Objectives: To assess the shear bond strength (SBS) between metal orthodontic brackets and zirconia after receiving different mechanical and chemical surface treatments, and different types of resin adhesive. The failure mode of each treatment protocol was also evaluated. Materials and methods: The present in vitro experimental study consisted of six surface treatment protocols with two different resin adhesives. One-hundred and forty-four rectangular-shaped 3 mol% yttrium-stabilized tetragonal zirconia polycrystal blocks were milled, sintered, and embedded in acrylic resin. They were randomly divided into three mechanical (none, air abrasion, and bur grinding) and two chemical surface treatment conditions (no primer and Z-primer). The specimens were divided into two groups according to the resin adhesive received: self-cured (RelyX U200) and light-cured adhesives (Transbond XT). The SBS between the metal bracket and zirconia was tested using a universal testing machine (1-mm/min crosshead speed), and the failure mode was evaluated. Differences in SBS and failure mode were analyzed using Welch ANOVA followed by post-hoc comparison and Fisher’s Exact test, respectively. Results: Bur grinding produced the highest SBS, followed by air abrasion. Z-primer application typically provided a higher SBS regardless of resin adhesive used (p < 0.001). Without primer application, RelyX U200 provided a higher SBS than Transbond XT (p < 0.001). After grinding, using Z-primer and RelyX U200 resulted in a higher SBS than no primer and using Transbond XT (p < 0.001). Adhesive failure at the zirconia–adhesive interface occurred only when Transbond XT was applied without bur grinding, and when using Transbond XT after grinding, but no Z-primer application. Conclusion: Bur grinding combined with applying an MDP-containing primer and resin adhesive enhances the SBS between zirconia and metal orthodontic brackets.

This study aimed to evaluate the shear bond strength (SBS) of zirconia to dual-cured resin cement following various cleaning protocols and surface treatments after cement contamination. Seventy-seven zirconia specimens (5 × 5 × 2.5 mm³) were fabricated, polished, and randomly divided into seven groups (n = 11). Ten specimens per group were tested for SBS, and one was reserved for scanning electron microscopy. Group C− was cemented without surface treatment, while group C+ received air abrasion prior to cementation. Groups F − , F + , FT + , S − , and S+ were initially air-abraded and then contaminated with resin cement. F-series groups were cleaned using a furnace, and S-series with a piezoelectric scaler. Among these, F + , FT + , and S+ received additional air abrasion prior to re-cementation, whereas F− and S− did not. Groups F+ and S+ were re-cemented immediately, whereas FT+ was re-cemented 7 days after surface re-treatment. All specimens were artificially aged before SBS testing. One-way ANOVA followed by Tukey's HSD post-hoc test was used for statistical analysis (α = 0.05). Statistically significant differences in SBS were found among the groups (p < 0.05). Group F+ demonstrated the highest bond strength (6.60 ± 1.10 MPa), followed by groups C+ (6.59 ± 0.94 MPa) and S+ (5.42 ± 0.87 MPa), with no significant differences among these three. The lowest SBS was observed in group C− (2.66 ± 0.51 MPa). Intermediate values were recorded in groups F− (4.17 ± 0.95 MPa), FT+ (4.41 ± 0.95 MPa), and S− (4.60 ± 1.17 MPa), which did not differ significantly from each other. Cleaning cement-contaminated zirconia using a furnace or piezoelectric scaler, followed by air abrasion and immediate re-cementation, significantly improves SBS to levels comparable with clean, air-abraded zirconia. Air abrasion enhances bonding efficacy, while delayed re-cementation may diminish bond strength even after surface re-treatment. Article published online: 22 August 2025 © 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/) Thieme Medical and Scientific Publishers Pvt. Ltd. A-12, 2nd Floor, Sector 2, Noida-201301 UP, India

Recurrent acidic exposure in patients with gastroesophageal reflux disease (GERD) accelerates the degradation of provisional restorative materials, whereas approaches to enhance the acid resistance of 3D-printed restorations remain inadequately characterized. This study aimed to evaluate the effect of graphene oxide (GO) incorporation on the surface properties and acid resistance of 3D-printed provisional restorative materials under simulated gastroesophageal reflux conditions. GO was synthesized using the Hummers’ method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. XRD analysis demonstrated a pronounced shift in the characteristic peak (2θ) from 26° to 12°, consistent with an expansion of interlayer spacing after oxidation. FTIR confirmed the presence of oxygen-containing functional groups (hydroxyl, carbonyl, and epoxy), while Raman spectroscopy identified the characteristic D and G bands, confirming successful GO synthesis. Temporary Crown & Bridge resin (TC100) was modified with GO at six concentrations (0, 0.025, 0.05, 0.1, 0.5, and 1.0 wt %) using a planetary ball milling technique. Standardized 3D-printed specimens (n = 24 per group) were fabricated. Surface roughness and Vickers microhardness were measured before and after 45 h of immersion in simulated gastric acid (pH 2). Data were analyzed using one-way ANOVA and paired t-tests (α = 0.05). After acid exposure, the control group (0 wt % GO) exhibited significant surface deterioration, showing the highest surface roughness and a marked reduction in hardness (p < 0.05). Conversely, GO-modified groups demonstrated a concentration-dependent improvement in resistance to acid-induced degradation. The 0.5 wt % GO group showed the most favorable performance, maintaining both surface roughness and hardness with no significant difference from baseline values (p > 0.05). These findings indicate that GO incorporation enhances the surface integrity and acid resistance of 3D-printed provisional resins, with 0.5 wt % identified as the optimal concentration for minimizing acid-induced surface deterioration.