Marginal and Internal Adaptation of Crowns Fabricated on Models From Digital and Conventional Impressions: An In Vitro Study.

Objective

To evaluate the marginal and internal adaptation of monolithic crowns fabricated from lithium disilicate (LD), zirconia (Zr), and fiber-reinforced composite (FRC) using five different model types derived from digital and conventional impressions.

Materials And Methods

A maxillary first molar was prepared on a phantom model for full-coverage crown restoration. Conventional and digital impressions were used to produce five types of working models: scanned impression STL (CS), plaster (CP), 3D-printed resin from scanned impressions (CR), direct digital STL (DS), and 3D-printed resin from digital impressions (DR). A total of 150 crowns (n = 10 per group) were fabricated using CAD/CAM. The marginal and internal adaptation were assessed using the silicone replica technique and analyzed under a light microscope (×40). Data were statistically analyzed using two-way MANOVA and ANOVA (α = 0.05).

Results

Both model type and restorative material significantly affected adaptation values (p < 0.05). The best adaptation was observed in LD crowns fabricated on 3D-printed resin models derived from digital impressions. In general, crowns fabricated on digitally derived 3D-printed resin models demonstrated lower gap values than those fabricated on plaster and STL models. FRC crowns on plaster models exhibited the highest gap values. All measured gap values remained within clinically acceptable limits (< 120 μm).

Conclusions

Crowns fabricated on 3D-printed resin models derived from digital impressions showed the most favorable adaptation among tested groups. Both model type and restorative material significantly influenced restoration fit. Based on the findings of this in vitro study, digital workflows incorporating 3D-printed resin models may be considered reliable alternatives to conventional plaster models in CAD/CAM systems.