Predictability of incisal labiolingual inclination, overjet, and overbite changes, and the prevalence of open gingival embrasures in patients with mandibular incisor extraction treated with Invisalign: A retrospective cohort study.

Abstract

Introduction: This retrospective study aimed to assess differences between the planned Invisalign (Align Technology, San Jose, Calif) ClinCheck tooth movements and the achieved outcomes for patients with single mandibular incisor extraction with respect to overjet, overbite, and labiolingual inclination for the initial series of aligners and to assess the prevalence of open gingival embrasures (OGEs) in the former extraction sites.

Methods: The records of 83 patients who received Invisalign treatment with extraction of a single mandibular incisor were evaluated. The predicted and achieved overjet and overbite measurements were compared using the Invisalign ClinCheck software. The prevalence of an OGE was assessed visually using posttreatment digital models. The labiolingual inclination of the mandibular incisors was measured through superimposition of the pretreatment, predicted posttreatment, and achieved posttreatment digital models using Geomagic Control X (version 2018 1.0; 3D Systems, Rock Hill, SC) metrology software.

Results: Differences between predicted and achieved labiolingual inclination changes of the mandibular incisors were minor in the lingual direction (90.4%); however, planned labial movements were significantly underexpressed (59.0%). A comparison of the predicted and achieved overjet values revealed a clinical expression of 49.6% and 76.0% when the overjet was planned to decrease and increase, respectively. With respect to the predicted and achieved overbite changes, no significant difference was found when the overbite was predicted to increase. In contrast, when the overbite was predicted to decrease, only 50.5% of this planned overbite reduction was clinically achieved. Most patients (95.2%) displayed an OGE in the former extraction space.

Conclusions: Extraction of a single mandibular incisor in conjunction with Invisalign treatment resulted in an underexpression of the predicted proclination of the mandibular incisors, overjet changes, and overbite reduction. The development of an OGE was highly probable after the initial CAT aligner series.