Bond strength and durability of glass ionomer cements used as bonding agents in the placement of orthodontic brackets.

One potential risk of orthodontic treatment is the development of surface decalcification in association with use of brackets and bands. A bonding agent that could render tooth structure more resistant to the caries process clearly would reduce the negative iatrogenic outcomes of orthodontic therapy and thereby benefit the patient. Glass ionomer cement (GIC) bonds chemically to both enamel and dentin. In addition its high fluoride content makes enamel more resistant to caries. The purpose of this study was to evaluate the bond strength and durability of GIC when used as a bonding agent in the placement of orthodontic brackets. The materials tested were three GICs (Ketac-Fil, Ketac-Cem, and Chelon) and a standard bonding agent currently in widespread use (Rely-A-Bond). Brackets were attached to the facial surface of 96 premolar specimens and half the specimens for each bonding agent were thermocycled. Bond shear strength was determined with an Instron testing device by applying a load to the occlusal margin of each bracket to the point of failure. A two-way ANOVA indicated a significant bonding agent by thermocycling interaction (F = 4.78, p less than 0.01). Thermocycling decreased bond strength significantly for all materials, but had the greatest impact on Rely-A-Bond. However, Rely-A-Bond provided the strongest bond with and without thermocycling. Although bond strength for the standard orthodontic bonding agent deteriorates significantly under thermal stress, these results suggest that it is still greater than the bond strength provided by GIC materials.