Author/Editor		Zupančič, Rok; Legat, Andraž; Funduk, Nenad
Title		Tensile strength and corrosion resistance of brazed and laser-welded cobalt-chromium alloy joints
Type		članek
Source		J Prosthet Dent
Vol. and No.		Letnik 96, št. 4
Publication year		2006
Volume		str. 273-82
Language		eng
Abstract		STATEMENT OF PROBLEM: The longevity of prosthodontic restorations is often limited due to the mechanical or corrosive failure occurring at the sites where segments of a metal framework are joined together. PURPOSE: The purpose of this study was to determine which joining method offers the best properties to cobalt-chromium alloy frameworks. Brazed and 2 types of laser-welded joints were compared for their mechanical and corrosion characteristics. MATERIAL AND METHODS: Sixty-eight cylindrical cobalt-chromium dental alloy specimens, 35 mm long and 2 mm in diameter, were cast. Sixteen specimens were selected for electrochemical measurements in an artificial saliva solution and divided into 4 groups (n=4). In the intact group, the specimens were left as cast. The specimens of the remaining 3 groups were sectioned at the center, perpendicular to the long-axis, and were subsequently rejoined by brazing (brazing group) or laser welding using an X- or I-shaped joint design (X laser and I laser groups, respectively). Another 16 specimens were selected for electrochemical measurements in a more acidic artificial saliva solution. These specimens were also divided into 4 groups (n=4) as described above. Electrochemical impedance spectroscopy and potentiodynamic polarization were used to assess corrosion potentials, breakdown potentials, corrosion current densities, total impedances at lowest frequency, and polarization charge-transfer resistances. The remaining 36 specimens were used for tensile testing. They were divided into 3 groups in which specimen pairs (n=6) were joined by brazing or laser welding to form 70-mm-long cylindrical rods. The tensile strength (MPa) was measured using a universal testing machine. Differences between groups were analyzed using 1-way analysis of variance (alpha=.05). The fracture surfaces and corrosion defects were examined with a scanning electron microscope. (Abs. trunc. at 2000 ch.)
Descriptors		DENTAL ALLOYS COBALT CHROMIUM ALLOYS TENSILE STRENGTH CORROSION DENTAL SOLDERING SALIVA, ARTIFICIAL SPECTROPHOTOMETRY