Metallurgical and electrochemical characterization of contemporary silver-based soldering alloys

Metallurgy in orthodontic-A systematic review and meta-analysis on the types of metals used

A variety of metals and alloys are employed in the field of orthodontics, primary of which happen to be the construction of wires. Through this systematic review, we aimed to assess the various metallurgical characteristics of the said metals and alloys. Four hundred and eighty-two documents in total were found after a thorough search of the online journals, and 169 of the papers were initially chosen. Ultimately, 16 documents were selected that satisfied the necessary inclusion and exclusion criteria, primarily in vitro studies, literature reviews, and comparative analyses. NiTi alloy was found to be the most commonly used alloy in construction of orthodontic wires across all the studies that we had selected for our review. It also had better performance and consistency in terms of its usage as depicted by the meta-analysis performed, with stainless steel wires being a close second primarily due to its lesser cost compared to the former. Metallurgy and orthodontics are inextricably linked with one another. The various components of orthodontics such as wires, pliers, and other instruments utilize the metallurgical characteristics of metals and alloys that are specially prepared for the challenges of this field. PROSPERO Registration Number: CRD42022378444.

Comparison between traditional and alternative biocompatible welding techniques used in orthodontic devices

OBJECTIVE

To compare the mechanical strength of joints made by conventional soldering with those made by alternative, more biocompatible, methods (spot, tungsten inert gas [TIG] and laser welding), and to compare the microstructural morphology of wires welded with these techniques.

DESIGN

In vitro, laboratory study.

METHODS

Forty stainless-steel wire segments with 0.8-mm diameter were joined by silver soldering, spot, laser and TIG welding. Ten specimens were produced for each one. Tensile strength test was performed 24 h after welding on the Emic DL2000™ universal testing machine, using a load cell of 1000 N with a crosshead speed of 10 mm/min.

RESULTS

The highest tensile strength mean values were obtained with silver soldering (532 N), next were laser (420 N), spot (301 N) and TIG (296 N) welding. Statistically significant differences were observed between the groups; the Dunn post-hoc test revealed differences between laser and spot welding (p=0.046), laser and TIG (p = 0.016), spot and silver (p <0.001), and silver and TIG (p <0.001).

CONCLUSION

Laser welding strength is high, and comparable to silver welding. Spot and TIG techniques present comparable and significantly lower strengths. The four methods presented resistance values compatible with orthodontic use. The microstructural morphology is different for each technique. The association between the mechanical performance and the microstructure evaluation shows that laser presented the highest quality joint.

Metallurgical characterization of experimental Ag-based soldering alloys

AIM

To characterize microstructure, hardness and thermal properties of experimental Ag-based soldering alloys for dental applications.

MATERIALS AND METHODS

Ag12Ga (AgGa) and Ag10Ga5Sn (AgGaSn) were fabricated by induction melting. Six samples were prepared for each alloy and microstructure, hardness and their melting range were determined by, scanning electron microscopy, energy dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD), Vickers hardness testing and differential scanning calorimetry (DSC).

RESULTS

Both alloys demonstrated a gross dendritic microstructure while according to XRD results both materials consisted predominately of a Ag-rich face centered cubic phase The hardness of AgGa (61 ± 2) was statistically lower than that of AgGaSn (84 ± 2) while the alloys tested showed similar melting range of 627-762 °C for AgGa and 631-756 °C for AgGaSn.

CONCLUSION

The experimental alloys tested demonstrated similar microstructures and melting ranges. Ga and Sn might be used as alternative to Cu and Zn to modify the selected properties of Ag based soldering alloys.