# Fracture strength of roots restored with relined and milled glass fiber posts

## TL;DR

This study compares the strength and fracture patterns of two types of glass fiber posts used in dental restorations, finding that CAD/CAM-milled posts perform better.

## Contribution

The study provides new empirical evidence on the superior fracture strength and reduced catastrophic failure of CAD/CAM-milled glass fiber posts compared to relined posts.

## Key findings

- CAD/CAM-milled glass fiber posts showed significantly higher fracture strength than relined posts.
- Milled posts had fewer catastrophic fractures compared to the relined group.

## Abstract

Computer-aided design/computer-aided manufacturing (CAD/CAM)-milled glass fiber posts offer notable advantages. However, their performance compared to that of prefabricated, composite-reinforced glass fiber posts is controversial. This study aimed to evaluate the fracture strength and fracture patterns of canine roots restored with relined glass fiber posts and CAD/CAM-milled glass fiber posts.

In total, 20 decoronated canine roots underwent endodontic treatment (n = 10). In the relined group (control), prefabricated glass fiber posts (Reforpost Angelus #1, Angelus, Brazil) were relined with a resin composite (Z350, 3M ESPE, USA). In the milled group, the root canal was modeled using a post (Pinjet, Angelus) and red acrylic resin (Pattern Bright Kit, Kota Ind., Brazil). The acrylic resin patterns were scanned and milled from a glass fiber block (Fiber CAD Post & Core, Angelus). A dual-cure self-adhesive resin luting agent (RelyX™ U200, 3M ESPE) was used for post cementation in both groups. The specimens were subjected to compressive loading, applied at a 45° angle to the long axis of the tooth using a universal testing machine with 200 kgf of compressive force at a crosshead speed of 1 mm/min, until failure. The failure mode was classified as catastrophic (fracture extended to the middle and/or apical third) or repairable (glass fiber post and/or coronal core or limited to the cervical region). A statistical analysis was performed using an independent samples t-test (α = 0.05).

A statistically significant difference was observed in the mean fracture strength, with higher values for the milled group (p = 0.004). Furthermore, the milled group had fewer catastrophic failures.

The CAD/CAM-milled glass fiber posts exhibited greater fracture strength and a reduced incidence of catastrophic fractures.