Clinical expression of programmed maxillary buccal expansion and buccolingual crown inclination with Invisalign EX30 and SmartTrack aligners and the effect of 1-week vs. 2-week aligner change regimes: A retrospective cohort study.

Objective : This retrospective cohort study aimed to assess and compare the accuracy of 3 different Invisalign® treatment regimens in terms of variations of aligner change frequency and type of aligner material in achieving maxillary dental buccal expansion. Methods : Altogether, 120 adult patients whose treatment involved maxillary dental expansion with Invisalign® were included. The patients were divided into 3 groups, with each group comprising 40 patients as follows: SmartTrack® 1-week changes (ST1), SmartTrack® 2-week changes (ST2), and EX30® 2-week changes (EX2). The groups were assessed by comparing actual changes achieved with those prescribed by ClinCheck®. The rates of clinically significant inaccuracies (CSI) observed for buccal expansion (≥ 0.5 mm) and buccolingual inclination (≥ 2°) during expansion were then determined. Results : In terms of expansion, the ST1 group demonstrated the highest CSI rate at all tooth levels, whereas the ST2 group had the lowest rate of CSI and the lowest mean inaccuracy for each tooth level. In terms of buccolingual inclination, the ST1 group had the highest CSI rate across all tooth levels, whereas the EX2 group had the lowest CSI rate at all tooth levels except for the canine level where the ST2 group had the lowest CSI rate. A tendency toward overexpression of buccal crown inclination, and underexpression of buccal expansion was observed at all tooth levels. Conclusions : Two-week aligner change regimens offer improved accuracy compared with 1-week aligner changes. SmartTrack® 2-week changes were the most accurate for buccal expansion, whereas EX30® 2-week changes were the most accurate for buccolingual inclination.