Comparison of torch with electric arc casting in the lost wax technique for the cast dental stud protocol

Abstract

The aim of this study was to compare the compressive strength, microstructural characteristics, and cost-effectiveness of cast dental posts fabricated using two techniques: torch casting (TC) and electric arc casting (EAC), both integral to the lost wax method. Employing an applied research approach with an experimental design, the study analyzed 40 non-precious gold (NPG) alloy cast posts, divided equally into two groups of 20 for each technique. The selection process was non-probabilistic and based on convenience, with specific inclusion and exclusion criteria to ensure precision and relevance. The results reveal a significant advantage for the EAC technique. In Essay 1, EAC posts exhibited a mean compressive strength of 206.102 MPa, compared to 157.207 MPa for TC posts. Similarly, in Essay 2, EAC posts showed a mean strength of 172.625 MPa versus 136.303 MPa for TC posts. These differences were statistically significant (p < 0.05), with EAC posts also displaying smaller failure diameters and areas, suggesting better load distribution. Morphological and microstructural analysis using scanning electron microscopy (SEM) revealed a porous surface with irregular topography in both techniques. However, EAC samples displayed crystalline growths within the copper matrix, indicating a non-homogeneous stoichiometry, while TC samples showed aluminum-enriched zones, suggesting a non-uniform elemental distribution. Chemical composition analysis via energy-dispersive spectroscopy (EDS) identified copper (Cu) as the predominant element in both samples, with trace elements such as aluminum (Al), nickel (Ni), and iron (Fe) also present. X-ray diffraction (XRD) analysis further revealed distinct crystalline phases, with EAC samples exhibiting a higher proportion of Cu₃Zn and gamma-Fe phases compared to TC samples. A cost analysis using Python 3.13 and Monte Carlo simulation with 1,000 iterations revealed that EAC is more expensive, with a total cost per unit of 2.181compared to 1.467 for TC, primarily due to higher operational costs. The Mann-Whitney U test confirmed significant differences in cost distributions (p < 0.001), indicating that EAC has higher and more variable costs. In conclusion, the study demonstrates that EAC produces dental models with significantly higher compressive strength and a more refined microstructure compared to TC, enhancing restoration durability. However, its higher operational costs must be considered. These findings provide valuable information for dental professionals, particularly in low- to middle-income countries, and suggest that future research should explore additional properties such as corrosion resistance and biocompatibility to further validate the clinical applicability of these materials.