Fracture strength of teeth with coronal destruction after core build-up restoration with bulk fill materials

This study aimed to evaluate the fracture strength and failure modes of different core techniques in teeth with simulated coronal destruction.

Forty teeth were endodontically prepared and the specimens were divided into four experimental groups (n = 10) according to the core composition: Filtek One Bulk Fill-FOBF, Filtek Z350 XT-FZ350 (standard group), Filtek Bulk Fill Flow-FBFF, and LuxaCore Z-LCZ. CAD/CAM Monolithic zirconia crowns were obtained and cemented with RelyX U200. After storage in distilled water at 37°C for 48 h, the specimens were subjected to thermal cycling and to compressive strength mechanical tests. Statistical analyses (α = 0.05) were performed by non-parametric Kruskal-Wallis, Dunn post hoc, and Fisher's exact tests.

No significant differences (p > 0.05) were observed among FOBF, FZ350, and FBFF (mean ranks = 20.30, 12.20, and 23.20, respectively). LCZ (mean rank = 26.30) produced results similar to those of FOBF and FBFF (p > 0.05) and higher than those of FZ350 (p = 0.042). The most frequent type of failure was irreparable, regardless of the experimental condition. The lowest percentages of reparable fractures were produced by FOBF group (10%).

The use of bulk fill materials, including the "core-and-post" LCZ dual-cure resin composite, did not impair the fracture strength of endodontically treated teeth with coronal destruction.

Resin composite bulk fill materials that can be used as a core-and-post cementation in an only stage are interesting, since they enable clinicians to work with one only material, and avoid several materials interfaces, technical sensitivity, and longer chair-time due to multistep procedures.