title: Retention Load of Telescopic Crowns with Different Taper Angles between Cobalt-Chromium and Polyetheretherketone Made with Three Different Manufacturing Processes Examined by Pull-Off Test.
abstract: OBJECTIVE
  To investigate the retention loads of differently fabricated secondary telescopic polyetheretherketone (PEEK) crowns on cobalt-chromium primary crowns with different tapers.
  
  
  METHODS
  Cobalt-chromium primary crowns with 0°, 1°, and 2° tapers were constructed, milled, and sintered. Corresponding secondary crowns were fabricated by milling, pressing from pellets, and pressing from granules. For these nine test groups, the pull-off tests of each crown combination were performed 20 times, and the retention loads were measured (Zwick 1445, 50 mm/min). Data were analyzed using linear regression, covariance analysis, mixed models, Kruskal-Wallis, and Mann-Whitney U-test, together with the Benferroni-Holm correction.
  
  
  RESULTS
  The mixed models covariance analysis reinforced stable retention load values (p = 0.162) for each single test sequence. There was no interaction between the groups and the separation cycles (p = 0.179). Milled secondary crowns with 0° showed the lowest mean retention load values compared to all tested groups (p = 0.003) followed by those pressed form pellets with 1°. Regarding the different tapers, no effect of manufacturing method on the results was observed within 1° and 2° groups (p = 0.540; p = 0.052); however, among the 0° groups, the milled ones showed significantly the lowest retention load values (p = 0.002). Among the manufacturing methods, both pressed groups showed no impact of taper on the retention load values (p > 0.324 and p > 0.123, respectively), whereas among the milled secondary crowns, the 0° taper showed significantly lower retention load values than the 1° and 2° taper (p < 0.002).
  
  
  CONCLUSIONS
  Based on these results, telescopic crowns made of PEEK seem to show stable retention load values for each test sequence; however, data with thermo-mechanical aging are still required. In addition, further developments in CAD/CAM manufacturing of PEEK materials for telescopic crowns are warranted, especially for 0°.
authors.affiliation: Department of Prosthodontics, Dental School, Ludwig-Maximilian-University Munich, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Wagner
authors.affiliation: Department of Prosthodontics, Dental School, Ludwig-Maximilian-University Munich, Germany.
authors.forename: Veronika
authors.initials: V
authors.lastname: Stock
authors.affiliation: Department of Prosthodontics, Dental School, Ludwig-Maximilian-University Munich, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Merk
authors.affiliation: Clinic of Preventive Dentistry, Periodontology and Cariology, Center of Dental Medicine, University of Zurich, Switzerland.
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Schmidlin
authors.affiliation: Division of Biostatistics, Epidemiology Biostatistics and Prevention Institute, University of Zurich, Switzerland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Roos
authors.affiliation: Department of Prosthodontics, Dental School, Ludwig-Maximilian-University Munich, Germany.
authors.forename: Marlis
authors.initials: M
authors.lastname: Eichberger
authors.affiliation: Department of Prosthodontics, Dental School, Ludwig-Maximilian-University Munich, Germany.
authors.forename: Bogna
authors.initials: B
authors.lastname: Stawarczyk
mesh_terms: D001577:Benzophenones; D002858:Chromium Alloys; D003442:Crowns / Q000009:adverse effects; D003764:Dental Materials; D017267:Dental Prosthesis Design / Q000009:adverse effects; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D006801:Humans; D007659:Ketones; D011092:Polyethylene Glycols; D011108:Polymers
chemical_list: D001577:Benzophenones; D002858:Chromium Alloys; D003764:Dental Materials; D007659:Ketones; D011108:Polymers; C063834:polyetheretherketone; D011092:Polyethylene Glycols
keywords: Cobalt chrome molybdenum alloy; conus crown; telescopic crown