title: Effect of different implant positions on strain developed around four implants supporting a mandibular overdenture with rigid telescopic copings.
abstract: OBJECTIVE
  To evaluate and compare the effect of three different implant positions on strain developed around four implants supporting a mandibular overdenture with rigid telescopic attachments.
  
  
  METHODS
  Three experimental acrylic resin overdentures were fabricated on three edentulous mandibular acrylic models. Four implants were placed in each model. According to the implant positions, the models were classified into three groups: in group I (quadrilateral design) the implants were placed at canine and first molar areas; in group II (curved design) the implants were placed at canine and second premolar areas; and in group III (linear design) the implants were placed at lateral incisor and first premolar areas. Overdentures were connected to the implants with rigid telescopic attachments. Eight linear strain gauges were bonded to the acrylic resin around each implant at two sites (mesial and distal). Strains were measured for anterior (lateral incisor and canine) and posterior (premolar and molar) implants at both mesial and distal sites during bilateral and unilateral load applications.
  
  
  RESULTS
  For bilateral and unilateral load applications, group II recorded the highest strain values while group I recorded the lowest. In group II and group III, strain values at distal sites were significantly higher than values at mesial sites. Strain values of posterior implants were significantly higher than values of anterior implants in all groups. The greatest strain values were recorded at the loading side during unilateral load application.
  
  
  CONCLUSIONS
  Quadrilateral design showed minimal peri-implant strain compared to curved or linear designs. This design may be recommended when rigid telescopic crowns are used to connect mandibular overdentures to four implants.
authors.affiliation: Department of Removable Prosthodontics, Faculty of Dentistry, Mansoura University, Eldakahlia, Egypt. M_syad@mans.edu.eg
authors.forename: Moustafa Abdou
authors.initials: MA
authors.lastname: ELsyad
authors.forename: Maged Gaber
authors.initials: MG
authors.lastname: Elsaadawy
authors.forename: Anwar Mahmoud
authors.initials: AM
authors.lastname: Abdou
authors.forename: Ahmed Ali
authors.initials: AA
authors.lastname: Habib
mesh_terms: D000180:Acrylic Resins; D000044:Dental Abutments; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D003779:Denture Design; D003828:Denture, Overlay; D006801:Humans; D066298:In Vitro Techniques; D007575:Jaw, Edentulous / Q000534:rehabilitation; D008334:Mandible; D003765:Models, Dental
chemical_list: D000180:Acrylic Resins; D015921:Dental Implants