# Fracture Resistance of 3D-Printed Hybrid Abutment Crowns Made from a Tooth-Colored Ceramic Filled Hybrid Composite: A Pilot Study

## TL;DR

This pilot study tested the fracture resistance of 3D-printed hybrid abutment crowns made from a tooth-colored ceramic composite and found them to be strong enough for potential clinical use.

## Contribution

The study introduces a new 3D-printable, tooth-colored ceramic-reinforced composite for hybrid abutment crowns and evaluates its fracture resistance.

## Key findings

- The mean fracture load for non-aged specimens was 389.04 N, exceeding a clinically acceptable threshold.
- Artificial aging did not significantly reduce the fracture load, with a mean of 391.19 N observed.
- FEM analysis revealed high tensile stress (173.37 MPa) under mechanical loading.

## Abstract

The aim of this pilot in vitro study is to investigate the fracture strength of hybrid abutment crowns (HACs) made of a 3D-printable, tooth-colored, ceramic-reinforced composite (CRC). Based on an upper first premolar, a crown was designed, and specimens were additively fabricated from a composite material (VarseoSmile Crown plus) (N = 32). The crowns were bonded to standard abutments using a universal resin cement. Half (n = 16) of the samples were subjected to artificial aging, during which three samples suffered minor damage. All specimens were mechanically loaded at an angle of 30° to the implant axis. In addition, an FEM simulation was computed. Statistical analysis was performed at a significance level of p < 0.05. The mean fracture load without aging was 389.04 N (SD: 101.60 N). Two HACs suffered screw fracture, while the crowns itself failed in all other specimens. In the aged specimens, the mean fracture load was 391.19 N (SD: 143.30 N). The failure mode was predominantly catastrophic crown fracture. FEM analysis showed a maximum compressive stress of 39.79 MPa, a maximum tensile stress of 173.37 MPa and a shear stress of 60.29 MPa when loaded with 389 N. Within the limitations of this pilot study, the tested 3D-printed hybrid abutment crowns demonstrated fracture resistance above a clinically acceptable threshold, suggesting promising potential for clinical application. However, further investigations with larger sample sizes, control groups, and clinical follow-up are required.