# High-Temperature Hydrofluoric Acid Etching Increases the Debonding Resistance of Zirconia Copings Cemented to Titanium Bases: An In Vitro Study

## TL;DR

A new method using high-temperature hydrofluoric acid etching improves the bond strength between zirconia copings and titanium bases, reducing the risk of debonding in dental applications.

## Contribution

High-temperature hydrofluoric acid etching followed by silanization is shown to significantly enhance the retention and stability of zirconia-titanium bonds.

## Key findings

- High-temperature acid etching increased initial pull-out forces by 125% compared to the control group.
- Acid-etched specimens maintained higher retention after thermocycling compared to airborne-particle abrasion.
- Acid etching improved wettability and resulted in stronger zirconia–cement interfaces.

## Abstract

This protocol represents an effective surface-conditioning strategy to improve the stability of zirconia copings cemented to titanium bases.Potentially reduce the risk of clinical debonding.

This protocol represents an effective surface-conditioning strategy to improve the stability of zirconia copings cemented to titanium bases.

Potentially reduce the risk of clinical debonding.

This study compared three internal surface treatments of zirconia copings—silane alone (control), airborne-particle abrasion followed by silane, and high-temperature hydrofluoric acid etching followed by silane—regarding initial pull-out retention strength, retention after thermocycling, failure mode assessed by scanning electron microscopy (SEM), and surface wettability. Sixty-three monolithic zirconia copings were allocated to three groups (n = 21) according to surface treatment and cemented to titanium bases with a self-adhesive resin cement. Initial pull-out tests were performed. A subset (n = 10 per group) underwent thermocycling followed by repeat testing. Failure modes were analysed by SEM, and wettability was measured using the sessile drop method. Surface roughness and crystalline phase were additionally characterized by white-light interferometry and X-ray diffraction (XRD), respectively. High-temperature acid etching produced significantly higher initial pull-out forces than airborne-particle abrasion and silane alone, with mean values 125% higher than control and 42.6% higher than airborne-particle abrasion. After thermocycling, acid-etched specimens maintained the highest retention, whereas airborne-particle abrasion showed critical loss. SEM revealed predominantly cement remnants on zirconia in the acid-etched group, indicating a stronger zirconia–cement interface. Acid etching also yielded significantly lower contact angles, reflecting improved wettability. High-temperature hydrofluoric acid etching followed by silanization provided superior and more stable retention, more favourable failure modes, and improved wettability.