Evaluation of mechanical properties of anatomically customized fiber posts using E-glass short fiber-reinforced composite to restore weakened endodontically treated premolars

Abstract

Objective: This study was conducted to assess the influence of combining different forms of fiber-reinforced composites (FRC) on the mechanical behavior and bond strength of compromised endodontically treated teeth (ETT).

Materials and methods: Eighty extracted human premolar teeth were randomly divided into five experimental groups according to the type of intra-radicular restoration and the canal preparation design which was either non-flared (Group 1), flared (Groups 2-5), closed-apex (Groups 1,3,5) or open-apex (Groups 2,4). Standard prefabricated fiber posts were used as intra-radicular restoration for Groups 1-3 while Groups 4-5 were restored with anatomically customized relined fiber posts. After composite core fabrication, all samples were sent for an artificial aging process. Fracture resistance and push-out bond strength tests were then carried out through a universal testing machine followed by mode of failure analysis via a stereomicroscope and scanning electron microscope.

Results: Pairwise Log-Rank comparisons revealed that the survival rate of Group 2 and Group 3 was significantly lower than all other groups after artificial aging. The highest fracture resistance value (1796 N) was recorded in Group 5 and was significantly higher than that of the other groups (p < 0.05), while Group 2 exhibited the lowest fracture resistance (758 N), which was significantly lower compared to the other groups. Group 5 and Group 4 demonstrated a significantly higher push-out bond strength, at all root thirds, than Group 3, Group 2, and Group 1 (p < 0.05). The most frequently observed failure mode in the tested groups occurred between the resin cement and radicular dentin.

Conclusion: The use of short fiber-reinforced composite (SFRC) to reline the prefabricated FRC post has been proven to have superior fracture resistance with favorable failure patterns and increased push-out bond strength values compared to standard prefabricated FRC posts.

Keywords: Endodontically treated teeth; Fiber-reinforced composite Post; Post and core; Short fiber-Reinforced composite.

Fig. 1

Flowchart of the study design

Fig. 2

Different failure patterns after artificial aging. (A–C) Complete core fracture. (D) Complete debonding of the post/core complex

Fig. 3

Thermo-mechanical aging survival curve (Kaplan-Meier survival analysis) for experimental groups loaded with 50 N

Fig. 4

Fracture patterns following load to failure test. (A) Favorable fracture. (B) Unfavorable (catastrophic) fracture

Fig. 5

Interaction between the mean push-out bond strength of the restorative group and the root third

Fig. 6

Different failure modes as seen by stereomicroscope. (a) Type I failure magnification of 5x. (b) Type II failure magnification 15x. (c) Type IV failure magnification 5x. (D, Dentin; C, Resin Cement; FP, Fiber Post; Rc, EverX Resin Composite)

Fig. 7

Representative SEM microimages for the tested specimens under x100 and x200 showing different adhesive failures: (1a, b) between resin cement and dentin (Type IV) in a sample restored with standard FRC post, (2a, b) between resin cement and resin composite (Type III) in a sample restored with anatomically customized FRC post, (3a, b) between fiber post and resin composite (Type II) in a sample restored with anatomically customized FRC post. (De, Dentin; Ce, Resin Cement; Rc, Resin composite Fp, Fiber Post)