74 research outputs found
Ueber geometrische Gesteinsanalysen : ein einfacher Weg zur ziffernmÀssigen Feststellung des QuantitÀtsverhÀltnisses der Mineralbestandtheile gemengter Gesteine
Electrochemical Disinfection of Dental Implants Experimentally Contaminated with Microorganisms as a Model for Periimplantitis
Despite several methods having been described for disinfecting implants affected by
periimplantitis, none of these are universally effective and may even alter surfaces and mechanical
properties of implants. Boron-doped diamond (BDD) electrodes were fabricated from niobium wires
and assembled as a single instrument for implant cleaning. Chemo-mechanical debridement and
air abrasion were used as control methods. Different mono-species biofilms, formed by bacteria
and yeasts, were allowed to develop in rich medium at 37 âŠC for three days. In addition, natural
multi-species biofilms were treated. Implants were placed in silicone, polyurethane foam and bovine
ribs for simulating different clinical conditions. Following treatment, the implants were rolled on
blood agar plates, which were subsequently incubated at 37 âŠC and microbial growth was analyzed.
Complete electrochemical disinfection of implant surfaces was achieved with a maximum treatment
time of 20 min for Candida albicans, Candida dubliniensis, Enterococcus faecalis, Roseomonas mucosa,
Staphylococcus epidermidis and Streptococcus sanguinis, while in case of spore-forming Bacillus pumilus
and Bacillus subtilis, a number of colonies appeared after BDD electrode treatment indicating an
incomplete disinfection. Independent of the species tested, complete disinfection was never achieved
when conventional techniques were used. During treatment with BDD electrodes, only minor changes
in temperature and pH value were observed. The instrument used here requires optimization so that
higher charge quantities can be applied in shorter treatment timesITI Foundation, Switzerlan
Pilot Study on the Use of a Laser-Structured Double Diamond Electrode (DDE) for Biofilm Removal from Dental Implant Surfaces
No proper treatment option for peri-implantitis exists yet. Based on previous studies
showing the in vitro effectiveness of electrochemical disinfection using boron-doped diamond
electrodes, novel double diamond electrodes (DDE) were tested here. Using a ceramic carrier and
a laser structuring process, a clinically applicable electrode array was manufactured. Roughened
metal discs (n = 24) made from Ti-Zr alloy were exposed to the oral cavities of six volunteers for
24 h in order to generate biofilm. Then, biofilm removal was carried out either using plastic curettes
and chlorhexidine digluconate or electrochemical disinfection. In addition, dental implants were
contaminated with ex vivo multispecies biofilm and disinfected using DDE treatment. Bacterial growth
and the formation of biofilm polymer were determined as outcome measures. Chemo-mechanical
treatment could not eliminate bacteria from roughened surfaces, while in most cases, a massive
reduction of bacteria and biofilm polymer was observed following DDE treatment. Electrochemical
disinfection was charge- and time-dependent and could also not reach complete disinfection in
all instances. Implant threads had no negative effect on DDE treatment. Bacteria exhibit varying
resistance to electrochemical disinfection with Bacillus subtilis, Neisseria sp., Rothia mucilaginosa,
Staphylococcus haemolyticus, and Streptococcus mitis surviving 5 min of DDE application at 6 V.
Electrochemical disinfection is promising but requires further optimization with respect to charge
quantity and application time in order to achieve disinfection without harming host tissue
Preclinical Testing of Boron-Doped Diamond Electrodes for Root Canal DisinfectionâA Series of Preliminary Studies
While numerous approaches have meanwhile been described, sufficient disinfection of root
canals is still challenging, mostly due to limited access and the porous structure of dentin. Instead of
using different rinsing solutions and activated irrigation, the electrolysis of saline using boron-doped
diamond (BDD) electrodes thereby producing reactive oxygen species may be an alternative approach.
In a first step, experiments using extracted human teeth incubated with multispecies bacterial biofilm
were conducted. The charge quantities required for electrochemical disinfection of root canals were
determined, which were subsequently applied in an animal trial using an intraoral canine model. It
could be shown that also under realistic clinical conditions, predictable disinfection of root canals
could be achieved using BDD electrodes. The parameters required are in the range of 5.5 to 7.0 V and
9 to 38 mA, applied for 2.5 to 6.0 min with approximately 5 to 8 mL of saline. The direct generation
of disinfective agents inside the root canal seems to be advantageous especially in situations with
compromised access and limited canal sizes. The biologic effect with respect to the host reaction on
BDD-mediated disinfection is yet to be examined
Electrochemical Disinfection of Experimentally Infected Teeth by Boron-Doped Diamond Electrode Treatment
Disinfection and prevention of re-infection are the decisive treatment steps in endodontic therapy. In this study, boron-doped diamond (BDD) electrodes have been fabricated and used for disinfecting the root canals of extracted human teeth, which had been covered with bacterial biofilms formed by Bacillus subtilis and Staphylococcus epidermidis. The growth of B. subtilis could be successfully impaired, achieving a complete disinfection after 8.5 min treatment time with the success of disinfection depending on the insertion depth of the electrode in the root canal. S. epidermidis could completely be removed after 3.5 min treatment time. A clinically applicable electrode array led to complete disinfection after treatment times of 10 min for S. epidermidis and 25 min for B. subtilis. BDD electrode application allowed for the improved disinfection of root canals and dentin tubules based on a continuous production of reactive oxygen species and their enhanced penetration of dentin tubules most likely due the formation of a continuous stream of small gas bubbles. The treatment times that are required here will be shortened in clinical application, as mechanical shaping of the canal system would precede the disinfection process
Root Canal Obturation by Electrochemical Precipitation of Calcium Phosphates
Achieving adequate disinfection and preventing reinfection is the major goal in endodontic
treatment. Variation in canal morphology and open porosity of dentine prevents achieving complete
disinfection. Questionable biocompatibility of materials as well as a lack of sealing ability questions
the usefulness of current obturation methods. With a novel disinfection approach based on the
use of boron-doped diamond (BDD) electrodes having shown promising results it was the goal
of this series of experiments to investigate the possibility of BDD-mediated in situ forming of a
biocompatible obturation material. A combination of calcium phosphate and maleic acid was used
as precursor solution while Ion Chromatography Mass Spectrometry (IC-MS), Raman spectroscopy
(RAMAN), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron
microscopy (SEM), dye penetration and micro-computed tomography (”CT) were applied for characterizing the precipitate. It was possible to achieve a BDD-mediated precipitation of brushite in a
clinically applicable timeframe. However, tight sealing of the canal system based on brushite could
not be achieved
Avoiding Pitfalls in Comparison of Activity and Selectivity of Solid Catalysts for Electrochemical HMF Oxidation
Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) offers a renewable approach to produce the value-added platform chemical 2,5-furandicarboxylic acid (FDCA). The key for the economic viability of this approach is to develop active and selective electrocatalysts. Nevertheless, a reliable catalyst evaluation protocol is still missing, leading to elusive conclusions on criteria for a high-performing catalyst. Herein, we demonstrate that besides the catalyst identity, secondary parameters such as materials of conductive substrates for the working electrode, concentration of the supporting electrolyte, and electrolyzer configurations have profound impact on the catalyst performance and thus need to be optimized before assessing the true activity of a catalyst. Moreover, we highlight the importance of those secondary parameters in suppressing side reactions, which has long been overlooked. The protocol is validated by evaluating the performance of free-standing Cu-foam, and CuCoO modified with NaPO2H2 and Ni, which were immobilized on boron-doped diamond (BDD) electrodes. Recommended practices and figure of merits in carefully evaluating the catalyst performance are proposed. © 2021 The Authors. Published by The Chemical Society of Japan & Wiley-VCH Gmb
Avoiding Pitfalls in Comparison of Activity and Selectivity of Solid Catalysts for Electrochemical HMF Oxidation
Electrocatalytic oxidation of 5âhydroxymethylfurfural (HMF) offers a renewable approach to produce the valueâadded platform chemical 2,5âfurandicarboxylic acid (FDCA). The key for the economic viability of this approach is to develop active and selective electrocatalysts. Nevertheless, a reliable catalyst evaluation protocol is still missing, leading to elusive conclusions on criteria for a highâperforming catalyst. Herein, we demonstrate that besides the catalyst identity, secondary parameters such as materials of conductive substrates for the working electrode, concentration of the supporting electrolyte, and electrolyzer configurations have profound impact on the catalyst performance and thus need to be optimized before assessing the true activity of a catalyst. Moreover, we highlight the importance of those secondary parameters in suppressing side reactions, which has long been overlooked. The protocol is validated by evaluating the performance of freeâstanding Cuâfoam, and CuCoO modified with NaPOâHâ and Ni, which were immobilized on boronâdoped diamond (BDD) electrodes. Recommended practices and figure of merits in carefully evaluating the catalyst performance are proposed
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