The Use of an Adhesion Promoter in the Bonding of Orthodontic Brackets

Abstract

This study was designed to determine whether the use of a proprietary adhesion promoter would increase the bond strength of an orthodontic BIS-GMA direct bonding adhesive system to tooth enamel. Another purpose was to determine whether use of the promoter would allow a decrease in the traditional etch time of 60 seconds, while maintaining adequate bond strength. Such a reduction would result in less damage to the tooth. A total of 150 bicuspid teeth were mounted in a testing jig, and orthodontic brackets were bonded according to their testing group. The teeth were divided into two groups, one group bonded with the adhesion promoter and one without. Each group was subdivided into three subgroups of 25 samples each, with etching times of 60, 30, and 15 seconds. After bonding, the samples were stored in water at 37°C 24 hours before being thermocycled 2500 cycles. Thermocycling range was 15-55°C. The samples were then returned to the 37°C storage until testing. One week after bonding the samples were tested in tension using an Instron testing machine. The location and force required to produce bond failure were recorded. Only two samples of the 136 samples tested had bond failure other than at the resin-bracket interface. These two fractures were cohesive in nature. All groups were compared using a two-way analysis of variance. There was no significant difference in bond strength between 15, 30 and 60-second etch times. This study indicates that etch times can be reduced from the traditional 60-second etch time and still maintain adequate bond strength. Many resin manufacturers continue to recommend 60-second etch times in their directions for use. The findings of this study indicate that this practice is no longer necessary. The adhesion promoter has been shown by other means to increase bond strength. However, this study failed to prove that the adhesion promoter increases the bonding strength when tested with orthodontic brackets, since all but two samples failed at the resin-bracket interface.