A histological and micro-CT investigation in to the effect of NGF and EGF on the periodontal, alveolar bone, root and pulpal healing of replanted molars in a rat model - a pilot study

Background: This study aims to investigate, utilising micro-computed tomography (micro-CT) and histology, whether the topical application of nerve growth factor (NGF) and/or epidermal growth factor (EGF) can enhance periodontal, alveolar bone, root and pulpal tissue regeneration while minimising the risk of pulpal necrosis, root resorption and ankylosis of replanted molars in a rat model. Methods: Twelve four-week-old male Sprague-Dawley rats were divided into four groups: sham, collagen, EGF and NGF. The maxillary right first molar was elevated and replanted with or without a collagen membrane impregnated with either the growth factors EGF or NGF, or a saline solution. Four weeks after replantation, the animals were sacrificed and the posterior maxilla was assessed using histological and micro-CT analysis. The maxillary left first molar served as the control for the corresponding right first molar. Results: Micro-CT analysis revealed a tendency for all replanted molars to have reduced root length, root volume, alveolar bone height and inter-radicular alveolar bone volume. It appears that the use of the collagen membrane had a negative effect while no positive effect was noted with the incorporation of EGF or NGF. Histologically, the incorporation of the collagen membrane was found to negatively affect pulpal, root, periodontal and alveolar bone healing with pulpal inflammation and hard tissue formation, extensive root resorption and alveolar bone fragmentation. The incorporation of EGF and NGF did not improve root, periodontal or alveolar bone healing. However, EGF was found to improve pulp vascularisation while NGF improved pulpal architecture and cell organisation, although not to the level of the control group.Conclusions: Results indicate a possible benefit on pulpal vascularisation and pulpal cell organisation following the incorporation of EGF and NGF, respectively, into the alveolar socket of replanted molars in the rat model. No potential benefit of EGF and NGF was detected in periodontal or root healing, while the use of a collagen membrane carrier was found to have a negative effect on the healing response

Fundamental research into the role of intermetallic phases in joining of aluminium alloys to steel

Bildung und Wachstum intermetallischer Phasensäume am Übergang zwischen Fe bzw. Stahl und sowohl reinem als auch Si-Legiertem Al wurden bei verschiedenen Werkstoffzuständen untersucht, ebenso wie der Einfluss von Phasensaumdicke und -Aufbau auf die mechanischen Verbindungseigenschaften. In elementaren Interdiffusionsversuchen ist die Saumdicke wesentlich durch das parabolische Wachstum der $\eta$ Phase (Al$_{5}$Fe$_{2}$) bestimmt. Die Zugabe von Si in Al, welche bekanntermaßen das Phasenwachstum bei der Reaktion mit Al Schmelzen hemmt, bewirkte ein beschleunigtes Wachstum bei 600°C Reaktionstemperatur. Untersuchungen der Verformungs-Mikrostruktur unter Härteeindrücken offenbarten einen deutlichen Einfluss der äußeren und inneren Phasengrenzen auf die Härtewerte. Wärmebehandlung von Stahl/Al Rührreibschweißungen zeigte, dass die Verbindungsfestigkeit mit reinem Al durch die Bildung von Kirkendall-Poren an der Grenzfläche Phasensaum/Al bestimmt wird, mit Al-Si hingegen durch die Dicke der $\eta$ Phase.Formation and evolution of intermetallic reaction layers at the interface between Fe or low C steel and both pure and Si containing Al was studied in different material states, as well as the impact of layer thickness and build-up on mechanical properties of joints. In basic interdiffusion experiments, width of reaction layers is governed mainly by the parabolic growth of the $\eta$ phase (Al$_{5}$Fe$_{2}$). The addition of Si to Al, which is known to decelerate layer growth during interdiffusion with Al melts, was found to accelerate the growth at 600°C. Investigations of the deformation microstructure beneath hardness indentations elicited a pronounced influence of the reaction layers outer and inner interfaces on the observed hardness. Heat treating of dissimilar friction stir welds showed that with pure Al, the joint strength is governed by the formation of Kirkendall-porosity at the reaction layer/Al interface; in joints with Al-Si it is controlled by the thickness of the $\eta$ phase layer

Reduction of relative centrifugation force within injectable platelet-rich-fibrin (PRF) concentrates advances patients’ own inflammatory cells, platelets and growth factors : the first introduction to the low speed centrifugation concept

Purpose: The aim of this study was to analyze systematically the influence of the relative centrifugation force (RCF) on leukocytes, platelets and growth factor release within fluid platelet-rich fibrin matrices (PRF). Materials and methods: Systematically using peripheral blood from six healthy volunteers, the RCF was reduced four times for each of the three experimental protocols (I–III) within the spectrum (710–44 g), while maintaining a constant centrifugation time. Flow cytometry was applied to determine the platelets and leukocyte number. The growth factor concentration was quantified 1 and 24 h after clotting using ELISA. Results: Reducing RCF in accordance with protocol-II (177 g) led to a significantly higher platelets and leukocytes numbers compared to protocol-I (710 g). Protocol-III (44 g) showed a highly significant increase of leukocytes and platelets number in comparison to -I and -II. The growth factors’ concentration of VEGF and TGF-β1 was significantly higher in protocol-II compared to -I, whereas protocol-III exhibited significantly higher growth factor concentration compared to protocols-I and -II. These findings were observed among 1 and 24 h after clotting, as well as the accumulated growth factor concentration over 24 h. Discussion: Based on the results, it has been demonstrated that it is possible to enrich PRF-based fluid matrices with leukocytes, platelets and growth factors by means of a single alteration of the centrifugation settings within the clinical routine. Conclusions: We postulate that the so-called low speed centrifugation concept (LSCC) selectively enriches leukocytes, platelets and growth factors within fluid PRF-based matrices. Further studies are needed to evaluate the effect of cell and growth factor enrichment on wound healing and tissue regeneration while comparing blood concentrates gained by high and low RCF