# Effect of simulated root canal morphology and post space depth on fracture performance of glass fiber-reinforced post-core buildups

## TL;DR

This study tested how different root canal shapes and post depths affect the strength and failure of dental post-core systems made with various fiber-reinforced composites.

## Contribution

The study identifies specific fiber-reinforced composite materials that perform comparably to a control in simulated dental post-core systems.

## Key findings

- everStick and everX-posterior posts showed fracture performance comparable to Itena posts.
- everX-flow had significantly lower fracture strength in certain canal models and post depths.
- A 6 mm post space depth was associated with more favorable failure modes compared to 4 mm.

## Abstract

This in vitro study evaluated the effect of simulated root canal morphology, post space depth (PSD), and type of glass fiber-reinforced composite (GFRC) on the fracture strength and failure mode of post-core buildups.

A total of 168 3D-printed maxillary premolar root models were allocated into 24 groups (n = 7) based on simulated canal morphology (single-circle, oval, double-circle), PSD (4 mm, 6 mm), and GFRC type (everStick, everX-flow, everX-posterior), with Itena post as the control. A standardized adhesive protocol was used, followed by GFRC application and dual-cure core buildup. Fracture strength was tested under a 45° compressive load. Failure modes were categorized as favorable (type I, II, III) or unfavorable (type IV). Data were analyzed using ANOVA with Tukey’s post hoc test, independent t-tests, and chi-square tests (α = 0.05).

GFRC type significantly affected fracture strength (p < 0.001), whereas neither simulated canal morphology nor PSD showed a significant effect. At 4 mm PSD, everX-flow exhibited significantly lower fracture strength than Itena and everStick posts in single-circle and oval canal models (p < 0.05). At 6 mm PSD, everX-flow recorded the lowest fracture strength in single-circle canal models (p < 0.05). Failure mode was significantly influenced by PSD (p = 0.01) and GFRC type (p < 0.001). A 6 mm PSD was associated with a higher percentage of each favorable failure type compared to 4 mm PSD. EverStick and Itena posts showed the highest percentage of favorable failures.

The intra-canal reinforcing material is the primary determinant of the fracture performance of post-core buildups. The mechanical reinforcement materials of everStick and everX-posterior posts but not everX-flow are comparable to that of Itena post.

Everstick and everX-posterior can replace Itena posts as safe reinforcing materials in single-canaled premolars.