# Mechanical Properties of Additively Manufactured Composite Resin vs. Subtractively Manufactured Hybrid Ceramic Implant-Supported Permanent Crowns Before and After Thermal Aging

## TL;DR

This study compares the durability and surface quality of crowns made using two different manufacturing methods after simulating a year of use in the mouth.

## Contribution

The study evaluates composite resin and hybrid ceramic crowns under realistic clinical conditions with thermal aging and varying thicknesses.

## Key findings

- Composite resin crowns had lower surface roughness but also lower fracture resistance compared to hybrid ceramic crowns.
- At 1.5 and 2.0 mm thickness, hybrid ceramic crowns showed significantly higher fracture resistance than composite resin crowns.
- A 1.0 mm thickness may not be sufficient for high bite forces, posing a potential risk for composite resin and hybrid ceramic crowns.

## Abstract

This study aims to compare the surface roughness and fracture resistance of implant-supported permanent crowns additively manufactured using composite resins (Crowntec, VarseoSmile) versus subtractively manufactured polymer-infiltrated hybrid ceramic (VITA Enamic) at various wall thicknesses using an experimental setup as close to clinical as possible. 180 crowns were fabricated in three thicknesses (1.0, 1.5, and 2.0 mm) and cemented onto titanium abutments. Experimental groups underwent thermal aging (10,000 cycles) to simulate one year of clinical service. Surface roughness was measured via profilometry, and fracture resistance was assessed using a universal testing machine. Composite resin crowns exhibited lower surface roughness and lower fracture resistance than subtractively manufactured crowns. No significant difference in fracture resistance was found between materials at 1.0 mm (p > 0.05). However, at 1.5 and 2.0 mm, hybrid ceramic network crowns showed significantly higher resistance (p < 0.01). It was concluded that, within the limitations of this 1-year simulated study, both material-method combinations met the biological threshold for surface roughness. Regarding fracture resistance, composite resins and hybrid ceramics satisfied clinical requirements for molar bite forces only at thicknesses of 1.5 mm and above. 1.0 mm thickness may pose a risk under high occlusal loads.