A comparison between different methods of applications of a surface tension reducing agent on castings nodules
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Objectives: This study compared different methods of application of a surface tension reducing agent on casting nodules. This was in order to reduce a technicians’ workflow in removing nodules as this is time consuming. Method and Materials: 60 copings were fabricated on a stone die and were randomly divided into three groups. The samples were sprued using a 2.5mm diameter sprue at a 45-degree angle. Group A sprayed conventionally with a surface tension reducing agent, group B surface tension reducing agent applied with a paint brush and, group C was used as a control with no surface tension reducing agent applied. The samples were invested using a ratio of 360 grams to 90 ml of phosphate bonded investment powder, (Skillvest) and liquid (Skillvest HS Expansion Liquid). The samples were cast with a nickel chrome bonding alloy. Digital callipers were used to measure the widest point of the nodules that were present. Results: The sprayed group presented the least number of nodules with 11 samples, the painted group 5 samples presented nodules, for the control group 15 samples had nodules. Some samples showed more than one nodule across three groups. The average size of nodules was considerably larger for the control (1.29mm) and sprayed (0.88mm) group than the painted (0.08mm) samples. Conclusion: Application of a surface tension reducing agent using a paint brush reduced the size and number of nodules compared to the sprayed and control group
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