Effect of photopolymerization time on shear bond strength and microleakage of orthodontic adhesives: An in vitro study

Aim: The aim of this investigation was to assess the shear bond strength and microleakage of three different adhesives at 10, 15 and 20s of photopolymerization time. Materials and Methods: Depending on the adhesive employed, 45 teeth were split into 3 groups. (Enlight, Transbond XT and Orthofix) and 3 subgroups based on polymerization time of 10, 15, 20s. After bonding, the specimens were placed in 0.5% solution of methylene blue dye for 6 days and then the Universal Testing Machine was used to assess the shear bond strength. The debonded specimens were then examined for microleakage using 3D Optical profiler. One-way ANOVA test and repeated-measures ANOVA were used in inferential statistics to determine differences between and within the groups. Results: The mean shear bond strength was found highest for Enlight cured for 20s (22.45 +/- 4.22MPa) and lowest for Orthofix cured for 10s (4.58 +/- 1.60MPa). In all three groups, there was a discernible rise in shear bond strength as the curing time increased. The mean microleakage was found highest in Orthofix cured for 10s (0.04 +/- 0.007mm) and lowest in Transbond XT cured for 15s (0.01 +/- 0.002mm). Mean microleakage decreased with an increase in curing time which was statistically significant in all groups. Conclusions: With an increase in polymerization time, the shear bond strength increases and microleakage decreases. Enlight light cure composite showed maximum shear bond strength and Orthofix showed the least shear bond strength at all three polymerization times. Microleakage at the gingival area was more when compared to the occlusal area in all the groups.