview of the critical issues that need to be considered when developing bioactive glasses for healthcare applications. The aim is to provide knowledge-based tools towards guiding young researchers in the design of new bioactive glass compositions, taking into account the desired functional properties.

The Effectiveness of Preimplantation Recellularization of Acellular Rat-Esophagus Matrices Using GFP-Positive Cells

The use of recellularized matrices allows obtaining tissue-engineered structures that largely reproduce the morphofunctional features of native organs and tissues. Doubts as to the advisability of preimplantation recellularization of the scaffold, which are associated with the death of prepopulation cells on the scaffold in vivo, require studying the behavior of cells on plastic and biological implants after recellularization. Rat esophagus that had undergone detergent-enzymatic decellularization was repopulated with GFP-positive cells intensely fluorescing in the green spectrum, which allowed us to trace the status of the initial cell population during cultivation on plastic and after transplantation, determine the viability and metabolic activity of cells, and conduct fluorescent detection of the cells on the scaffold before and after implantation. There were no data on the apparent cell proliferation on the matrix; however, there were indirect indications of metabolic activity and GFP synthesis by the cells that populated the scaffold before implantation.

Comparative Analysis of Structural Responses of Rat Subcutaneous Fat on the Implantation of Samples of Polymethyl Methacrylate with Hydrophobic and Hydrophilic Surface

Morphological analysis of the subcutaneous fat was performed in rats after subcutaneous implantation of basic dental plastic materials with different hydrophobic and hydrophilic properties. It was shown that subcutaneous implantation of dental plastics with mostly hydrophobic surface and low biocompatibility induced destructive and inflammatory processes of various intensities, sometimes with allergic component; morphological signs of processes persisted for 6 weeks. Modification of basic plastics using glow-discharge plasma and enhancement of their hydrophilicity and biocompatibility significantly reduced the intensity of destructive and inflammatory processes and ensured more rapid (in 2 weeks) repair of the destroyed tissues with the formation of fibrous capsule around the implant.

Osteointegration in Cranial Bone Reconstruction: A Goal to Achieve

The number of cranioplasty procedures is steadily increasing, mainly due to growing indications for decompressive procedures following trauma, tumor or malformations. Although autologous bone is still considered the gold standard for bone replacement in skull, there is an urgent need for synthetic porous implants able to guide bone regeneration and stable reconstruction of the defect. In this respect, hydroxyapatite scaffolds with highly porous architecture are very promising materials, due to the excellent biocompatibility and intrinsic osteogenic and osteoconductive properties that enable deep bone penetration in the scaffold and excellent osteointegration. Osteointegration is here highlighted as a key aspect for the early recovery of bone-like biomechanical performance, for which custom-made porous hydroxyapatite scaffolds play a major role. There are still very few cases documenting the clinical performance of porous scaffolds following cranioplasty. This paper reports 2 clinical cases where large cranial defects were repaired by the aid of porous hydroxyapatite scaffolds with customized shapes and 3D profiles (Fin-Ceramica, Faenza, Italy). In the long term (i.e., after 2 years), these scaffolds yielded extensive osteointegration through formation and penetration of new organized bone. These results confirm that porous hydroxyapatite scaffolds, uniquely possessing chemico-physical and morphological/mechanical properties very close to those of bone, can be considered as a tool to provide effective bone regeneration in large cranial bone defects. Moreover, they may potentially prevent most of the postsurgical drawbacks related to the use of metal or plastic implants.

Progress in orthopedic biomaterials and drug delivery

Musculoskeletal conditions, including arthritis, back pain, and skeletal injuries/trauma, affect 50 % of the adult population in the U.S.A., and account for the second greatest cause of disability worldwide (www.bjdonline.org). The aggregate total annual cost of musculoskeletal diseases was $796 billion in 2011. While most musculoskeletal injuries and diseases have lowmortality, they have a tremendous impact of quality of life and morbidity. Biomaterials have a long history in orthopedics—metal and plastic implants have been used over the last 60 years to treat end-stage joint degeneration and skeletal tissue loss, and alleviate the resulting pain and disability. First-generation orthopedic implants were designed to be biologically inert and selected primarily for their mechanical properties. However, they do not replicate the function of normal tissue and have a limited life span in the body, which is especially problematic in younger patients. Recent decades have focused on the development of biomaterials that are biodegradable and incorporate tissue-specific physicochemical cues to guide cell processes and tissue morphogenesis, with the goal of restoring natural tissue structure and function. These advances in biomaterials provide critical enabling technologies for the delivery of stem cells, gene therapies, and new biologics in the orthopedic field. This special issue highlights the recent advances and future directions in orthopedic biomaterials and drug delivery systems, and showcases emerging pharmaceutical and regenerative approaches to treat injuries, diseases, and disorders of the musculoskeletal system. Non-union bone fractures are a significant clinical challenge, and bone tissue engineering could have a key impact in improving current clinical options. Telvin et al. review the application of stem cells from various sources towards bone tissue engineering. The ability of transplanted stem cells to survive, continue to differentiate, and form bone tissue is key to making stem cell-mediated bone tissue regeneration approaches successful. The research article by Wen et al. precisely address this challenge. Their study compares the in vivo bone tissue forming ability of human bone marrow derived stem cells and human embryonic stem cells using osteoinductive mineralized materials as a scaffold. The article by Nyberg et al. reviews progress and challenges in achieving precise temporal and spatial control of growth factor presentation for functional bone tissue engineering ex vivo and in vivo. Ultimately, successful bone regeneration requires integration between the repair and native bone tissue. Botchway and colleagues address this critical issue, by modifying the surface of a bone allograft with FTY720, a synthetic analog of sphingosine 1-phosphate, to promote endogenous bone formation and osseous integration at the interface. Another key hurdle for the success of bone tissue engineering is vascularization in vivo. The review by Garcia and Garcia summarizes the current strategies and new developments targeted at vascularization of engineered bone, including growth factor and cell delivery, gene therapy, biomaterials, and combination approaches. The article by Tonello et al. demonstrates the potential of human placental matrix for promoting angiogenesis and its controlled release from biodegradable microparticles. In addition to bone, this special issue contains articles that highlight advances in cartilage tissue regeneration and osteoarthritis (OA) therapies. Osteoarthritis is the leading cause of * Blanka Sharma blanka.sharma@bme.ufl.edu

Highly porous transcutaneous implants of varying material and pore geometry promote healing and in-growth of skin after surgical implantation into rabbits

Event Abstract Back to Event Highly porous transcutaneous implants of varying material and pore geometry promote healing and in-growth of skin after surgical implantation into rabbits Kyle J. Spivack1, Ian D. Dickey2, James A. Weber3, Alex Caddell1, Anne B. Lichtenwalner3 and David J. Neivandt1, 2 1 University of Maine, Department of Chemical and Biological Engineering, United States 2 University of Maine, Graduate School of Biomedical Sciences and Engineering, United States 3 University of Maine, School of Food and Agriculture, United States Recent developments in additive manufacturing have enabled the production of implantable metallic devices with highly mutable structures, including porous designs, and it is now possible to perform systematic studies of the efficacy of porous materials for supporting tissue in-growth. Studies of porous implants performed to date have largely focused on orthopedic applications. While a small number of studies have shown that highly porous devices, when implanted into subcutaneous tissue, facilitate fibrous tissue in-growth with significant attachment strength[1]-[7], the exact mechanism of soft tissue in-growth remains unclear. Further, no in-vivo analyses of transcutaneous porous implants, in which the implants penetrate through all dermal layers and into subcutaneous tissue, have been performed. Such studies are required in order to determine the potential for porous implants to promote wound healing in applications where contamination of the tissue-implant interface is unavoidable, such as percutaneous pin fixation of orthopedic fractures. We hypothesized that skin in-growth into a transcutaneous implant may form an effective biological seal, which would prevent bacteria from migrating into the subcutaneous and deeper tissues, causing infections. Reduction of infections could promote the development of healthy tissue in-growth in subcutaneous layers. The present pilot study was performed to determine the efficacy of additively manufactured, highly porous devices implanted in a transcutaneous fashion, and to qualitatively analyze the soft tissue in-growth capacity of such devices. A rabbit model was employed in the present study. Each of eight rabbits received four transcutaneous implants (two plastic, two titanium) for durations of one, two, three or seven weeks (two rabbits per time period). Implants harbored a rhombic dodecahedral porous network, or separately, a random highly porous foam network. Histology and histomorphometry were performed on implants from one rabbit at each post-surgical time period, including surrounding tissues, after surgical removal on the day of sacrifice. Implants were evaluated for responses consistent with inflammation and infection. The percentage of in-growth of soft tissues (granulation tissue, subcutaneous tissue and dermis) based on surface area was evaluated. Transcutaneous, porous implants comprised of either titanium or plastic promoted soft tissue in-growth as early as one week post-surgery and remained uninfected at, or deep to, the biologic interface between the dermal layer and the implant for up to seven weeks post surgery. Histological and histomorphological analyses showed that skin, subcutaneous and granular tissue grew into the porous networks of both the titanium and plastic implants. The present study demonstrated the efficacy of highly porous transcutaneous implants. Skin in-growth into porous transcutaneous implants formed an effective biological seal, preventing the establishment of infection-causing bacteria in tissues adjacent to the implants. Titanium implants with dodecahedral pore geometries performed better in several aspects than the plastic implants with dodecahedral pore geometries. Titanium implants with random highly porous foam geometry were more successful at promoting dermal tissue in-growth than titanium implants with uniform dodecahedral geometry. The authors gratefully acknowledge the University of Maine Institute for Molecular Biophysics for funding, AccelLab (Montreal, Canada) for performing histology and histomorphology analyses, Alexander French of the University of Maine Advanced Manufacturing Center for CAD design work, and GROWit, and Stryker Corporation for manufacturing the implants used in the present study.

Complications of Biodegradable Materials: Anchors and Interference Screws.

Metal, plastic, and biodegradable implants can all cause problems. The advantage of the biodegradable implant is clarity in postoperative imaging, easier revision, and fewer concerns about associated tissue damage. Although biodegradable implants do degrade over time, this time varies considerably, depends upon the polymer present, and is often measured in years. Before that occurring, the implant is a rigid device. Problems in the operative or immediate postoperative period include implant breakage during insertion, loss of initial fixation, incompletely buried or "proud" implants within a joint that could damage articular cartilage, and possible implant migration. Later occurring problems include the development of inflammatory reactions leading to lytic changes, cyst formation, intra-articular granuloma formation along with swelling, and sterile pretibial abscesses. Despite this list of potential problems on balance biodegradable implants are safe and effective and present no greater concerns (and arguably fewer ones) than metal or plastic implants.

Digital volume correlation and micro-CT: An in-vitro technique for measuring full-field interface micromotion around polyethylene implants

Micromotion around implants is commonly measured using displacement-sensor techniques. Due to the limitations of these techniques, an alternative approach (DVC-μCT) using digital volume correlation (DVC) and micro-CT (μCT) was developed in this study. The validation consisted of evaluating DVC-μCT based micromotion against known micromotions (40, 100 and 150μm) in a simplified experiment. Subsequently, a more clinically realistic experiment in which a glenoid component was implanted into a porcine scapula was carried out and the DVC-μCT measurements during a single load cycle (duration 20min due to scanning time) was correlated with the manual tracking of micromotion at 12 discrete points across the implant interface. In this same experiment the full-field DVC-μCT micromotion was compared to the full-field micromotion predicted by a parallel finite element analysis (FEA). It was found that DVC-μCT micromotion matched the known micromotion of the simplified experiment (average/peak error=1.4/1.7μm, regression line slope=0.999) and correlated with the micromotion at the 12 points tracked manually during the realistic experiment (R2=0.96). The DVC-μCT full-field micromotion matched the pattern of the full-field FEA predicted micromotion. This study showed that the DVC-μCT technique provides sensible estimates of micromotion. The main advantages of this technique are that it does not damage important parts of the specimen to gain access to the bone–implant interface, and it provides a full-field evaluation of micromotion as opposed to the micromotion at just a few discrete points. In conclusion the DVC-μCT technique provides a useful tool for investigations of micromotion around plastic implants.

Peri‐Implant Bone Density in Senile Osteoporosis‐Changes from Implant Placement to Osseointegration

The aim of this study was to examine healing over time after implant body placement in a senile osteoporosis model and a control group. In this study, 16-week-old male mice were used. The senile osteoporosis model consisted of senescence-accelerated prone 6 mice and the control group consisted of senescence-accelerated resistant 1 mice. Titanium-coated plastic implants were used as experimental implants whose dimensions were 3.0 mm in length, 1.1 mm in apical diameter, and 1.2 mm in coronal diameter. Bone samples were collected at 5, 7, 14, 21, and 28 days after implant placement. A micro-quantitative computed tomography (QCT) system was used to scan these samples and a phantom in order to quantitate bone mineral measurements. Bone mineral density (BMD) of each sample was measured. Each sample was also examined by light microscopy after QCT imaging. At 14 and 28 days after implant placement, the bone-implant contact (BIC) ratios were calculated from light microscopy images and were divided into cortical bone and bone marrow regions. When BMD was compared between the osteoporosis and control groups using micro-QCT, the osteoporosis group had a significantly lower BMD in the region 0-20 µm from the implant surface in the bone marrow region at 14 days onward after implant placement. Compared with the control group, the osteoporosis model also had significantly lower BMD in all regions 0-100 µm from the implant surface in the bone marrow region at 14 days after placement. However, in the cortical bone region, no statistically significant difference was observed in the regions at the bone-implant interface. Light microscopy revealed osseointegration for all implants 28 days after implant placement. The osteoporosis model tended to have lower BICs compared with that of the control group, although this did not reach statistical significance. Our results showed that osseointegration was achieved in the osteoporosis model. However, the BMD was 30-40% lower than that of the control group in the region closest to the implant surface in bone marrow region. Peri-implant BMD was lower in a relatively large area in the osteoporosis model during an important time for osseointegration. Therefore, this result suggests that osteoporosis might be considered as a risk factor in implant therapy. The osteoporosis model had a lower BMD than the control group in the region closest to the implant during an important time for osseointegration. This result suggests that senile osteoporosis might be a risk factor in implant therapy. However, the osteoporosis model and the control group had no difference in peri-implant BMD in the cortical bone region. This suggests that risk might be avoided by implant placement that effectively uses the cortical bone.

Chronological Changes in the Ultrastructure of Titanium‐Bone Interfaces: Analysis by Light Microscopy, Transmission Electron Microscopy, and Micro‐Computed Tomography

The objectives of this study were to chronologically examine the titanium-bone interfaces and to clarify the process of osseointegration using light microscopy, transmission electron microscopy (TEM), and micro-computed tomography (CT). Experimental implants (Ti-coating plastic implants) were placed into tibiae of 8-week-old rats. Animals were sacrificed at 1 to 28 days after implant placement and prepared tissue specimens for a light microscope, a TEM, and micro-CT. New bone formation began 5 days after implant placement, and osseointegration was obtained by 14 days after implant placement. Osseointegration was well developed by 28 days after implant placement. TEM and quantitative computer tomography (QCT) results indicated that bone formation in osseointegration of titanium implants did not occur from the surfaces of the implant or preexisting bone, but it was likely that bone formation progressed at a site a small distance away from the surface. The bone formation took place in a scattered manner. Small bone fragments adhered to each other and transformed into reticular-shaped bone, and finally these bones became lamellar bone. Comparative analysis of the titanium-bone interfaces using light microscopy, TEM, and QCT by micro-CT revealed the precise process of osseointegration.

Ultrastructure of the Interface Between Titanium and Surrounding Tissue in Rat Tibiae – A Comparison Study on Titanium‐Coated and ‐Uncoated Plastic Implants

The purposes of this study were to prepare experimental titanium-coated plastic implants suitable for electron microscopy examination of the titanium-bone interface and the response of tissue surrounding titanium, and to histologically compare surrounding tissue responses in coated and uncoated implants. Experimental plastic implants were prepared from a plastic rod coated with a thin film of titanium. Plastic implants without coatings were used as controls. The implants were placed into tibiae of 10-week-old male rats. The specimens with implants were harvested 4 weeks after placement and observed under a light microscope, a transmission electron microscope, and a scanning electron microscope. In the transmission electron microscopy, the titanium layer of the experimental implant was a uniform layer that was approximately 150- to 250-nm wide. The new bone formation was observed around both titanium-coated implants and plastic implants. However, there was no direct bone contact with the plastic implant. The responses of tissue surrounding the experimental implants varied. Under an electron microscope, the following areas were observed: (1) an area with a direct contact between the titanium and bone, (2) an area at the interface where an amorphous layer was observed, (3) an area with progressing calcification in the surrounding tissue where the cells were adjacent to the titanium surface, and (4) an area in which bone resorption and apposition were observed and remodeling was thought to be occurring. The experimental titanium was homogenous and was considered to be highly useful in observing the responses of the surrounding tissue to the titanium surface.

Opportunities and challenges for psychiatry.

Opportunities and challenges for psychiatry.

An immunocytochemical study for lysosomal cathepsins B and D related to the intracellular degradation of titanium at the bone-titanium interface.

The morphological relationship between titanium and lysosomal proteinases, cathepsins B and D, at the bone-titanium interface using titanium-coated plastic implants placed for 28 days in the tibiae of 6-week-old rats was immunocytochemically investigated by the colloidal immunogold-silver method. Under light microscopy the titanium layer appeared to make direct contact with the bone and one or a few layers of slender cells were interposed between the bone and titanium. Ultrastructurally, the titanium came in contact with the bone or the slender cell layer through a 20 to 40 nm thin amorphous zone. The slender cells at the bone-titanium interface consisted of two types; one was an osteoblast type with glycogen granules which was found along the newly-formed bone facing titanium layer. The other was a fibroblast type which came in contact with the titanium layer and occasionally endocytosed the detached titanium fragments. In addition, some of the slender cells also showed degenerative changes. Immunocytochemically, cathepsins B and/or D were sometimes colocalized in some phagolysosomes with titanium fragments. These findings suggested that the fibroblast types at the bone-titanium interface may act as scavengers to remove both cell debris and titanium by means of some endocytotic ability, and lysosomal cathepsins also developed in response to the endocytosed titanium. The osteoblast type also appears to show a high degree of osteogenic activity around the titanium-coated plastic implants.

An in vitro study of silicone migration from intravenous fluid tubing.

Migration of particulate matter from plastic tubing and solid plastic implants has been documented in a number of studies, including some with the use of cardiac bypass, haemodialysis, and pump-assisted intravenous infusions. In order to ascertain whether silicone embolisation occurs when children have an Ivac 560 pump-assisted IV infusion, we passed 180 ml of pumped fluid through a microfilter and compared the scanning electron micrographs of those filters with unused filters and with others through which a similar volume had been passed without using the pump. The particles on the filters were analysed for their elemental content using energy-dispersive X-ray analysis. In addition, the appearance of the silicone tubing used in the pump over 3 and 72 h was assessed and compared to that of flow-only and unused tubing. More particles were found on the microfilter when fluid had been delivered via the pump than on those through which non-pumped fluid had passed or that were unused. Elemental silicon-containing particles were only found on the filter when a pump had been attached to the IV line. The flow-only and unused tubing were found to have adherent particles on the inner surface that were not seen once the tubing had been used for 3 h in the Ivac 560 pump. Also, after 72 h use, the silicone tubing had a deformed inner layer. The clinical significance of these findings is yet to be determined, but it does appear that silicone embolisation occurs during pump-assisted infusions in children.