Objective: The objectives of this study were to evaluate the degree of conversion (DC) for Transbond XT curing light of intensity 1,600 mW/cm2 by using variable curing durations and to determine the effect of the tested curing durations adopted in the current experiment on shear bond strength of Transbond XT resin cement.
Materials and methods: A total of 85 orthodontic ceramic brackets (Victory series; 3M Unitek) were utilized in the current experiment. The bonding system used in the current study was Transbond XT Primer followed by Transbond PLUS Color Change Adhesive (3M Unitek) that cured for 3, 6, and 9 seconds. The method was done by polymerization of the adhesive under a ceramic bracket for 40 ceramic brackets. The other 45 brackets were divided into three groups (n=15) according to the curing time duration (3, 6, and 9 seconds). The bonded specimens in each group were debonded using a shear load applied at the bracket bases by the blades of an Instron universal testing machine (ElectroPlus E1000; Instron) and directed in an occlusogingival direction with a crosshead speed of 0.5 mm/min utilizing 50 kg load cell.
Results: One-way ANOVA revealed that 6 and 9 seconds curing by the Ortholux light cure scored significantly higher values when compared to the 3 seconds curing.
Conclusion: Curing the Transbond XT for 6 and 9 seconds recorded a significant improvement of bond strength and DC.
Keywords: FTIR/ATR; bond strength; degree of conversion; orthodontics.