Comparative Evaluation of Marginal and Internal Fit of CAD/CAM-Fabricated Zirconia and Cobalt-Chromium Copings- An In- Vitro Study

Abstract

Background: Marginal and internal adaptation of dental copings is a critical factor influencing the longevity and success of fixed prostheses. Inadequate fit may lead to cement dissolution, microleakage, secondary caries, and periodontal complications. With the increasing use of CAD/CAM technology, zirconia and cobalt-chromium (Co-Cr) copings have gained popularity; however, their precision of fit remains a subject of comparison.

Purpose: To evaluate and compare the marginal fit and internal fit of zirconia copings and cobalt-chromium copings fabricated using CAD/CAM technology.

Materials and Methods: This in-vitro study was conducted on forty extracted mandibular premolars, randomly divided into two groups: Group I (n=20) – zirconia copings and Group II (n=20) – Co-Cr copings. Standardized tooth preparations were performed and scanned using an intraoral scanner. The obtained STL files were used to design copings, which were milled and luted with resin cement. All samples were sectioned and evaluated for marginal and internal fit under a scanning electron microscope. Data were analysed using the Mann–Whitney U test and independent t-test, with statistical significance set at p<0.05.

Results: Statistically significant differences were observed between the groups. The mean marginal gap was 37.18 ± 18.21 µm for zirconia and 95.33 ± 22.04 µm for Co-Cr copings. The mean internal gap was 88.58 ± 34.61 µm for zirconia and 126.40 ± 31.77 µm for Co-Cr copings.

Conclusion: Zirconia copings exhibited superior marginal and internal fit compared to cobalt-chromium copings fabricated by CAD/CAM technology.