Contamination of zirconia restorations before cementation can impair the resin–zirconia bonding durability. The objective of this study was to evaluate the effect of human saliva or blood decontamination with 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP)-containing cleaner on the resin–zirconia shear bond strength (SBS). Methods: A total of 220 zirconia specimens were prepared and air-abraded and randomly distributed into 11 groups (n = 20 per group). Except for the control group (no contamination), zirconia specimens were contaminated with either human saliva (five groups) or blood (five groups), and then subjected to one of five cleaning methods: water rinsing, 38% phosphoric acid etchant (Pulpdent Corp., Watertown, MA, USA), 70% isopropanol alcohol (Avalon Pharma, Riyadh, Saudi Arabia), Ivoclean (Ivoclar Vivadent, Schaan, Lichtenstein) and Katana Cleaner (Kuraray Noritake, Tokyo, Japan). The resin–zirconia SBS was tested at 24 h and after thermocycling (10 k cycles). Three-way ANOVA followed by Tukey’s multiple comparisons test were utilized to analyze the SBS data. Failure modes were evaluated using a scanning electron microscope. Results: Both blood and saliva significantly affected resin–zirconia SBS as contaminants. After thermocycling, there was no statistically significant difference between SBS obtained after decontamination with the Katana Cleaner (blood, 6.026 ± 2.805 MPa; saliva, 5.206 ± 2.212 MPa) or Ivoclean (blood, 7.08 ± 3.309 MPa; saliva, 6.297 ± 3.083 MPa), and the control group (no contamination, 7.479 ± 3.64 MPa). Adhesive and mixed failures were the most frequent among the tested groups. Conclusion: Both 10-MDP-containing cleaner (Katana Cleaner) and zirconium oxide-containing cleaner (Ivoclean) could eliminate the negative effect of saliva and blood contamination on resin–zirconia SBS.

The present study aimed to compare the color stability of different types of zirconia with and without grit blasting (GB) after they were immersed in staining drinks. Two hundred and forty zirconia samples (N = 240) belonging equally to three different types of zirconia (Cercon^® xt multilayer, xt extra translucent, and ht high translucent) were used in this study. Forty samples from each zirconia group were roughened with GB, while the other forty remained non-GB (NGB). Eight GB and NGB zirconia samples from each sub-group were immersed in artificial saliva, coffee, protein shake, chlorhexidine mouthwash, and a soft drink. Besides chlorhexidine mouthwash (immersion time: 14 days), the samples were immersed in the liquids for 28 days. A spectrophotometer was utilized to observe the color differences (∆E) at baseline (T0), 7 days post-immersion (T1), 14 days post-immersion (T2), 21 days post-immersion (T3), and 28 days post-immersion (T4). For the multilayer zirconia, the greatest ∆E (8.45 for GB and 5.97 for NGB samples) was observed after immersion in coffee at T4. For the extra translucent zirconia, the greatest ∆E (9.10 for GB and 6.81 for NGB samples) was also observed after immersion into the coffee at T4. For the high translucent zirconia, the greatest ∆E (4.53 for GB and 3.62 for NGB samples) was observed after immersion into the coffee at T4 and T3. Protein shake and soft drink immersion also significantly discolored some zirconia samples. Overall, GB zirconia samples presented with greater ∆E values than their NGB counterparts. It can be concluded that coffee immersion of zirconia samples caused a more significant discoloration (increased ∆E values) than any other liquid. Future clinical studies should be carried out to corroborate the current study’s findings.

Introduction: Enamel demineralization during orthodontic treatment may occur due to changes in the oral environments. This study aimed to assess the influence of flash-free polymeric adhesive systems on debonding behavior and subsurface enamel hardness under erosive and cariogenic conditions, compared with conventional orthodontic adhesives. Methods: Sixty premolars ( n = 60) were randomly divided into two groups ( n = 30 each): Group C, consisting of uncoated brackets, and Group F, comprising flash-free adhesive precoated brackets. Each group was further subdivided into three subgroups ( n = 10) based on the storage medium used. In the artificial saliva subgroup (control group), specimens were stored in artificial saliva for 24 h. In the artificial cariogenic subgroup, specimens were alternately exposed to an artificial cariogenic solution and artificial saliva for 28 days. In the gastric acid subgroup, specimens were subjected to simulated gastric acid (pH = 1.2) by immersion for 2 min, six times daily, over a period of 9 days. All specimens underwent adhesive remnant index (ARI) testing and cross-sectional microhardness evaluation. Two-way ANOVA and Tukey's test were conducted to analyze cross-sectional microhardness. The chi-square test was used to analyze ARI scores. Results: Across all storage media, conventional brackets demonstrated higher frequencies of ARI score 1, whereas flash-free brackets consistently showed higher frequencies of ARI score 2. Across all storage media, the flash-free bracket system exhibited significantly higher overall microhardness (323.8 HV) compared with the conventional adhesive system (293.06 HV) ( p < 0.05), indicating superior enamel protection under all tested conditions. Conclusions: Under cariogenic and erosive conditions, flash-free brackets demonstrated higher enamel cross-sectional microhardness and distinct adhesive remnant patterns. These findings suggest that flash-free polymeric adhesive systems may offer enhanced enamel protection during orthodontic treatment, particularly in patients exposed to cariogenic or gastric acid challenges.