title: Evaluation of removal forces of implant-supported zirconia copings depending on abutment geometry, luting agent and cleaning method during re-cementation.
abstract: OBJECTIVE
  To evaluate the effects of different abutment geometries in combination with varying luting agents and the effectiveness of different cleaning methods (prior to re-cementation) regarding the retentiveness of zirconia copings on implants.
  
  
  METHODS
  Implants were embedded in resin blocks. Three groups of titanium abutments (pre-fabricated, height: 7.5 mm, taper: 5.7°; customized-long, height: 6.79 mm, taper: 4.8°; customized-short, height: 4.31 mm, taper: 4.8°) were used for luting of CAD/CAM-fabricated zirconia copings with a semi-permanent (Telio CS) and a provisional cement (TempBond NE). Retention forces were evaluated using a universal testing machine. Furthermore, the influence of cleaning methods (manually, manually in combination with ultrasonic bath or sandblasting) prior to re-cementation with a provisional cement (TempBond NE) was investigated with the pre-fabricated titanium abutments (height: 7.5 mm, taper: 5.7°) and SEM-analysis of inner surfaces of the copings was performed. Significant differences were determined via two-way ANOVA.
  
  
  RESULTS
  Significant interactions between abutment geometry and luting agent were observed. TempBond NE showed the highest level of retentiveness on customized-long abutments, but was negatively affected by other abutment geometries. In contrast, luting with Telio CS demonstrated consistent results irrespective of the varying abutment geometries. Manual cleaning in combination with an ultrasonic bath was the only cleaning method tested prior to re-cementation that revealed retentiveness levels not inferior to primary cementation.
  
  
  CONCLUSIONS
  No superiority for one of the two cements could be demonstrated because their influences on retentive strength are also depending on abutment geometry. Only manual cleaning in combination with an ultrasonic bath offers retentiveness levels after re-cementation comparable to those of primary luting.
authors.affiliation: Department of Prosthodontics, School of Dentistry, University Medical Center Goettingen, Goettingen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Rödiger
authors.affiliation: Department of Prosthodontics, School of Dentistry, University Medical Center Goettingen, Goettingen, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Rinke
authors.affiliation: Department of Prosthodontics, School of Dentistry, University Medical Center Goettingen, Goettingen, Germany.
authors.forename: Fenja
authors.initials: F
authors.lastname: Ehret-Kleinau
authors.affiliation: Department of Prosthodontics, School of Dentistry, University Medical Center Goettingen, Goettingen, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Pohlmeyer
authors.affiliation: Department of Medical Statistics, University Medical Center Goettingen, Goettingen, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Lange
authors.affiliation: Department of Prosthodontics, School of Dentistry, University Medical Center Goettingen, Goettingen, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Bürgers
authors.affiliation: Department of Prosthodontics, School of Dentistry, University Medical Center Goettingen, Goettingen, Germany.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Gersdorff
keywords: CAD/CAM; Cleaning method; Implant abutments; Semi-permanent cementation; Temporary cementation; Zirconia copings