Lithium Disilicate Endocrowns Show Greater Fracture Resistance: Study

A new study published in the journal of BMC Oral Health showed that in laboratory tests, lithium disilicate endocrowns outperformed direct restorative materials in terms of fracture resistance.

It is difficult for Endodontically Treated Teeth (ETT) to withstand occlusal stresses without breaking. Thus, this study evaluated the fracture resistance (FR) of endodontically treated premolar teeth restored using a novel self-adhesive bulk-fill resin-based composite (RBC) (Stela, SDI Limited, Australia), a short-fiber-reinforced composite (SFRC) (EverX flow, GC., Tokyo, Japan), a conventional nanohybrid (RBC) (Filtek Z250 XT, 3M ESPE, St. Paul, MN, USA), and a computer-aided design/computer-aided manufacturing (CAD/CAM) Lithium Disilicate (Emax, Dentsply Sirona, Bensheim, Germany).

44 human removed maxillary premolars were used in the FR test. Following endodontic treatment, a single operator created standardized mesio-occlusal-distal (MOD) cavities in teeth, which were then split into 4 groups (n=11) based on the kind of restorative material utilized. Group (F1): A single 5 mm increment of Stela resin-based composite was put into the cavity to reestablish the ETT. Group (F2): A 2 mm occlusal layer was left to be repaired using nanohybrid composite (Filtek Z250 XT) after ETT was restored using EverX Flow composite, which was packed and light-cured for 20 seconds. Group (F3): Only Filtek Z250 XT resin-based composite was used to rebuild the ETT. Group (F4): Preparations were scanned using the Omnicam, restorations were prepared using CEREC Premium Software (version 4.4), and ETT was restored using (CAD/CAM Cerec MCXL) Lithium Disilicate endocrown.

A tofflemire matrix retainer and band were used to restore the proximal walls for the direct repair groups. Using a universal testing apparatus (Bluehill Lite Software on an Instron®; each specimen's failure load was recorded in Newton), all repaired teeth underwent FR testing. With the acrylic block fastened to the bottom fixed head, each specimen was placed separately on the computer-controlled device that had a 5 kN load cell.

Microsoft Excel 2016, GraphPad Prism®, and SPSS 27® were used for statistical analysis. The Shapiro-Wilk and Kolmogorov-Smirnov tests were used to evaluate the normality of the data, and the results showed a nonparametric distribution. When compared to other direct restoration materials, Group F4 (Endocrown) performed the best (1427.73 ± 156.96), with a significant difference (P<0.0001). On the other hand, despite minor variations in their means, the three direct restoration groups did not differ significantly.

Group F2 (EverX+Z250, mean: 619.87 ± 186.41) outperformed Group F1 (Stella, mean: 561.75 ± 173.74) with P = 1.000 and Group F3 (Z250, mean: 452.22 ± 202.72) with P = 0.471. Although Group F1 (Stella) outperformed Group F3 (Z250), the difference was not statistically significant (P = 0.838). Overall, although direct restorative materials may be a therapeutically acceptable substitute for normal applications, lithium disilicate endocrowns show greater fracture resistance. 

Source:

El Gezawy, E. A. G., Bedair, S. S., Abbas, K. F., Algizawi, S., & Kamh, R. (2026). Fracture behavior of endodontically treated premolars restored with direct and indirect restorations: an in vitro study. BMC Oral Health, 26(1). https://doi.org/10.1186/s12903-026-08736-2