title: Fatigue resistance of CAD/CAM complete crowns with a simplified cementation process.
abstract: BACKGROUND
  Various computer-aided design and computer-aided manufacturing (CAD/CAM) materials are available to fabricate complete crowns. The type of material may have an effect on the longevity of these restorations.
  
  
  OBJECTIVE
  To evaluate the fatigue resistance, load-to-failure, failure mode, and antagonistic wear of complete molar computer-aided design and computer-aided manufacturing (CAD/CAM) crowns made of resin nanoceramic (RNC), feldspathic glass ceramic (FEL), or lithium disilicate (LD) placed with a simplified cementation process.
  
  
  METHODS
  Forty-five molars received a standardized complete crown preparation and were restored with CAD/CAM crowns (1.5-mm thickness, n=15) made of RNC, FEL, and LD. After cementation, the restorations were submitted to cyclic isometric loading: 200 (×5000), 400, 600, 800, 1000, 1200, and 1400 N at a maximum of 30 000 cycles each. Surviving specimens were axially loaded until failure or to a maximum load of 4500 N. The specimens were analyzed as to failure mode: catastrophic, possibly repairable, and repairable. The groups were compared by using the life table survival analysis and the t test (α=.05).
  
  
  RESULTS
  All the specimens survived the fatigue process until the 800-N step. The survival rate of RNC was 80%, LD 93.3%, and FEL 6.6%. The survival of RNC and LD crowns did not differ from each other but exceeded that of FEL. Postfatigue load-to-failure test was 2500 N (FEL), 3122 N (RNC), and 3237 N (LD). No catastrophic failure occurred in the fatigue test, whereas all of the specimens in the load-to-failure test exhibited catastrophic fractures. Crowns made of RNC seemed to generate the least amount of antagonistic wear.
  
  
  CONCLUSIONS
  Posterior crowns made of RNC and LD were not statistically different, and both had significantly higher fatigue resistance than FEL. All materials survived beyond the normal range of masticatory forces, and all failures were possibly re-restorable except those in the load-to-failure test. RNC crowns seemed to cause less wear of the antagonist.
authors.affiliation: Graduate student, Department of Restorative Dentistry, Piracicaba School of Dentistry, Campinas State University, Piracicaba, SP, Brazil. Electronic address: aoc1981@hotmail.com.
authors.forename: Adriana O
authors.initials: AO
authors.lastname: Carvalho
authors.affiliation: Graduate student, Department of Operative Dentistry, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil.
authors.forename: Greciana
authors.initials: G
authors.lastname: Bruzi
authors.affiliation: Associate Professor, Department of Restorative Dentistry, Piracicaba School of Dentistry, Campinas State University, Piracicaba, SP, Brazil.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Giannini
authors.affiliation: Don and Sybil Harrington Professor of Esthetic Dentistry, Restorative Sciences, Ostrow School of Dentistry, University of Southern California, Los Angeles, Calif.
authors.forename: Pascal
authors.initials: P
authors.lastname: Magne
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000538:Aluminum Silicates / Q000737:chemistry; D002484:Cementation / Q000379:methods*; D002516:Ceramics / Q000737:chemistry; D017076:Computer-Aided Design; D003442:Crowns; D045662:Dental Etching / Q000379:methods; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D017269:Dental Prosthesis Repair; D019232:Dental Restoration Failure; D019554:Dental Restoration Wear; D003799:Dental Stress Analysis; D006801:Humans; D015993:Life Tables; D008422:Materials Testing; D053761:Nanocomposites / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D016019:Survival Analysis
chemical_list: D000538:Aluminum Silicates; D003764:Dental Materials; D017680:Potassium Compounds; C493120:lithia disilicate; D003776:Dental Porcelain; C016447:feldspar; C023506:Glass ceramics