19 research outputs found

    Polyoxymethylene as Material for Removable Partial Dentures—A Literature Review and Illustrating Case Report

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    Compared to thermoplastic manufacturing techniques, computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies make it easier to process modern restorative and prosthetic materials with improved material properties. In dentistry, tooth-colored alternatives to metal-based frameworks for application in removable dental prostheses (RDP) emerged. With regard to this aspect, the current article provides an overview of the specific material properties of polyoxymethylene (POM). Furthermore, it reviews scientific literature indexed in PubMed and Web of Science that focuses on RDPs fabricated from POM within the last 10 years. Finally, a prosthetic rehabilitation of a patient with a RDP fabricated from POM is illustrated and observations during a follow-up over 10 months are described. Scientific data and clinical observations indicate that polyoxymethylene is a promising material that bridges gaps in dental therapeutic options. While survival time may be limited due to wear, POM might be a favorable option for application in semi-permanent restorations

    Is Micro X-ray Computer Tomography a Suitable Non-Destructive Method for the Characterisation of Dental Materials?

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    The aim of the study was to investigate the effect of X-rays used in micro X-ray computer tomography (”XCT) on the mechanical performance and microstructure of a variety of dental materials. Standardised bending beams (2 × 2 × 25 mm3) were forwarded to irradiation with an industrial tomograph. Using three-dimensional datasets, the porosity of the materials was quantified and flexural strength was investigated prior to and after irradiation. The thermal properties of irradiated and unirradiated materials were analysed and compared by means of differential scanning calorimetry (DSC). Single ”XCT measurements led to a significant decrease in flexural strength of polycarbonate with acrylnitril-butadien-styrol (PC-ABS). No significant influence in flexural strength was identified for resin-based composites (RBCs), poly(methyl methacrylate) (PMMA), and zinc phosphate cement (HAR) after a single irradiation by measurement. However, DSC results suggest that changes in the microstructure of PMMA are possible with increasing radiation doses (multiple measurements, longer measurements, higher output power from the X-ray tube). In summary, it must be assumed that X-ray radiation during ”XCT measurement at high doses can lead to changes in the structure and properties of certain polymers

    Characterisation of the Filler Fraction in CAD/CAM Resin-Based Composites

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    The performance of dental resin-based composites (RBCs) heavily depends on the characteristic properties of the individual filler fraction. As specific information regarding the properties of the filler fraction is often missing, the current study aims to characterize the filler fractions of several contemporary computer-aided design/computer-aided manufacturing (CAD/CAM) RBCs from a material science point of view. The filler fractions of seven commercially available CAD/CAM RBCs featuring different translucency variants were analysed using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), Micro-X-ray Computed Tomography (”XCT), Thermogravimetric Analysis (TG) and X-ray Diffractometry (XRD). All CAD/CAM RBCs investigated included midifill hybrid type filler fractions, and the size of the individual particles was clearly larger than the individual specifications of the manufacturer. The fillers in Shofu Block HC featured a sphericity of ≈0.8, while it was <0.7 in all other RBCs. All RBCs featured only X-ray amorphous phases. However, in Lava Ultimate, zircon crystals with low crystallinity were detected. In some CAD/CAM RBCs, inhomogeneities (X-ray opaque fillers or pores) with a size <80 ”m were identified, but the effects were minor in relation to the total volume (<0.01 vol.%). The characteristic parameters of the filler fraction in RBCs are essential for the interpretation of the individual material’s mechanical and optical properties

    Boron Trifluoride Anionic Side Groups in Polyphosphazene Based Polymer Electrolyte with Enhanced Interfacial Stability in Lithium Batteries

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    A modified polyphosphazene was synthesized using a mixed substitution at phosphorus consisting of 2-(2-methoxyethoxy)ethoxy side groups and anionic trifluoroborate groups. The primary goal was to increase the low lithium ion conductivities of the conventional lithium salt containing poly[2-(2-methoxyethoxy)ethoxy-phosphazene] (MEEP) by the immobilized anionic groups. As in previous studies, the mechanical stability was stabilized by UV induced radiation cross linking. By variation of the molar ratio between different side groups, mechanical and electrochemical properties are controllable. The polymer demonstrated large electrochemical stability windows ranging between 0 and 4.5 V versus the Li/Li+ reference. Total and lithium conductivities of 3.6 &#215; 10&#8722;4 S&#183;cm&#8722;1 and 1.8 &#215; 10&#8722;5 S&#183;cm&#8722;1 at 60 &#176;C were revealed for the modified MEEP. When observed in special visualization cells, dendrite formation onset time and short-circuit time were determined as 21 h and 90 h, respectively, under constant current polarization (16 h and 65 h for MEEP, both with 15 wt % LiBOB), which hints to a more stable Li/polymer interface compared to normal MEEP. The enhanced dendrite suppression ability can be explained by the formation of a more conductive solid electrolyte interphase (SEI) and the existence of F-contained SEI components (such as LiF). With the addition of ethylene carbonate&#8315;dimethyl carbonate (EC/DMC) to form MEE-co-OBF3P gel polymer, both total and lithium conductivity were enhanced remarkably, and the lithium transference numbers reached reasonable values (&#963;total = 1.05 mS&#183;cm&#8722;1, &#963;Li+ = 0.22 mS&#183;cm&#8722;1, t Li + = 0.18 at 60 &#176;C)

    Polyoxymethylene as Material for Removable Partial Dentures—A Literature Review and Illustrating Case Report

    No full text
    Compared to thermoplastic manufacturing techniques, computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies make it easier to process modern restorative and prosthetic materials with improved material properties. In dentistry, tooth-colored alternatives to metal-based frameworks for application in removable dental prostheses (RDP) emerged. With regard to this aspect, the current article provides an overview of the specific material properties of polyoxymethylene (POM). Furthermore, it reviews scientific literature indexed in PubMed and Web of Science that focuses on RDPs fabricated from POM within the last 10 years. Finally, a prosthetic rehabilitation of a patient with a RDP fabricated from POM is illustrated and observations during a follow-up over 10 months are described. Scientific data and clinical observations indicate that polyoxymethylene is a promising material that bridges gaps in dental therapeutic options. While survival time may be limited due to wear, POM might be a favorable option for application in semi-permanent restorations

    Polyoxymethylene as Material for Removable Partial Dentures—A Literature Review and Illustrating Case Report

    No full text
    Compared to thermoplastic manufacturing techniques, computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies make it easier to process modern restorative and prosthetic materials with improved material properties. In dentistry, tooth-colored alternatives to metal-based frameworks for application in removable dental prostheses (RDP) emerged. With regard to this aspect, the current article provides an overview of the specific material properties of polyoxymethylene (POM). Furthermore, it reviews scientific literature indexed in PubMed and Web of Science that focuses on RDPs fabricated from POM within the last 10 years. Finally, a prosthetic rehabilitation of a patient with a RDP fabricated from POM is illustrated and observations during a follow-up over 10 months are described. Scientific data and clinical observations indicate that polyoxymethylene is a promising material that bridges gaps in dental therapeutic options. While survival time may be limited due to wear, POM might be a favorable option for application in semi-permanent restorations

    Acid resistance of self-adhesive resin luting cements – changes in surface texture parameters and microhardness

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    Objectives: When consumed in excess, acidic foods and beverages can cause dental ero-sions leading to irreversible loss of tooth substance. In many cases, prosthetic rehabilita-tion of the damaged teeth is mandatory. The aim of this in vitro study was to investigate, for the first time on this scale, the resistance of various commonly used self-adhesive resin luting cements (Bifix SE, VOCO; G-Cem LinkAce, GC; RelyX Unicem, 3 M Oral Care; SpeedCEM Plus, Ivoclar ) against acidic media, and to find out whether they can withstand long-term exposure. These results were compared with an adhesive resin luting cement (Panavia V5, Kuraray) that functioned as reference gold standard. Furthermore we applied area roughness parameters for surface texture analysis in the present investigation, to highlight their advantages for investigations on the surface quality of resin luting cements.Methods: Six specimens with identical diameter (10 mm) and thickness (3 mm) were pre-pared from each self-adhesive and adhesive resin luting cement and forwarded to an in-cubation in various acidic media for a period of 232 h. Conductivity and pH-values of each acidic medium was analyzed for each material group prior (t 0) and after exposure (t 1). The specimens were examined for Vickers microhardness and surface quality. For the eva-luation of surface roughness, the parameters Sa, Sdr, Spc Spk, Sk, and Svk were in-vestigated by using different filtered surfaces (S-L; S-F) according to ISO 25 178. Statistical analysis was conducted at a significance level of alpha = 0.050.Results: For the evaluation of the acid resistance of self-adhesive resin luting cements in-vestigations on conductivity and pH-value assessment of storage solution appear unsuitable, while the assessment of microhardness and surface analysis revealed valid data. It could be shown that changes in surface texture of the resin luting cements can be determinend in qualitative and quantitative manner. While the microhardness and sur-face quality of some resin luting cements hardly changed, others showed significantly reduced values in microhardness and changes in their surface quality (p < 0.001).Significance: The data of the current study emphasize the relevance of interactions between resin luting cements and acids and suggest further laboratory and clinical studies to elu-cidate its impact on the clinical performance of the materials investigated (c) 2022 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved

    Is Micro X-ray Computer Tomography a Suitable Non-Destructive Method for the Characterisation of Dental Materials?

    No full text
    The aim of the study was to investigate the effect of X-rays used in micro X-ray computer tomography (”XCT) on the mechanical performance and microstructure of a variety of dental materials. Standardised bending beams (2 × 2 × 25 mm3) were forwarded to irradiation with an industrial tomograph. Using three-dimensional datasets, the porosity of the materials was quantified and flexural strength was investigated prior to and after irradiation. The thermal properties of irradiated and unirradiated materials were analysed and compared by means of differential scanning calorimetry (DSC). Single ”XCT measurements led to a significant decrease in flexural strength of polycarbonate with acrylnitril-butadien-styrol (PC-ABS). No significant influence in flexural strength was identified for resin-based composites (RBCs), poly(methyl methacrylate) (PMMA), and zinc phosphate cement (HAR) after a single irradiation by measurement. However, DSC results suggest that changes in the microstructure of PMMA are possible with increasing radiation doses (multiple measurements, longer measurements, higher output power from the X-ray tube). In summary, it must be assumed that X-ray radiation during ”XCT measurement at high doses can lead to changes in the structure and properties of certain polymers

    Improved Interfaces of Mechanically Modified Lithium Electrodes with Solid Polymer Electrolytes

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    The combination of mechanically modified lithium electrodes and solid polymer electrolytes (SPEs) is investigated. So far, modified lithium electrodes, e.g., via structuring, are successfully used in combination with liquid electrolytes like ionic liquid‐based and organic solvent‐based ones. Specific SPEs have proven to be well compatible with lithium metal, even better than with liquid electrolytes. Nevertheless, the interface between lithium and SPEs is a complex issue. In this work, the challenge of the adequate wetting of the lithium electrode surface, especially a structured lithium surface, with a solid polymer is faced to successfully improve the interfacial properties and thus the performance, by a new method for the coating of such electrodes. The wetting of the micropatterned lithium surface by the SPE and the directed lithium electrodeposition in the patterns are verified by scanning electron microscopy analysis. The electrochemical properties of Li|SPE assemblies are investigated on the basis of constant current cycling and impedance experiments

    Is Micro X-ray Computer Tomography a Suitable Non-Destructive Method for the Characterisation of Dental Materials?

    No full text
    The aim of the study was to investigate the effect of X-rays used in micro X-ray computer tomography (”XCT) on the mechanical performance and microstructure of a variety of dental materials. Standardised bending beams (2 × 2 × 25 mm3) were forwarded to irradiation with an industrial tomograph. Using three-dimensional datasets, the porosity of the materials was quantified and flexural strength was investigated prior to and after irradiation. The thermal properties of irradiated and unirradiated materials were analysed and compared by means of differential scanning calorimetry (DSC). Single ”XCT measurements led to a significant decrease in flexural strength of polycarbonate with acrylnitril-butadien-styrol (PC-ABS). No significant influence in flexural strength was identified for resin-based composites (RBCs), poly(methyl methacrylate) (PMMA), and zinc phosphate cement (HAR) after a single irradiation by measurement. However, DSC results suggest that changes in the microstructure of PMMA are possible with increasing radiation doses (multiple measurements, longer measurements, higher output power from the X-ray tube). In summary, it must be assumed that X-ray radiation during ”XCT measurement at high doses can lead to changes in the structure and properties of certain polymers
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