title: Influence of Abutment Design on Stiffness, Strength, and Failure of Implant-Supported Monolithic Resin Nano Ceramic (RNC) Crowns.
abstract: BACKGROUND
  Recent technical development allows the digital manufacturing of monolithic reconstructions with high-performance materials. For implant-supported crowns, the fixation requires an abutment design onto which the reconstruction can be bonded.
  
  
  OBJECTIVE
  The aim of this laboratory investigation was to analyze stiffness, strength, and failure modes of implant-supported, computer-assisted design and computer-aided manufacturing (CAD/CAM)-generated resin nano ceramic (RNC) crowns bonded to three different titanium abutments.
  
  
  METHODS
  Eighteen monolithic RNC crowns were produced and loaded in a universal testing machine under quasi-static condition according to DIN ISO 14801. With regard to the type of titanium abutment, three groups were defined: (1) prefabricated cementable standard; (2) CAD/CAM-constructed individualized; and (3) novel prefabricated bonding base. Stiffness and strength were measured and analyzed statistically with Wilcoxon rank sum test. Sections of the specimens were examined microscopically.
  
  
  RESULTS
  Stiffness demonstrated high stability for all specimens loaded in the physiological loading range with means and standard deviations of 1,579 ± 120 N/mm (group A), 1,733 ± 89 N/mm (group B), and 1,704 ± 162 N/mm (group C). Mean strength of the novel prefabricated bonding base (group C) was 17% lower than of the two other groups. Plastic deformations were detectable for all implant-abutment crown connections.
  
  
  CONCLUSIONS
  Monolithic implant crowns made of RNC seem to represent a feasible and stable prosthetic construction under laboratory testing conditions with strength higher than the average occlusal force, independent of the different abutment designs used in this investigation.
authors.affiliation: Division of Fixed Prosthodontics, School of Dental Medicine, University of Bern, Bern, Switzerland.|Department of Prosthetic Dentistry, Center for Dental and Oral Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Joda
authors.affiliation: Division of Fixed Prosthodontics, School of Dental Medicine, University of Bern, Bern, Switzerland.
authors.forename: Samuel
authors.initials: S
authors.lastname: Huber
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Bern, Switzerland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Bürki
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Bern, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Zysset
authors.affiliation: Division of Fixed Prosthodontics, School of Dental Medicine, University of Bern, Bern, Switzerland.
authors.forename: Urs
authors.initials: U
authors.lastname: Brägger
mesh_terms: D002516:Ceramics; D003188:Composite Resins; D017076:Computer-Aided Design; D003442:Crowns; D059605:Dental Implant-Abutment Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D066298:In Vitro Techniques
chemical_list: D003188:Composite Resins
keywords: DIN ISO 14801; abutment connection; dental implants; failure mode; resin nano ceramic (RNC); stiffness; strength; titanium