Fracture resistance of custom-milled CAD/CAM post and core using two different materials: an in vitro study

Introduction
Restoration of endodontically treated teeth could be challenging for dentists, as these teeth would be biomechanically compromised at multiple levels, such as tissue components and tooth structures.

Objective
This study aimed to evaluate fracture resistance and failure modes of teeth restored with custom-milled posts and cores fabricated from polyetherketoneketone, fiber-reinforced resin materials, and prefabricated fiber posts.

Material and methods
Thirty mandibular premolars were used in the present study. After endodontic treatment, teeth were randomly assigned into three groups, i.e., MPP: restored with custom-milled posts and cores fabricated from polyetherketoneketone (PEKK); MFP: restored with custom-milled posts and cores fabricated from fiber-reinforced resin; and PFP: restored with prefabricated fiber-reinforced resin posts, then all samples were restored with metal crowns. Samples were subjected to a 45o shear force at the inner slope of buccal cusp to failure. One-way ANOVA for independent groups and χ2 test at 0.05 statistical significance were applied.

Results
Differences between fracture resistance means of the three groups were not statistically significant (p = 0.279 > 0.05). The fracture resistance means for the MPP group was 423.2 ± 113.28 N; 356.90 ± 141.050 N for the MFP group; and 439.5 ± 100.616 N for the PFP group. As for failure types, no significant difference among the three groups was detected (p = 0.366 > 0.05). Regarding the failure modes, the reparable failure modes in each group, i.e., MPP, MFP, and PFP were 60%, 80%, and 50%, respectively.

Conclusions
Teeth restored with custom-milled posts and cores fabricated from PEKK and fiber-reinforced composite displayed an acceptable performance. Consequently, within the limitations of this study, these posts may be considered a good alternative to prefabricated fiber-reinforced posts.