title: Comparative study of retentive anchor systems for overdentures.
abstract: OBJECTIVE
  This study aimed to evaluate the retention on two or four implants of eight resilient and nonresilient retentive anchors used in overdentures.
  
  
  METHODS
  Eight groups of retentive anchors were used: Dyna and Shiner (magnets); Dalla Bona and O-Ring (balls); Ceka Revax and Zaag attachments (studs); the cast bar (Dolder type) system with plastic clips; and the milled bars system. These specimens with their respective overdentures were prepared on two similar acrylic resin models with four implants (3.75 x 13 mm). Ten tensile strength tests (Instron) were performed on each group at a speed of 3 mm per minute. The statistical analysis (one-way analysis of variance, Tukey's HSD test) was considered significant.
  
  
  RESULTS
  The pull force values ranged between 0.400 and 3.800 daN (International System of Units). There was a significant difference in retention in favor of the milled bars in comparison with the Ceka Revax, Hader bars, Zaag attachments, O-Ring, and Dyna groups, and a marginally significant difference compared with the Dalla Bona group. There was a highly significant difference with the Shiner magnets.
  
  
  CONCLUSIONS
  The milled bar system was the most retentive anchor, with the Dalla Bona, Ceka Revax, Hader Bar, Zaag attachment, and O-Ring groups being the second most retentive. The least retentive groups were the Shiner and Dyna magnets. Proper abutment placement in the mandible and the correct selection of the retentive anchor will improve overdenture retention.
authors.affiliation: Department of Clinical Fixed Prosthetics, Dental School, National University of Córdoba, Córdoba, Argentina.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Svetlize
authors.forename: Enrique Fernández
authors.initials: EF
authors.lastname: Bodereau
mesh_terms: D000704:Analysis of Variance; D000044:Dental Abutments; D016734:Dental Clasps; D017268:Dental Prosthesis Retention / Q000295:instrumentation*; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D003834:Denture Precision Attachment; D003828:Denture, Overlay; D006801:Humans; D008280:Magnetics / Q000295:instrumentation; D013718:Tensile Strength