1. Compared to  Invisalign aligners previously made from single-layer (EX30) material.  aligners made from SmartTrack material provide better fit, better comfort, and are easier to insert and remove compared to Invisalign aligners made from single-layer  (EX30) material. **In a study Miller et al, with adults measuring pain in the first week of treatment. Kevin Miller et al.  “A comparison of treatment impacts between Invisalign aligner and fixed appliance therapy during the first week of treatment.”  American Journal of Orthodontics and Dentofacial Orthopedics.  Volume 131, Issue 3, pp. 302. e1-302.e9, March 2007.”