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Christoph H. F. Hämmerle – One of the best experts on this subject based on the ideXlab platform.

  • Effect of blasting pressure, abrasive Particle size and grade on phase transformation and morphological change of dental zirconia surface
    Surface & Coatings Technology, 2012
    Co-Authors: Lubica Hallmann, Peter Ulmer, Eric Reusser, Christoph H. F. Hämmerle
    Abstract:

    Abstract This study aimed to evaluate the effect of different blasting pressures and Airborne Particle composition and size on phase transformation and surface morphological change of yttria-stabilized tetragonal polycrystalline zirconia (Y-TZP). Specimens sintered at 1350 °C for 2 h were abraded with 50 and 110 μm alumina and 30 and 110 μm silica-coated alumina Particle at pressures of 1, 1.5, 2, 2.5, 3 and 3.5 bar. It was found that air abrasion changes the morphology of the Y-TZP ceramic surface. Flaws, microcracks, plastic deformations, pits, embedding of Airborne Particle on the ceramic surface, cluster of loosely nano-silica Particle, melting of ceramic surface, coating of surface with non-uniform loosely nano-silica Particle and t–m phase transformation were observed after air abrasion process. The extent of morphological change and t–m phase transformation of abraded surface depended on the pressures and size of abrasive Particle. Higher pressure and larger size resulted in more extensive morphological change and more frequent t–m phase transformation. Conclusion The extent of morphological change of ceramic surface depends on the blasting pressures and grain size of Airborne Particle. Nano-silica Particle loosely covered the ceramic surface after air abrasion. The abrasion of the ceramic surface with 50 or 110 μm alumina Airborne Particle at pressures of 2.5 or 1.5 bar, respectively, was regarded as the optimum blasting condition.

  • effect of surface conditioning with Airborne Particle abrasion on the tensile strength of polymeric cad cam crowns luted with self adhesive and conventional resin cements
    Journal of Prosthetic Dentistry, 2012
    Co-Authors: Bogna Stawarczyk, Mutlu Ozcan, Tobias Basler, Andreas Ender, Malgorzata Roos, Christoph H. F. Hämmerle
    Abstract:

    Statement of problem Adhesively bonded, industrially polymerized resins have been suggested as definitive restorative materials. It is claimed that such resins present similar mechanical properties to glass ceramic. Purpose The purpose of this study was to assess the tensile strength of polymeric crowns after conditioning with 2 different protocols: luted with self-adhesive or with conventional resin cements to dental abutments. Material and methods Human teeth were prepared for crowns and divided into 13 groups (N=312, n=24 per group). Polymeric crowns were CAD/CAM fabricated and divided into 3 groups depending on different surface conditioning methods: A) No treatment, B) AirborneParticle abrasion with 50 μm alumina, and C) AirborneParticle abrasion with 110 μm alumina. Thereafter, the crowns were luted on dentin abutments with the following cements: 1) RXU (RelyX Unicem, self-adhesive), 2) GCM (G-Cem, self-adhesive), 3) ACG (artCem GI, conventional), and 4) VAR (Variolink II, conventional). Glass ceramic crowns milled and cemented with dual-polymerized resin cement (Variolink II) served as the control group. The tensile strength was measured initially (n=12) and after aging by mechanical thermocycling loading (1 200 000 cycles, 49 N, 5°C to 50°C) (n=12). The tensile strength (MPa) of all crowns was determined by the pull-off test (Zwick/Roell Z010; Ulm, Germany, 1mm/min). Subsequently, the failure types were classified. Data were analyzed with 2-way and 1-way ANOVA followed by a post hoc Scheffe test and t test (α=.05). Results No adhesion of the tested cements was observed on unconditioned polymeric CAD/CAM crowns and those luted with VAR. Among the tested cements, GCM showed significantly higher values after AirborneParticle abrasion with 110 μm (initial: 2.8 MPa; after aging: 1 MPa) than 50 μm alumina (initial: 1.4 MPa; after aging: 0 MPa). No significant effect was found between 50 and 110 μm Particle size alumina in combination with the other 2 cements. After aging, the tensile strength of the crowns luted with GCM (50 μm: 0 MPa and 110 μm: 1 MPa) and ACG (50 μm: 1 MPa and 110 μm: 1.2 MPa) was significantly lower than those luted with RXU (50 μm: 1.9 MPa and 110 μm: 2 MPa). All Airborne Particle abraded polymeric CAD/CAM crowns (initial: 1.4-2.8; 0-2 MPa) showed significantly lower tensile strength values than the control group (initial: 7.3 MPa; after aging: 6.4 MPa). Although with all polymeric specimens, failure type was adhesive between the cement and the crowns, the control group showed exclusively cohesive failures within the ceramic. Conclusions AirborneParticle abrasion before cementation of polymeric CAD/CAM crowns minimally improved the tensile strength. Both the failure types and the tensile strength values of adhesively luted glass ceramic crowns showed superior results to adhesively cemented polymeric ones. Although the tensile strength results were low, crowns cemented with RXU showed, after aging, the highest tensile strength of all other tested groups.

  • Effect of surface conditioning with AirborneParticle abrasion on the tensile strength of polymeric CAD/CAM crowns luted with self-adhesive and conventional resin cements
    The Journal of prosthetic dentistry, 2012
    Co-Authors: Bogna Stawarczyk, Mutlu Ozcan, Tobias Basler, Andreas Ender, Malgorzata Roos, Christoph H. F. Hämmerle
    Abstract:

    Statement of problem Adhesively bonded, industrially polymerized resins have been suggested as definitive restorative materials. It is claimed that such resins present similar mechanical properties to glass ceramic. Purpose The purpose of this study was to assess the tensile strength of polymeric crowns after conditioning with 2 different protocols: luted with self-adhesive or with conventional resin cements to dental abutments. Material and methods Human teeth were prepared for crowns and divided into 13 groups (N=312, n=24 per group). Polymeric crowns were CAD/CAM fabricated and divided into 3 groups depending on different surface conditioning methods: A) No treatment, B) AirborneParticle abrasion with 50 μm alumina, and C) AirborneParticle abrasion with 110 μm alumina. Thereafter, the crowns were luted on dentin abutments with the following cements: 1) RXU (RelyX Unicem, self-adhesive), 2) GCM (G-Cem, self-adhesive), 3) ACG (artCem GI, conventional), and 4) VAR (Variolink II, conventional). Glass ceramic crowns milled and cemented with dual-polymerized resin cement (Variolink II) served as the control group. The tensile strength was measured initially (n=12) and after aging by mechanical thermocycling loading (1 200 000 cycles, 49 N, 5°C to 50°C) (n=12). The tensile strength (MPa) of all crowns was determined by the pull-off test (Zwick/Roell Z010; Ulm, Germany, 1mm/min). Subsequently, the failure types were classified. Data were analyzed with 2-way and 1-way ANOVA followed by a post hoc Scheffe test and t test (α=.05). Results No adhesion of the tested cements was observed on unconditioned polymeric CAD/CAM crowns and those luted with VAR. Among the tested cements, GCM showed significantly higher values after AirborneParticle abrasion with 110 μm (initial: 2.8 MPa; after aging: 1 MPa) than 50 μm alumina (initial: 1.4 MPa; after aging: 0 MPa). No significant effect was found between 50 and 110 μm Particle size alumina in combination with the other 2 cements. After aging, the tensile strength of the crowns luted with GCM (50 μm: 0 MPa and 110 μm: 1 MPa) and ACG (50 μm: 1 MPa and 110 μm: 1.2 MPa) was significantly lower than those luted with RXU (50 μm: 1.9 MPa and 110 μm: 2 MPa). All Airborne Particle abraded polymeric CAD/CAM crowns (initial: 1.4-2.8; 0-2 MPa) showed significantly lower tensile strength values than the control group (initial: 7.3 MPa; after aging: 6.4 MPa). Although with all polymeric specimens, failure type was adhesive between the cement and the crowns, the control group showed exclusively cohesive failures within the ceramic. Conclusions AirborneParticle abrasion before cementation of polymeric CAD/CAM crowns minimally improved the tensile strength. Both the failure types and the tensile strength values of adhesively luted glass ceramic crowns showed superior results to adhesively cemented polymeric ones. Although the tensile strength results were low, crowns cemented with RXU showed, after aging, the highest tensile strength of all other tested groups.

Yong-jun Kim – One of the best experts on this subject based on the ideXlab platform.

  • Micromachined electrical mobility analyzer for wide range Airborne Particle classification
    2008 IEEE 21st International Conference on Micro Electro Mechanical Systems, 2008
    Co-Authors: Il-hyun Jung, Yong-ho Kim, Dongho Park, Jungho Hwang, Yong-jun Kim
    Abstract:

    This paper reports a micromachined nano electrical mobility analyzer (nEMA) for nano- sized Airborne Particle classification. The micromachined nEMA is a Particle classifier that uses both the inertia and electrical mobility of the Particles for the classification. The microchannel of the nEMA is defined by silicon bulk micromachining. The collection efficiency of the solid Particle, NaCl with a diameter of less than 50 nm, was examined using the nEMA by applying an electrical potential. For various electric field magnitude ranging from 10 to 160 V, the Particle diameter collected in the outlet was measured. The collection efficiency of 40 nm Particles was investigated by increasing an electric field, and it was highest at 70 V.

  • Electrically tunable Airborne Particle classifier using a virtual impactor
    2008 IEEE 21st International Conference on Micro Electro Mechanical Systems, 2008
    Co-Authors: Youngsub Kim, Jungho Hwang, Dongho Park, Yong-jun Kim
    Abstract:

    This paper reports an Airborne Particle classifier based on a virtual impactor (VI) which is capable of actively tuning a cut-off diameter by applying the electric potential. The VI aerodynamically classifies Airborne Particles according to their size. An electrode pair is integrated in the VI, which make possible to electrically control the cut-off diameter of the VI without additional fabrications. The VI with a cut-off diameter of 1 mum was designed, and its cut-off characteristics were examined. Thereafter, the cut-off diameter was successfully tuned to from 35 nm to 70 nm by applying electric potentials from 1 kV to 3 kV.

  • micromachined cascade virtual impactor with a flow rate distributor for wide range Airborne Particle classification
    Applied Physics Letters, 2007
    Co-Authors: Yong-ho Kim, Il-hyun Jung, Dongho Park, Jungho Hwang, Jwayoung Maeng, Yong-jun Kim
    Abstract:

    This letter reports a module for Airborne Particle classification, which consists of a micromachined three-stage virtual impactor for classifying Airborne Particles according to their size and a flow rate distributor for supplying the required flow rate to the virtual impactor. Dioctyl sebacate Particles, 100–600nm in diameter, and carbon Particles, 0.6–10μm in diameter, were used for Particle classification. The collection efficiency and cutoff diameter were examined. The measured cutoff diameters of the first, second, and third stages were 135nm, 1.9μm, and 4.8μm, respectively.

De Souza G.m.d. – One of the best experts on this subject based on the ideXlab platform.

Hideo Matsumura – One of the best experts on this subject based on the ideXlab platform.

  • the effect of different surface treatments on the bond strength of a gingiva colored indirect composite veneering material to three implant framework materials
    Clinical Oral Implants Research, 2012
    Co-Authors: Mai Koizuka, Futoshi Komine, Markus B Blatz, Ryosuke Fushiki, Kohei Taguchi, Hideo Matsumura
    Abstract:

    Objectives To evaluate and compare the shear-bond strength of a gingiva-colored indirect composite material to three different implant framework materials (zirconia ceramics, gold alloy, and titanium), and to investigate the effect of surface pretreatment by air-Particle abrasion and four priming agents. Material and methods A gingiva-colored indirect composite (Ceramage) was bonded to three framework materials (n = 80): commercially pure titanium (CP- Ti ), ADA (American Dental Association)-type 4 casting gold alloy (Type IV), and zirconia ceramics (Zirconia) with or without AirborneParticle abrasion. Before bonding, the surface of the specimens was treated using no (control) or one of four priming agents: Alloy Primer (ALP), Estenia Opaque Primer (EOP), Metal Link Primer (MLP), and V-Primer (VPR). Shear-bond strength was determined after 24-h wet storage. Data were analyzed using Steel–Dwass for multiple comparisons, and Mann–Whitney U-test (P = 0.05). Results For both CP- Ti and Zirconia substrates, three groups, ALP, EOP, and MLP, showed significantly higher bond strengths (P < 0.05) than the other groups with or without AirborneParticle abrasion. For Type IV substrates, significantly higher bond strengths were obtained in ALP and MLP groups (P < 0.01) compared with the other groups with AirborneParticle abrasion. Conclusions Application of priming agents containing specific phosphoric esteester groups significantly enhances the bond strength of a gingiva-colored composite material to commercially pure titanium and zirconia frameworks. Combined use of a thione monomer with a phosphoric monomer enhances the bond strengths to AirborneParticle abraded type IV gold alloy.

  • effect of surface treatment on bond strength between an indirect composite material and a zirconia framework
    Journal of Oral Science, 2012
    Co-Authors: Futoshi Komine, Mai Koizuka, Ryosuke Fushiki, Kohei Taguchi, Shingo Kamio, Hideo Matsumura
    Abstract:

    The present study evaluated the effect of various surface treatments for zirconia ceramics on shear bond strength between an indirect composite material and zirconia ceramics. In addition, we investigated the durability of shear bond strength by using artificial aging (20,000 thermocycles). A total of 176 Katana zirconia disks were randomly divided into eight groups according to surface treatment, as follows: group CON (as-milled); group GRD (wet-ground with 600-grit silicon carbide abrasive paper); groups 0.05, 0.1, 0.2, 0.4, and 0.6 MPa (AirborneParticle abrasion at 0.05, 0.1, 0.2, 0.4, and 0.6 MPa, respectively); and group HF (9.5% hydrofluoric acid etching). Shear bond strength was measured at 0 thermocycles in half the specimens after 24-h immersion. The remaining specimens were subjected to 20,000 thermocycles before shear bond strength testing. Among the eight groups, the 0.1, 0.2, 0.4, and 0.6 MPa AirborneParticle abraded groups had significantly higher bond strengths before and after thermocycling. The Mann-Whitney U-test revealed no significant difference in shear bond strength between 0 and 20,000 thermocycles, except in the 0.2 MPa group (P = 0.013). From the results of this study, use of AirborneParticle abrasion at a pressure of 0.1 MPa or higher increases initial and durable bond strength between an indirect composite material and zirconia ceramics.

Paolo Baldissara – One of the best experts on this subject based on the ideXlab platform.

  • effect of Particle size on the flexural strength and phase transformation of an Airborne Particle abraded yttria stabilized tetragonal zirconia polycrystal ceramic
    Journal of Prosthetic Dentistry, 2013
    Co-Authors: Renata Garcia Fonseca, Filipe De Oliveira Abirached, Jose Mauricio Dos Santos Nunes Reis, Elisa Rambaldi, Paolo Baldissara
    Abstract:

    Statement of problem Because AirborneParticle abrasion is an efficient method of improving the bond at the zirconia-cement interface, understanding its effect on the strength of yttria-stabilized tetragonal zirconia polycrystal is important. Purpose The purpose of this study was to evaluate the effect of the Particle size used for AirborneParticle abrasion on the flexural strength and phase transformation of a commercially available yttria-stabilized tetragonal zirconia polycrystal ceramic. Material and Methods For both flexural strength (20.0 × 4.0 × 1.2 mm) (n=14) and phase transformation (14.0-mm diameter × 1.3-mm thickness) (n=4), the zirconia specimens were made from Lava, and their surfaces were treated in the following ways: as-sintered (control); with 50-μm aluminum oxide (Al 2 O 3 ) Particles; with 120-μm Al 2 O 3 Particles; with 250-μm Al 2 O 3 Particles; with 30-μm silica-modified Al 2 O 3 Particles (Cojet Sand); with 120-μm Al 2 O 3 Particles, followed by 110-μm silica-modified Al 2 O 3 Particles (Rocatec Plus); and with Rocatec Plus. The phase transformation (%) was assessed by x-ray diffraction analysis. The 3-point flexural strength test was conducted in artificial saliva at 37°C in a mechanical testing machine. The data were analyzed by 1-way ANOVA and the Tukey honestly significant difference post hoc test (α=.05). Results Except for the Cojet Sand group, which exhibited statistically similar flexural strength to that of the as-sintered group and for the group abraded with 250-μm Al 2 O 3 Particles, which presented the lowest strength, AirborneParticle abrasion with the other Particle sizes provided the highest values, with no significant difference among them. The as-sintered specimens presented no monoclinic phase. The groups abraded with smaller Particles (30 μm and 50 μm) and those treated with the larger ones (110 μm and/or 120 μm Particles and 250 μm) exhibited percentages of monoclinic phase that varied from 4% to 5% and from 8.7% to 10%. Conclusions Except for abrasion with Cojet Sand, depending on the Particle size, zirconia exhibited an increase or a decrease in its flexural strength. AirborneParticle abrasion promoted phase transformation (tetragonal to monoclinic), and the percentage of monoclinic phase varied according to the Particle size.