title: [Effect of sintering gold paste coating on the bonding strength of pure titanium and three low-fusing porcelains].
abstract: OBJECTIVE
  To study the effect of sintering gold paste coating of pure titanium on the adhesion of three porcelains following the protocol ISO 9693, and to investigate the titanium-porcelains interfaces.
  
  
  METHODS
  Sixty machined pure titanium samples were prepared in a rectangular shape according to ISO 9693 and divided equally into six groups. Half of the strips were coated with gold paste (Deckgold) and sintered. Three ultra-low-fusing dental porcelains (I: Initial Ti, S: Super porcelain Ti-22, T: TitanKeramik) were fused onto the titanium surfaces. A thin layer of bonding agent was only applied on the surfaces of uncoated gold specimens. The interface of the porcelain and titanium was observed with a field emission scanning electron microscope (FE-SEM) after metallographic preparation and sputtered with a very thin carbon layer of the embedded titanium-porcelain interface. After three-point bending test was performed, optical stereomicroscope was used to characterize the titanium-porcelains adhesion and determine the mode of failure.
  
  
  RESULTS
  FE-SEM illustrated intermetallic compounds of Au-Ti formed with some visible microcracks in the gold layer and the interface of gold layer and ceramic. All the uncoated gold titanium-porcelain system showed predominately adhesive fracture at the titanium oxidation, whereas the failure modes in all gold coated systems were cohesive and adhesive, mainly cohesive. The three-point-bending test showed that the bonding strength of GS and GI groups [(37.08 ± 4.32) and (36.20 ± 2.40) MPa] were higher than those in uncoated groups [(31.56 ± 3.74) and (30.88 ± 2.60) MPa, P < 0.05], while no significant difference was found between T group and GT group (P > 0.05).
  
  
  CONCLUSIONS
  The gold paste intermediate coatings can improve bond strengths of Super porcelain Ti-22 system and Initial Ti system, which have potential applications in clinical fields.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Nanjing University & Nanjing Stomatological Hospital, Nanjing 210008, China.
authors.forename: Ya-li
authors.initials: YL
authors.lastname: Zhang
authors.forename: Xiao-ping
authors.initials: XP
authors.lastname: Luo
authors.forename: Li
authors.initials: L
authors.lastname: Zhou
mesh_terms: D001840:Dental Bonding; D003776:Dental Porcelain / Q000737:chemistry; D003799:Dental Stress Analysis; D006046:Gold / Q000737:chemistry; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D008855:Microscopy, Electron, Scanning; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D016876:Metal Ceramic Alloys; D003776:Dental Porcelain; D006046:Gold; D014025:Titanium