Effect of Acid Etching, Silane and Thermal Cycling on the Bond Strength of Metallic Brackets to Ceramic

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.

Influence of different treatments of the ceramic surface and thermal cycling on the bond strength of brackets to ceramic

“…The results indicated that the second hypothesis was not accepted. The results of the present work are in agreement with those of previous studies, which found significant difference in bond strength values when the specimens were submitted to thermal cycling 2,4 . On the other hand, other studies are not in agreement showing no significant difference for bond strength of specimens submitted to thermal cycling 11,16 .…”

“…When HF acid was used on the ceramic surface before other treatments, the results were more effective, except for group 3, when the Ambar Universal Adhesive was used. Some studies have shown that different treatments, such as phosphoric acid, aluminum oxide or without etching presented lower bond strength in relation to surface HF acid etching 2,11,13 . However, previous studies have shown that HF acid may promoted severe problems for dental personnel and patients because this solution is extremely toxic, reactive and corrosive 10,15 , and the severity depends on the acid concentration, exposure time and penetration into the exposed Figure 1.…”

“…Ceramics have gained great notoriety due to markable improvement of the ability to mimic dental tissues, mechanical strength and this material is the most commonly used for indirect restorative in Dentistry 1 . However, bonding orthodontic brackets to ceramic surface needs special care because they can exhibit a higher degree of failure in relation to enamel bond 2 . On the other hand, some studies showed no negative effects on ceramic surface, since the most failures was adhesive between the bonding material and the ceramic surface [3][4][5] .…”

“…The thermal cycling test has been recommended and used to verify if temperature changes may influence the reduction of bond strength values between the ceramic surface, bonding materials and brackets 2 . Previous studies showed that the reduction of the bond strength could be due to continuous action of the water on the ceramic-bonding materials-brackets interface with hydrolytic degradation of the components 24 .…”

“…ARI values showed a predominance of debonding failures with score 0 (no bonding resin on the ceramic surface). Clinically, this fact may be advantageous because there is less bonding material to remove from the ceramic surface after bracket debonding [2][3][4] . In summary, the results of this study showed that acid etching before CCP silane influenced significantly the SBS.…”