Polymerization of orthodontic adhesives using modern high-intensity visible curing lights

This study was undertaken to assess the efficacy of 3 visible curing lights: a conventional halogen light and 2 high-intensity halogen lights in the polymerization of a polymer-based and resin-modified glass ionomer orthodontic cement. Degree of polymerization was measured by Fourier transform infrared spectroscopy and the development of mechanical properties by Barcol hardness. The results were analyzed with either 2- or 3-way analysis of variance. It was shown that, for the polymer-based material, there was a significant increase in degree of cure and hardness with time of application of the light for each light source. For chemical conversion, there was no significant difference between the lights. However, there was a difference in hardness: the higher intensity lights produced greater hardness in shorter time. Thus, there was poor correlation between degree of polymerization and hardness. For the resin-modified glass ionomer, similar trends were found, but there was a difference in hardness between the top and the bottom of the specimens. It was concluded that the higher intensity lights could aid in the more rapid development of mechanical properties of the tested adhesives.