Novelty of digital press stereolithography (DPS) with MIDAS system in crown fabrication: marginal and internal fit evaluation

Background: The marginal and internal fit of full-coverage crowns is essential for their long-term clinical success. Computer-aided design and manufacturing (CAD/CAM) technologies have enhanced the precision of restorations. However, the performance of emerging three-dimensional (3D) printing systems, such as the Midas system based on digital press stereolithography (DPS), requires further investigation.
Methods: This in vitro study evaluated and compared the marginal, cervical, axial, and occlusal gaps of crowns fabricated using five different materials. A total of forty crowns were fabricated using subtractive milling (Empress CAD, Vita Enamic, Cerasmart, and zirconia; n = 10 each), and ten crowns were fabricated using additive 3D printing with the Midas DPS system. A standardized molar preparation was scanned and used to produce fifty resin dies. Crowns were designed using dedicated software, cemented on the dies, and subjected to thermocycling (5000 cycles between 5 °C and 55 °C). Each specimen was sectioned and examined under 40× magnification using a stereomicroscope. A total of 160 gap measurements were recorded for each crown across four anatomical regions. Statistical analysis was performed using the Shapiro-Wilk, Kruskal-Wallis, and Mann-Whitney U tests with a significance level set at 0.05.
Results: All groups exhibited gap values within clinically acceptable ranges. Zirconia crowns demonstrated the lowest mean gaps and variability, especially in the cervical (66.0 micrometers, coefficient of variation: 6.1%) and axial (122.7 micrometers, coefficient of variation: 2.9%) regions. The Midas 3D-printed group presented greater variability, particularly in the occlusal region (211.9 micrometers, coefficient of variation: 52.1%). Statistically significant differences were found in cervical gap values among the materials tested.
Conclusions: Crowns fabricated using the Midas DPS 3D printing system exhibited acceptable adaptation, although with greater variability compared to those produced via subtractive methods. Zirconia demonstrated superior dimensional consistency, supporting its continued use as a reference material. These findings indicate that the Midas system holds promise as a clinically viable alternative, warranting further validation through clinical studies.