title: A microstrain comparison of passively fitting screw-retained and cemented titanium frameworks.
abstract: BACKGROUND
  An imprecise fit between frameworks and supporting dental implants in loaded protocols increases the strain transferred to the periimplant bone, which may impair healing or generate microgaps.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the microstrain between premachined 1-piece screw-retained frameworks (group STF) and screw-retained frameworks fabricated by cementing titanium cylinders to the prefabricated framework (group CTF). This procedure was developed to correct the misfit between frameworks and loaded implants.
  
  
  METHODS
  Four internal hexagon cylindrical implants were placed 10 mm apart in a polyurethane block by using the surgical guides of the corresponding implant system. Previously fabricated titanium frameworks (n=10) were divided into 2 groups. In group STF, prefabricated machined frameworks were used (n=5), and, in group CTF, the frameworks were fabricated by using a passive fit procedure, which was developed to correct the misfit between the cast titanium frameworks and supporting dental implants (n=5). Both groups were screw-retained under torque control (10 Ncm). Six strain gauges were placed on the upper surface of the polyurethane block, and 3 strain measurements were recorded for each framework. Data were analyzed with the Student t test (α=.05).
  
  
  RESULTS
  The mean microstrain values between the framework and the implants were significantly higher for group STF (2517 mε) than for group CTF (844 mε) (P<.05).
  
  
  CONCLUSIONS
  Complete-arch implant frameworks designed for load application and fabricated by using the passive fit procedure decreased the strain between the frameworks and implants more than 1 piece prefabricated machined frameworks.
authors.affiliation: Professor, Department of Dental Materials and Prosthodontics, Sao Paulo State University Dental School (UNESP), Sao José dos Campos, Brazil.
authors.forename: Diego Klee
authors.initials: DK
authors.lastname: de Vasconcellos
authors.affiliation: Professor, Department of Dental Materials and Prosthodontics, Sao Paulo State University Dental School (UNESP), Sao José dos Campos, Brazil. Electronic address: kojima@fosjc.unesp.br.
authors.forename: Alberto Noriyuki
authors.initials: AN
authors.lastname: Kojima
authors.affiliation: Professor, Department of Dental Materials and Prosthodontics, Paulista University (UNIP), São Paulo, Brazil.
authors.forename: Alfredo Mikail Melo
authors.initials: AM
authors.lastname: Mesquita
authors.affiliation: Professor, Department of Dental Materials and Prosthodontics, Sao Paulo State University Dental School (UNESP), Sao José dos Campos, Brazil.
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: Bottino
authors.affiliation: Professor, Dental Materials Unit, Center for Dental and Oral Medicine, Clinic for Fixed and Removable Prosthodontics and Dental Materials Science, University of Zürich, Zürich, Switzerland.
authors.forename: Mutlu
authors.initials: M
authors.lastname: Ozcan
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D002484:Cementation / Q000379:methods*; D015921:Dental Implants; D018772:Dental Marginal Adaptation / Q000145:classification; D003764:Dental Materials / Q000737:chemistry*; D019094:Dental Prosthesis, Implant-Supported; D003781:Denture Retention / Q000295:instrumentation*; D006801:Humans; D008334:Mandible / Q000033:anatomy & histology; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008953:Models, Anatomic; D010710:Phosphates / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013871:Thiones / Q000737:chemistry; D014025:Titanium / Q000737:chemistry*; D019415:Torque
chemical_list: D000180:Acrylic Resins; C521707:Alloy Primer; D015921:Dental Implants; D003764:Dental Materials; D008689:Methacrylates; C093719:Panavia TPN-S; D010710:Phosphates; D011140:Polyurethanes; D019279:Resin Cements; D013871:Thiones; D014025:Titanium