title: [Cyclic fatigue test of cobalt-chromium alloy cast clasps].
abstract: OBJECTIVE
  To investigate the change of retentive forces of cast cobalt-chromium (Co-Cr) alloy clasp in cyclic fatigue test.
  
  
  METHODS
  Samples of three types of cast Co-Cr alloy (Group A: Hardalloy; B: Regalloy™; C: Vera PDN™) clasps were fabricated and placed at undercut depths of 0.25 mm, 0.50 mm. The clasps were drawn from the model molar cyclicly to simulate 5 years of clinical use in an universal testing machine. Retentive force were record at 21 different time point for each clasp during the whole fatigue testing process. Data were subjected to ANOVA, Chi-square test and linear regression analysis.
  
  
  RESULTS
  All clasps showed decreasing retention during the cyclic fatigue test. Clasps engaged in 0.50 mm undercut depth exhibited greater initial retentive force [Group A: (8.714 +/- 1.104) N, B: (9.072 +/- 0.653) N, C: (9.588 +/- 1.980) N] as well as greater loss of retention [Group A: (4.408 +/- 0.662) N, B: (3.484 +/- 0.494) N, C: (3.290 +/- 1.484) N] at the end of the test than clasps engaged in 0.25 mm undercut did [initial forces were (7.940 +/- 0.357), (7.834 +/- 1.308) and (8.156 +/- 1.067) N for Group A, B, C, respectively; loss of retention were (2.444 +/- 0.736) N, (2.954 +/- 1.048) N and (1.832 +/- 1.180) N for group A, B, C, respectively]. Negative correlation was found between the clasp retention and the logarithm of cycling times.
  
  
  CONCLUSIONS
  Co-Cr alloy cast clasp could provide adequate retentive force for 5 years of clinical use.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Fujian Medical University, Fuzhou 350002, China.
authors.forename: Min-rui
authors.initials: MR
authors.lastname: Xu
authors.forename: Hui
authors.initials: H
authors.lastname: Cheng
authors.forename: Ming
authors.initials: M
authors.lastname: Zheng
authors.forename: Xiu-rong
authors.initials: XR
authors.lastname: Li
authors.forename: Wei-qing
authors.initials: WQ
authors.lastname: Wu
authors.forename: Dong
authors.initials: D
authors.lastname: Chen
mesh_terms: D002858:Chromium Alloys / Q000737:chemistry*; D003722:Dental Alloys / Q000737:chemistry*; D003735:Dental Casting Technique; D016734:Dental Clasps; D003799:Dental Stress Analysis; D003781:Denture Retention
chemical_list: D002858:Chromium Alloys; D003722:Dental Alloys