A Comparative Study on the Fracture Resistance of CAD/CAM-Fabricated Single-Piece Post-Crowns

Recently, CAD/CAM materials have become popular in dental clinics; however, information about their fracture resistance as post-crowns remains limited. This study compared the initial fracture resistance of potential single-piece post-crown materials made with CAD/CAM milling to sound teeth.

Fifty freshly extracted, non-carious human central incisor teeth underwent endodontic treatment. The roots were then randomly divided into five groups based on the post systems: the control group included teeth filled only with gutta-percha. Monoblock post-crowns were made using four different systems for the other groups: LDS (IPS e.max CAD®, lithium disilicate glass-ceramic), YTZP (inCoris ZI®, Yttrium tetragonal zirconia polycrystal), RNC (Lava Ultimate®, resin-based nanoceramic), and PICN (VITA Enamic®, polymer-infiltrated ceramic network). The post-crowns were cemented with resin cement and tested with a universal testing machine at a crosshead speed of 1.0 mm/min. Data analysis used one-way ANOVA and multiple comparison post-hoc Tukey tests (α = 0.05).

Significant differences were found between the groups (p < 0.001). The control group exhibited the highest fracture resistance (749.25 ± 225.02 N). YTZP showed similar resistance to the control (p = 0.99) and LDS (447.28 ± 168.72 N, p = 0.081), but was significantly higher than RNC (343.79 ± 157.08 N, p = 0.0051) and PICN (348.78 ± 157.44 N, p = 0.0059). LDS, RNC, and PICN did not differ significantly. YTZP experienced more non-repairable fractures (5/10), while PICN predominantly failed in a repairable manner (9/10).

All CAD/CAM post-crowns exceeded functional loads for the anterior region. YTZP and LDS demonstrated greater strength, whereas PICN and RNC, despite being weaker, favored repairable failures-highlighting the importance of balancing strength and clinical manageability.