title: Failure rate of single-unit restorations on posterior vital teeth: A systematic review.
abstract: BACKGROUND
  No knowledge synthesis exists concerning when to use a direct restoration versus a complete-coverage indirect restoration in posterior vital teeth.
  
  
  OBJECTIVE
  The purpose of this systematic review was to identify the failure rate of conventional single-unit tooth-supported restorations in posterior permanent vital teeth as a function of remaining tooth structure.
  
  
  METHODS
  Four databases were searched electronically, and 8 selected journals were searched manually up to February 2015. Clinical studies of tooth-supported single-unit restorative treatments with a mean follow-up period of at least 3 years were selected. The outcome measured was the restorations' clinical or radiological failure. Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines, the Cochrane Collaboration procedures for randomized control trials, the Strengthening the Reporting of Observational Studies in Epidemiology criteria for observational studies, 2 reviewers independently applied eligibility criteria, extracted data, and assessed the quality of the evidence of the included studies using the American Association of Critical Care Nurses' system. The weighted-mean group 5-year failure rates of the restorations were reported according to the type of treatment and remaining tooth structure. A metaregression model was used to assess the correlation between the number of remaining tooth walls and the weighted-mean 5-year failure rates.
  
  
  RESULTS
  Five randomized controlled trials and 9 observational studies were included and their quality ranged from low to moderate. These studies included a total of 358 crowns, 4804 composite resins, and 303582 amalgams. Data obtained from the randomized controlled trials showed that, regardless of the amount of remaining tooth structure, amalgams presented better outcomes than composite resins. Furthermore, in teeth with fewer than 2 remaining walls, high-quality observational studies demonstrated that crowns were better than amalgams. A clear inverse correlation was found between the amount of remaining tooth structure and restoration failure.
  
  
  CONCLUSIONS
  Insufficient high-quality data are available to support one restorative treatment or material over another for the restoration of vital posterior teeth. However, the current evidence suggests that the failure rates of treatments may depend on the amount of remaining tooth structure and types of treatment.
authors.affiliation: Teaching and Research Assistant, Division of Prosthodontics and Restorative Dentistry, Faculty of Dentistry, McGill University, Montreal, Quebec, Canada; Research Associate, Division of Oral Health and Society, McGill University, Montreal, Quebec, Canada; and Visiting Scholar, Department of Reconstructive Dentistry, School of Dental Medicine, University of Bern, Berne, Switzerland.
authors.forename: Kelvin I
authors.initials: KI
authors.lastname: Afrashtehfar
authors.affiliation: Associate Professor, Department of Restorative Dentistry, Faculty of Dentistry, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Elham
authors.initials: E
authors.lastname: Emami
authors.affiliation: Research Assistant, Oral Health and Rehabilitation Research Unit, Faculty of Dentistry, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Motahareh
authors.initials: M
authors.lastname: Ahmadi
authors.affiliation: Teaching and Research Assistant, Faculty of Medicine, McGill University, Montreal, Quebec, Canada.
authors.forename: Owis
authors.initials: O
authors.lastname: Eilayyan
authors.affiliation: Division Director and Associate Professor, Division of Prosthodontics and Restorative Dentistry, Faculty of Dentistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Samer
authors.initials: S
authors.lastname: Abi-Nader
authors.affiliation: Associate Professor, Division of Prosthodontics and Restorative Dentistry, Faculty of Dentistry, McGill University, Montreal, Quebec, Canada. Electronic address: faleh.tamimimarino@mcgill.ca.
authors.forename: Faleh
authors.initials: F
authors.lastname: Tamimi
mesh_terms: D003188:Composite Resins / Q000009:adverse effects / Q000627:therapeutic use; D003723:Dental Amalgam / Q000009:adverse effects / Q000627:therapeutic use; D003731:Dental Caries / Q000628:therapy; D003764:Dental Materials / Q000627:therapeutic use; D019232:Dental Restoration Failure / Q000706:statistics & numerical data*; D003793:Dental Restoration, Permanent / Q000009:adverse effects / Q000379:methods* / Q000706:statistics & numerical data*; D006801:Humans; D015201:Meta-Analysis as Topic; D008963:Molar; D016032:Randomized Controlled Trials as Topic; D019228:Tooth Crown; D016896:Treatment Outcome
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D003723:Dental Amalgam