Influence of Light Source, Thermocycling and Silane on the Shear Bond Strength of Metallic Brackets to Ceramic

Abstract

The objective of this study was to evaluate the effects of different light sources, thermocycling and silane on the bond strength of metallic brackets to ceramic. Cylinders of feldspathic ceramic were etched with 10% hydrofluoric acid for 60 s. Half of the cylinders (Groups 1 to 4) received two layers of silane. Metallic brackets were bonded to the cylinders using Transbond XT and divided into 8 groups (n=20), according to light source (Radii Plus LED - 40 s; Groups 1, 2, 5 and 6 and XL 2500 halogen light - 40 s; Groups 3, 4, 7 and 8) and experimental conditions with (Groups 2, 4, 6 and 8) without thermocycling (Groups 1, 3, 5 and 7). Shear bond testing was carried out after 24 h of deionized water storage (Groups 1, 3, 5 and 7) and thermocycling (Groups 2, 4, 6 and 8; 7,000 cycles - 5°/55 °C). Date were submitted to three-way ANOVA and Tukey's post hoc test (α=0.05). The Adhesive Remnamt Index (ARI) was evaluated at 8× magnification. The application of silane was effective in increasing the shear bond strength of the brackets to ceramic (p<0.05). Significant difference (p<0.05) on the bond strength was observed between light sources with or without thermocycling. The ARI showed a predominance of scores 0 for all groups, with an increase in scores 1, 2 and 3 for the silane groups. In conclusion, silane improved significantly the shear bond strength of the brackets to ceramic. The thermocycling and light sources influence on the bond strength.

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 .…”

“…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] .…”

“…After bonded to ceramic surface, the orthodontic brackets are exposed to the oral environment and failure may occur at interface among orthodontic brackets, bonding material and dental ceramic due to thermal changes and heavy forces produced by the archwire in the oral cavity 4 . The literature is still not conclusive about thermal cycling protocols.…”

“…The literature is still not conclusive about thermal cycling protocols. Temperature between 500 and 7,000 cycles have been used to verify if temperature changes promoted stresses at the interface causing deteriorations in simulated oral conditions, before the mechanical test 4,16 .…”

“…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.…”