title: Survival rate of lithium disilicate restorations at 4 years: A retrospective study.
abstract: BACKGROUND
  Ceramic restorations are frequently being placed due to the esthetic demand and the cost of noble metals that has increased considerably. One major disadvantage of ceramic restoration is failure of the material due to fracture by crack propagation. In vitro studies are of little clinical significance and in vivo studies are too short to support clinical success.
  
  
  OBJECTIVE
  The purpose of this retrospective study was to evaluate the failure rate of lithium disilicate restorations (monolithic and layered) at 4 years.
  
  
  METHODS
  Data were collected over 45 months from 2 commercial laboratories. Restorations were categorized into monolithic restorations and layered restorations. Each category was further classified into complete coverage single crowns, fixed dental prostheses, e.max veneers, and inlay/onlay restorations. Failure rates were compared and analyzed using Chi-square (α=.05).
  
  
  RESULTS
  A total of 21,340 restorations were evaluated in this study and included 15,802 monolithic restorations and 5538 layered restorations. The failure rate for single crown monolithic restorations was 0.91% and was 1.83% for single crown layered restorations. For fixed dental prostheses, 4.55% of monolithic restorations failed. For e.max veneers, 1.3% of monolithic veneers fractured and 1.53% of layered veneers fractured. Of the inlay/onlay restorations group, 1.01% of monolithic restorations fractured.
  
  
  CONCLUSIONS
  In the short term (45 months), restorations fabricated with the lithium disilicate material (IPS e.max) had relatively low fracture rates. Layered single crowns fractured at approximately 2 times the rate of monolithic crowns.
authors.affiliation: Visiting scholar, Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, NC; and Doctoral student, Department of Prosthetic Dentistry, Institute of Dentistry, University of Turku, Turku, Finland.
authors.forename: Taiseer A
authors.initials: TA
authors.lastname: Sulaiman
authors.affiliation: Clinical Assistant Professor, Department of Restorative Sciences Division of Operative Dentistry, University of Florida, Gainesville, Fla. Electronic address: adelgado@dental.ufl.edu.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Delgado
authors.affiliation: Professor and Section Head, Biomaterials Sciences, Department of Operative Dentistry, University of North Carolina, Chapel Hill, NC.
authors.forename: Terence E
authors.initials: TE
authors.lastname: Donovan
mesh_terms: D003442:Crowns; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent; D003830:Denture, Partial, Fixed; D006801:Humans; D012189:Retrospective Studies
chemical_list: C493120:lithia disilicate; D003776:Dental Porcelain