title: The Effect of Gap Angle on Tensile Strength of Preceramic Base Metal Solder Joints.
abstract: BACKGROUND
  Soldering is a process commonly used in fabricating dental prosthesis. Since most soldered prosthesis fail at the solder joints; the joint strength is of utmost importance.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the effect of gap angle on the tensile strength of base metal solder joints.
  
  
  METHODS
  A total number of 40 Ni-Cr samples were fabricated according to ADA/ISO 9693 specifications for tensile test. Samples were cut at the midpoint of the bar, and were placed at the considered angles by employing an explicitly designed device. They were divided into 4 groups regarding the gap angle; Group C (control group) with parallel gap on steady distance of 0.2mm, Group 1: 10°, Group 2: 20°, and Group3: 30° gap angles. When soldered, the specimens were all tested for tensile strength using a universal testing machine at a cross-head speed of 0.5 mm/min with a preload of 10N. Kruskal-Wallis H test was used to compare tensile strength among the groups (p< 0.05).
  
  
  RESULTS
  The mean tensile strength values obtained from the study groups were respectively 307.84, 391.50, 365.18, and 368.86 MPa. The tensile strength was not statistically different among the four groups in general (p≤ 0.490).
  
  
  CONCLUSIONS
  Making the gap angular at the solder joints and the subsequent unsteady increase of the gap distance would not change the tensile strength of the joint.
authors.affiliation: Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Science, Shiraz, Iran.
authors.forename: Farnaz
authors.initials: F
authors.lastname: Fattahi
authors.affiliation: Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Science, Shiraz, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Hashemi Ardakani
authors.affiliation: Undergraduate Student, School of Dentistry, Shiraz University of Medical Science, Shiraz, Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Hashemi Ardakani
keywords: Base Metal; Solder Gap angle; Solder Joint; Tensile Strength