344 results on '"Fischer, Kai"'
Search Results
302. Vapor−Liquid Equilibria and Excess Enthalpies for Binary Mixtures of N-Methylacetamide with 1-Octene, Dipropylamine, Triethylamine, Pyridine, and Methanol at 125 °C
- Author
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de Haan, André B., primary, Fischer, Kai, additional, Haacke, Michael, additional, and Gmehling, Jürgen, additional
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- 1997
- Full Text
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303. Vapor-liquid equilibria for the system water + tert.-pentanol at 4 temperatures
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Fischer, Kai, primary, Shulgin, Ivan, additional, Rarey, Jürgen, additional, and Gmehling, Jürgen, additional
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- 1996
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304. Vapor-liquid equilibria, activity coefficients at infinite dilution and heats of mixing for mixtures of N-methyl pyrrolidone-2 with C5 or C6 hydrocarbons and for hydrocarbon mixtures
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Fischer, Kai, primary and Gmehling, Jürgen, additional
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- 1996
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305. Vapor−Liquid Equilibria and Enthalpies of Mixing for the Binary System Water + N-Methyl-2-pyrrolidone in the Temperature Range 80−140 °C
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Noll, Oliver, primary, Fischer, Kai, additional, and Gmehling, Jürgen, additional
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- 1996
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- View/download PDF
306. Vapor-Liquid Equilibria and Excess Enthalpies for Octane + N-Methylacetamide, Cyclooctane + N-Methylacetamide, and Octane + Acetic Anhydride at 125 .degree.C
- Author
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de Haan, Andre B., primary, Heine, Antje, additional, Fischer, Kai, additional, and Gmehling, Juergen, additional
- Published
- 1995
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- View/download PDF
307. A data bank for azeotropic data — status and applications
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Gmehling, Jürgen, primary, Menke, Jochen, additional, Krafczyk, Jörg, additional, and Fischer, Kai, additional
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- 1995
- Full Text
- View/download PDF
308. Excess Volumes for Alkanol + Morpholine Systems at 298.15 and 308.15 K
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Park, So-Jin, primary, Fischer, Kai, additional, and Gmehling, Juergen, additional
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- 1994
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309. P-x and .gamma..infin. Data for the Different Binary Butanol-Water Systems at 50.degree.C
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Fischer, Kai, primary and Gmehling, Juergen, additional
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- 1994
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310. Integrated optical pressure sensor with coupling structures
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Mueller, Joerg, primary, Zurhelle, Dieter, additional, Fischer, Kai H., additional, Loeffler-Peters, Andrea, additional, and Hoffmann, Rainer, additional
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- 1993
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311. Integrated optical pressure sensor with coupling structures.
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Mueller, Joerg, Zurhelle, Dieter, Fischer, Kai H., Loeffler-Peters, Andrea, and Hoffmann, Rainer
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- 1993
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312. Horizontal Augmentation of Chronic Mandibular Defects by the Guided Bone Regeneration Approach: A Randomized Study in Dogs.
- Author
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Friedmann, Anton, Fickl, Stefan, Fischer, Kai R., Dalloul, Milad, Goetz, Werner, and Kauffmann, Frederic
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GUIDED bone regeneration ,PERICARDIUM ,BONE substitutes ,TOLUIDINE blue ,BONE growth ,BEAGLE (Dog breed) - Abstract
Various biomaterial combinations have been studied focusing on their ability to stabilize blood clots and maintain space under soft tissue to support new bone formation. A popular combination is Deproteinized Bovine Bone Mineral (DBBM) placed with a native collagen membrane (NCM) tacked to native bone. In this study, we compared the outcome of this treatment option to those achieved with three different graft/membrane combinations with respect to total newly occupied area and the mineralized compound inside. After bi-lateral extraction of two mandibular premolars in five adult beagles L-shaped alveolar defects were created. A total of 20 defects healed for 6 weeks resulting in chronic type bone defects. At baseline, four options were randomly allocated to five defects each: a. DBBM + NCM with a four-pin fixation across the ridge; b. DBBM + RCLC (ribose cross-linked collagen membrane); c. DBBM + NPPM (native porcine pericardium membrane); and d. Ca-sulfate (CS) + RCLC membrane. Membranes in b/c/d were not fixed; complete tensionless wound closure was achieved by CAF. Termination after 3 months and sampling followed, and non-decalcified processing and toluidine blue staining were applied. Microscopic images obtained at standardized magnification were histomorphometrically assessed by ImageJ software (NIH). An ANOVA post hoc test was applied; histomorphometric data are presented in this paper as medians and interquartile ranges (IRs). All sites healed uneventfully, all sites were sampled and block separation followed before Technovit embedding. Two central sections per block for each group were included. Two of five specimen were lost due to processing error and were excluded from group b. New bone area was significantly greater for option b. compared to a. (p = 0.001), c. (p = 0.002), and d. (p = 0.046). Residual non-bone graft area was significantly less for option d. compared to a. (p = 0.026) or c. (p = 0.021). We conclude that collagen membranes with a prolonged resorption/barrier profile combined with bone substitutes featuring different degradation profiles sufficiently support new bone formation. Tacking strategy/membrane fixation appears redundant when using these biomaterials. [ABSTRACT FROM AUTHOR]
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- 2022
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313. Solubility of H2S and CO2 in N-octyl-2-pyrrolidone and of H2S in methanol and benzene.
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Fischer, Kai, Chen, Jian, Petri, Martin, and Gmehling, Jürgen
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- 2002
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314. Correction to: Gingival phenotype assessment methods and classifications revisited: a preclinical study.
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Fischer, Kai R., Büchel, Jasmin, Testori, Tiziano, Rasperini, Giulio, Attin, Thomas, and Schmidlin, Patrick
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GINGIVA , *PHENOTYPES , *CLASSIFICATION - Abstract
A Correction to this paper has been published: https://doi.org/10.1007/s00784-021-03898-5 [ABSTRACT FROM AUTHOR]
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- 2021
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315. Comparison of Direct Intersection and Sonogram Methods for Acoustic Indoor Localization of Persons.
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Schott, Dominik Jan, Saphala, Addythia, Fischer, Georg, Xiong, Wenxin, Gabbrielli, Andrea, Bordoy, Joan, Höflinger, Fabian, Fischer, Kai, Schindelhauer, Christian, and Rupitsch, Stefan Johann
- Subjects
ACOUSTIC localization ,IMPULSE response ,COMPUTATIONAL complexity ,TIME management ,CASE goods - Abstract
We discuss two methods to detect the presence and location of a person in an acoustically small-scale room and compare the performances for a simulated person in distances between 1 and 2 m. The first method is Direct Intersection, which determines a coordinate point based on the intersection of spheroids defined by observed distances of high-intensity reverberations. The second method, Sonogram analysis, overlays all channels' room impulse responses to generate an intensity map for the observed environment. We demonstrate that the former method has lower computational complexity that almost halves the execution time in the best observed case, but about 7 times slower in the worst case compared to the Sonogram method while using 2.4 times less memory. Both approaches yield similar mean absolute localization errors between 0.3 and 0.9 m. The Direct Intersection method performs more precise in the best case, while the Sonogram method performs more robustly. [ABSTRACT FROM AUTHOR]
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- 2021
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316. Automatic measurement of surface height with the interferoscope.
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Carlsson, Torgny E., Abramson, Nils H., and Fischer, Kai H.
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- 1996
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317. Experimental determination of the critical line for (carbon dioxide +ethane) and calculation of various thermodynamic properties for (carbon dioxide +n-alkane) using the PSRK model
- Author
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Horstmann, Sven, Fischer, Kai, Gmehling, Jürgen, and Kolář, Petr
- Abstract
The binary (carbon dioxide +ethane) exhibits an unusual and interesting phase equilibrium behaviour especially in the critical region of the pure components and their mixtures. The critical line of this system was determined by using a flow apparatus. The experimental results were compared with the predictive Soave–Redlich–Kwong (PSRK) model. In this paper the PSRK model was also applied to the calculation of critical points, (vapour +liquid) equilibria, azeotropic points, excess enthalpies (HE), excess volumes (VE), and Henry’s coefficients (H12). The investigated systems included (carbon dioxide +ethane, or propane, or n-butane, or n-hexadecane). In the PSRK calculations only one pair of temperature-dependent interaction parameters is required for (carbon dioxide +an n-alkane). The calculated results were compared with experimental data. The relation of excess properties with phase equilibria in (carbon dioxide +ethane) was discussed in detail.
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- 2000
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318. Integrating design and costing.
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BLECK, KATHERINE, BREING, MARKUS, EMONTS, MICHAEL, and FISCHER, KAI
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LIGHTWEIGHT materials ,ACTIVITY-based costing ,NEW product development ,MANAGERIAL economics ,PRODUCT design - Published
- 2017
319. Hybridisation - A toolbox for efficient lightweight production.
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Fischer, Kai and Emonts, Michael
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HYBRID materials ,LIGHTWEIGHT materials ,THERMOPLASTICS ,MOLDING (Founding) ,POLYURETHANES - Published
- 2017
320. Ridge preservation of compromised extraction sockets applying a soft cortical membrane: A canine proof-of-principle evaluation.
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Fischer, Kai R., Götz, Werner, Kauffmann, Frederic, Schmidlin, Patrick R., and Friedmann, Anton
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BONE substitutes ,TOOTH socket ,ALVEOLAR process ,BONES ,BONE resorption ,BONE regeneration - Abstract
To explore whether placement of a soft cortical membrane can restore and regenerate the original alveolar ridge contour in deficient sockets. One Beagle dog was used in this proof-of-principle evaluation. In a first intervention, a standardized buccal dehiscence defect was artificially created at the distal roots of the 3rd and 4th mandibular premolars. Four weeks later, following endodontic treatment of the mesial roots, teeth were hemisected and the distal roots were extracted without raising a flap. A cortical membrane (Lamina®, Osteobiol) was placed outside of the bony envelope of the extraction socket to rebuild the buccal bone contour. Afterwards, sockets were filled with a collagen-modified porcine bone graft material (Gen-Os®, Osteobiol) to the level of the surrounding bone height. The socket orifice was closed with a porcine dermal matrix (Derma®). After four months, block specimens containing the socket-sites and remaining roots were retrieved, histologically processed and analyzed. Surgery and post-operative healing were uneventful. Histologically, bone formation under the membrane was found, i.e. bony protrusions and ossicles by osteoblasts could be identified. Concomitantly, the membrane showed clear signs of degradation. Bone substitute was well integrated in newly formed bone and resorption of particles was found. Three major observations were made in the present proof-of-principle study: (i) regeneration of a compromised socket seems possible when applying the presented approach, (ii) the soft cortical membrane was sufficiently stable to allow for the establishment of the contour and to inhibit soft tissue invasion and (iii) the applied xenogenic graft material was undergoing remodelling processes while allowing adequate bone regeneration. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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321. How Industry 4.0 affects the composite production landscape.
- Author
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BREHNG, MARKUS, STENDER, SEBASTIAN, EMONTS, MICHAEL, and FISCHER, KAI
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COMPOSITE material manufacturing ,INDUSTRIAL revolution - Abstract
The article discusses the change in production systems within Industry 4.0, stating that it will affect the landscape of the composite manufacturing sector as the productivity would be on rise.
- Published
- 2016
322. New potential for composite technologies in buildings and infrastructure.
- Author
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KALT, LUKAS, WEILER, THOMAS, EMONTS, MICHAEL, and FISCHER, KAI
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COMPOSITE materials industry ,BUILDING design & construction - Published
- 2017
323. Improving accuracy of robot-guided 3D laser surface processing by workpiece measurement in a blink
- Author
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Kaierle, Stefan, Heinemann, Stefan W., Schares, Richard, Schmitt, Stefan, Emonts, Michael, Fischer, Kai, Moser, Rüdiger, and Frühauf, Boris
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- 2018
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324. AZL -- The one-stop shop for the composite industry.
- Author
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EMONTS, MICHAEL, FISCHER, KAI, and EFFING, MICHAEL
- Subjects
RESEARCH institutes ,COMPOSITE materials ,TECHNOLOGY - Abstract
An interview with Michael Emonts and Kai Fischer of the Aachen Center for Integrative Lightweight Production (AZL) and Michael Effing of the Advanced Materials Advisory & Consultancy (AMAC) is presented. They talk about the objective of AZL and its difference from other light-weight research centers in Germany. They cite the reasons why composite technology can thrive in European countries like Germany. They discuss the services to be provided by AZL.
- Published
- 2013
325. Analysis of defects in the cylindrical area of a type-IV hydrogen pressure vessel on the mechanical laminate properties.
- Author
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Hopmann, Christian, Müller, Robert, Schneider, Daniel, and Fischer, Kai
- Subjects
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PRESSURE vessels , *TENSILE tests , *LAMINATED materials , *FILAMENT winding , *DIGITAL twins , *SAFETY factor in engineering - Abstract
Type-IV pressure vessels are increasingly being applied for hydrogen storage purposes in mobile and stationary applications. Due to manufacturing defects in the wet filament winding process these pressure vessels currently have to be oversized beyond the legal safety factor of 2.25, which requires high avoidable costs. With the aim of reducing the costs and weight of type-IV pressure vessels, the Institute for Plastics Processing (IKV) is developing a quality assurance system with location-resolved data visualisation in the form of a digital twin of pressure vessels, whereby process-induced defects can be detected. Against this background, this publication shows insights into the change of defects in the form of gaps and overlaps between neighbouring fibre bands after the curing process and quantifies their influence on the mechanical properties of ring test specimens. The extent of the defect is determined during the process by using the authors' optical measuring systems. Afterwards, the effect of defects on the tensile strength is analysed by using the split-disc-test-method. It is shown that all intentionally introduced defects can no longer be clearly distinguished by means of microscopical analysis from the rest of the laminate after the curing process. In the mechanical tests, the effect of gaps and overlaps on the tensile strength of ring test specimens varies in terms of direction and extend. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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326. Review of piston reactors for the production of chemicals.
- Author
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Ashok, Anchu, Katebah, Mary Anna, Linke, Patrick, Kumar, Dharmesh, Arora, Dhruv, Fischer, Kai, Jacobs, Timothy, and Al-Rawashdeh, Ma'moun
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CHEMICAL reactors , *PISTONS , *CHEMICAL plants , *HIGH temperatures , *LITERATURE reviews - Abstract
To explore options for simple, safe, and compact chemical reactors that preserve wanted metastable initial products from sequential unwanted reactions, academic and industrial researchers have tried to repurpose reciprocating piston equipment or an "engine-like" design to be used as a chemical reactor. Piston reactors offer the benefit of achieving very high temperature and pressure conditions at very short and defined residence times. Such conditions offer promise for enhanced performance for several chemical conversions. This paper provides a review of the published literature and patents in the field of piston reactors to provide an overview of the current state-of-the-art. The review covers multiple aspects of piston reactors and their applications, reactor design options and their operation, catalyst and ignition placement, tested reactions, experimental setups as well as modeling and simulation. Several research gaps are highlighted as a motivation for future research in the field. To help interested readers into the topic, basic concepts and fundamentals of piston reactors are provided. [ABSTRACT FROM AUTHOR]
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- 2023
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327. Experimental study of roving configuration's influence on the flow field in a full-scale transparent pultrusion injection box.
- Author
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Hopmann, Christian, Wruck, Lorenz, Schneider, Daniel, and Fischer, Kai
- Subjects
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PULTRUSION , *FORCE & energy , *VOLATILE organic compounds - Abstract
Resin injection pultrusion gains increasing attention as it enables the use of highly reactive resins and resins sensitive to environmental conditions, while also decreasing the emission of harmful volatile organic compounds. Nevertheless, a comprehensive understanding of the flow field based on the geometric characteristics within open injection boxes is lacking due to a multitude of interdependent parameters. In this research, a novel setup for an experimental evaluation of the flow field in injection pultrusion practically is proposed. The setup consists of a full size, two-dimensionally tapered, transparent injection box that is installed within a pultrusion line and is operated with non-reactive fluids. Investigations are conducted with two different guide plate setups. Pulling forces and filling degree are evaluated for four pulling speeds, four fiber volume fractions and for four fluids. The non-reactive fluids are three grades of sucrose solution and Mesamoll with viscosities ranging from 13 to 246 mPa.s. Obtained pulling forces correlate linearly with the product of viscosity and pulling speed. Better fiber wettability properties and additional fiber guiding plates result in lower pulling forces. Backflow fill length displays an asymptotic correlation to pulling forces, indicating different governing mechanisms for these two phenomena. Backflow fill length corresponds directly with resin residence time, which ranges from about 10 to 3 min. The results indicate the possibility of manipulating pressure build-up and resin residence time separately, which would enable tailoring injection box cavity geometries systematically to a specific profile. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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328. Impact of winding parameters on the fiber bandwidth in the cylindrical area of a hydrogen pressure vessel for generating a digital twin.
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Hopmann, Christian, Magura, Nadine, Müller, Robert, Schneider, Daniel, and Fischer, Kai
- Subjects
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PRESSURE vessels , *FIBER-reinforced plastics , *BANDWIDTHS , *FIBERS , *BANDS (Musical groups) , *WIND power - Abstract
The wet winding process is an established manufacturing technology for the production of rotationally symmetrical components made of fiber‐reinforced plastic (FRP), such as type‐IV hydrogen pressure vessels. In this process, the FRP laminate is produced by continuously depositing an impregnated fiber band on the winding core in a winding pattern adapted to the component stress. Despite a long history of the process, there are shortcomings in the understanding of the process, without which further optimization in terms of cost and material efficiency will reach its limits in the future. Currently, the fiber band is assumed to have a constant rectangular cross‐section in most simulations, which neglects manufacturing influences such as fiber spreading. The investigations carried out aim to extend the process understanding by a realistic description of the fiber bandwidth when deposited on the winding core. The investigations show that the fiber spreading, as well as the absolute fiber bandwidth, depend on the resin loading and the fiber band tension, independent of the winding pattern in the cylindrical area of a pressure vessel shaped winding core. In addition, the fiber bandwidth changes by 15%–20% during circumferential winding, depending on the machine movement. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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329. Gingival phenotype assessment methods and classifications revisited: a preclinical study
- Author
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Giulio Rasperini, Kai R. Fischer, Patrick R. Schmidlin, Thomas Attin, Jasmin Büchel, Tiziano Testori, University of Zurich, and Fischer, Kai R
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Soft tissue thickness ,business.industry ,Dentistry ,Soft tissue ,610 Medicine & health ,Gingival phenotype ,Phenotype classification ,Predictive value ,Periodontal probe ,3500 General Dentistry ,Phenotype probe ,Periodontal morphotype ,Probe transparency ,Assessment methods ,10066 Clinic of Conservative and Preventive Dentistry ,Medicine ,Original Article ,Experience level ,business ,General Dentistry - Abstract
Objective To compare gingival phenotype assessment methods based on soft tissue transparency on different backgrounds and assessor experience levels. Methods For this purpose, 24 gingival specimens were retrieved from pig jaws with tissue thicknesses from 0.2 to 1.25 mm. Three methods were assessed: periodontal probe PCP12 (thin/thick), double-ended periodontal probe DBS12 (thin/moderate/thick) and colour-based phenotype probe CBP (thin/moderate/thick/very thick). Each sample was photographed with each probe underneath and categorized whether the probe was visible or not using different coloured backgrounds. To measure experience level influence, dentists, dental undergraduate students and laypersons (n = 10/group) performed the evaluation. Results PCP12 probe showed a threshold between 0.4 and 0.5 mm. To distinct between thin and moderate thick gingiva, a comparable range for DBS12 was found while moderate thickness was between 0.5 and 0.8 mm and for thick above 0.8 mm. CBP also showed a comparable threshold of 0.5 mm for thin versus moderate as compared with the other methods; above 0.8 mm, predominantly a very thick tissue was measured. In general, the background colour had a minor impact on PCP12 and DBS12, and investigator experience showed no clear influence on GP assessment. Conclusion Based on probe transparency and within the limitation of a preclinical study, we suggest GP differentiation into three entities: thin (< 0.5 mm; high risk), moderate (0.5–0.8 mm; medium risk) and thick (> 0.8 mm; low risk). Clinical relevance All three GP assessment methods are easy to perform and seem to have a high predictive value with a three entities classification for DBS12 and CBP.
- Published
- 2021
330. (Vapour+liquid+liquid) equilibria and excess molar enthalpies of binary and ternary mixtures of isopropanol, water, and propylene
- Author
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Grigiante, Maurizio, Stringari, Paolo, Scalabrin, Giancarlo, Ihmels, E. Christian, Fischer, Kai, and Gmehling, Jürgen
- Subjects
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PROPENE , *ISOPROPYL alcohol , *WATER , *CALORIMETERS - Abstract
Abstract: A static VLE apparatus has been used for the measurement of the (vapour+liquid+liquid) equilibrium of the (propylene+isopropanol+water) system at T =313.15K and pressures between (1.381 and 1.690)MPa. Using an isothermal flow calorimeter, values have been obtained for the binary system (isopropanol+water) over the temperature range from (313.15 to 353.15)K and pressures from (3.8 to 4.19)MPa. For the pseudo-binary mixture (propylene+(isopropanol+water)), values have been measured in the temperature range from (313.15 to 353.15)K and pressures from (1.997 to 5.89)MPa. This last mixture was studied starting from (isopropanol+water) at 0.25, 0.50, and 0.75 molar compositions in isopropanol. The new data, together with the available phase equilibrium and data from the literature, have been regressed by a conventional model reaching satisfactory results, except for the VLLE representation. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
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331. PSRK group contribution equation of state: comprehensive revision and extension IV, including critical constants and a-function parameters for 1000 components
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Horstmann, Sven, Jabloniec, Anna, Krafczyk, Jörg, Fischer, Kai, and Gmehling, Jürgen
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- *
MATHEMATICAL optimization , *MATHEMATICAL analysis , *MATHEMATICS , *EXPERIMENTAL design - Abstract
Abstract: As a part of an ongoing process, the predictive Soave¿Redlich¿Kwong (PSRK) group contribution equation of state was extended by the introduction of additional structural groups (F2, Cl2, Br2, HCN, NO2, CF4, O3 and ClNO) and fitting of the corresponding group interaction parameters. Interaction parameters between already existing main groups were also optimized to the growing literature data base. Overall, 75 new parameter sets are given herein, and typical results are presented for various systems. For the sake of completeness, not only the group new interaction parameters but all available PSRK/UNIFAC interaction parameter sets (more than 900) are given as supplementary material. Moreover, the required pure component properties (critical properties, acentric factors, and Mathias¿Copeman constants) were revised and are also included for about 1000 components. [Copyright &y& Elsevier]
- Published
- 2005
- Full Text
- View/download PDF
332. Alveolar ridge alterations after lateral guided bone regeneration with and without hyaluronic acid: a prospective randomized trial with morphometric and histomorphometric evaluation.
- Author
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Kauffmann F, Fickl S, Sculean A, Fischer KR, and Friedmann A
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- Male, Female, Humans, Animals, Cattle, Middle Aged, Hyaluronic Acid therapeutic use, Prospective Studies, Bone Regeneration, Alveolar Process, Collagen therapeutic use, Bone Substitutes therapeutic use, Alveolar Ridge Augmentation methods
- Abstract
Objective: To clinically and histologically evaluate the potential effect of a cross-linked, high molecular weight hyaluronic acid (xHyA) on the outcomes of guided bone regeneration performed with a demineralized bovine bone mineral (DBBM) covered with a natural collagen membrane., Method and Materials: Eleven patients (eight females and three males, mean age 53 years) with a total of 27 surgical sites were treated. Treatments were performed with either DBBM and natural collagen membrane fixed with tacks (group A) or DBBM mixed with xHyA and subsequently covered with natural collagen membrane (group B). Clinical evaluations were made at baseline (T1), immediately after guided bone regeneration (T2), and at the time of implant placement (T3). Additionally, at the time of implant placement, core biopsies were retrieved and submitted for histologic analysis., Results: Healing was uneventful in all cases. At 6 months, group B revealed a statistically significantly higher crestal ridge dimension compared to group A (P = .007). The histologic analysis revealed a tendency for greater mineralized tissue formation in group B compared to group A (67.5% versus 41.6%) and contained a higher amount of new bone (37.2%) and less DBBM residues (20.9%) than group A (12.8% new bone and 28.8% DBBM residues, respectively)., Conclusions: Within their limits, the present data indicate that, during guided bone regeneration with natural collagen membrane, the combination of DBBM and xHyA may improve the quality and quantity of bone formed with DBBM alone.
- Published
- 2023
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333. Properties of three collagen scaffolds in comparison with native connective tissue: an in-vitro study.
- Author
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Solderer A, Widmer N, Gubler A, Fischer KR, Hicklin SP, and Schmidlin PR
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- Swine, Animals, Collagen pharmacology, Collagen chemistry, Connective Tissue, Collagenases, Tissue Scaffolds chemistry, Acellular Dermis
- Abstract
Purpose: To evaluate collagen scaffolds (CS) in terms of their in vitro resorption behavior, surface structure, swelling behavior, and mechanical properties in physiologically simulated environments, compared with porcine native connective tissue., Materials and Methods: Three test materials-one porcine collagen matrix (p-CM), two acellular dermal matrices (porcine = p-ADM, allogenic = a-ADM)-and porcine native connective tissue (p-CTG) as a control material were examined for resorption in four solutions using a high-precision scale. The solutions were artificial saliva (AS) and simulated body fluid (SBF), both with and without collagenase (0.5 U/ml at 37 °C). In addition, the surface structures of CS were analyzed using a scanning electron microscope (SEM) before and after exposure to AS or SBF. The swelling behavior of CS was evaluated by measuring volume change and liquid absorption capacity in phosphate-buffered saline (PBS). Finally, the mechanical properties of CS and p-CTG were investigated using cyclic compression testing in PBS., Results: Solutions containing collagenase demonstrated high resorption rates with significant differences (p < 0.04) between the tested materials after 4 h, 8 h and 24 h, ranging from 54.1 to 100% after 24 h. SEM images revealed cross-linked collagen structures in all untreated specimens. Unlike a-ADM, the scaffolds of p-CM and p-ADM displayed a flake-like structure. The swelling ratio and fluid absorption capacity per area ranged from 13.4 to 25.5% among the test materials and showed following pattern: p-CM > a-ADM > p-ADM. P-CM exhibited higher elastic properties than p-ADM, whereas a-ADM, like p-CTG, were barely compressible and lost structural integrity under increasing pressure., Conclusions and Clinical Implications: Collagen scaffolds vary significantly in their physical properties, such as resorption and swelling behavior and elastic properties, depending on their microstructure and composition. When clinically applied, these differences should be taken into consideration to achieve the desired outcomes., (© 2023. Deutsche Gesellschaft für Implantologie im Zahn‐, Mund‐ und Kieferbereich e.V., Japanese Society of Oral Implantology.)
- Published
- 2023
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334. Nonsurgical cleaning potential of deep-threaded implants and titanium particle release: A novel in vitro tissue model.
- Author
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Fischer KR, Büchel J, Gubler A, Liu CC, Sahrmann P, and Schmidlin PR
- Subjects
- Animals, Swine, Titanium, Powders, Surface Properties, Dental Scaling, Microscopy, Electron, Scanning, Dental Implants
- Abstract
Objectives: To measure the efficiency of three cleaning modalities on two implant designs with similar diameters but different thread depths as well as the presence of titanium particles., Methods: Sixty dyed implants (30 × 4.8 apically tapered (ATAP) and 30 × 5.0 fully tapered (FTAP)) were fixed in plastic models. The horizontal bone defects were surrounded with porcine soft tissue. Three instrumentation modalities were used to clean for 150 s: Curette (CUR), ultrasonic scaler (US), and air powder waterjet device (APWJ) with erythritol powder. Afterward, implants were photographed and scanning electron microscopic (SEM) images were taken. Titanium in the soft tissues was quantified in dissolved samples and histologically confirmed., Results: For ATAP and FTAP implants, the percentage of the cleaned surface was 26.4 ± 3.0 and 17.1 ± 2.4% for CUR, 33.7 ± 3.8% and 28.1 ± 2.3% for US, and 45.5 ± 4.1% and 24.7 ± 3.8% for APWJ, respectively. SEM images showed significant implant surface changes, especially after instrumentation with CUR and US, whereas APWJ had little to no effect. Most titanium residues were found after cleaning ATAP implants with CUR (152.0 ± 75.5), followed by US (89.5 ± 73.8) and APWJ (0.3 ± 0.8). For the FTAP implants, respective values accounted for 129.5 ± 58.6 μg and 67.0 ± 14.4 μg for CUR and US, respectively. No titanium residues were detected on ATAP with APWJ., Conclusion: Based on in vitro data, erythritol-powered APWJ still appears to be the most efficient and gentle cleaning method. All three instruments, however, were found to have unprocessed areas depending on different implant designs, hence, clinical relevance for non-surgical approaches remains challenging and warrants further improvement., (© 2023 The Authors. Clinical Oral Implants Research published by John Wiley & Sons Ltd.)
- Published
- 2023
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- View/download PDF
335. Soft tissue-related complications around anterior implants: commentary and clinical checklist.
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Fischer KR, Scaini R, Chackartchi T, Solderer A, Schmidlin PR, and Testori T
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- Humans, Checklist, Esthetics, Dental, Dental Implants, Dental Implants, Single-Tooth
- Abstract
Implant-based rehabilitation is a clinical challenge, especially in the esthetic area. Numerous factors influence the outcome of the rehabilitation; however, the two main factors are the bone and soft-tissue deficiencies at the intended implant site. Peri-implant soft tissue complications can arise from a combination of factors that can be summarized as two categories: diagnostic errors and surgical planning management errors. Most of the complications can be corrected after each step of the treatment and even after the delivery of the prosthetic restoration with adequate soft tissue management in order to give the patient an esthetically pleasing outcome. The aims of this article were: to present the current literature, to propose a clinical checklist to guide clinicians in evaluating the prognosis of the treatment utilizing soft tissue grafting, and to illustrate a case series partially employing the proposed clinical checklist. The proposed checklist could be helpful in evaluating the prognosis of the treatment utilizing only soft tissue grafting. In clinical cases in which the prognosis is classified as good, soft tissue management could be a viable treatment option before attempting more radical procedures like implant removal.
- Published
- 2023
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336. Enamel Matrix Derivatives as an Adjunct to Alveolar Ridge Preservation-A Systematic Review.
- Author
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Fakheran O, Fischer KR, and Schmidlin PR
- Abstract
Purpose: To systematically assess the current evidence regarding the adjunctive application of enamel matrix derivatives (EMDs) during alveolar ridge preservation (ARP) following tooth extraction., Methods: A comprehensive literature search was conducted in MEDLINE, Cochrane Library, PsycINFO, Web of Science, Google Scholar, and Scopus to identify relevant randomized controlled clinical trials (RCTs). The primary outcome parameters of this systematic review were histomorphometric and radiographic data; secondary outcomes were the feasibility of implant placement after ARP as well as patient-related outcomes such as postoperative discomfort., Results: The search identified 436 eligible articles published from 2011 to 2022, but only five were ultimately included for data extraction (146 patients). Given the substantial heterogeneity among the included studies, no meta-analysis could be performed. The authors' qualitative analysis showed marginally improved outcomes regarding an increased percentage of new bone formation after tooth extraction and a reduction in postoperative discomfort., Conclusions: Given the potential value of EMDs in other fields of regenerative dentistry, more consideration should be given to EMDs as an adjunctive treatment option in ARP. However, more well-controlled randomized clinical trials are necessary to evaluate the exact potential and impacts of EMDs.
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- 2023
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337. Bone envelope for implant placement after alveolar ridge preservation: a systematic review and meta-analysis.
- Author
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Fischer KR, Solderer A, Arlt K, Heumann C, Liu CC, and Schmidlin PR
- Subjects
- Animals, Cattle, Humans, Alveolar Process surgery, Dental Implants, Bone Resorption, Alveolar Ridge Augmentation, Health Status
- Abstract
Purpose: To assess the dimensional establishment of a bony envelope after alveolar ridge preservation (ARP) with deproteinized bovine bone mineral (DBBM) in order to estimate the surgical feasibility of standard diameter implants placement without any additional augmentation methods., Methods: PubMed, Embase and CENTRAL databases were searched for suitable titles and abstracts using PICO elements. Inclusion criteria were as follows: randomized controlled trials (RCTs) comprising at least ten systemically healthy patients; test groups comprised placement of (collagenated) DBBM w/o membrane and control groups of no grafting, respectively. Selected abstracts were checked regarding their suitability, followed by full-text screening and subsequent statistical data analysis. Probabilities and number needed to treat (NNT) for implant placement without any further need of bone graft were calculated., Results: The initial database search identified 2583 studies. Finally, nine studies with a total of 177 implants placed after ARP with DBBM and 130 implants after SH were included for the quantitative and qualitative evaluation. A mean difference of 1.13 mm in ridge width in favour of ARP with DBBM could be calculated throughout all included studies (95% CI 0.28-1.98, t2 = 1-1063, I2 = 68.0%, p < 0.01). Probabilities for implant placement with 2 mm surrounding bone requiring theoretically no further bone augmentation ranged from 6 to 19% depending on implant diameter (3.25: 19%, RD = 0.19, C = 0.06-0.32, p < 0.01/4.0: 14%, RD = 0.14, C = 0.05-0.23, p < 0.01/5.0: 6%, RD = 0.06, C = 0.00-0.12, p = 0.06)., Conclusion: ARP employing DBBM reduces ridge shrinkage on average by 1.13 mm and improves the possibility to place standard diameter implants with up to 2 mm circumferential bone housing; however, no ARP would have been necessary or additional augmentative bone interventions are still required in 4 out of 5 cases., (© 2022. The Author(s).)
- Published
- 2022
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338. What cannot be cured must be endured: The long-lasting effect of a COVID-19 infection on workplace productivity.
- Author
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Fischer K, Reade JJ, and Schmal WB
- Abstract
The COVID-19 pandemic has triggered economic shock waves across the globe. Exploiting a natural experiment, this paper estimates how being infected with the virus shapes individual-level productivity after having recovered. Studying the performance of professional athletes in Germany and Italy and applying a staggered difference-in-differences design, we find that individual performance drops by around 6 percent after a previously infected athlete returns to the pitch. This striking deterioration remains persistent over time - amounting to 5% eight months after the infection. The effect increases with age and infection severity, and is spread disproportionally over the course of a match. We detect no productivity effects for other respiratory infections. We take these findings as first evidence that the pandemic might cause long-lasting effects on worker productivity and economic growth., Competing Interests: None., (© 2022 Elsevier B.V. All rights reserved.)
- Published
- 2022
- Full Text
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339. The effectiveness of adjunctive measures in managing peri-implant mucositis: an umbrella review.
- Author
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Chuachamsai S, Acharya A, Fischer K, Nibali L, Ho D, and Pelekos G
- Subjects
- Dental Care, Humans, MEDLINE, Systematic Reviews as Topic, Mucositis, Peri-Implantitis
- Abstract
Objectives: The purpose of this umbrella review was to gather and summarize the data from published systematic reviews (SRs) that compared non-surgical mechanical debridement (NSMD) with and without the use of adjunctive treatments on the management of peri-implant mucositis (PIM)., Materials and Methods: A protocol was developed and registered in PROSPERO (CRD42021254350) before the systematic search for the SRs. Seven electronic databases, including Cochrane Library, Embase (via Ovid), MEDLINE (via Pubmed), Proquest, Prospero, Scopus and Web of Science, were searched for published reviews. The search for unpublished and informally published reviews was further attempted in the last four databases. The methodological quality of the included reviews was assessed using AMSTAR 2., Results: Twelve included SRs assessed clinical studies published between 2014 and 2020, including a total of seventeen primary clinical trials. All SRs summarized data from individual studies and provided a narrative conclusion regarding the effectiveness of the adjunctive treatments. Only six SRs performed a meta-analysis (MA) of additional benefits of the adjunctive therapy for PIM, with results indicating no significant difference between the different treatment modalities. The overall confidence was adjudged ranging from critically low to low using AMSTAR 2 and significant additional benefits of any adjunctive treatments in comparison with NSMD were not apparent., Conclusion: Overall, the reviewed evidence did not support the use of adjunctive treatments for improvement of clinical outcomes in PM management as compared to NSMD alone., (© 2022. The Author(s).)
- Published
- 2022
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340. Horizontal Augmentation of Chronic Mandibular Defects by the Guided Bone Regeneration Approach: A Randomized Study in Dogs.
- Author
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Friedmann A, Fickl S, Fischer KR, Dalloul M, Goetz W, and Kauffmann F
- Abstract
Various biomaterial combinations have been studied focusing on their ability to stabilize blood clots and maintain space under soft tissue to support new bone formation. A popular combination is Deproteinized Bovine Bone Mineral (DBBM) placed with a native collagen membrane (NCM) tacked to native bone. In this study, we compared the outcome of this treatment option to those achieved with three different graft/membrane combinations with respect to total newly occupied area and the mineralized compound inside. After bi-lateral extraction of two mandibular premolars in five adult beagles L-shaped alveolar defects were created. A total of 20 defects healed for 6 weeks resulting in chronic type bone defects. At baseline, four options were randomly allocated to five defects each: a. DBBM + NCM with a four-pin fixation across the ridge; b. DBBM + RCLC (ribose cross-linked collagen membrane); c. DBBM + NPPM (native porcine pericardium membrane); and d. Ca-sulfate (CS) + RCLC membrane. Membranes in b/c/d were not fixed; complete tensionless wound closure was achieved by CAF. Termination after 3 months and sampling followed, and non-decalcified processing and toluidine blue staining were applied. Microscopic images obtained at standardized magnification were histomorphometrically assessed by ImageJ software (NIH). An ANOVA post hoc test was applied; histomorphometric data are presented in this paper as medians and interquartile ranges (IRs). All sites healed uneventfully, all sites were sampled and block separation followed before Technovit embedding. Two central sections per block for each group were included. Two of five specimen were lost due to processing error and were excluded from group b. New bone area was significantly greater for option b. compared to a. ( p = 0.001), c. ( p = 0.002), and d. ( p = 0.046). Residual non-bone graft area was significantly less for option d. compared to a. ( p = 0.026) or c. ( p = 0.021). We conclude that collagen membranes with a prolonged resorption/barrier profile combined with bone substitutes featuring different degradation profiles sufficiently support new bone formation. Tacking strategy/membrane fixation appears redundant when using these biomaterials.
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- 2021
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341. Assessing the links between childhood trauma, C-reactive protein and response to antidepressant treatment in patients with affective disorders.
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Fischer KF, Simon MS, Elsner J, Dobmeier J, Dorr J, Blei L, Zill P, Obermeier M, and Musil R
- Subjects
- Biomarkers blood, Case-Control Studies, Depressive Disorder, Treatment-Resistant, Humans, Treatment Outcome, Adverse Childhood Experiences, Antidepressive Agents therapeutic use, Bipolar Disorder blood, Bipolar Disorder drug therapy, C-Reactive Protein analysis, Depressive Disorder blood, Depressive Disorder drug therapy
- Abstract
Adverse Childhood Experiences (ACE) are a well-known risk-factor for depression. Additionally, (high-sensitive) C-reactive Protein (hsCRP) is elevated in subgroups of depressed patients and high following ACE. In this context the literature considers hsCRP and ACE to be associated with treatment resistant depression. With the data being heterogenous, this study aimed to explore the associations of ACE, hsCRP levels and response to antidepressant treatment in uni- and bipolar depression. N = 76 patients diagnosed with uni- or bipolar depression and N = 53 healthy controls were included. Treatment was over 6 weeks in an inpatient psychiatric setting within an observatory study design. Depressive symptoms were assessed by the Montgomery-Asberg Depression Rating Scale (MADRS), ACE were assessed by the Childhood Trauma Questionnaire (CTQ); the body-mass-index (BMI) and hsCRP were measured. HsCRP levels did not differ between the study population and the healthy controls. While the depressive symptoms decreased, the hsCRP levels increased. Sexual abuse was associated with significant higher and emotional abuse with lower levels of hsCRP after 6 weeks. The baseline hsCRP levels and the ACE subgroups did not show significant associations with the treatment response in unipolar depressed patients. The long-lasting effects of specific forms of ACE may have relevant impact on inflammation, supporting hsCRP to be a suitable biomarker. With ACE and hsCRP not showing any significant associations with treatment response in the unipolar depressed subgroup, a more differentiate research concerning biomarkers and treatment regimens is needed when talking about treatment response., (© 2021. The Author(s).)
- Published
- 2021
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342. Gingival phenotype assessment methods and classifications revisited: a preclinical study.
- Author
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Fischer KR, Büchel J, Testori T, Rasperini G, Attin T, and Schmidlin P
- Subjects
- Animals, Cell Differentiation, Humans, Microsurgery, Phenotype, Swine, Gingiva, Maxilla
- Abstract
Objective: To compare gingival phenotype assessment methods based on soft tissue transparency on different backgrounds and assessor experience levels., Methods: For this purpose, 24 gingival specimens were retrieved from pig jaws with tissue thicknesses from 0.2 to 1.25 mm. Three methods were assessed: periodontal probe PCP12 (thin/thick), double-ended periodontal probe DBS12 (thin/moderate/thick) and colour-based phenotype probe CBP (thin/moderate/thick/very thick). Each sample was photographed with each probe underneath and categorized whether the probe was visible or not using different coloured backgrounds. To measure experience level influence, dentists, dental undergraduate students and laypersons (n = 10/group) performed the evaluation., Results: PCP12 probe showed a threshold between 0.4 and 0.5 mm. To distinct between thin and moderate thick gingiva, a comparable range for DBS12 was found while moderate thickness was between 0.5 and 0.8 mm and for thick above 0.8 mm. CBP also showed a comparable threshold of 0.5 mm for thin versus moderate as compared with the other methods; above 0.8 mm, predominantly a very thick tissue was measured. In general, the background colour had a minor impact on PCP12 and DBS12, and investigator experience showed no clear influence on GP assessment., Conclusion: Based on probe transparency and within the limitation of a preclinical study, we suggest GP differentiation into three entities: thin (< 0.5 mm; high risk), moderate (0.5-0.8 mm; medium risk) and thick (> 0.8 mm; low risk)., Clinical Relevance: All three GP assessment methods are easy to perform and seem to have a high predictive value with a three entities classification for DBS12 and CBP., (© 2021. The Author(s).)
- Published
- 2021
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343. [Level of personality functioning and attachment style as predictors of the successful referral to outpatient psychotherapy].
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Nikendei C, Mölle C, Fischer K, Granov M, Huber J, Dinger U, Herzog W, Schauenburg H, and Ehrenthal JC
- Subjects
- Humans, Prognosis, Treatment Outcome, Mental Disorders psychology, Mental Disorders therapy, Object Attachment, Outpatients psychology, Personality, Psychotherapy, Quality of Life, Referral and Consultation standards
- Abstract
Level of personality functioning and attachment style as predictors of the successful referral to outpatient psychotherapy Objectives: Outpatient psychotherapy is a key element in the effective treatment of mental health problems. First results suggest that interpersonal problems lead to difficulties in receiving outpatient psychotherapeutic treatment. The relationship between these difficulties, attachment style, and the level of personality functioning is still unclear. Methods: We invited 1011 patients of a psychosomatic-psychotherapeutic university outpatient clinic to participate in the study. The clinical diagnoses according to ICD-10, as well as symptoms of depression (PHQ-D), and quality of life (SF-36) were recorded. Hypothesized predictors for the successful referral to outpatient therapy were patient age, availability of local outpatient treatment, number of ICD-10 diagnoses, the motivation for psychotherapy (FPTM), fear of stigmatization (Stig-9), level of personality functioning (OPD-SQ), and attachment style (ECR-RD). Results: We were able to catamnestically reassess n = 300 patients (67.3 % of patients initially referred to outpatient therapy). A smaller number of clinical diagnoses, greater availability of psychotherapeutic care and higher therapy motivation, as well as a lower level of personality functioning predicted the successful referral to outpatient psychotherapy, while the combination of impaired personality functioning and avoidant attachment style was a negative predictor. Conclusions: Contrary to expectations, patients with a lower level of personality functioning are more successful in receiving outpatient psychotherapy. However, patients with a combination of impaired personality functioning and a high degree of attachment avoidance run the risk of not asserting their need for treatment.
- Published
- 2020
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344. Dimensional Evaluation of Different Ridge Preservation Techniques with a Bovine Xenograft: A Randomized Controlled Clinical Trial.
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Fischer KR, Mühlemann S, Jung RE, Friedmann A, and Fickl S
- Subjects
- Adolescent, Adult, Aged, Aged, 80 and over, Alveolar Bone Loss surgery, Alveolar Bone Loss therapy, Animals, Bone Density, Bone Substitutes therapeutic use, Cattle, Collagen therapeutic use, Dental Implantation, Endosseous, Dental Materials therapeutic use, Female, Humans, Male, Materials Testing, Maxilla surgery, Membranes, Artificial, Middle Aged, Prospective Studies, Tooth surgery, Tooth Extraction, Treatment Outcome, Young Adult, Alveolar Ridge Augmentation methods, Bone Transplantation methods, Dental Implants, Heterografts transplantation, Tooth Socket surgery, Transplantation, Heterologous methods
- Abstract
The objectives of this study were to determine the quantitative changes after different ridge preservation techniques (primary aim) and to assess the possibility of placing a dental implant, the bone quality, and the need for bone augmentation (secondary aim). A total of 35 patients who required extraction of at least one tooth (incisor, canine, or premolar) provided 35 single-gap extraction sites. After minimally invasive tooth removal, the sockets were randomly scheduled for one of four treatment modalities: placement of a deproteinized bovine bone mineral (DBBM; Endobon, Biomet 3i) covered with a soft tissue punch from the palate (T1); placement of DBBM alone (T2); placement of DBBM covered with a resorbable collagen membrane (OsseoGuard, Biomet 3i) (T3); or no additional treatment (T4). Silicone impressions were taken before and 6 months after extraction for quantitative-volumetric evaluation (primary outcome). The possibility of placing an implant, bone quality, and need for further bone augmentation were also noted (secondary outcomes). During the study period, no adverse events were observed. No statistically significant difference was found between the four treatments regarding the primary and secondary outcome parameters (P > .05). However, T4 showed double the buccal contour change, with the highest variance compared to the other three groups (T1 -0.874 ± 0.713; T2 -0.968 ± 0.344; T3 -1.26 ± 0.942; T4 -2.15 ± 1.349). Although no statistically significant difference was found between the four treatment modalities, placement of DBBM resulted in only half the contour change (< 1 mm) compared to control sites (> 2 mm). Ridge preservation with a DBBM with or without soft tissue punch should be considered in esthetically demanding cases and delayed or late implant placement.
- Published
- 2018
- Full Text
- View/download PDF
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