designed asbestos jig for stabilization. The wire specimen was placed .... soldered connectors of two base metal ceramic alloys". J. Prosthet Dent 1994; 71: 339 ...
___________________________________________________________________________________ ISSN 0970 - 4388
A Comparative Evaluation of the Tensile Strength of Silver Soldered Joints of Stainless Steel and Cobalt Chromium Orthodontic Wires with Band Material - An In vitro Study. DUA Ra, NANDLAL Bb
ABSTRACT
MATERIALS AND METHOD
The present study was conducted to compare and evaluate the tensile strength of silver soldered joints of stainless steel and cobalt chromium orthodontic wires with band material. An attempt was made to observe the effect of joint site preparation by incorporation of tack welding and increasing metal to metal surface contact area by flattening an end of the wire prior to soldering along with the regularly used round wires without tack welding. A total of 180 wire specimens were soldered to 180 band specimens. Fifteen samples according to joint site preparation were included for each of the wire groups i.e. Gloria (S.S.), Remanium (S.S.) and Remaloy (Co-Cr) wires of 0.036" in diameter. The findings of the study were suggestive that all three wires may be used for preparing silver soldered joints irrespective of the quality of the wire. However, when subjecting the wire to joint site preparation, Gloria (S.S.) wire showed less tensile strength as compared to Remanium and Remaloy.
Keywords: Cobalt chromium, Silver solder, Stainless Steel, Tack welding.
INTRODUCTION The strength of silver soldered joints used to fabricate space maintainers and orthodontic appliances is critical to their 1,2 success . The appliance must be able to withstand the forces generated while masticating. Broken appliances compell patients for unscheduled office visits. Complications of broken appliances include soft tissue irritation, lost orthodontic anchorage, untoward movement of teeth and swallowing or 2
aspiration of broken parts . Research is meagred in terms of new materials and methods to help dental surgeons to fabricate stronger silver soldered joints. Various authors have 1-13 evaluated different soldering techniques than the incorporation of different orthodontic wires to study the tensile strength of soldered joints. Hence, the present study was undertaken to compare the tensile strength of silver soldered joints using stainless steel and cobalt chromium wires. The effect of tack welding on increasing the surface area, by flattening the end of the wire prior to soldering was also studied as it may have an effect 2 on the tensile strength of silver soldered joints .
a. Post Graduate Student, b. Professor and Head, Department of Pedodontics and Preventive Dentistry J. S. S. Dental College
Three types of wires were used to test the tensile strengths of silver soldered joints in the study. Orthodontic Stainless Steel wires 0.036 inch (Gloria and Remanium-Dentaurum) and 0.036 inch Cobalt Chromium wire (Remaloy- Dentaurum) were soldered to stainless steel band material (.018" X .005" Orthotec and Dentaurum). The tensile strength of silver soldered joints was tested by preparing a total of 180 specimens; i.e. 180 wire specimens (50mm in length) soldered to 180 band specimens (50mm in length). 60 samples were prepared for each wire group used in the study. The various wire groups tested were; Gloria (S.S.) wire soldered to Orthotec band material, Remanium (S.S.) wire soldered to Dentaurum band material, Remaloy (Co-Cr) wire soldered to Dentaurum band material. Fifteen samples each for the various subgroups according to joint site preparation for each wire group tested were; Round non-tack welded; Round tack welded; Flattened non-tack welded; Flattened tack welded. The specimens to be soldered were placed in a specially designed asbestos jig for stabilization. The wire specimen was placed in a groove 50mm long, 0.9mm in depth overlapping 9mm of band material which was placed in a slot 50mm long (0.75" x 0.25" x 0.05"). Areas other than joint site were protected from unnecessary exposure to heat from the soldering torch by plaster of paris blocks. For tack welded samples, the wire was tack welded to the band material prior to soldering. Two tack welds were prepared, spaced 2mm apart on each 4mm joint (i.e. 4mm of wire overlapping the band material) using Dentaurum assistant 2000 electric welding unit set at the # 2 position. For flattened samples, 4mm length of the wire end to be soldered was flattened in order to increase metal to metal contact area to 0.6mm from the original diameter of the wire i.e., 0.9mm with the diamond disc mounted on a high speed trimming lathe. A custom block was used to check the amount of wire reduction which had a groove 50mm long and 0.9mm in depth a 4mm length of the groove reduced to a depth of 0.6mm. Dentaurum silver solder and flux were used for soldering all joints which were uniformly 4mm in length. For each specimen the amount of
Tensile Strength of Silver Soldered Joints
The joint site was adequately heated after application of the flux, with the reducing zone of the flame (Piezo gas burner2000,
RESULTS
Japanese) and as soon as the site reached solder flow temperature, 6mm of solder was held in a tweezer and introduced at the joint site. th The flame was kept approximately 3/4 inch long throughout the soldering procedure. The flame was withdrawn when the solder had flown over the joint site in a feather edge
The mean tensile strength values of soldered joints for the various wire groups used in the study, Gloria (S.S.), Remanium (S.S.) and Remaloy (Co-Cr) were 6.08 ±1.11 kg/ mm, 6.99 ± 0.89 kg/mm and 6.71 ± 0.65 kg/mm respectively. Two way ANOVA (Table 1) was conducted for different wire
configuration. All specimens were immediately quenched in 14 cold water as recommended by Phillips . Tensile strength measurements were made of the joints using a Universal Testing Machine (Make: Hounsefield U.K., Model 50KM with a capacity of 50KN) with a uniform crosshead speed of 2.00mm/min. The load at failure was recorded in kgf. The broken samples were examined visually to determine where the failure had occurred, within the solder joint, wire or band fracture respectively. The tensile strength values in kg/mm of the joint length were then determined / calculated for comparative evaluation of the tensile strength of silver soldered joints.
groups and it revealed that between different wires, a significant difference existed in their mean tensile strength values of soldered joints, at 0.1% level (F = value 32.891, p< 0.001). Further, Scheffe's Post-Hoc test (Table 1) at 0.05 level revealed that Gloria (S.S.) wire had significantly lesser tensile strength compared to Remanium (S.S.) and Remaloy (Co-Cr) wires. However, no significant difference was found between Remanium (S.S.) and Remaloy (Co-Cr) wires. The mean tensile strength values of soldered joints for the various subgroups according to joint site preparation i.e. round nontack welded, round tack welded, flattened non-tack welded, and flattened tack welded were 7.18 + 0.74 kg/mm, 7.04 ± 0.72 kg/mm, 5.80 ± 0.85 kg/mm and 6.34 ± 0.93 kg/mm
Two way ANOVA "Tensile strength values were significantly different at 0.1 percent level for various joint site preparations and tensile strength values were also significantly at 0.1 percent level for the wire groups. **Mean with similar letters are not significantly different from each other S.S: Stainless steel Co-Cr: Cobalt chromium values were also significantly at 0.1 percent level for the wire groups. Table 1: Mean tensile strength of soldered joints of Gloria (S.S), Remanium (S.S) and Remaloy (Co-Cr) wires
Tensile Strength of Silver Soldered Joints
respectively. Two way ANOVA (Table 1) according to joint site preparation revealed a statistically significant difference among the mean tensile strength values at 0.1% level (F = 46.50, p
