Abstract
The aim of this study was to evaluate the effect of silanes, thermal cycling and acid etching on the shear bond strength (SBS) of metallic brackets to feldspathic ceramic. Feldspathic ceramic cylinders (Groups 1, 2, 5 and 6) were etched for 60 s with 10% hydrofluoric acid and Groups 3, 4, 7 and 8, without acid etching. Two layers of silane Clearfil Ceramic Primer (CCP, Groups 1 to 4) and two layers of RelyX Ceramic Primer (RCP, groups 5 to 8) were applied and dried for 60 s. Brackets were bonded to the cylinders with Transbond XT and light-activated for 40 s with Bluephase G2. All specimens were stored in deionized water at 37 °C for 24 h, and the specimens of groups 1, 3, 5 and 7 were submitted to 7,000 thermal cycles (5 °C/55 °C). After storage, the SBS test was performed at a crosshead speed of 1 mm/min. Data were subjected to three-way ANOVA and Tukey's post hoc test (α=0.05). The adhesive remnant index (ARI) was evaluated at 8x magnification. The SBS of CCP was significantly greater than of RCP (p<0.05), with or without thermal cycling. Thermal cycling significantly reduced the SBS (p<0.05). The groups submitted to acid etching showed significantly higher SBS than those without acid etching (p<0.05). In conclusion, thermal cycling reduced SBS for all groups. The best ceramic surface treatment for bracket bonding was achieved by acid etching and CCP silane. The ARI results showed predominance of score 0 for all groups.
Highlights
In the last years, the number of young and old patients with ceramic restorations looking for orthodontic treatment has been increasing
The current study showed that the acid etching influenced significantly the shear bond strength (SBS), regardless of silane or thermal cycling
The ceramic surface etching by hydrofluoric acid was shown to be more effective in relation to other treatments
Summary
The number of young and old patients with ceramic restorations looking for orthodontic treatment has been increasing. In addition to dental enamel, ceramic restorations may serve as substrates for bonding of orthodontic brackets in clinical conditions. The hydrofluoric acid (HF) has been used in orthodontics for etching ceramic surfaces where the orthodontic bracket is bonded, for 60 s [1]. The HF acid promotes dissolution of the glass ceramic providing a rough surface, increased contact surface area to the ceramic, producing a stronger bond between dental ceramics and composite resin [4,5]. The CCP is a singlecomponent adhesive primer used to enhance the bond strength between resin-based materials and some types of restorative ceramics and composites. The CCP contains the MDP phosphate monomer, which bonds very strongly to metal oxides, and MPS silane coupling agent that promotes strong adhesion to esthetic restoration materials [9,10], without association with HF acid
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