title: Influence of cold working and thermal treatment on the fit of implant-supported metal-ceramic fixed partial dentures.
abstract: BACKGROUND
  The application of porcelain may alter the fit of metal-ceramic frameworks. In fixed partial denture frameworks, this altered fit may cause marginal opening and require sectioning and soldering of the prosthesis.
  
  
  OBJECTIVE
  The purpose of this study was to compare the fit of implant-supported metal-ceramic fixed partial dentures when different thermal treatments were performed.
  
  
  METHODS
  Fifteen implant-supported metal-ceramic fixed partial denture frameworks were fabricated and divided into 3 treatment groups: Group 1 = cold working and thermal oxidation; Group 2 = unrestrained thermal treatment, cold working, and oxidation; and Group 3 = investment-restrained thermal treatment, cold working, and oxidation. After the appropriate treatment procedures, porcelain was applied. Measurements were made with a digital caliper, with the help of fiduciary marks, after each step in 3 dimensions and at 2 locations. These measurements were compared with those of the as-cast framework (baseline) to determine framework distortion. Distortion data among groups were compared with repeated-measures analysis of variance and Tukey's Studentized range test (P<.05).
  
  
  RESULTS
  Absolute values of distortion (regardless of direction) after thermal treatment and after porcelain application were not significantly different among groups. However, total raw values of distortion, which describe the specific direction of distortion, were significantly different for 4 of the 6 recorded measurements between Groups 1 and 3 (P<.05). Although the absolute distortion values did not differ among groups, heat treatment and finishing of the alloy affected the timing and direction of distortion.
  
  
  CONCLUSIONS
  Within the limitations of this study, heat treatment of implant-supported metal-ceramic fixed partial denture frameworks before cold working did not decrease the total absolute distortion. Definite patterns of distortion were, however, found in Groups 1 and 3, suggesting that specific manipulations and heat treatments of the alloy affected the direction of distortion.
authors.affiliation: Division of Prosthodontics, Eastman Dental Center, University of Rochester, Rochester, NY 14620, USA.
authors.forename: Salman A
authors.initials: SA
authors.lastname: Lakhani
authors.forename: Carlo
authors.initials: C
authors.lastname: Ercoli
authors.forename: Mark E
authors.initials: ME
authors.lastname: Moss
authors.forename: Gerald N
authors.initials: GN
authors.lastname: Graser
authors.forename: Ross H
authors.initials: RH
authors.lastname: Tallents
mesh_terms: D000704:Analysis of Variance; D003080:Cold Temperature; D003734:Dental Casting Investment; D003735:Dental Casting Technique; D019094:Dental Prosthesis, Implant-Supported; D003779:Denture Design; D003830:Denture, Partial, Fixed; D004055:Differential Thermal Analysis; D006358:Hot Temperature; D006801:Humans; D016876:Metal Ceramic Alloys; D017755:Prosthesis Fitting; D018709:Statistics, Nonparametric
chemical_list: D003734:Dental Casting Investment; D016876:Metal Ceramic Alloys