Comparison of Fracture Resistance Based on Ferrule Presence vs Material Type in Maxillary Central Incisor Endocrown Restorations

BACKGROUND In endodontically-treated anterior teeth, prognosis depends on remaining tooth structure and restorative material. This in vitro study evaluated how ferrule presence and material type affect the fracture resistance of CAD/CAM endocrowns in maxillary central incisors. MATERIAL AND METHODS Forty extracted maxillary central incisors were randomly divided into 4 groups (n=10 each group): Ferrule (+) e.max, Ferrule (-) e.max, Ferrule (+) Celtra Duo, and Ferrule (-) Celtra Duo. Standardized endocrowns were fabricated using CAD/CAM technology and cemented with a dual-cure adhesive resin cement. Specimens were thermocycled (5000 cycles, 5-55 °C) and tested for fracture resistance with a universal testing machine. RESULTS The presence of a 2 mm circumferential ferrule significantly increased fracture resistance (P=0.001). Ferrule (+) specimens had a higher mean resistance (561.23 N) than ferrule (-) specimens (395.63 N). Celtra Duo showed slightly higher values (507.11 N) than e.max (449.74 N), although the difference was not statistically significant (P=0.304). A significant interaction between ferrule presence and material type was observed (P=0.00013). Most catastrophic fractures occurred in ferrule (-) groups, especially with Celtra Duo (P<0.05). CONCLUSIONS A 2-mm ferrule markedly improved fracture resistance of anterior endocrowns, regardless of ceramic type. While both materials performed similarly with a ferrule, ZLS demonstrated better resistance and fewer catastrophic failures without it. Preserving a ferrule is strongly recommended, and ZLS may be preferable when a ferrule cannot be achieved. Further clinical studies are needed to validate these findings.