Comparison of dental student silver soldering using an orthodontic blowpipe or Hydroflame.

This study compared fabr/cation of silver solder joints by dental students using an orthodontic blowpipe .or a Hydroflame ® soldering unit. Fifty-eight students attended a lecture and observed demonstrations of silver solder/ng. Thirty students used a Hydroflame ® to prepare one practice solder joint and two technique solder joints. These students then prepared one practice solder joint and two technique joints utilizing the blowpipe. The remaining 28 students prepared similar solder joints but the orthodontic blowpipe was used prior to the Hydroflame ®. Solder joints were evaluated by the students and an independent examiner for amount of solder applied, contour of joints, and amount of surface porosity and oxidation. Solder joints prepared with the Hydrof/ame ® had significantly higher (p < .03) evaluations for contour (2.34 -2.85 vs. 1.88 -2.57) and amount of solder utilized (2.39-2.90 vs. 1.93-2.48). No significant difference was found in the amount of surface oxidation or porosity between techniques. Silver solder can be applied using several techniques. One method involves the production of heat with a natural g~is and compressed air mixture in the orthodontic blowpipe.1’2’a An electrosoldering technique creates high temperatures at a carbon tip and minimizes the area heated. 4,s An indirect technique relies on production of heat by a gas-air flame or electricity and conveyance of heat to the workpieces through an intermediate material such as brass wire. G Another technique utilizes the Hydroflame® device which electrolytically generates hydrogen and oxygen for combustion in a well-focused flame. Studies have compared silver solder joints produced by various methods.4,G Gardiner and Aamodt compared the gas-air flame, a plain gas flame, a gas-air flame heated brass wire, an electrically heated brass wire, and the electrosoldering technique.~ Their results indicated that the strongest joints and the least annealing were produced by the gas-air flame heated brass wire. Laird a Hydroflame II Precision Soldering Unit, Unitek Corp., Monrovia, Calif. and von Fraunhofer compared the gas-air flame and electrosoldering techniques. ~ They found no significant differences between the tensile strength or microhardness of the joints produced by either method. A recent investigation by Brown et al. indicates that the Hydroflame® can produce solder joints with tensile strengths equivalent to or slightly higher than those produced with other techniques. 7 Dental students at the Medical College of Georgia traditionally had been taught to use the orthodontic blowpipe in a pedodontic technique course; however, faculty found that students had difficulty mastering this technique. The purpose of this study was to determine the soldering technique preferred by dental students and to compare the quality of silver solder joints fabricated by dental students using an orthodontic blowpipe or a Hydroflame. ® Methods and Materials Fifty-eight second-year dental students with no previous experience in dental soldering procedures attended a one-hour lecture describing silver soldering techniques with the orthodontic blowpipe and the Hydroflame ®. The lecture included: properties of stainless steel and silver soldier; the importance of cleanliness; contact between workpieces; control of heat; model and hand stabilization; application of flux; use of the orthodontic blowpipe and Hydroflame®; and the appearance, size and contour of ideal solder joints. In groups of six to eight, all students observed demonstrations of each soldering technique by the same skilled operator. Major points of the soldering lecture were reinforced during the demonstrations, questions were answered, and the samples of solder joints with a quality range of excellent to poor were displayed. At this time students were divided randomly into two groups. Students in Group A (N -30) would first fabricate solder joints with the Hydroflame ®, then with the blowpipe (Figure 1). Students in Group B (N = 28) would first prepare solder joints using the blowpipe, then with the Hydroflame ®. Three students at a time from Group A came to an isolated area of a laboratory to perform soldering proPEDIATRIC DENISTRY: Volume 5, Number 1 65 Figure 1. The orthodontic blowpipe and Hydroflame unit. nique. Fifty percent felt that the Hydroflame® technique was easier to learn, while only 9% felt that the blowpipe technique was easier to learn. Seventy-one percent responded that the Hydroflame® was easier to use, while only 9% felt that the blowpipe was easier to use. Sixtysix percent of the students felt that better solder joints were produced with the Hydroflame®, while only 17% felt that better solder joints were produced with the blowpipe. The differences between the students who favored the Hydroflame® and those who favored the blowpipe in questions 3-5 were significant at the .01 level. Evaluations of the solder joints by the independent examiner are summarized in Table 2. Mean scores for surface porosity were similar with both techniques and ranged from 3.85 to 4.00. Mean scores for surface oxidation were also similar with both techniques and ranged from 2.82 to 3.38. Since minimal variance occurred between scores for surface porosity or oxidation using either technique, further analysis of this data was not indicated. Mean scores for contour using the Hydroflame® ranged from 2.34 to 2.85, while mean scores using the blowpipe were lower and ranged from 1.88 to 2.57. Mean scores for amount of solder used were also higher with the Hydroflame®, ranging from 2.39 to 2.90, while mean and surface porosity were each evaluated using prepared standards which demonstrated the following degrees of quality: 0 — no solder joint, 1 — poor, 2 — fair, 3 — good, 4 — excellent. An independent examiner, who was unaware of which technique had been used, subsequently evaluated all solder joints on three separate occasions at monthly intervals using the same rating scale and standards.