title: Strength and wear resistance of a dental glass-ionomer cement with a novel nanofilled resin coating.
abstract: OBJECTIVE
  To evaluate the influence of different resin coating protocols on the fracture strength and wear resistance of a commercial glass-ionomer cement (GIC).
  
  
  METHODS
  A new restorative concept [Equia (GC Europe)] has been introduced as a system application consisting of a condensable GIC (Fuji IX GP Extra) and a novel nanofilled resin coating material (G-Coat Plus). Four-point fracture strength (FS, 2 x 2 x 25 mm, 14-day storage, distilled water, 37 degrees C) were produced and measured from three experimental protocols: no coating GIC (Group 1), GIC coating before water contamination (Group 2), GIC coating after water contamination (Group 3). The strength data were analyzed using Weibull statistics. Three-body wear resistance (Group 1 vs. Group 2) was measured after each 10,000 wear cycles up to a total of 200,000 cycles using the ACTA method. GIC microstructure and interfaces between GIC and coating materials were investigated under SEM and CLSM.
  
  
  RESULTS
  The highest FS of 26.1 MPa and the most homogenous behavior (m = 7.7) has been observed in Group 2. The coated and uncoated GIC showed similar wear resistance until 90,000 cycles. After 200,000 wear cycles, the coated version showed significantly higher wear rate (ANOVA, P< 0.05). The coating protocol has been shown to determine the GIC fracture strength. Coating after water contamination and air drying is leading to surface crack formation thus significantly reducing the FS. The resin coating showed a proper sealing of GIC surface porosities and cracks. In terms of wear, the coating did not improve the wear resistance of the underlying cement as similar or higher wear rates have been measured for Group 1 versus Group 2.
authors.affiliation: Dental Clinic 1 - Operative Dentistry and Periodontology, Glueckstr. 11, D-91054 Erlangen, Germany. lohbauer@dent.uni-erlangen.de
authors.forename: Ulrich
authors.initials: U
authors.lastname: Lohbauer
authors.forename: Norbert
authors.initials: N
authors.lastname: Krämer
authors.forename: Gustavo
authors.initials: G
authors.lastname: Siedschlag
authors.forename: Edward W
authors.initials: EW
authors.lastname: Schubert
authors.forename: Brigitte
authors.initials: B
authors.lastname: Lauerer
authors.forename: Frank A
authors.initials: FA
authors.lastname: Müller
authors.forename: Anselm
authors.initials: A
authors.lastname: Petschelt
authors.forename: Johannes
authors.initials: J
authors.lastname: Ebert
mesh_terms: D020099:Coated Materials, Biocompatible; D003188:Composite Resins / Q000737:chemistry*; D019554:Dental Restoration Wear; D003799:Dental Stress Analysis; D005899:Glass Ionomer Cements / Q000737:chemistry*; D008422:Materials Testing; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites; D018583:Pliability; D016062:Porosity; D016019:Survival Analysis; D017155:Wettability
chemical_list: D020099:Coated Materials, Biocompatible; D003188:Composite Resins; C000614715:EQUIA composite; D005899:Glass Ionomer Cements