title: Load Transfer Characteristics of Three-Implant-Retained Overdentures with Different Interimplant Distances.
abstract: OBJECTIVE
  Implant-retained overdentures are the first choice of rehabilitation for edentulous mandibles. Bone morphology and anatomical landmarks may be influenced by the location and angulation of implants and distances between the implants. The purpose of this study was to investigate stress distribution characteristics and to compare stress levels of three different attachment designs of three-implant-retained mandibular overdentures with three different interimplant distances.
  
  
  METHODS
  Three photoelastic mandibular models with three implants were fabricated using an edentulous mandible cast with moderate residual ridge resorption. The center implants were embedded parallel to the midline, and the distal implants were aligned at a 20-degree angulation corresponding to the center implants. Distances between the center and distal implants were set at 11, 18, and 25 mm at the photoelastic models. Bar, bar-ball, and Locator attachment-retained overdentures were prepared for the models. Vertical loads were applied to the overdentures, and stress levels and distribution were evaluated by a circular polariscope.
  
  
  RESULTS
  The greatest observed stress level was moderate for the tested overdenture designs. The Locator attachment system showed the lowest stress level for the 11-mm and 25-mm photoelastic models. The bar attachment design transmitted less stress compared with the other tested designs for the 18-mm photoelastic model.
  
  
  CONCLUSIONS
  Stresses were observed on the loaded side of the photoelastic models. The lowest stress was found with the Locator and bar attachments for the 11-mm photoelastic model, which transmitted little or no discernible stress around the implants.
authors.forename: Emre
authors.initials: E
authors.lastname: Tokar
authors.forename: Bulent
authors.initials: B
authors.lastname: Uludag
authors.forename: Ozgul
authors.initials: O
authors.lastname: Karacaer
mesh_terms: D001696:Biomechanical Phenomena; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D003779:Denture Design; D003781:Denture Retention / Q000295:instrumentation* / Q000592:standards; D003826:Denture, Complete, Lower; D003828:Denture, Overlay; D006801:Humans; D007575:Jaw, Edentulous / Q000534:rehabilitation*; D008334:Mandible / Q000473:pathology / Q000601:surgery; D008422:Materials Testing; D003765:Models, Dental; D013314:Stress, Mechanical