Torsional Bond Strengths of Metal Brackets Using a Glass Ionomer Cement, Light-Activated Resin, and Chemically Cured Composite Resin

Abstract

Glass ionomer cements (GIC) and visible light-activated composite (VLC) adhesives offer several advantages over conventional autopolymerizing (CA) adhesives for orthodontic bonding. GIC adhere chemically to enamel thus eliminating the need for acid etching. Long-term fluoride release into the oral environment is another attractive property of the GIC in preventing enamel decalcification. VLC adhesives extend working time and result in more accurate bracket placement. The purpose of this study was to compare the torsional bond strengths of a GIC (Ketac-fil™) and a VLC (Sequence™) with a CA resin (System 1+™). Stainless steel brackets were bonded to 90 bovine teeth with one of the three adhesives according to the manufacturers' instructions. Following bonding, all specimens were stored in deionized water at 37° and then subjected to thermocycling (30 seconds in 5°C and 45°C water baths for a total of 2500 cycles).Two weeks following bonding, the samples were subjected to torsion using a MTS Bionix testing machine. GIC had a significantly (p=0.0001) lower torsional bond strength (195.3 N-mm) than VLC (349.3 N-mm) and CA resin (537.7 N-mm). The VLC had significantly (p=0.0001) lower torsional bond strength than CA resin. Although glass ionomer cements and visible light-activated composite adhesives offer advantages, these results suggest that the bond strengths are inferior to that of the conventional autopolymerizing adhesives. Discriminate use of these adhesives would be advised.