title: Survival and reasons for failure of amalgam versus composite posterior restorations placed in a randomized clinical trial.
abstract: BACKGROUND
  Failure of dental restorations is a major concern in dental practice. Replacement of failed restorations constitutes the majority of operative work. Clinicians should be aware of the longevity of, and likely reasons for the failure of, direct posterior restorations. In a long-term, randomized clinical trial, the authors compared the longevity of amalgam and composite. SUBJECTS, METHODS AND MATERIALS: The authors randomly assigned one-half of the 472 subjects, whose age ranged from 8 through 12 years, to receive amalgam restorations in posterior teeth and the other one-half to receive resin-based composite restorations. Study dentists saw subjects annually to conduct follow-up oral examinations and take bitewing radiographs. Restorations needing replacement were failures. The dentists recorded differential reasons for restoration failure.
  
  
  RESULTS
  Subjects received a total of 1,748 restorations at baseline, which the authors followed for up to seven years. Overall, 10.1 percent of the baseline restorations failed. The survival rate of the amalgam restorations was 94.4 percent; that of composite restorations was 85.5 percent. Annual failure rates ranged from 0.16 to 2.83 percent for amalgam restorations and from 0.94 to 9.43 percent for composite restorations. Secondary caries was the main reason for failure in both materials. Risk of secondary caries was 3.5 times greater in the composite group.
  
  
  CONCLUSIONS
  Amalgam restorations performed better than did composite restorations. The difference in performance was accentuated in large restorations and in those with more than three surfaces involved.
  
  
  CONCLUSIONS
  Use of amalgam appears to be preferable to use of composites in multisurface restorations of large posterior teeth if longevity is the primary criterion in material selection.
authors.affiliation: Community and Preventive Dentistry, Faculdade de Medicina Dentária, Universidade de Lisboa, Portugal.
authors.forename: Mario
authors.initials: M
authors.lastname: Bernardo
authors.forename: Henrique
authors.initials: H
authors.lastname: Luis
authors.forename: Michael D
authors.initials: MD
authors.lastname: Martin
authors.forename: Brian G
authors.initials: BG
authors.lastname: Leroux
authors.forename: Tessa
authors.initials: T
authors.lastname: Rue
authors.forename: Jorge
authors.initials: J
authors.lastname: Leitão
authors.forename: Timothy A
authors.initials: TA
authors.lastname: DeRouen
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D002648:Child; D003188:Composite Resins / Q000737:chemistry*; D016001:Confidence Intervals; D003723:Dental Amalgam / Q000737:chemistry*; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000379:methods*; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D016012:Poisson Distribution; D011140:Polyurethanes / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D011140:Polyurethanes; D003723:Dental Amalgam