Assessment of Marginal Fit of Single Fixed Posterior Interim Restorations with Chamfer and Feather Edge Finish Lines Implementing CAD-CAM and 3D Printing Technologies: An In-Vitro Study

Abstract

This in vitro study aimed to assess the combined effects of several digital manufacturing techniques (subtractive versus 3D printing) and distinct finish line designs (chamfer versus feather edge) on the marginal fit of posterior single interim crowns. Materials and Methods: Two specially designed stainless-steel dies, resembling mandibular first molars, were constructed to receive forty interim crowns (die A featuring a chamfer finish line and die B featuring a feather edge finish line). The interim crowns were designed (n=40) and categorized based on digital fabrication techniques into two primary groups (n=20): subtractive and 3-D printing. Each group is further subdivided into two equal subgroups (n=10) based on finish line design (chamfer and feather edge) as follows: Subtractive with Chamfer finish line group; SC, Subtractive with Feather edge finish line group; SF, 3D Printing with Chamfer finish line group; PC, 3D Printing with Feather edge finish line group; PF. Two-way ANOVA and Shapiro-Wilk tests were conducted for analysis. The findings indicated a significant interaction between finish line design and fabrication method (p=0.015), with SF exhibiting markedly higher marginal gap values than SC (p<0.001). The difference for printed restorations was not statistically significant (p=0.137). Furthermore, it was demonstrated that irrespective of finish line design, milled restorations exhibited substantially greater gap values than printed restorations (p<0.001). Conclusions: Interim crowns fabricated using 3D printing technology possess superior marginal fit compared to those that are milled.