Marginal fit of nanocomposite 3D-printed crowns with horizontal and vertical preparation geometries: An in vitro comparative analysis

Objectives: This study aimed to evaluate the marginal fit of crowns fabricated using a 3D-printer with either horizontal or vertical tooth preparation geometries. Methods: Two abutments representing a standard maxillary first premolar were designed using CAD software, featuring either a horizontal (Ho) or vertical (Ve) tooth preparation. These abutments were milled in resin and positioned on a reference typodont. For each preparation design, ten crowns were 3D printed using a resin nanocomposite. Cementation was simulated for each crown on its corresponding tooth preparation geometry. The samples were then scanned using an industrial metrological machine, and the scans were analyzed with specialized software to assess marginal fit in micrometers (μm). Descriptive statistics, including a 95 ​% confidence interval, were calculated, and an independent sample test (α ​= ​.05) was performed to compare the two groups. Results: The mean marginal fit values for both preparation geometries were below the clinically acceptable threshold of 120 ​μm: Ho ​= ​76.83 ​μm, Ve ​= ​84.37 ​μm. No statistically significant differences were found between the two groups (Ho: p ​= ​.58; Ve: p ​= ​.83). Conclusions: The tested nanocomposite crowns exhibited similar mean marginal discrepancies for both vertical and horizontal preparation designs. Additionally, the marginal discrepancies observed in both cases were within clinically acceptable limits. Clinical significance: The nanocomposite crowns achieve a clinically accepted marginal fit for both vertical and horizontal tooth preparation geometries.