Development of experimental Ag-based brazing alloys for orthodontic applications

by Argyro-Aikaterini Ntasi

Institution: National and Kapodistrian University of Athens; Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών (ΕΚΠΑ)
Year: 2014
Keywords: Ορθοδοντικα μηχανήματα; Κραματα συγκόλλησης Ag; Διάβρωση; Orthodontic appliances; Ag based brazing alloys; Corrosion
Record ID: 1153587
Full text PDF: http://hdl.handle.net/10442/hedi/34650


Ag based soldering alloys are widely used in the fabrication of orthodontic appliances and always concerned the literature for their potential to release Cu and Zn through corrosion and/or wear mechanisms. Aim: The development of experimental Ag based brazing alloys free of Cu and Zn.Materials and Methods: Four commercially alloys were selected: Dentaurum Universal silver Soldering, Leone Orthodontic Solder, Nobil Metal Solder and Orthotechnology Silver Solder. The experimental alloys Ag12Ga, Ag10Ga5Sn, Ag20In and Ag7Sn were fabricated in an induction melting machine. 14 disk shape specimens were prepared for each alloy by melting each material in a reducing flame and after metallographic preparation SEM-EDX and XRD analysis was preformed. The hardness was measured employing Vickers testing. The electrochemical properties were evaluated by OCP, PDS, CP and EIS in a NaCl 0.9% and a Ringer’s electrolyte solution with the use of a mini cell system. Immersion testing was performed in the same solutions and the extracts of 4, 7 and 10 weeks were imposed to ICP analysis for the evaluation of ions concentrations. Hardness, OCP, Icorr and Ecorr were statistically analyzed by one way ANOVA and Holm-Sidak multiple comparison procedure (a=0.05). The results of the ICP were statistically analyzed using two way ANOVA and Holm-Sidak multiple comparison procedure (a= 0.05).Results: Commercially alloys belong to the Ag-Zn-Cu ternary system and are consisted of a Ag rich and a Cu rich FCC phase. AgGa and AgGaSn are two phase alloys whereas AgIn and AgSn single phase. All alloys demonstrated similar melting temperature range. The commercially alloys demonstrated higher hardness values. The OCP and Ecorr values were higher for the experimental alloys showing greater resistance to oxidation, whereas the Icorr magnitudes were lower indicating lower reaction kinetics. All alloys tested formed oxides and chlorides, though in the case of the commercially alloys a steady surface layer could not be formed and any salt depositions were vulnerable to pitting corrosion phenomena. Immersion testing revealed the release of Cu and Zn ions from the commercially alloys and Ga ions from AgGa and AgGaSn.Conclusions: The commercially alloys demonstrate an inferior behavior compared to the experimental ones. From the experimental alloys AgIn and AgSn showed a promising behavior as they did not release any ions in vitro and expressed low corrosion vulnerability. Οι κολλήσεις Ag χρησιμοποιούνται ευρύτατα για τη παρασκευή ορθοδοντικών μηχανημάτων αν και μπορούν να απελευθερώσουν Cu και Zn στο στοματικό περιβάλλον μέσω μηχανισμών διάβρωσης.Σκοπός: Η παρασκευή πειραματικών κραμάτων Ag που δε περιέχουν Cu και Zn.Μέθοδος – Υλικά: Χρησιμοποιήθηκαν 4 εμπορικά σκευάσματα: Dentaurum Universal silver Soldering, Leone Orthodontic Solder, Nobil Metal Solder και Orthotechnology Silver Solder και παρακευάστηκαν 4 πειραματικά κράματα: Ag12Ga, Ag10Ga5Sn, Ag20In and Ag7Sn. 14 δίσκοι από κάθε υλικό παρασκευάστηκαν λιώνοντας κατάλληλη ποσότητα σε αναγωική φλόγα και…