Vertical changes following alignment of palatally displaced maxillary lateral incisors with the Invisalign® appliance: A retrospective study

Introduction

The aim of this study was to examine the efficacy of planned vertical positioning of palatally displaced maxillary lateral incisors (PDMLI) in patients treated with an initial series of Invisalign® (Align Technology, Santa Clara, Calif) aligners.

Methods

The pre-treatment digital models, and models representing the planned and achieved treatment outcomes of adult patients, prescribed an initial series of Invisalign® aligners were analysed, using Geomagic Control X® (version 2017.0.3; 3D Systems, Rock Hill, SC). Clinical significance was determined according to the American Board of Orthodontics Objective Grading System.

Results

A total of 63 patients, comprising 90 PDMLIs, met the inclusion criteria. The mean (SD) difference between the planned and achieved vertical position of PDMLIs following wear of the initial series of aligners was 0.40 (0.5) mm. A clinically significant discrepancy between planned and achieved was observed in 39 (43.3%) PDMLIs. Extrusion was less accurately achieved than intrusion, particularly when accompanied by planned intrusion of the adjacent central incisor. Linear regression analysis showed that age, sex, presence of an attachment, and amount of planned root torque did not significantly influence the accuracy of vertical positioning (P > 0.05), whereas planned antero-posterior movement of the PDMLI crown did (P < 0.01).

Conclusions

The achieved vertical position of PDMLIs following an initial series of Invisalign® treatment differed significantly from the planned position with 43.3% showing a clinically significant difference. The amount of antero-posterior movement was significantly related to the efficacy in achieving the planned vertical movement.