An In Vitro Comparison of Marginal Fit of Single-Unit Copings Fabricated Using Computer-Aided Design/Computer-Aided Manufacturing Zirconia, Direct Metal Laser Sintering and Porcelain-Fused-to-Metal.

INTRODUCTION

The marginal fit of dental restorations is essential for longevity and effectiveness of fixed prostheses, particularly single-unit crowns. Direct digital scanning offers significant advantages over indirect methods, providing a non-invasive, accurate, and reproducible means to evaluate marginal fit. This study aimed to assess the marginal fit of single-unit copings fabricated using computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia, direct metal laser sintering (DMLS), and porcelain-fused-to-metal (PFM) utilizing direct three-dimensional (3D) scanning.

MATERIALS AND METHODS

The current in vitro investigation involved 60 right mandibular second premolar typodont teeth (Dentmark, Ambala, Haryana, India) designated for single-unit fixed dental prostheses. The specimens were categorized into three groups of 20 specimens each. Direct scanning for all groups was performed using the Helios 500 intraoral scanner (Orikam Healthcare India Pvt. Ltd., Haryana, India). Upon fabrication, all copings were directly scanned using a 3D scanner (Shining 3D EX Pro, California, USA). Marginal discrepancies were assessed using the Exocad software (CAD software, Darmstadt, Germany).

RESULTS

Mean marginal discrepancies of zirconia, DMLS, and PFM copings were evaluated and compared. Zirconia copings had the lowest mean discrepancy of 0.0172 mm whereas DMLS copings had a mean discrepancy of 0.0256 mm. The PFM copings had the highest mean discrepancy of 0.0375 mm. A one-way analysis of variance (ANOVA) indicated a significant difference in the marginal fit (p < 0.05). Post-hoc Tukey test comparisons revealed significant differences between the three groups (p < 0.05).

CONCLUSION

In conclusion, CAD/CAM-fabricated zirconia crowns exhibit superior marginal fit compared to DMLS and PFM copings, owing to precise digital design, milling, and material stability. DMLS copings, although less precise, still outperform PFM crowns, which display significant marginal gaps owing to the limitations of the lost-wax method.