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Bad Säckingen, Germany

Swain M.V.,Kuwait University | Coldea A.,Vita Zahnfabrik | Bilkhair A.,Albert Ludwigs University of Freiburg | Guess P.C.,Albert Ludwigs University of Freiburg
Dental Materials

Objectives This paper investigates the structure and some properties of resin infiltrated ceramic network structure materials suitable for CAD/CAM dental restorative applications. Methods Initially the basis of interpenetrating network materials is defined along with placing them into a materials science perspective. This involves identifying potential advantages of such structures beyond that of the individual materials or simple mixing of the components. Results Observations from a number of recently published papers on this class of materials are summarized. These include the strength, fracture toughness, hardness and damage tolerance, namely to pointed and blunt (spherical) indentation as well as to burr adjustment. In addition a summary of recent results of crowns subjected to simulated clinical conditions using a chewing simulator are presented. These results are rationalized on the basis of existing theoretical considerations. Significance The currently available ceramic-resin IPN material for clinical application is softer, exhibits comparable strength and fracture toughness but with substantial R-curve behavior, has lower E modulus and is more damage tolerant than existing glass-ceramic materials. Chewing simulation observations with crowns of this material indicate that it appears to be more resistant to sliding/impact induced cracking although its overall contact induced breakage load is modest. © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. Source

Rohr N.,University of Basel | Coldea A.,Vita Zahnfabrik | Zitzmann N.U.,University of Basel | Fischer J.,University of Basel
Dental Materials

Objective Recently a polymer infiltrated hybrid ceramic was developed, which is characterized by a low elastic modulus and therefore may be considered as potential material for implant supported single crowns. The purpose of the study was to evaluate the loading capacity of hybrid ceramic single crowns on one-piece zirconia implants with respect to the cement type. Methods Fracture load tests were performed on standardized molar crowns milled from hybrid ceramic or feldspar ceramic, cemented to zirconia implants with either machined or etched intaglio surface using four different resin composite cements. Flexure strength, elastic modulus, indirect tensile strength and compressive strength of the cements were measured. Statistical analysis was performed using two-way ANOVA (p = 0.05). Results The hybrid ceramic exhibited statistically significant higher fracture load values than the feldspar ceramic. Fracture load values and compressive strength values of the respective cements were correlated. Highest fracture load values were achieved with an adhesive cement (1253 ± 148 N). Etching of the intaglio surface did not improve the fracture load. Significance Loading capacity of hybrid ceramic single crowns on one-piece zirconia implants is superior to that of feldspar ceramic. To achieve maximal loading capacity for permanent cementation of full-ceramic restorations on zirconia implants, self-adhesive or adhesive cements with a high compressive strength should be used. © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. Source

Tholey M.J.,Vita Zahnfabrik | Berthold C.,University of Tubingen | Swain M.V.,The New School | Thiel N.,Vita Zahnfabrik
Dental Materials

Objectives: The metastability of the tetragonal crystal structure of yttria partial stabilized zirconia polycrystalline (Y-TZP) ceramics is a basis of concern for dental restorations. Reactions between the porcelain and the Y-TZP framework may result in a reduction of the stability of the zirconia and interface bonding caused by a transformation from tetragonal to monoclinic crystalline structure during veneering. Methods: XRD2 micro-diffraction measurements were carried out on tapered veneered cross-sections of the interface area to generate locally resolved information of the phase content in this region. To get a high intensity X-ray beam for short measurement times a focussing polycapillary with a spot size of app. 50 μm was used to evaluate the porcelain zirconia interface. Results: Under almost all conditions the phase composition of zirconia grains at the interface revealed both the monoclinic and tetragonal structure. These observations indicate that destabilization of the tetragonal phase of zirconia occurs at the interface during veneering with porcelain. Significance: These results and their relevance to the long-term stability of the interface adhesion between zirconia and veneering porcelain as well as the tetragonal to monoclinic crystal transformations at the interface are discussed. © 2010 Academy of Dental Materials. Source

Coldea A.,Vita Zahnfabrik | Coldea A.,University of Otago | Fischer J.,Vita Zahnfabrik | Fischer J.,University of Basel | And 3 more authors.
Dental Materials

Objective To analyze the damage tolerance of indirect restorative materials after grinding with diamond burs to simulate adjustments by clinicians and technicians. Methods Seven commercially available restorative materials (Mark II, ENAMIC, In-Ceram Alumina, VM 9, In-Ceram YZ, IPS e.max CAD) and an experimental one (PICN) were analyzed. Forty bending bars per material were fabricated according to manufacturer's instructions and lapped with 15 μm diamond suspension. The initial flexural strength was determined in three-point-bending on 10 specimens. Additionally the elastic modulus and Poisson's ratio were determined by the resonant frequency method. The remaining bending bars were divided into six groups (n = 5) and subjected to standardized grinding with three different diamond grit burs (coarse, 151 μm; medium, 107 μm and extra fine 25 μm) and two grinding directions (transversal and longitudinal). The ground specimens were subsequently loaded to fracture and analyzed by SEM. Results Except for the YTZP bending bars, the initial materials strength of all tested materials decreased significantly with all diamond burs upon adjustments in both transversal and longitudinal grinding directions. The resistance of the ground materials to strength reduction follow the order from highest to least damage tolerant material: PICN > ENAMIC > Mark II > VM 9 > In-Ceram Alumina > IPS e.max CAD. The loss in strength of all examined materials after longitudinal grinding is generally less compared to transversal grinding. The lowest loss in strength occurred for VM 9 (7.79%) and ENAMIC (9.18%) upon longitudinal grinding direction with extra fine and medium diamond grit bur, respectively. Significance The damage tolerance of restorative materials upon adjustments depends on specific mechanical properties and the adjustment procedure. The outcomes of the simulated grinding protocols of this study can be adopted clinically in terms of the selection of appropriate materials, burs and adjustment parameters. © 2015 Academy of Dental Materials. Source

Vita Zahnfabrik H. Rauter Gmbh & Co. Kg. and Vita Zahnfabrik | Date: 1973-09-04


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