A recent study has examined the effects of laser surface texturing (LST) on pre-sintered zirconia using a surface transition machine (STM). Researchers compared the impact of LST on zirconia’s surface characteristics and its shear bond strength (SBS) with resin cement against traditional sandblasting techniques.
Study: Improving Zirconia–Resin Cement Bonding Through Laser Surface Texturing: A Comparative Study. Image Credit: YURIMA/Shutterstock.com
Background
Zirconia is a staple in modern dentistry due to its durability and strength, making it well-suited for implant-supported crowns and posterior restorations. However, its non-silica crystalline structure presents adhesion challenges, particularly in cases where mechanical retention is minimal, such as overlay restorations, short crowns, and Maryland bridges.
To enhance bond strength, both mechanical and chemical surface treatments are commonly used. Alumina sandblasting, a frequently employed mechanical approach, increases surface roughness to improve micromechanical retention. However, it can also alter zirconia’s properties and potentially compromise its structural integrity.
To address these drawbacks, researchers have turned to surface modification techniques like LST. This high-intensity laser process creates specific microstructures on zirconia’s surface, enhancing wettability and adhesion without the downsides of sandblasting. While previous studies have focused on improving the bond between veneering porcelain and zirconia, research on zirconia’s adhesion to resin cement remains limited.
Methods
In this study, zirconia blocks underwent LST treatment for one hour before sintering using an STM and a fiber laser device. The texture and roughness of untreated and STM-treated zirconia samples were analyzed through white light interferometry (WLI) and scanning electron microscopy (SEM).
For comparison, additional samples underwent sandblasting with alumina beads. The study divided samples into three experimental groups: untreated zirconia (G-UT), STM-treated zirconia (G-STM), and sandblasted zirconia (G-SB). A goniometer was used to measure contact angles (for deionized water) on ten samples from each group to assess surface wettability.
To evaluate adhesion, square and cylindrical zirconia specimens were prepared and categorized based on their surface treatments and bonding conditions: STM + resin cement without primer (G-STM), STM + resin cement with primer (G-STM+P), sandblasting + resin cement without primer (G-SB), and sandblasting + resin cement with primer (G-SB+P).
Cylindrical samples were bonded to the center of square samples using resin cement (Ivoclar Variolink Esthetic) and primer (Monobond Plus), followed by a 20-second light curing process. Shear bond strength (SBS) was then tested using a universal testing machine, with the lower jig securing the zirconia samples while the upper jig applied load to the cylindrical specimens.
Results and Discussion
SEM imaging revealed significant differences in surface features among G-UT and G-STM specimens. The laser-generated heat caused localized melting and re-solidification of zirconia, creating a textured surface with improved microtopography. The G-STM surface exhibited consistent etching up to a depth of approximately 50 μm, resulting in macroscale texturing.
At higher magnifications, researchers observed the formation of micro-patterns, while zirconia’s overall crystalline structure remained unchanged. WLI images confirmed increased roughness, showing enhanced step heights, surface irregularities, and greater topographical complexity.
Contact angle measurements further supported these findings: G-UT, G-STM, and G-SB recorded contact angles of 78.2 ± 8.0°, 28.4 ± 10.0°, and 79.2 ± 5.7°, respectively. The significantly lower contact angle for G-STM compared to G-UT and G-SB indicated improved surface wettability, while G-UT and G-SB exhibited similar levels of wettability.
When measuring SBS, G-STM+P demonstrated the highest bond strength at 46.3 ± 8.3 MPa, whereas G-SB had the lowest at 9.8 ± 3.7 MPa. G-STM samples also exhibited strong bonding (43.4 ± 4.3 MPa), comparable to G-STM+P, with no significant difference due to the large standard deviation in the latter group.
The G-SB+P group, with an SBS of 30.06 ± 3.09 MPa, showed an improvement of nearly 20 MPa over G-SB. However, this value remained significantly lower than those of G-STM and G-STM+P.
Conclusion and Future Prospects
This study provides a detailed evaluation of STM-based LST as an alternative to sandblasting for enhancing the bond strength between zirconia and resin cement. The results indicate that STM-based LST can create a favorable microtopography and improve surface characteristics without the limitations of sandblasting, making it a promising technique for clinical applications.
However, the study does have some limitations. SBS measurements focused on zirconia–zirconia interfaces rather than tooth–zirconia interfaces, which are more clinically relevant. Additionally, the STM-based LST was compared to a limited number of surface treatments and primers.
Future research should focus on assessing long-term bond strength stability, optimizing laser parameters, and conducting ex vivo studies using extracted human teeth to evaluate the real-world efficacy and durability of this technique.
Journal Reference
Yoon, J.-Y. (2025). Improving Zirconia–Resin Cement Bonding Through Laser Surface Texturing: A Comparative Study. Prosthesis, 7(1), 19. DOI: 10.3390/prosthesis7010019, https://www.mdpi.com/2673-1592/7/1/19
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.