title: Effect of intermediate ZrO2-CaO coatings deposited by cold thermal spraying on the titanium-porcelain bond in dental restorations.
abstract: BACKGROUND
  Metal ceramic systems are used for the majority of dental crowns and fixed dental prostheses. However, problems with porcelain bonding are encountered when titanium is used as the substrate.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the effect of intermediate calcium oxide-stabilized zirconia (ZrO2-CaO) coatings deposited by cold thermal spraying on the titanium-porcelain bonding in dental restorations.
  
  
  METHODS
  Two different types of ZrO2-CaO coatings obtained by oxyacetylene cold thermal spraying deposition were applied on commercially pure titanium bars before adding the porcelain layer. Type 1 was obtained by directly spraying the ZrO2-CaO powder on the titanium substrate. Type 2 was obtained by spraying a bond coat of nickel-aluminum-molybdenum alloy before spraying the ZrO2-CaO powder. Three-point bend tests according to International Organization of Standardization 9693-1:2012 were carried out to evaluate the debonding strength for the ZrO2-CaO-coated specimens (types 1 and 2) in comparison with a noncoated group (control), which received a traditional bonder-based adhesive technique. The results were compared with ANOVA, followed by the Student-Newman-Keuls test for pairwise comparisons. Scanning electron microscopy and energy dispersion spectroscopy were used to examine the interfacial properties and the failure mode of each group.
  
  
  RESULTS
  Mean (±standard deviation) debonding strength values for type 1 coating (25.97 ±2.53 MPa) and control (23.51 ±2.94 MPa) were near the acceptable lower limit of 25 MPa indicated by the International Organization of Standardization 9693-1:2012 and were not significantly different (Student-Newman-Keuls test, P>.05). Type 2 coating produced an improved titanium-porcelain bonding (debonding strength=39.47 ±4.12 MPa), significantly higher than both type 1 (Student-Newman-Keuls test, P<.05) and control (Student-Newman-Keuls test, P<.05). Scanning electron microscopy-energy dispersion spectroscopy analysis confirmed these findings, which revealed a predominant cohesive failure mode for type 2.
  
  
  CONCLUSIONS
  An intermediate coating layer of ZrO2-CaO plus a substrate of bonding nickel-aluminum-molybdenum alloy applied by oxyacetylene cold thermal spraying deposition provided an improved titanium-porcelain bond.
authors.affiliation: Associate Professor, Experimental Diagnostic and Specialty Medicine Department, University of Bologna, Bologna, Italy. Electronic address: emanuela.marcelli@unibo.it.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Marcelli
authors.affiliation: Full Professor, Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta," Polytechnic University of Milan, Milan, Italy.
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Costantino
authors.affiliation: Assistant Professor, Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta," Polytechnic University of Milan; Istituti di Ricovero e Cura a Carattere Scientifico, Istituto Ortopedico Galeazzi, Milan, Italy.
authors.forename: Tomaso
authors.initials: T
authors.lastname: Villa
authors.affiliation: Postdoctoral Fellow, Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta," Polytechnic University of Milan, Milan, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Bagnoli
authors.affiliation: Full Professor, Experimental Diagnostic and Specialty Medicine Department, University of Bologna, Bologna, Italy.
authors.forename: Romano
authors.initials: R
authors.lastname: Zannoli
authors.affiliation: Assistant Professor, Experimental Diagnostic and Specialty Medicine Department, University of Bologna, Bologna, Italy.
authors.forename: Ivan
authors.initials: I
authors.lastname: Corazza
authors.affiliation: Postdoctoral Fellow, Experimental Diagnostic and Specialty Medicine Department, University of Bologna, Bologna, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Cercenelli
mesh_terms: D000480:Alkynes / Q000737:chemistry; D000535:Aluminum / Q000737:chemistry; D017610:Calcium Compounds / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003722:Dental Alloys / Q000737:chemistry; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008982:Molybdenum / Q000737:chemistry; D009532:Nickel / Q000737:chemistry; D010087:Oxides / Q000737:chemistry*; D018583:Pliability; D013052:Spectrometry, X-Ray Emission; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D000480:Alkynes; D017610:Calcium Compounds; D020099:Coated Materials, Biocompatible; D003722:Dental Alloys; D003764:Dental Materials; D010087:Oxides; D003776:Dental Porcelain; D009532:Nickel; D008982:Molybdenum; D015040:Zirconium; C016538:lime; D000535:Aluminum; D014025:Titanium; C028541:zirconium oxide