Micro-CT analysis of cement adaptation and porosity in 3D-Printed permanent resin crowns before and after chewing simulation.

Objective: This study evaluates cementation gap, cement volume, and porosity levels in three-dimensional crown restorations using four permanent resin materials and printers, and examines changes after thermomechanical ageing.

Materials and methods: In the study, phantom models prepared on the maxillary first premolar were used, and the digital scanning, CAD design, 3D printing, cementation, and ageing processes were carried out according to standard protocols. The samples were divided into four groups based on the permanent resin material used: Group C (Methacrylate-based resin), Group S (UDMA-based composite), Group P (Bis-GMA/TEGDMA-based), and Group V (Bis-EMA/UDMA-based). All samples were designed with a 50 μm virtual cementation gap and evaluated by micro-CT before and after ageing.

Results: The findings showed statistically significant differences between the groups in terms of cementation gap and porosity volume (p < 0.001). The lowest void volume and porosity were measured in the group C, while the highest values were observed in the group S. No significant difference was observed between the groups in terms of total cement volume. Additionally, a strong positive correlation was found between cement volume and porosity.

Conclusions: The obtained data reveal that the resin material used and the production process play a decisive role in the internal compatibility of restorations. Thermomechanical ageing, on the other hand, caused significant changes, particularly in structural properties. These results indicate that permanent resin restorations produced by 3D printing should be evaluated for their clinical viability considering cement gap and porosity behavior.

Clinical relevance: This study has revealed that the cementation gap and porosity levels of permanent resin crowns produced with a 3D printer vary significantly depending on the type of material used and the production process. Therefore, in clinical applications, not only aesthetic and mechanical properties but also cementation compatibility and microstructural properties should be taken into consideration.