مقايسه تاثير دو روش لحيم كاري قبل و بعد از پخت پرسلن به آلياژ ريختگي بر مقاومت كششي محل لحيم كاري

A comparison of two soldering techniqueon pre and post curing bond strength of procelain

Aim: The aim of this study was to compare tensile strength of pre-solder and post-solder joints for three dental alloys. 45 rods, 32mm in length and 25mm in diameter were made from degubond 4 (Au-Pd-Ag), porson 4 (Pd-Ag) and verabond (ni-Cr-Be). Material and Methods: 15 rods for each alloy randomly divided in to three groups of control, presolder and post-solder. 10 rods of each alloy were cut in half with a custom made cutting Jig and then positioned and stabilized at 13mm gap distance in an indexing Jig. Rods of deubond 4 and porson 4 were given a heat treatment to simulate porcelain firing. Specimens were soldered with manufacturers recommended solder with gas-oxygen torch (pre-soldering). Verabond specimens were soldered with gold and base-metal solder. Tensile testing was done on an instron machine. Model AB 725-AM.SM.At cross head speed of 2mm/min and result were recorded in kilogram. Results: 1- For Degubond 4, techniques of soldering has no sigificant effect on tensile strength of solder joints. 2- For Porson 4, tensile strength of presolder joints are significantly stronger than post-solder joints. 3- The tensile strength of presolder joints for degubond 4 and porson 4 are significantly stronger than verabond. Conclusion: Tensile strength of solder joints depends on different factors such as type of alloy and soldering technique however this is not dearly predictable.