Teriparatide improves microarchitectural characteristics of peri-implant bone in orchiectomized rats.

This study evaluated the peri-implant bone repair in orchiectomized rats receiving intermittently PTH 1-34. The treatment returned the bone quality and quantity of the animals to normal in the computerized microtomography, laser confocal microscopy, and histological analysis. The PTH 1-34 promoted marked bone formation with increased volume, improved quality, and greater bone turnover. INTRODUCTION: Osteoporosis can be a problem in implant osseointegration. So this study aimed to evaluate the quantity and quality of peri-implant bone repair in orchiectomized Wistar rats receiving intermittently administered PTH 1-34. METHODS: Animals (n = 24) were divided into 3 groups: healthy control (SHAM), orchiectomized (ORQ), and orchiectomized and treated with 0.5 µg/kg/day PTH 1-34 (TERI), and each received an implant in the right and left tibial metaphysis, which was allowed to repair for 60 days. The resultant bone formation was evaluated through computerized microtomography (micro-CT) to compare the percent bone volume (BV/TV), trabecular thickness (Tb.Th), trabecular number and separation (Tb.N, Tb.Sp), and bone implant contact (BIC) through the intersection surface (i.S) between groups. Laser confocal microscopy was used to evaluate fluorochrome areas for mineral apposition rate (MAR) and neoformed bone area (NBA). In addition, histological evaluation of calcified tissues with Stevenel blue and alizarin red staining was performed. RESULTS: Treatment with PTH 1-34 returned the bone quality and quantity of the osteoporotic animal to normal, as the TERI group presented statistically significant higher values for BV/TV, Tb.Th, and BIC parameters compared with ORQ (p < 0.05), but when compared with SHAM (p > 0.05), no statistical difference was noted. In addition, in the bone turnover analysis (MAR, NBA) for TERI, the highest results are presented, followed by SHAM, and then ORQ (TERI × ORQ: p < 0.05). CONCLUSIONS: Intermittent treatment with PTH 1-34 on orchiectomized animals promoted marked bone formation with increased volume, improved quality, and greater bone turnover in the peri-implant space, returning the bone quality and quantity to the present standard in healthy animals.

A search for apatite crystals in the gap zone of collagen fibrils in bone using dark-field illumination.

Bright-field transmission electron microscope (TEM) images of ion milled or focused ion beam (FIB) sections of cortical bone sectioned parallel to the long axis of collagen fibrils display an electron-dense phase in the gap zones of the fibrils, as well as elongated plates (termed mineral lamellae) comprised of apatite crystals, which surround and lie between the fibrils. Energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) studies by others have shown that the material in the gap zones is calcium phosphate. Dark-field (DF) images are capable of revealing the projected position of crystals of apatite in a section of bone. We obtained bright field (BF) images of ion milled sections of bovine femoral cortical bone cut parallel to fibril axes (longitudinal view), and compared them with DF images obtained using the (002) apatite reflection to test a widely held theory that most of the mineral in bone resides in the gap zones. Most apatite crystals which were illuminated in DF images and which projected onto gap zones were extensions of crystals that also project onto adjacent overlap zones. However, in BF images, overlap zones do not appear to contain significant amounts of mineral, implying that the crystals imaged in DF are actually in the interfibrillar matrix but projected onto images of fibrils. However a small number of "free" illuminated crystals did not extend into the overlap zones; these could be physically located inside the gap zones. We note that projections of gap zones cover 60% of the area of any longitudinal field of view; thus these "free" crystals have a high random probability of appearing to lie on a gap zone, wherever they physically lie in the section. The evidence of this study does not support the notion that most of the mineral of bone consists of crystals in the gap zone. This study leaves uncertain what is the Ca-P containing material present in gap zones; a possible candidate material is amorphous calcium phosphate.

Electrophoretic deposition of polymethylmethacrylate and composites for biomedical applications.

For the first time, an electrophoretic deposition (EPD) method has been developed for the deposition of polymethylmethacrylate (PMMA) and PMMA-alumina films for biomedical implant applications. The proposed biomimetic approach was based on the use of a bile salt, sodium cholate (NaCh), which served as a multifunctional solubilizing, charging, dispersing and film-forming agent. Investigations revealed PMMA-Ch- and PMMA-alumina interactions, which facilitated the deposition of PMMA and PMMA-alumina films. This approach allows for the use of a non-toxic water-ethanol solvent for PMMA. The proposed deposition strategy can also be used for co-deposition of PMMA with other functional materials. The PMMA and composite films were tested for biomedical implant applications. The PMMA-alumina films showed statistically improved metabolic results compared to both the bare stainless steel substrate and pure PMMA films. Alkaline phosphatase (ALP) activity affirmed the bioactivity and osteoconductive potential of PMMA and composite films. PMMA-alumina films showed greater ALP activity than both the PMMA-coated and uncoated stainless steel.

Biomimetic modification of poly-l-lysine and electrodeposition of nanocomposite coatings for orthopaedic applications.

For the first time, a biomimetic method has been developed for the chemical modification of poly-l-lysine (PLL) with catechol in order to improve polymer adhesion to inorganic particles and surfaces. The method is based on the Schiff base reaction of amino groups of PLL monomers and aldehyde groups of 3,4-dihydroxybenzylaldehyde (DHBA) molecules. It was found that adherent PLL-DHBA films can be prepared by cathodic electrophoretic deposition (EPD). Nanocomposite coating with dual micro-nano topography has been developed for orthopaedic and dental coating applications. The catechol groups of PLL-DHBA facilitated its adsorption on hydroxyapatite (HA) and rutile (TiO2) and allowed the fabrication of stable suspensions for EPD. PLL-DHBA was used as both a charging and film-forming agent for EPD of HA and TiO2. Moreover, the methods allowed co-deposition of HA and TiO2 and fabrication of composite films, which allows the benefits of both bioceramics to be combined. In addition to having dual scale topography, the films exhibited both sub-micron surface roughness and hydrophilic behaviour, which both have been found to promote osteoblast adhesion and proliferation. in vitro studies revealed that the fabricated coatings showed increased cell metabolism and alkaline phosphatase activity over the period studied, with PLL-DHBA-TiO2 showing the greatest increase. This work paves the way for both the development of the next generation of biomedical implant coatings, with improved osseointegration and lifespan, as well as one-step low-temperature processing.

Fabrication and evaluation of SixNy coatings for total joint replacements.

Wear particles from the bearing surfaces of joint implants are one of the main limiting factors for total implant longevity. Si(3)N(4) is a potential wear resistant alternative for total joint replacements. In this study, Si(x)N(y)-coatings were deposited on cobalt chromium-discs and Si-wafers by a physical vapour deposition process. The tribological properties, as well as surface appearance, chemical composition, phase composition, structure and hardness of these coatings were analysed. The coatings were found to be amorphous or nanocrystalline, with a hardness and coefficient of friction against Si(3)N(4) similar to that found for bulk Si(3)N(4). The low wear rate of the coatings indicates that they have a potential as bearing surfaces of joint replacements. The adhesion to the substrates remains to be improved.

Tips for better visual elements in posters and podium presentations.

CONTEXT: The ability to effectively communicate through posters and podium presentations using appropriate visual content and style is essential for health care educators. OBJECTIVES: To offer suggestions for more effective visual elements of posters and podium presentations. METHODS: We present the experiences of our multidisciplinary publishing group, whose combined experiences and collaboration have provided us with an understanding of what works and how to achieve success when working on presentations and posters. Many others would offer similar advice, as these guidelines are consistent with effective presentation. FINDINGS/SUGGESTIONS: Certain visual elements should be attended to in any visual presentation: consistency, alignment, contrast and repetition. Presentations should be consistent in font size and type, line spacing, alignment of graphics and text, and size of graphics. All elements should be aligned with at least one other element. Contrasting light background with dark text (and vice versa) helps an audience read the text more easily. Standardized formatting lets viewers know when they are looking at similar things (tables, headings, etc.). Using a minimal number of colors (four at most) helps the audience more easily read text. For podium presentations, have one slide for each minute allotted for speaking. The speaker is also a visual element; one should not allow the audience's view of either the presentation or presenter to be blocked. Making eye contact with the audience also keeps them visually engaged. CONCLUSIONS: Health care educators often share information through posters and podium presentations. These tips should help the visual elements of presentations be more effective.

Visualizing biointerfaces in three dimensions: electron tomography of the bone-hydroxyapatite interface.

A positive interaction between human bone tissue and synthetics is crucial for the success of bone-regenerative materials. A greater understanding of the mechanisms governing bone-bonding is often gained via visualization of the bone-implant interface. Interfaces to bone have long been imaged with light, X-rays and electrons. Most of these techniques, however, only provide low-resolution or two-dimensional information. With the advances in modern day transmission electron microscopy, including new hardware and increased software computational speeds, the high-resolution visualization and analysis of three-dimensional structures is possible via electron tomography. We report, for the first time, a three-dimensional reconstruction of the interface between human bone and a hydroxyapatite implant using Z-contrast electron tomography. Viewing this structure in three dimensions enabled us to observe the nanometre differences in the orientation of hydroxyapatite crystals precipitated on the implant surface in vivo versus those in the collagen matrix of bone. Insight into the morphology of biointerfaces is considerably enhanced with three-dimensional techniques. In this regard, electron tomography may revolutionize the approach to high-resolution biointerface characterization.