Bone morphogenetic protein 2 incorporated into biomimetic coatings retains its biological activity

We have previously shown that proteins can be incorporated into the latticework of calcium phosphate layers when biomimetically coprecipitated with the inorganic components, upon the surfaces of titanium-alloy implants. In the present study, we wished to ascertain whether recombinant human bone morphogenetic protein 2 (rhBMP-2) thus incorporated retained its bioactivity as an osteoinductive agent. Titanium alloy implants were coated biomimetically with a layer of calcium phosphate in the presence of different concentrations of rhBMP-2 (0.1-10 microg/mL). rhBMP-2 was successfully incorporated into the crystal latticework, as revealed by protein blot staining. rhBMP-2 was taken up by the calcium phosphate coatings in a dose-dependent manner, as determined by ELISA. Rat bone marrow stromal cells were grown directly on these coatings for 8 days. Their osteogenicity was then assessed quantitatively by monitoring alkaline phosphatase activity. This parameter increased as a function of rhBMP-2 concentrations within the coating medium. rhBMP-2 incorporated into calcium phosphate coatings was more potent in stimulating the alkaline phosphatase activity of the adhering cell layer than was the freely suspended drug in stimulating that of cell layers grown on a plastic substratum. This system may be of osteoinductive value in orthopedic and dental implant surgery.

Mechanical insertion properties of calcium-phosphate implant coatings

Abstract Objectives: To investigate the influence of protein incorporation on the resistance of biomimetic calcium-phosphate coatings to the shear forces that are generated during implant insertion. Materials and Methods: Thirty-eight standard (5 x 13 mm) Osseotite((R)) implants were coated biomimetically with a layer of calcium phosphate, which either lacked or bore a co-precipitated (incorporated) depot of the model protein bovine serum albumin (BSA). The coated implants were inserted into either artificial bone (n=18) or the explanted mandibles of adult pigs (n=12). The former set-up was established for the measurement of torque and of coating losses during the insertion process. The latter set-up was established for the histological and histomorphometric analysis of the fate of the coatings after implantation. Results: BSA-bearing coatings had higher mean torque values than did those that bore no protein depot. During the insertion process, less material was lost from the former than from the latter type of coating. The histological and histomorphometric analysis revealed fragments of material to be sheared off from both types of coating at vulnerable points, namely, at the tips of the threads. The sheared-off fragments were retained within the peri-implant space. Conclusion: The incorporation of a protein into a biomimetically prepared calcium-phosphate coating increases its resistance to the shear forces that are generated during implant insertion. In a clinical setting, the incorporated protein would be an osteogenic agent, whose osteoinductive potential would not be compromised by the shearing off of coating material, and the osteoconductivity of an exposed implant surface would not be less than that of a coated one. To cite this article: Hägi TT, Enggist L, Michel D, Ferguson SJ, Liu Y, Hunziker EB. Mechanical insertion properties of calcium-phosphate implant coatings. Clin. Oral Impl. Res. xx, 2010; 000-000. doi: 10.1111/j.1600-0501.2010.01916.x.

The influence of toothbrushing and coffee staining on different composite surface coatings

The aim of our study is to evaluate the performance of surface sealants and conventional polishing after ageing procedures. Eighty circular composite restorations were performed on extracted human molars. After standardised roughening, the restorations were either sealed with one of three surface sealants (Lasting Touch (LT), BisCover LV (BC), G-Coat Plus (GP) or a dentin adhesive Heliobond (HB)) or were manually polished with silicon polishers (MP) (n = 16). The average roughness (Ra) and colourimetric parameters (CP) (L*a*b*) were evaluated. The specimens underwent an artificial ageing process by thermocycling, staining (coffee) and abrasive (toothbrushing) procedures. After each ageing step, Ra and CP measurements were repeated. A qualitative surface analysis was performed with SEM. The differences between the test groups regarding Ra and CP values were analysed with nonparametric ANOVA analysis (α = 0.05). The lowest Ra values were achieved with HB. BC and GP resulted in Ra values below 0.2 μm (clinically relevant threshold), whereas LT and MP sometimes led to higher Ra values. LT showed a significantly higher discolouration after the first coffee staining, but this was normalised to the other groups after toothbrushing. The differences between the measurements and test groups for Ra and CP were statistically significant. However, the final colour difference showed no statistical difference among the five groups. SEM evaluation showed clear alterations after ageing in all coating groups. Surface sealants and dentin adhesives have the potential to reduce surface roughness but tend to debond over time. Surface sealants can only be recommended for polishing provisional restorations.

Comparative stability studies of poly(2-methyl-2-oxazoline) and poly(ethylene glycol) brush coatings

Non-fouling surfaces that resist non-specific adsorption of proteins, bacteria, and higher organisms are of particular interest in diverse applications ranging from marine coatings to diagnostic devices and biomedical implants. Poly(ethylene glycol) (PEG) is the most frequently used polymer to impart surfaces with such non-fouling properties. Nevertheless, limitations in PEG stability have stimulated research on alternative polymers that are potentially more stable than PEG. Among them, we previously investigated poly(2-methyl-2-oxazoline) (PMOXA), a peptidomimetic polymer, and found that PMOXA shows excellent anti-fouling properties. Here, we compare the stability of films self-assembled from graft copolymers exposing a dense brush layer of PEG and PMOXA side chains, respectively, in physiological and oxidative media. Before media exposure both film types prevented the adsorption of full serum proteins to below the detection limit of optical waveguide in situ measurements. Before and after media exposure for up to 2 weeks, the total film thickness, chemical composition, and total adsorbed mass of the films were quantified using variable angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS), and optical waveguide lightmode spectroscopy (OWLS), respectively. We found (i) that PMOXA graft copolymer films were significantly more stable than PEG graft copolymer films and kept their protein-repellent properties under all investigated conditions and (ii) that film degradation was due to side chain degradation rather than due to copolymer desorption.

Retention force of plastic clips on implant bars: a randomized controlled trial

Retention of overdentures is important for patients' satisfaction. The study tested whether the clinical performance of retentive clips made of poly-ether-ether-ketone (PEEK) is superior to those made of poly-oxy-methylene (POM).

Extending lifetime of plastic changes in the human brain

The ability of the brain to adjust to changing environments and to recover from damage rests on its remarkable capacity to adapt through plastic changes of underlying neural networks. We show here with an eye movement paradigm that a lifetime of plastic changes can be extended to several hours by repeated applications of theta burst transcranial magnetic stimulation to the frontal eye field of the human cortex. The results suggest that repeated application of the same stimulation protocol consolidates short-lived plasticity into long-lasting changes.

Architecture of European plastic surgery

The architecture of European Plastic Surgery was published in 1996 [Nicolai JPA, Scuderi N. Plastic surgical Europe in an organogram. Eur J Plast Surg 1996; 19: 253-256.] It is the objective of this paper to update information of that article. Continuing medical education (CME), science, training, examination, quality assurance and relations with the European Commission and Parliament all are aspects covered by the organisations to be discussed.

Asphyxial suicide by inhalation of helium inside a plastic bag

Asphyxial suicide by placing a plastic bag over the head, especially in combination with inhalation of gases, is a rarely described method of committing suicide. This article reports a case of suicidal asphyxiation by inhaling the inert gas helium inside a plastic bag. A 64-year-old man probably followed the instructions described in an article about committing suicide written by a medical practitioner from Zürich. This form of suicide is recommended by right-to-die groups and in the internet as a certain, fast, and painless suicide method. Additionally, it leaves only seldom externally visible marks or pathomorphological findings on the body. If the plastic bag and other auxiliary means are removed by another person, the forensic death investigation of cause and manner of death may be very difficult. Therefore, the death scene investigation and the inquiry ordered in the environment of the deceased are very important.