title: Comparison of the load at failure of soldered and nonsoldered porcelain-fused-to-metal crowns.
abstract: BACKGROUND
  The application of solder material to metal frameworks could affect the porcelain-to-metal failure load and possibly compromise the longevity of porcelain-fused-to-metal crowns.
  
  
  OBJECTIVE
  This in vitro study assessed the influence of solder on the porcelain failure load between metal and porcelain, using crown-shaped specimens.
  
  
  METHODS
  Forty standardized crown patterns were fabricated on a metal die and cast with noble alloy (Protocol). The specimens were divided into test (soldered, n=20) and control (nonsoldered, n=20) groups. A 2-mm-diameter perforation was produced on the buccal surface of the test specimens, 1.5 mm apical to the junction between occlusal and buccal surfaces. The perforation was repaired with high-fusing white ceramic solder material. All castings were finished with aluminum oxide stones and airborne-particle abraded with 50-microm aluminum oxide at 75 psi of pressure. Two layers each of opaque and dentin porcelain were applied on all specimens. All crowns were subjected to a vertical compressive load with a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. The loading apparatus of the device contacted the buccal cusp only. In both control and test groups, 10 crowns were loaded with a stainless steel pin (phase I) whereas the remaining 10 in each group were loaded with a carbon steel pin (phase II). Means of loads at failure were recorded in each group for each pin type and compared (soldered vs nonsoldered) by use of a t test (alpha=.05).
  
  
  RESULTS
  Mean failure load for nonsoldered crowns was 349 +/- 63 kgf in phase I and 228 +/- 49 kgf in phase II. Soldered crowns showed a significantly lower failure load (265 +/- 82 kgf [phase I; P<.02] and 154 +/- 108 kgf [phase II; P<.04]) and a greater standard deviation.
  
  
  CONCLUSIONS
  Soldered metal-porcelain crown specimens demonstrated a significantly lower load at failure. Within the limits of this study, it was concluded that solder material might negatively affect porcelain-metal crowns.
authors.affiliation: Division of Prosthodontics, Eastman Dental Center, University of Rochester, 625 Elmwood Avenue, Rochester, NY 14620, USA.
authors.forename: Min-Sok
authors.initials: MS
authors.lastname: Kang
authors.forename: Carlo
authors.initials: C
authors.lastname: Ercoli
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Galindo
authors.forename: Gerald N
authors.initials: GN
authors.lastname: Graser
authors.forename: Mark E
authors.initials: ME
authors.lastname: Moss
authors.forename: Ross H
authors.initials: RH
authors.lastname: Tallents
mesh_terms: D003442:Crowns; D003772:Dental Pins; D019232:Dental Restoration Failure; D012994:Dental Soldering; D003799:Dental Stress Analysis; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D018583:Pliability; D013193:Stainless Steel; D013232:Steel
chemical_list: D016876:Metal Ceramic Alloys; D013193:Stainless Steel; D013232:Steel