Scanning electron microscopy analysis of aligner fitting on anchorage attachments.

Abstract

The aims of the study were (1)to evaluate the fitting of three different aligners (Invisalign [Align Technology, Santa Clara, CA, USA], CA Clear Aligner [Scheu-Dental, Iserlohn, Germany] and F22 [Sweden&Martina, Due Carrare, Italy]) on anchorage attachments using scanning electron microscopy (SEM), and (2)to analyze the influence of 2 different types of resin used to build attachments on aligner fitting. Using STL files of apatient, six resin casts were obtained and rectangular attachments were bonded on them. Conventional bulk-fill resin was used to build upper attachments while aflowable resin was used to build the lower ones. Passive aligners were adapted on each cast and then sectioned buccolingually. Microphotographs of the obtained sections were performed using a SEM and then micrometric measurements of aligner fitting on anchorage attachments were recorded. Analyzing the overall fitting of upper arch aligners, Invisalign provided asignificantly better fitting with respect to F22 (P = 0.009); differences were not significant when comparing Invisalign with CA Clear Aligner, and CA Clear Aligner with F22. Analyzing the overall fitting of lower arch aligners, F22 provided asignificantly better fitting with respect to CA Clear Aligner (P = 0.008) and Invisalign (P = 0.011). The analysis showed asignificantly better fitting on upper attachments, built using conventional bulk-fill resin (P = 0.034). Invisalign, CA Clear Aligner and F22 have comparable performance in terms of fitting on anchorage attachments. Conventional bulk-fill resin provides the best fitting on anchorage attachments.