title: Retentive force and magnetic flux leakage of magnetic attachment in various keeper and magnetic assembly combinations.
abstract: BACKGROUND
  Magnetic attachments are commonly used for overdentures. However, it can be difficult to identify and provide the same type and size of magnetic assembly and keeper if a repair becomes necessary. Therefore, the size and type may not match.
  
  
  OBJECTIVE
  This study evaluated the retentive force and magnetic flux strength and leakage of magnetic attachments in different combinations of keepers and magnetic assemblies.
  
  
  METHODS
  For 6 magnet-keeper combinations using 4 sizes of magnets (GIGAUSS D400, D600, D800, and D1000) (n=5), retentive force was measured 5 times at a crosshead speed of 5 mm/min in a universal testing machine. Magnetic flux strength was measured using a Hall Effect Gaussmeter. Data were statistically analyzed using a 1-way ANOVA, and between-group differences were analyzed with Tukey's HSD post hoc test (α=.05).
  
  
  RESULTS
  The mean retentive force of the same-size magnet-keeper combinations was 3.2 N for GIGAUSS D400 and 5.1 N for GIGAUSS D600, but was significantly reduced when using larger magnets (P<.05). Magnetic flux leakage was significantly lower for corresponding size combinations.
  
  
  CONCLUSIONS
  Size differences influence the retentive force and magnetic flux strength of magnetic attachments. Retentive force decreased due to the closed field structure becoming incomplete and due to magnetic field leakage.
authors: Department of Partial Denture Prosthodontics, Nihon University School of Dentistry, Chiyoda-ku Tokyo, Japan. hasegawa-mk@dent.nihon-u.ac.jp
authors: Mikage
authors: M
authors: Hasegawa
authors: Yoshitada
authors: Y
authors: Umekawa
authors: Eiich
authors: E
authors: Nagai
authors: Tomohiko
authors: T
authors: Ishigami
mesh_terms: D017267:Dental Prosthesis Design; D003834:Denture Precision Attachment; D003781:Denture Retention / Q000295:instrumentation*; D008280:Magnetics