title: Dynamic fatigue and fracture resistance of non-retentive all-ceramic full-coverage molar restorations. Influence of ceramic material and preparation design.
abstract: OBJECTIVE
  The purpose of the study was to evaluate the influence of preparation design, and ceramic material, masticatory fatigue and fracture resistance of non-retentive all-ceramic full-coverage restorations luted on human mandibular molars.
  
  
  METHODS
  Full-coverage occlusal restorations were laboratory fabricated from leucite reinforced glass-ceramic (IPS Empress Esthetic) or lithium disilicate glass-ceramic (IPS e.max Press). For each ceramic material four groups with eight specimens each were randomly assigned. Groups had either a non-retentive, occlusal preparation with chamfer finishing line or straight-beveled finishing line and the preparation was either completely within enamel or within dentin with a finishing line in enamel. Restorations were adhesively luted to the teeth using composite resin. After storage in water for 1 week specimens were cyclic loaded 600,000 times with a weight of 10kg and additionally, thermocycled 3500 times (5/55 degrees C) in a masticatory simulator. Surviving specimens were loaded until, fracture in a universal testing machine. Statistical analysis was done using three-way ANOVA.
  
  
  RESULTS
  All specimens survived the masticatory fatigue. Mean fracture resistance ranged from 2895 to 4173N. Influence of ceramic material on fracture resistance was significant (p=0.0001). Lithium disilicate glass-ceramic restorations had higher fracture resistances than leucite reinforced glass-ceramic restorations. Different preparation designs showed no significant influence on fracture resistance (p=0.0969). The design of the finishing line did not influence the fracture resistance (p=0.9461).
  
  
  CONCLUSIONS
  The fracture resistance of adhesively luted non-retentive full-coverage molar restorations, made of lithium disilicate or leucite reinforced glass-ceramic is promising and seems to permit clinical application.
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Arnold-Heller-Strasse 16, Kiel, Germany.
authors.forename: Jan-Ole
authors.initials: JO
authors.lastname: Clausen
authors.forename: Milia
authors.initials: M
authors.lastname: Abou Tara
authors.forename: Matthias
authors.initials: M
authors.lastname: Kern
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000538:Aluminum Silicates / Q000737:chemistry; D001732:Bite Force; D002484:Cementation / Q000379:methods; D003188:Composite Resins / Q000737:chemistry; D003743:Dental Enamel / Q000033:anatomy & histology; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000033:anatomy & histology; D005898:Glass / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D019246:Tooth Preparation / Q000379:methods*; D014867:Water / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D003188:Composite Resins; C508050:IPS e.max Press; C075815:IPS-Empress ceramic; C469607:OptiBond FL; D019279:Resin Cements; C493120:lithia disilicate; D014867:Water; D003776:Dental Porcelain; C078519:leucite; C103502:Variolink