Gu, J et coll. Evaluation of Invisalign treatment effectiveness and efficiency compared with conventional fixed appliances using the Peer Assessment Rating index. Am J Orthod Dentofacial Orthop February 2017;151:259-66 Buschang, P et al. Comparative time efficiency of aligner therapy and conventional edgewise braces. Angle Orthodontist, Vol 84, No 3, 2014.