Effect of Wax Pattern Fabrication Technique and Convergence Angle of the Preparation on the Accuracy of Full Veneer Metal Crowns: An in Vitro Study

Background and aim: To compare the marginal and internal adaptation of full veneer crowns cast from wax patterns fabricated by three-dimensional printing and conventional wax-up technique employing two different convergence angles.Material and methods: Two metal master dies, each with a convergence angle of 6 and 12-degrees, were duplicated 24 times to obtain 48 stone dies. Twelve dies from each group were randomly chosen for conventional wax-up (Group A) and the other twelve for the three-dimensional printed wax pattern (Group B) fabrication. Cobalt-chromium full veneer crowns were cemented onto the dies using glass ionomer cement. The cemented crowns and dies were sectioned in the midline buccolingually to measure the marginal and internal gaps using a stereomicroscope and digital image analysis software (Image J). Data obtained were recorded in microns, and an independent ’t’ test was used to compare quantitative parameters between categories.Results: Group B showed a statistically significant reduction in marginal discrepancy in crowns with a 6-degree taper (114.4 ± 37.5) compared to Group A (160.4 ±58.1). Group B did not demonstrate any significant difference when the 6-degree and 12-degree tapers were compared, but Group A showed a significant improvement in marginal and internal adaptation with the 12-degree taper.Conclusions: For the 6-degree taper, three-dimensional printing resulted in better marginal and internal fit than conventional wax patterns. Conventional and three-dimensional Printing offered similar accuracy within the acceptable range for a 12-degree taper.