title: Strain gauges's analysis on implant-retained prosthesis' cast accuracy.
abstract: BACKGROUND
  A proper cast is essential for a successful rehabilitation with implant prostheses, in order to produce better structures and induce less strain on the implants.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the precision of four different mold filling techniques and verify an accurate methodology to evaluate these techniques.
  
  
  METHODS
  A total of 40 casts were obtained from a metallic matrix simulating three unit implant-retained prostheses. The molds were filled using four different techniques in four groups (n = 10): Group 1 - Single-portion filling technique; Group 2 - Two-step filling technique; Group 3 - Latex cylinder technique; Group 4 - Joining the implant analogs previously to the mold filling. A titanium framework was obtained and used as a reference to evaluate the marginal misfit and tension forces in each cast. Vertical misfit was measured with an optical microscope with an increase of 120 times following the single-screw test protocol. Strain was quantified using strain gauges. Data were analyzed using one-way ANOVA (Tukey's test) (α =0.05). The correlation between strain and vertical misfit was evaluated by Pearson test.
  
  
  RESULTS
  The misfit values did not present statistical difference (P = 0.979), while the strain results showed statistical difference between Groups 3 and 4 (P = 0.027).
  
  
  CONCLUSIONS
  The splinting technique was considered to be as efficient as the conventional technique. The strain gauge methodology was accurate for strain measurements and cast distortion evaluation. There was no correlation between strain and marginal misfit.
authors.affiliation: Department of Periodontology and Prosthodontics, Piracicaba Dental School, Campinas State University (UNICAMP), Piracicaba, São Paulo, Brazil.
authors.forename: Mariana A
authors.initials: MA
authors.lastname: Rodrigues
authors.forename: Leonardo F
authors.initials: LF
authors.lastname: Luthi
authors.forename: Jessica Mfk
authors.initials: JM
authors.lastname: Takahashi
authors.forename: Mauro Aa
authors.initials: MA
authors.lastname: Nobilo
authors.forename: Guilherme Ep
authors.initials: GE
authors.lastname: Henriques
mesh_terms: D002133:Calcium Sulfate / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry; D003734:Dental Casting Investment / Q000737:chemistry; D003735:Dental Casting Technique / Q000295:instrumentation / Q000592:standards*; D003760:Dental Impression Materials / Q000737:chemistry; D003761:Dental Impression Technique / Q000295:instrumentation; D018772:Dental Marginal Adaptation; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000295:instrumentation*; D006801:Humans; D007840:Latex / Q000737:chemistry; D008422:Materials Testing; D011145:Polyvinyls / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D002858:Chromium Alloys; D003734:Dental Casting Investment; D003760:Dental Impression Materials; D007840:Latex; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane; D002133:Calcium Sulfate