title: Longevity of conventional and bonded (sealed) amalgam restorations in a private general dental practice.
abstract: OBJECTIVE
  To compare and contrast the longevity of conventionally placed dental amalgam restorations with those placed using bonding techniques.
  
  
  METHODS
  Retrospective survival analysis (Kaplan Meier) of dental amalgam restorations placed by a single operator in a private general dental practice.
  
  
  METHODS
  The records relating to dental amalgam restorations placed between 1 August 1996 and 31 July 2006 were sourced. The details of these were placed into a database that permitted flexible interrogation. Survival data on conventionally placed amalgams (C) and those bonded with either Panavia Ex (PE) or Rely X ARC (RX) were exported into a statistical package to permit survival analysis by the method of Kaplan and Meier.Results The number of restorations available for analysis were C = 3,854, PE = 51 and RX = 1,797. Percentage survival at one year was C = 96.29, PE = 95.65, and RX = 97.58. Percentage survival at five years was C = 86.21, PE = 76.35 and RX = 82.59. A Log Rank test demonstrated no statistically significant difference (p >0.05) in survival between the restoration types. Amalgam restorations bonded with PE or RX exhibited an acceleration of failure rate around 1,000 days post-placement. Further survival analyses of the method of restoration versus type of restored teeth (molar/premolar) and cavity preparation (Class I/II) showed no significant difference in the survival curves in respect of type of restored tooth. In the comparison of Class I and II cavities, the survival curves for the restorations differed significantly (p <0.0001), however when the curves for the Class I restorations alone were compared, no significant difference was found (p = 0.2634). This was also the case for the Class II restorations (p = 0.2260).
  
  
  CONCLUSIONS
  Within the limitations of the study, bonding amalgams, compared to placing them conventionally, afforded no significant benefit upon restoration longevity. This, coupled with the emerging trend of an accelerating decline in longevity of bonded amalgams from 1,000 days onwards and with the greater cost, challenges the justification for routine bonding of amalgams.
authors.affiliation: General Dental Practitioner, The Dental Practice, 21 Rubislaw Terrace, Aberdeen. steve.b@thedentalpracticeaberdeen.co.uk
authors.forename: S J
authors.initials: SJ
authors.lastname: Bonsor
authors.forename: R G
authors.initials: RG
authors.lastname: Chadwick
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate; D003723:Dental Amalgam; D001840:Dental Bonding; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000379:methods*; D006801:Humans; D053208:Kaplan-Meier Estimate; D010710:Phosphates; D011092:Polyethylene Glycols; D011109:Polymethacrylic Acids; D011331:Private Practice; D019279:Resin Cements; D012189:Retrospective Studies
chemical_list: D010710:Phosphates; D011109:Polymethacrylic Acids; C462240:RelyX ARC; D019279:Resin Cements; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D003723:Dental Amalgam; C052304:Panavia EX