title: Influence of different tightening forces before laser welding to the implant/framework fit.
abstract: OBJECTIVE
  The aim of the present study was to evaluate the influence of abutment screw tightening force before laser welding procedures on the vertical fit of metal frameworks over four implants.
  
  
  METHODS
  To construct the frameworks, prefabricated titanium abutments and cylindrical titanium bars were joined by laser welding to compose three groups: group of manual torque (GMT), GT10 and GT20. Before welding, manual torque simulating routine laboratory procedure was applied to GTM. In GT10 and GT20, the abutment screws received 10 and 20 Ncm torque, respectively. After welding, the implant/framework interfaces were assessed by optical comparator microscope using two methods. First, the single screw test (SST) was used, in which the interfaces of the screwed and non-screwed abutments were assessed, considering only the abutments at the framework extremities. Second, the interfaces of all the abutments were evaluated when they were screwed.
  
  
  RESULTS
  In the SST, intergroup analysis (Kruskal Wallis) showed no significant difference among the three conditions of tightening force; that is, the different tightening force before welding did not guarantee smaller distortions. Intragroup analysis (Wilcoxon) showed that for all groups, the interfaces of the non-screwed abutments were statistically greater than the interfaces of the screwed abutments, evidencing distortions in all the frameworks. ANOVA was applied for the comparison of interfaces when all the abutments were screwed and showed no significant difference among the groups.
  
  
  CONCLUSIONS
  Under the conditions of this study, pre-welding tightness on abutment screws did not influence the vertical fit of implant-supported metal frameworks.
authors.affiliation: Department of Fixed Prosthodontics, Occlusion and Dental Materials, Dental School of Federal University of Uberlandia, Minas Gerais, Brazil. clebiodomingues@yahoo.com.br
authors.forename: Clebio Domingues
authors.initials: CD
authors.lastname: da Silveira-Júnior
authors.forename: Flávio Domingues
authors.initials: FD
authors.lastname: Neves
authors.forename: Alfredo Júlio
authors.initials: AJ
authors.lastname: Fernandes-Neto
authors.forename: Célio Jesus
authors.initials: CJ
authors.lastname: Prado
authors.forename: Paulo César
authors.initials: PC
authors.lastname: Simamoto-Júnior
mesh_terms: D000044:Dental Abutments; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry; D017268:Dental Prosthesis Retention; D019094:Dental Prosthesis, Implant-Supported; D012994:Dental Soldering; D006801:Humans; D007834:Lasers; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D019415:Torque
chemical_list: D015921:Dental Implants; D003764:Dental Materials; D014025:Titanium