title: Clinical evaluation and microstructural analysis of a direct placement gallium restorative alloy.
abstract: OBJECTIVE
  The objective of this study was to assess the clinical performance of a direct placement gallium alloy sealed with an established dentine adhesive system. In addition, microanalysis of a few gallium restorations that failed in clinical service was performed. Clinical factors such as pulpal sensitivity, fracture of the restoration and of the tooth, marginal deterioration, and tarnish were assessed.
  
  
  METHODS
  Sixty-five restorations of Galloy and 62 of Tytin (49 and 51 Class II restorations, respectively) were placed according to a predetermined scheme for randomisation in 37 patients by two operators using rubber dam isolation. For the Galloy restorations, the enamel and dentine were etched, and then sealed with PAAMA 2 dentine adhesive according to the manufacturer's instructions. After carving, PAAMA 2 was applied to the Galloy and light-cured. Cavity preparations for Tytin received no adhesive sealer. All restorations were polished at least 24 h post-operatively. Microstructural analysis of retrieved fragments of failed restorations was conducted using electron probe microanalysis.
  
  
  RESULTS
  At 1 year, only one Tytin restoration was found to have failed due to an isthmus fracture. The remaining restorations of Tytin were intact with no reported sensitivity. Of the 65 Galloy restorations placed, 28 had to be removed, including restorations in teeth, which were symptomatic, non-vital and/or fractured, and teeth with fractured restorations. Tarnish was present on many of the Galloy restorations. Retrieved fragments of failed Galloy restorations exhibited a dark surface at the pulpal wall interface and small cracks were observed in that surface. Internal cracks and extensive corrosion was observed using the microprobe. Gallium oxides and chlorides were identified as the predominant corrosion products.
  
  
  CONCLUSIONS
  The gallium alloy, Galloy, sealed with PAAMA 2 dentine adhesive system demonstrated a high clinical failure rate.
authors.affiliation: Department of Restorative Dentistry, National University of Singapore, National University Hospital. rsdnnj@nus.edu.sg
authors.forename: J
authors.initials: J
authors.lastname: Neo
authors.forename: C L
authors.initials: CL
authors.lastname: Chew
authors.forename: J W
authors.initials: JW
authors.lastname: Osborne
authors.forename: D B
authors.initials: DB
authors.lastname: Mahler
mesh_terms: D003722:Dental Alloys / Q000032:analysis; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000145:classification / Q000379:methods / Q000706:statistics & numerical data; D004577:Electron Probe Microanalysis; D005260:Female; D005500:Follow-Up Studies; D005708:Gallium / Q000032:analysis; D006801:Humans; D008297:Male; D008689:Methacrylates; D019279:Resin Cements; D013997:Time Factors
chemical_list: D003722:Dental Alloys; C100747:Galloy; D008689:Methacrylates; C086114:PAAMA 2; D019279:Resin Cements; C036886:tytin; D005708:Gallium