Accuracy of Invisalign? on Upper Incisors: A Systematic Review

The current systematic review appraises the effectiveness of the types of tooth movements performed with Invisalign (R) clear aligner on the maxillary incisors. An electronic literature search of published trials was performed through PubMed, LILACS, Scopus, Cochrane Library, and Web of Science databases, and selected journals, from 2009 to 2020. Out of 291 references, five relevant publications were identified for analysis: four studies were performed retrospectively and one prospectively, all non-randomized. Despite the limited set of selected articles, the sample size is significant, with 148 subjects included in the reviewed studies involving the orthodontic treatment of upper incisors. We concluded that movements with the Invisalign (R) clear aligner on the upper incisors present distinct accuracy, possibly related with movement complexity; intrusion of the incisors has low accuracy (in some cases, 0% of accuracy was reported when the tooth extruded), while incisor extrusion exhibit some of the highest accuracy values reported in the included studies (45%-142%, when the achieved movement was greater than the predicted). Besides, axial (i.e., torque and tip) and horizontal (i.e., translation and rotation) movements are usually effective, with accuracy values between 39%-156% and 42%-79%, respectively. Overall, we determined that the efficiency of aligner to reach the desired movements in the upper incisors was low, as often refinements were required in the included studies. The use of aligner features must be more often considered to improve movement accuracy.