title: Maximum dislodging forces of mandibular implant-assisted removable partial dentures: in vitro assessment.
abstract: OBJECTIVE
  The initial retention of implant-assisted removable partial dentures (IARPDs) is unknown. The purpose of this in vitro study was to compare maximum dislodging forces of distal extension mandibular IARPD with two different attachments and three clasp designs.
  
  
  METHODS
  A simulated class I partially edentulous mandible was prepared with two screw-type 3.75 × 12 mm implants in the first molar regions and 2 metal-ceramic crowns on distal abutments. Fifteen bilateral distal extension frameworks were conventionally fabricated in three clasp designs (suprabulge, infrabulge, no clasp). Locator attachments were connected to the 15 denture bases with autopolymerized resin. Each specimen was subject to four types of retention pulls (main, anterior, posterior, unilateral pull) five times with a universal testing machine. Locator attachments were replaced with O-ring attachments, and the same procedure was performed. Therefore, the study groups included: IRPD with Locator attachment and suprabulge clasp (group 1), IRPD with Locator attachment and infrabulge clasp (group 2), IRPD with Locator attachment and no clasp (group 3), IRPD with O-ring attachment and suprabulge clasp (group 4), IRPD with O-ring attachment and infrabulge clasp (group 5), IRPD with O-ring attachment and no clasp (group 6). Data were analyzed using one-way ANOVA, two-way ANOVA, and Tukey tests.
  
  
  RESULTS
  The highest mean value was 22.99 lb for prostheses with a Locator attachment and suprabulge clasp. The lowest retentive values were recorded for IARPDs with O-ring attachments.
  
  
  CONCLUSIONS
  The results of this in vitro study suggest that the precise selection of attachments with or without clasp assemblies may affect the clinical success of mandibular IARPDs.
authors.affiliation: Professor of Prosthodontics, Dental Research Center, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Jafar
authors.initials: J
authors.lastname: Gharehchahi
authors.affiliation: Associate Professor of Prosthodontics, Dental Research Center, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Nafiseh
authors.initials: N
authors.lastname: Asadzadeh
authors.affiliation: Assistant Professor of Prosthodontics, Dental Material Research Center, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Amirtaher
authors.initials: A
authors.lastname: Mirmortazavi
authors.affiliation: Associate Professor of Community Medicine and Public Health, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Mohammad Taghi
authors.initials: MT
authors.lastname: Shakeri
mesh_terms: D003442:Crowns; D000044:Dental Abutments; D016734:Dental Clasps; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D003819:Denture Bases; D003779:Denture Design; D003781:Denture Retention / Q000295:instrumentation; D003832:Denture, Partial, Removable; D006801:Humans; D007575:Jaw, Edentulous / Q000145:classification; D008334:Mandible / Q000473:pathology; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008953:Models, Anatomic; D013314:Stress, Mechanical
chemical_list: D016876:Metal Ceramic Alloys
keywords: Dental implant; attachment; removable partial denture; retention, clasp