Evaluation of the marginal fit of metal copings fabricated on three different marginal designs using conventional and accelerated casting techniques: An in vitro study.

Introduction: Abundant resources and techniques have been used for complete coverage crown fabrication. Conventional investing and casting procedures for phosphate-bonded investments require a 2- to 4-h procedure before completion. Accelerated casting techniques have been used, but may not result in castings with matching marginal accuracy. Aims and Objectives: The study measured the marginal gap and determined the clinical acceptability of single cast copings invested in a phosphate-bonded investment with the use of conventional and accelerated methods. Materials and Methods: One hundred and twenty cast coping samples were fabricated using conventional and accelerated methods, with three finish lines: Chamfer, shoulder and shoulder with bevel. Sixty copings were prepared with each technique. Each coping was examined with a stereomicroscope at four predetermined sites and measurements of marginal gaps were documented for each. Statistical Analysis: A master chart was prepared for all the data and was analyzed using Statistical Package for the Social Sciences version. Evidence of marginal gap was then evaluated by t-test. Analysis of variance and Post-hoc analysis were used to compare two groups as well as to make comparisons between three subgroups . Results: Measurements recorded showed no statistically significant difference between conventional and accelerated groups. Conclusion: Among the three marginal designs studied, shoulder with bevel showed the best marginal fit with conventional as well as accelerated casting techniques. Accelerated casting technique could be a vital alternative to the time-consuming conventional casting technique. The marginal fit between the two casting techniques showed no statistical difference.

Evaluation of marginal gap of Ni-Cr copings made with conventional and accelerated casting techniques.

Context: Conventional casting techniques following the manufacturers' recommendations are time consuming. Accelerated casting techniques have been reported, but their accuracy with base metal alloys has not been adequately studied. Aim: We measured the vertical marginal gap of nickel-chromium copings made by conventional and accelerated casting techniques and determined the clinical acceptability of the cast copings in this study. Settings and Design: Experimental design, in vitro study, lab settings. Materials and Methods: Ten copings each were cast by conventional and accelerated casting techniques. All copings were identical, only their mold preparation schedules differed. Microscopic measurements were recorded at ×80 magnification on the perpendicular to the axial wall at four predetermined sites. The marginal gap values were evaluated by paired t test. Results: The mean marginal gap by conventional technique (34.02 μm) is approximately 10 μm lesser than that of accelerated casting technique (44.62 μm). As the P value is less than 0.0001, there is highly significant difference between the two techniques with regard to vertical marginal gap. Conclusion: The accelerated casting technique is time saving and the marginal gap measured was within the clinically acceptable limits and could be an alternative to time-consuming conventional techniques.