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- ItemFirst insights on plasma orthodontics - Application of cold atmospheric pressure plasma to enhance the bond strength of orthodontic brackets(Amsterdam [u.a.] : Elsevier, 2016) Metelmann, Philine H.; Quooß, Alexandra; Woedtke, Thomas von; Krey, Karl-FriedrichObjective: The development of an ideal adhesive system has long been subject of research. Recent studies show that treatment with cold atmospheric pressure plasma (CAP) positively affects the bonding properties of enamel. Conditioning with CAP could therefore improve the mechanical and physical properties of bracket adhesives, e.g. Glass ionomer cement (GIC). Material and methods: Laser-structured brackets (Dentaurum, Ispringen) were bonded onto 60 bovine mandibular incisors using different orthodontic adhesives. For 20 specimens FujiOrthoLC (GC America Corp, Alsip, USA) was used according to manufacturer's instructions. Another 20 specimens received a 60 s CAP-treatment (kINPen med, Neoplas tool, Greifswald, Germany) before bracket bonding, of which 10 were re-moistened before applying FujiOrthoLC and 10 remained dry. Onto 20 specimens, brackets were bonded with the Composite Transbond XT (3M/Unitek, St. Paul, USA) following manufacturer's instructions. The shear bond strength of brackets on the teeth was determined with the universal testing machine Zwick BZ050/TH3A (Zwick, Ulm, Germany). Results: Brackets bonded with FujiOrthoLC in standard method, showed average shear bond strength of 5.58±0.46 MPa. Specimens treated with plasma showed clinically unacceptable adhesion values (re-moistened group: 2.79±0.38 MPa, dry group: 1.01±0.2 MPa). Bonding onto dried out teeth also led to spontaneous bracket losses (4 of 10 specimens). The composite group (Transbond XT) showed clinically acceptable adhesion values (7.9±1.03 MPa). Conclusions: Despite promising potential, surface conditioning with CAP could not improve the adhesive properties of GIC. By contrast, a decrease in shear bond strength was noticed after CAP treatment. Further investigations have to show whether it is possible to increase the retention values of other orthodontic adhesives by CAP application and thus take advantage of positive characteristics and reduce side effects.
- ItemCold physical plasma-induced oxidation of cysteine yields reactive sulfur species (RSS)(Amsterdam [u.a.] : Elsevier, 2019) Bruno, Giuliana; Heusler, Thea; Lackmann, Jan-Wilm; Woedtke, Thomas von; Weltmann, Klaus-Dieter; Wende, KristianPurpose: Studying plasma liquid chemistry can reveal insights into their biomedical effects, i.e. to understand the direct and indirect processes triggered by the treatment in a model or clinical application. Due to the reactivity of the sulfur atom, thiols are potential targets for plasma- derived reactive species. Being crucial for protein function and redox signaling pathways, their controllable modification would allow expanding the application range. Additionally, models to control and standardize CAP sources are desired tools for plasma source design. Methods: Cysteine, a ubiquitous amino acid, was used as a tracer compound to scavenge the reactive species produced by an argon plasma jet (kINPen). The resulting product pattern was identified via high-resolution mass spectrometry. The Ellman´s assay was used to screen CAP derived thiol consumption, and long-lived species deposition (hydrogen peroxide, nitrite, nitrate) was monitored in relation to the presence of cysteine. Results: The intensity of cysteine oxidation increased with treatment time and availability of oxygen in the feed gas. A range of products from cysteine was identified, in part indicative for certain treatment conditions. Several non-stable products occur transiently during the plasma treatment. Bioactive reactive sulfur species (RSS) have been found for mild treatment conditions, such as cysteine sulfoxides and cysteine-S-sulfonate. Considering the number of cysteine molecules in the boundary layer and the achieved oxidation state, short-lived species dominate in cysteine conversion. In addition, a boundary layer depletion of the tracer was observed. Conclusion: Translating these data into the in-vivo application, strong direct oxidation of protein thiol groups with subsequent changes in protein biochemistry must be considered. Plasma-derived RSS may in part contribute to the observed biomedical effects of CAP. Care must be taken to control the discharge parameter tightly as chemical dynamics at or in the liquid are subject to change easily. © 2019