title: Push-out bond strength of CAD/CAM-ceramic luted to dentin with self-adhesive resin cements.
abstract: OBJECTIVE
  This study evaluated the initial and the artificially aged push-out bond strength between ceramic and dentin produced by one of five resin cements.
  
  
  METHODS
  Two-hundred direct ceramic restorations (IPS Empress CAD) were luted to standardized Class I cavities in extracted human molars using one of four self-adhesive cements (SpeedCEM, RelyX Unicem Aplicap, SmartCem2 and iCEM) or a reference etch-and-rinse resin cement (Syntac/Variolink II) (n=40/cement). Push-out bond strength (PBS) was measured (1) after 24h water storage (non-aged group; n=20/cement) or (2) after artificial ageing with 5000 thermal cycles followed by 6 months humid storage (aged group; n=20/cement). Nonparametrical ANOVA and pairwise Wilcoxon rank-sum tests with Bonferroni-Holm adjustment were applied for statistical analysis. The significance level was set at alpha=0.05. In addition, failure mode and fracture pattern were analyzed by stereomicroscope and scanning electron microscopy.
  
  
  RESULTS
  Whereas no statistically significant effect of storage condition was found (p=0.441), there was a significant effect of resin cement (p<0.0001): RelyX Unicem showed significantly higher PBS than the other cements. Syntac/Variolink II showed significantly higher PBS than SmartCEM2 (p<0.001). No significant differences were found between SpeedCEM, SmartCem2, and iCEM. The predominant failure mode was adhesive failure of cements at the dentin interface except for RelyX Unicem which in most cases showed cohesive failure in ceramic.
  
  
  CONCLUSIONS
  The resin cements showed marked differences in push-out bond strength when used for luting ceramic restorations to dentin. Variolink II with the etch-and-rinse adhesive Syntac did not perform better than three of the four self-adhesive resin cements tested.
authors.affiliation: Department of Preventive, Restorative and Pediatric Dentistry, School of Dental Medicine, University of Bern, Freiburgstrasse 7, CH-3010 Bern, Switzerland. simon.flury@zmk.unibe.ch
authors.forename: Simon
authors.initials: S
authors.lastname: Flury
authors.forename: Adrian
authors.initials: A
authors.lastname: Lussi
authors.forename: Anne
authors.initials: A
authors.lastname: Peutzfeldt
authors.forename: Brigitte
authors.initials: B
authors.lastname: Zimmerli
mesh_terms: D017076:Computer-Aided Design; D001840:Dental Bonding; D003737:Dental Cavity Preparation; D003776:Dental Porcelain; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents; D006801:Humans; D008422:Materials Testing / Q000379:methods; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements; D016369:Smear Layer; D018709:Statistics, Nonparametric
chemical_list: D017220:Dentin-Bonding Agents; D019279:Resin Cements; D003776:Dental Porcelain