[An in-vitro study of the bonding and fracture pattern of light-hardening, fluoride-releasing bonding materials in metal brackets].

Three hundred bovine incisors, which were divided into 6 groups of 50 teeth each, were used in this study. Two types of metal brackets, 1 with a conventional foil mesh base and the other with a photo-etched Micro-Loc base, were adhered to the teeth with 3 different bonding agents, namely, Sequence, a fluoride-releasing, light-activated composite, Photac-Fil, a light-hardened glass ionomer cement, and, in the control group, Concise, a 2-component composite which hardens chemically. A universal testing machine was employed to test tensile bonding strength and the site of failure was visually determined and analyzed. The study showed that Sequence can be considered as a qualitatively equal alternative to Concise. Both composites demonstrate equal tensile bonding strength. The use of Photac-Fil, the light-hardened glass ionomer bonding agent, cannot be recommended. It possesses significantly less tensile bonding strength than the other 2 bonding agents. Sequence and Concise, which showed better results with the brackets with conventional foil mesh base than with the brackets with photo-etched Micro-Loc base, had no significant differences in their failure sites. The interface of the composite with the bracket was the main failure site. Both composites demonstrated a significantly reduced rate of failure at the interface of the composite with the enamel, when they were used with the brackets with the Micro-Loc base. This differed from the failure site of Photac-Fil, when the photo-etched base was used. With Photac-Fil the main site of failure came at the interface of the enamel with this glass ionomer cement.(ABSTRACT TRUNCATED AT 250 WORDS)