Polymerization of orthodontic resin cement with light-emitting diode curing units

Commercially available light-emitting diode (LED) light-curing units recently have been introduced to the dental products market. No published studies have evaluated the adequacy of cure of commercially available LEDs. The purpose of this study was to compare the shear bond strength of orthodontic brackets bonded to teeth with conventional halogen-based light-curing units and commercially available LED curing units. Two LED light-curing units (LumaCure and VersaLux) and 2 halogen-based light-curing units (Optilux 501 and ProLite) were tested. One hundred standard metal orthodontic brackets were bonded to extracted human third molars with a light-cured adhesive system. The specimens were divided into 4 groups of 25 teeth each. In each group, the brackets were cured for 40 seconds with a different light-curing unit. The specimens were stored in water at 37 degrees C for 24 hours and then tested in shear with an Instron universal testing machine at a crosshead speed of 1 mm/min until the brackets debonded. One-way analysis of variance detected no differences in bond strength between the 4 groups (P =.78). Chi-square analysis detected no difference in the adhesive remnant index scores of the 4 groups (P =.89). Under the conditions of this study, the LED light-curing units bonded brackets to etched tooth enamel as well as the halogen-based light-curing units. Additional clinical studies are necessary before routine use of commercial LED light-curing units can be recommended.