# Shear Bond Strength of Additively and Subtractively Manufactured CAD/CAM Restorative Materials After Different Surface Treatments and Adhesive Strategies: An In Vitro Study

## TL;DR

This study compares how different surface treatments and adhesives affect the bond strength of dental restorative materials made using additive and subtractive manufacturing.

## Contribution

The study provides new insights into optimal surface treatments and adhesive strategies for additively and subtractively manufactured dental materials.

## Key findings

- Additively manufactured materials showed consistent bond strength without surface treatment.
- Subtractively manufactured materials required specific surface treatments for reliable adhesion.
- Etch-and-rinse adhesive systems achieved the highest bond strength with additively manufactured materials.

## Abstract

This study aims to evaluate the effects of different surface treatments and adhesive systems on the shear bond strength (SBS) of additively manufactured (AM) and subtractively manufactured (SM) restorative materials. A total 675 rectangular specimens of three AM (Saremco Crowntec/SC, VarseoSmile CrownPlus/VC, and VarseoSmile TriniQ/VT) and two SM (Vita Enamic/VE and Cerasmart/CS) restorative materials were fabricated. Each material was randomly divided into three groups regarding surface treatments: control/C, sandblasting/S, and etching/E. Following surface treatments, each AM and SM restorative material was then divided into three subgroups (15 specimens/subgroup) on the basis of adhesive systems (etch-and-rinse, self-etch, and universal). All specimens were thermocycled at 10,000 cycles, 5–55 °C, 30 s dwell time, and tested under SBS until failure, and failure types were examined under a stereomicroscope. Representative specimens were examined by SEM to evaluate fracture morphology. Statistical analysis was set at p < 0.05. There were significant differences in bond strength according to the material, surface treatment, adhesives, and their interactions (p < 0.05). The highest SBS value was obtained with SC × sandblasting × etch-and-rinse (16.45 ± 0.93 MPa), while the lowest value was found in the CS × control × universal interaction (4.68 ± 1.1 MPa). Outcomes varied according to the materials, surface treatment, and adhesive strategy. Clinically, these findings indicate that SM materials may require various surface treatment to achieve reliable adhesion, whereas AM materials provide more similar bond strength performance with no surface treatment.