title: A comparison of fatigue resistance of three materials for cusp-replacing adhesive restorations.
abstract: OBJECTIVE
  To investigate the fatigue resistance and failure behaviour of cusp-replacing restorations in premolars using different types of adhesive restorative materials.
  
  
  METHODS
  A class 2 cavity was prepared and the buccal cusp was removed in an extracted sound human upper premolar. By using a copy-milling machine this preparation was copied to 60 human upper premolars. In groups of 20 premolars each, direct resin composite restorations, indirect resin composite restorations and ceramic restorations were made. All restorations were cusp replacements made in standardized shape and with adhesive techniques. Cyclic load (5 Hz) was applied starting with a load of 200 N (10,000 cycles) followed by stages of 400, 600, 800 and 1000 N at a maximum of 50,000 cycles each. Samples were loaded until fracture or to 2,10,000 cycles maximum. In case of fracture, the failure mode was recorded.
  
  
  RESULTS
  No differences were seen in fracture strength between the three groups (Wilcoxon P = 0.16). No differences were observed with regard to failure mode above or below the cemento enamel junctions (chi2 P = 0.63). The indirect resin composite and ceramic restorations showed significantly more combined cohesive and adhesive fractures than the direct resin composite restorations, which showed more adhesive fractures (chi2 P = 0.03 and 0.002).
  
  
  CONCLUSIONS
  The results of this study suggest that ceramic, indirect resin composite and direct resin composite restorations provide comparable fatigue resistance and exhibit comparable failure modes in case of fracture, although the indirect restorations tend to fracture more cohesively than the direct restorations.
authors.affiliation: Department of Preventive and Curative Dentistry, Radboud University Medical Centre Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. r.kuijs@dent.umcn.nl
authors.forename: R H
authors.initials: RH
authors.lastname: Kuijs
authors.forename: W M M
authors.initials: WM
authors.lastname: Fennis
authors.forename: C M
authors.initials: CM
authors.lastname: Kreulen
authors.forename: F J M
authors.initials: FJ
authors.lastname: Roeters
authors.forename: N
authors.initials: N
authors.lastname: Verdonschot
authors.forename: N H J
authors.initials: NH
authors.lastname: Creugers
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D002516:Ceramics / Q000737:chemistry*; D016009:Chi-Square Distribution; D003188:Composite Resins / Q000737:chemistry*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000379:methods*; D006801:Humans; D011140:Polyurethanes / Q000737:chemistry*; D018709:Statistics, Nonparametric
chemical_list: D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D011140:Polyurethanes