Effect of light-curing units in shear bond strength of metallic brackets: an in vitro study

ABSTRACT

OBJECTIVES: To determine the influence of the light curing units on the shear bond strength of orthodontic brackets. MATERIAL AND METHODS: Seventy-two premolars were divided into six groups (n=12) Group I brackets bonded with Transbond and polymerization with halogen light; Group II Transbond and LED; Group III Fuji Ortho and halogen light; Group IV Fuji Ortho and LED; Group V Fuji Ortho, without acid and halogen light; Group VI Fuji Ortho, without acid and LED. The groups were tested to shear strength in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by ANOVA and Tukey's test. RESULTS: The composite resin presented higher shear bond strength than the resin-modified glass ionomer cement (p<0.05). The halogen light and LED sources produced similar shear bond strength (p>0.05). CONCLUSION: The shear bond strength was influenced by the material but not by the light-curing unit. The use of LED reduced the experimental time by approximately 60 percent, with the same curing efficiency.