title: Fracture strength of CAD/CAM composite and composite-ceramic occlusal veneers.
abstract: OBJECTIVE
  To determine the effect of material type and restoration thickness on the fracture strength of posterior occlusal veneers made from computer-milled composite (Paradigm MZ100) and composite-ceramic (Lava Ultimate) materials.
  
  
  METHODS
  60 maxillary molars were prepared and restored with CAD/CAM occlusal veneer restorations fabricated from either Paradigm MZ100 or Lava Ultimate blocks at minimal occlusal thicknesses of 0.3, 0.6, and 1.0mm. Restorations were adhesively bonded and subjected to vertical compressive loading. The maximum force at fracture and mode of failure were recorded. 2-Way ANOVA was used to identify any statistically significant relationships between fracture strength and material type or thickness. Spearman's rank correlation coefficient was used to analyze mode of failure with regard to fracture strength.
  
  
  RESULTS
  The average maximum loads (N) at fracture for the Paradigm MZ100 groups were 1620 ± 433, 1830 ± 501, and 2027 ± 704 for the material thicknesses of 0.3, 0.6, and 1.0mm, respectively. The Lava Ultimate groups fractured at slightly higher loads (N) of 2078 ± 605, 2141 ± 473, and 2115 ± 462 at the respective 0.3, 0.6, and 1.0mm thickness. Statistical analyses revealed that, while no significant difference existed among the various restoration thicknesses in terms of fracture strength (P>0.05), the material type was found to be influential (P=0.04). The maximum load at fracture (N) for Lava Ultimate averaged over all thicknesses (2111 ± 500) was significantly higher than that of the Paradigm MZ100 (1826 ± 564). No correlation between mode of failure and fracture strength was found.
  
  
  CONCLUSIONS
  Under the conditions of this study, the maximal loads at fracture for these "non-ceramic" occlusal veneer restorations were found to be higher than human masticatory forces. Occlusal veneers made from the two materials tested are likely to survive occlusal forces regardless of restoration thickness, with those fabricated from the composite-ceramic hybrid material being more likely to survive heavier loads.
authors.affiliation: Advanced Prosthodontic Program, Department of Prosthodontics, University of Tennessee Health Science Center, College of Dentistry, Memphis, TN, United States.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Johnson
authors.affiliation: Department of Bioscience Research, University of Tennessee Health Science Center, College of Dentistry, Memphis, TN, United States.
authors.forename: Antheunis
authors.initials: A
authors.lastname: Versluis
authors.affiliation: Department of Restorative Dentistry, University of Tennessee Health Science Center, College of Dentistry, Memphis, TN, United States.
authors.forename: Daranee
authors.initials: D
authors.lastname: Tantbirojn
authors.affiliation: Department of Prosthodontics, University of Tennessee Health Science Center, College of Dentistry, Memphis, TN, United States. Electronic address: sahuja@uthsc.edu.
authors.forename: Swati
authors.initials: S
authors.lastname: Ahuja
mesh_terms: D001732:Bite Force; D003188:Composite Resins; D019245:Compressive Strength; D017076:Computer-Aided Design; D003764:Dental Materials; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D003801:Dental Veneers; D006801:Humans; D013314:Stress, Mechanical
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D003776:Dental Porcelain
keywords: CAD/CAM; Conservative; Milled; Occlusal veneer; Posterior