Effect of Hydrofluoric Acid Concentration and Thermal Cycling on the Bond Strength of Brackets to Ceramic

Abstract

This study to evaluate the effects of different hydrofluoric acid (HF) concentrations and thermal cycling on the shear bond strength (SBS) of brackets to ceramic. Cylinders of ceramic were divided into 10 groups (n=15), according to HF concentrations: 1-1%;2-2.5%;3-5%;4-7.5%;5-10% (storage 24 h); 6-1%;7-2.5%;8-5%;9-7.5%; and, 10-10% (thermal cycling). All cylinders were etched for 60s and received one layer of silane. Metallic brackets were bonded to the cylinders using Transbond-XT, light activated for 40 s, using a LED (Radii Plus) and stored in deionized water at 37o C for 24h. The groups 6 to 10 were submitted to thermal cycling (7,000 cycles - 5o/55oC). SBS was performed in an Instron at crosshead speed of 1.0 mm/min. Data were submitted to two-way ANOVA and Tukey’s post-hoc test (α=0.05). The Adhesive Remaining Index (ARI) was evaluated at 40x magnification. The different HF acid concentrations influenced on the SBS of the brackets to ceramic (p<0.05). The thermal cycling decreased the SBS of the brackets to ceramic for all acid concentrations (p<0.05). The ARI showed a predominance of scores 0 for all groups, with an increase in scores 1, 2 and 3 for the group storage for 24 h. In conclusion, the different HF acid concentrations 5.0%, 7.5% and 10% influenced on the SBS of brackets to ceramic. The thermal cycling decreased significantly the SBS of brackets to ceramic.

Orthodontic Attachment Adhesion to Ceramic Surfaces

“…32 In a study performed in 2019, higher concentrations of hydrofluoric acid seem to increase SBS. 20 Larmour et al 33 by comparing phosphoric acid to hydrofluoric show that HF produces better results, confirmed also by other research teams. 16,[34][35][36] Contradicting this, Ajlouni and collaborators 37 find two similar bonding sequences with similar results: HF, followed by silane and composite and phosphoric acid, followed by selfetching primer-adhesive and composite.…”

“…13 Reliability of studies increases when efforts are made to achieve similarity with the oral environment, for example, through thermocycling of the tested samples, as this influences bond strength. [14][15][16][17][18][19][20][21][22] Throughout the articles included in this review, minimal bonding strengths were 6-8 MPa. 23 Many studies rely on mean shear bond strength when comparing different primers or different ceramic surface preparation techniques, as few of them obtain statistically significant results.…”