The biodegradation of hydroxyapatite bone graft substitutes in vivo

Hydroxyapatite (HA) ceramics are widely used for bone reconstruction. They are osteoconductive and serve as structural scaffolds for the deposition of new bone. Generally, scaffold materials should be degradable as they affect the mechanical properties of the reconstructed bone negatively. Degradation by osteoclasts during the bone remodelling process is desirable but often does not take place. In the current study we analysed by light microscopy the degradation of two granular HA implants in critically sized defects in the mandibula of Goettingen mini-pigs five weeks after implantation. Bio-Oss® consists of sintered bovine bone and NanoBone® is a synthetic HA produced in a sol-gel process in the presence of SiO2. We found that both biomaterials were degraded by osteoclasts with ruffled borders and acid phosphatase activity. The osteoclasts created resorption lacunae and resorptive trails and contained mineral particles. Frequently, resorption surfaces were in direct contact with bone formative surfaces on one granule. Granules, especially of NanoBone®, were also covered by osteoclasts if located in vascularised connective tissue distant from bone tissue. However, this usually occurred without the creation of resorption lacunae. The former defect margins consisted of newly formed bone often without remnants of bone substitutes. Our results show that the degradation of both biomaterials corresponds to the natural bone degradation processes and suggest the possibility of complete resorption during bone remodelling

Bone functions and the requirements for bone grafts and substitutes in the orofacial region

Bone is the largest calcium storage, has distinctive plasticity and adaptability and is part of the supporting tissue. An adequate composition is thus necessary. The bone matrix consists of organic and anorganic structures. Osteoblasts, osteoclasts and osteocytes are responsible for bone formation, resorption and metabolism. The periosteum, endosteum and bone tissue are a functional unit and provide protection, nutrition and growth. Bone is subject to continuous remodelling

Wound management after the application of bone grafting substitutes in the orofacial region

Surgical dressing after the application of bone grafting material depends on the type and size of the defect. A complete and tension-free wound closure has proved to be successful. In this context the infection problem needs special attention. Bone graft substitutes with an adequate surface structure, porosity and chemical properties, in combination with sufficient blood circulation, hold osteoconductive potential. They serve as a guide rail for the osteoblast-induced formation of new bone tissue, which at best may lead to complete replacement of the grafting material

Critical considerations on the diagnostic appraisal, adaptation and remodelling of bone graft substitutes

The diagnostic assessment of skeletal defects has a long-standing tradition. As a result of the development of new bone grafting materials, the demands on diagnostic assessment have also increased. The mode and quality of diagnostic appraisal are crucial to further clinical use and outcome prediction. Alongside traditional clinical and biological techniques, molecular biological methods have gained a broad scope of application and will be used even more frequently in the future

Uncoupled excitons in semiconductor microcavities detected in resonant Raman scattering

We present an outgoing resonant Raman-scattering study of a GaAs/AlGaAs based microcavity embedded in a p-i-n junction. The p-i-n junction allows the vertical electric field to be varied, permitting control of exciton-photon detuning and quenching of photoluminescence which otherwise obscures the inelastic light scattering signals. Peaks corresponding to the upper and lower polariton branches are observed in the resonant Raman cross sections, along with a third peak at the energy of uncoupled excitons. This third peak, attributed to disorder activated Raman scattering, provides clear evidence for the existence of uncoupled exciton reservoir states in microcavities in the strong-coupling regime

Spintronics: Fundamentals and applications

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes from the published versio

Berechnung nach Maß

Bei Konstruktion und Projektierung von Förder- und Transportanlagen steht der Kettentrieb als Zug- und Tragorgan oft im Vordergrund. Funktionssicherheit und hohe Lebensdauer sind Forderungen, die Anlagenhersteller an den Kettentrieb richten. Mit der neuen CD 1.0 beschreitet Ketten Wulf, seit 75 Jahren Entwickler und Hersteller von Förder- und Transportketten, neue Wege beim Kundenservice. Die CD bietet nicht nur die üblichen Informationen über Produkte und Produktionsbereiche des Unternehmens. Sie umfaßt auch elektronische Produktkataloge für Ketten und Kettenräder und als Herzstück den "Berechnungsassistentenx", eine gemeinsam mit dem Fraunhofer-Institut für Materialfluss und Logistik IML entwickelte Software zur Auswahl, Berechnung und Optimierung von Ketten und Kettenrädern

Analysis of P2X7 Receptor and Panx1 Expression in Osteoporosis

It has been found that there exist certain crystalline aluminosilicates which provide regular net-works of channels with diameters no bigger than those of molecules. Such crystals can act as sieves (thus the name molecular sieves now marketed by the Linde Air Products Company) and bring about a separation of molecular species by occluding small molecules while not adsorbing larger molecules or molecules with shapes that do not fit. The aluminosilicates were termed zeolites first by Baron Cronstedt (1) some 200 years ago. He observed that certain mineral crystals, when heated, appeared to melt and to boil at the same time. Thus, from the Greek zeo, to boil, and lithos, stone, Cronstedt coined the term zeolite. The use of zeolite (molecular sieves) has increased during the past several years. The earlier work (1930- 1950) involved the study of the naturally occurring zeolites. During the last ten years the activity has been concerned with the use of synthetic crystalline zeolites in separating both gaseous and liquid components by the molecular sieve action