The Impact of Covering Different Base Materials With CAD/CAM-Milled and 3D-Printed Inlays on the Fracture Resistance of Structurally Compromised Premolars.

OBJECTIVES

This study aimed to evaluate the effect of different bulk-fill base materials and inlay fabrication techniques on the fracture resistance of structurally compromised premolars.

MATERIAL AND

METHODS

Sixty intact premolars were randomly allocated to five groups (n = 12). Standardized slot-type mesio-occluso-distal cavities with undermined cusps were prepared in all groups except the intact control group. Teeth were restored with different base materials: flowable bulk-fill composite resin (BF-RBC) or short fiber-reinforced composite (SFRC) resin. Each group was further subdivided according to the fabrication technique of the CAD/CAM inlays (milled hybrid nano-ceramic composite or 3D-printed ceramic-filled hybrid composite resin). Fracture resistance was evaluated after thermocycling aging for 10,000 cycles, and the failure mode was inspected. Data were analyzed using heteroscedasticity-corrected two-way ANOVA with post hoc pairwise comparisons of the significant main effect (α = 0.05).

RESULTS

Fracture resistance was significantly influenced by inlay fabrication technique (p < 0.001) but not by base material or their interaction. In milled groups, SFRC exhibited a statistically more favorable failure mode than BF-RBC, whereas no significant differences were observed in 3D-printed groups.

CONCLUSIONS

CAD/CAM-milled restorations demonstrated superior fracture resistance compared with 3D-printed restorations in structurally compromised premolars.

CLINICAL SIGNIFICANCE: Selecting restorative materials with appropriate compliance is essential to accommodate tooth flexure and minimize fracture risk. CAD/CAM composite restorations provide a conservative approach for restoring structurally compromised premolars, and base material selection should be considered to enhance the stress distribution of the overlying inlay and support overall restoration longevity.