title: Influence of implant angulation and cyclic dislodging on the retentive force of two different overdenture attachments - an in vitro study.
abstract: OBJECTIVE
  This in vitro study evaluated the influence of implant angulations on the retentive behavior of two overdenture attachments during cyclic dislodging.
  
  
  METHODS
  Models simulating a two-implant overdenture situation were fabricated. They were divided into five groups based on their simulated implant angulations (Groups: 1 = 0°; 2 = 20°; 3 = 30°; 4 = 40°; and 5 = 60°; n = 90). Each group was further divided into two subgroups based on its attachment system (control attachment: LOCATOR(®) ; test attachment: SFI-Anchor(®) ) except for group 5 which had no LOCATOR(®) group. All models underwent 10,000 insertion-removal cycles in a wet environment. Mean retentive forces were recorded. ANOVA and linear regression models were used for statistical analyses, and the level of significance was at P < 0.05.
  
  
  RESULTS
  The ANOVA model revealed an effect of dislodging cycles for both attachments (P = 0.0070). The linear regression model with repeated measures revealed a significant effect of angulation within the LOCATOR(®) groups (0° vs. 20°: P < 0.0001; 0° vs. 30°: P < 0.0001; 0° vs. 40°: P < 0.0001), but was insignificant within the SFI-Anchor(®) groups (0° vs. 20°: P = 0.544; 0° vs. 30°: P = 0.134; 0° vs. 40°: P = 0.254; 0° vs. 60°: P = 0.979). It further revealed a significant increase in the retentive force between the LOCATOR(®) and the SFI-Anchor(®) (20°: P = 0.041; 30°: P < 0.0001; 40°: P < 0.0001), although there was no significant difference between the attachments at 0° (P = 0.623).
  
  
  CONCLUSIONS
  This study confirms that the retentive behavior of SFI-Anchor(®) is not influenced by implant axial inclination even at angulations of up to 60°. The SFI-Anchor(®) may therefore be particularly indicated for clinical situations with marked implant axial discrepancies.
authors.affiliation: Division of Gerodontology and Removable Prosthodontics, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland.
authors.forename: Murali
authors.identifier: http://orcid.org/0000-0003-3365-576X
authors.initials: M
authors.lastname: Srinivasan
authors.affiliation: Division of Gerodontology and Removable Prosthodontics, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland.|Division of Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Schimmel
authors.affiliation: Division of Bone Diseases, Department of Internal Medicine Specialties, University of Geneva, Geneva, Switzerland.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Badoud
authors.affiliation: Division of Bone Diseases, Department of Internal Medicine Specialties, University of Geneva, Geneva, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ammann
authors.affiliation: Division of Geriatrics, Department of Internal Medicine, Rehabilitation and Geriatrics, University Hospitals of Geneva, Thônex, Switzerland.
authors.forename: François R
authors.initials: FR
authors.lastname: Herrmann
authors.affiliation: Division of Gerodontology and Removable Prosthodontics, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland.|Division of Geriatrics, Department of Internal Medicine, Rehabilitation and Geriatrics, University Hospitals of Geneva, Thônex, Switzerland.
authors.forename: Frauke
authors.initials: F
authors.lastname: Müller
mesh_terms: D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D003781:Denture Retention / Q000295:instrumentation*; D003828:Denture, Overlay; D006801:Humans
chemical_list: D015921:Dental Implants
keywords: LOCATOR
  ®; SFI-Anchor®; artificial saliva; dislodging cycles; implant overdentures; in vitro testing; overdentures; retentive force