title: Twelve-year survival of 2-surface composite resin and amalgam premolar restorations placed by dental students.
abstract: BACKGROUND
  Composite resin and amalgam restorations are indicated for the restoration of posterior teeth. With increased esthetic demands, long-term clinical studies are required to evaluate the restorative success and reasons for failure of these materials.
  
  
  OBJECTIVE
  The purpose of this retrospective study was to determine the survival and reasons for failure of directly placed 2-surface composite resin restorations and directly placed 2-surface amalgam restorations on premolars placed by Canadian dental students.
  
  
  METHODS
  Using The University of Manitoba's dental management software and paper charts, all 2-surface composite resin and 2-surface amalgam restorations placed on premolars between January 1, 2002, and May 30, 2014, were included. Short-term failure (within 2 years), long-term failure, and reasons for failure were collected. A Kaplan-Meier survival estimate with an associated P value comparing composite resin to amalgam restoration curves was performed using SPSS statistical software.
  
  
  RESULTS
  Over 12 years, 1695 composite resin and 1125 amalgam 2-surface premolar restorations were placed. Of these restorations, 134 composite resins (7.9%) and 66 amalgams (5.9%) failed. Short-term failures (2 years or less) consisted of 57 composite resin (4%) and 23 amalgam (2.3%) restorations. Long-term failures (greater than 2 years) consisted of 77 composite resin (4.5%) and 43 amalgam (3.8%) restorations. After 12 years of service, the survival probability of composite resin restorations was 86% and that of amalgam restorations 91.5%. The differences in composite resin and amalgam survival curves were also found to be statistically significant (P=.009 for Log-rank test). The main reasons for failure were recurrent caries and fracture of the tooth being restored.
  
  
  CONCLUSIONS
  Within the limitations of this study, both composite resin and amalgam restorations had acceptable success rates and similar failure modes. Recurrent caries was still the most common reason for failure.
authors.affiliation: Dental student, College of Dentistry, University of Manitoba, Winnipeg, Manitoba, Canada. Electronic address: safa.2113@gmail.com.
authors.forename: Safa
authors.initials: S
authors.lastname: Naghipur
authors.affiliation: Associate Professor, Head Division of Prosthodontics, Department of Restorative Dentistry, College of Dentistry, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Igor
authors.initials: I
authors.lastname: Pesun
authors.affiliation: Assistant Professor, Department of Restorative Dentistry, College of Dentistry, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Anthony
authors.initials: A
authors.lastname: Nowakowski
authors.affiliation: Assistant Professor, Director of Clinics, College of Dentistry, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Aaron
authors.initials: A
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001641:Bicuspid / Q000601:surgery*; D003188:Composite Resins / Q000627:therapeutic use*; D003723:Dental Amalgam / Q000627:therapeutic use*; D019232:Dental Restoration Failure / Q000706:statistics & numerical data; D003793:Dental Restoration, Permanent / Q000379:methods / Q000592:standards; D006801:Humans; D008875:Middle Aged; D012189:Retrospective Studies; D013335:Students, Dental; D013997:Time Factors; D055815:Young Adult
chemical_list: D003188:Composite Resins; D003723:Dental Amalgam