title: Marginal and internal fit of heat pressed versus CAD/CAM fabricated all-ceramic onlays after exposure to thermo-mechanical fatigue.
abstract: OBJECTIVE
  The aim of the study was to evaluate the marginal and internal fit of heat-pressed and CAD/CAM fabricated all-ceramic onlays before and after luting as well as after thermo-mechanical fatigue.
  
  
  METHODS
  Seventy-two caries-free, extracted human mandibular molars were randomly divided into three groups (n=24/group). All teeth received an onlay preparation with a mesio-occlusal-distal inlay cavity and an occlusal reduction of all cusps. Teeth were restored with heat-pressed IPS-e.max-Press* (IP, *Ivoclar-Vivadent) and Vita-PM9 (VP, Vita-Zahnfabrik) as well as CAD/CAM fabricated IPS-e.max-CAD* (IC, Cerec 3D/InLab/Sirona) all-ceramic materials. After cementation with a dual-polymerising resin cement (VariolinkII*), all restorations were subjected to mouth-motion fatigue (98 N, 1.2 million cycles; 5°C/55°C). Marginal fit discrepancies were examined on epoxy replicas before and after luting as well as after fatigue at 200× magnification. Internal fit was evaluated by multiple sectioning technique. For the statistical analysis, a linear model was fitted with accounting for repeated measurements.
  
  
  RESULTS
  Adhesive cementation of onlays resulted in significantly increased marginal gap values in all groups, whereas thermo-mechanical fatigue had no effect. Marginal gap values of all test groups were equal after fatigue exposure. Internal discrepancies of CAD/CAM fabricated restorations were significantly higher than both press manufactured onlays.
  
  
  CONCLUSIONS
  Mean marginal gap values of the investigated onlays before and after luting as well as after fatigue were within the clinically acceptable range. Marginal fit was not affected by the investigated heat-press versus CAD/CAM fabrication technique. Press fabrication resulted in a superior internal fit of onlays as compared to the CAD/CAM technique.
  
  
  CONCLUSIONS
  Clinical requirements of 100 μm for marginal fit were fulfilled by the heat-press as well as by the CAD/CAM fabricated all-ceramic onlays. Superior internal fit was observed with the heat-press manufacturing method. The impact of present findings on the clinical long-term behaviour of differently fabricated all-ceramic onlays warrants further investigation.
authors.affiliation: Department of Prosthodontics, School of Dentistry, Albert-Ludwigs-University Freiburg, Germany. Electronic address: petra.guess@uniklinik-freiburg.de.
authors.forename: Petra C
authors.initials: PC
authors.lastname: Guess
authors.affiliation: Department of Prosthodontics, School of Dentistry, Albert-Ludwigs-University Freiburg, Germany.
authors.forename: Thaleia
authors.initials: T
authors.lastname: Vagkopoulou
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Institute of Medical Biometry and Medical Informatics, Albert-Ludwigs-University Freiburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wolkewitz
authors.affiliation: Department of Prosthodontics, School of Dentistry, Albert-Ludwigs-University Freiburg, Germany.
authors.forename: Joerg R
authors.initials: JR
authors.lastname: Strub
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000179:Acrylates / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D002484:Cementation / Q000379:methods*; D017076:Computer-Aided Design; D055117:Curing Lights, Dental; D003737:Dental Cavity Preparation / Q000145:classification; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D006801:Humans; D007284:Inlays; D008409:Mastication; D008422:Materials Testing; D008963:Molar; D058105:Polymerization; D017680:Potassium Compounds / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature
chemical_list: D000179:Acrylates; D000538:Aluminum Silicates; C520133:IPS e.max CAD LT; C508050:IPS e.max Press; D017680:Potassium Compounds; D019279:Resin Cements; D012821:Silanes; C493120:lithia disilicate; D003776:Dental Porcelain; C016447:feldspar; C103502:Variolink; C040415:heliobond
keywords: All-ceramic materials; CAD/CAM; Internal fit; Marginal fit; Onlay restoration; Thermo-mechanical fatigue