title: Evaluation of stable retentive properties of overdenture attachments.
abstract: OBJECTIVE
  To evaluate fatigue of stud (ERA Overdenture (orange and white), Locator Root (pink) and OP anchor # 4) and magnetic (Magfit EX600W) attachments by measuring maximum retentive force. To compare retentive force of overdenture attachments after their reach stable retention. To determine minimum number of cycles required to reach stable retention.
  
  
  METHODS
  Three specimens of each type of attachment were used. Micromaterial testing machine (MMT-250NB-10, Shimadzu Co., Tokyo, Japan) with a sensor interface PCD-320 and software package PCD-30A (Kyowa Electronic Instruments Co., Tokyo, Japan) was used to performe 2000 insertion-removal cycles with 50 mm/min cross head speed. Maximum retentive force was measured initially and after each 40 cycles.
  
  
  METHODS
  paired-samples t-test, one-way ANOVA and Scheffe post-hoc tests (P<0.05).
  
  
  RESULTS
  Before and after fatigue simulation statistically significant differences existed among the five types of attachments. Decrease of retention was characteristic for all attachments except OP. After fatigue LRP was most retentive. Magnetic attachments preserved maximum amount of retention measured at the baseline (98%). EO and EW attachments have preserved only 25% and 37% of initial retention respectively.
  
  
  CONCLUSIONS
  Due to fatigue overdenture attachments gradually loose their retention. Stud attachments are more susceptible to fatigue than magnets. Eight hundred cycles are required to achieve relatively stable retention of overdenture attachments.
authors.affiliation: Center of Prosthodontics, Institute of Odontology, Faculty of Medicine, Vilnius University, Zalgirio str. 115, Room #231, 08217 Vilnius, Lithuania. vygandasr@gmail.com
authors.forename: Vygandas
authors.initials: V
authors.lastname: Rutkunas
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mizutani
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D000044:Dental Abutments; D003779:Denture Design; D003781:Denture Retention; D003828:Denture, Overlay; D006801:Humans; D008280:Magnetics / Q000295:instrumentation; D008422:Materials Testing; D013314:Stress, Mechanical; D013997:Time Factors