Changes in primary outcomes
CPD
REGRESSION, GROUP B, LITTLE
Retention, post-retention and post-treatment changes are summarized with means and 95 per cent confidence intervals in Retention (T2−T1), post-retention (T3−T2) and post-treatment (T3−T1) changes. Results on intention-to-treat basis represented by means and 95 per cent confidence intervals (CI). Tests were conducted with Kruskal–Wallis test Boxplots showing the changes in Little’s irregularity index (mm) during the 2-year retention period (T2–T1), followed by 1 year without retention (T3–T2) and the whole post-treatment period (T3–T1). Group A: bonded retainer 13–23 (blue), Group B: bonded retainer 12–22 (light blue), Group C: vacuum-formed retainer (orange).Changes in LII during the 2-year retention period (T2–T1) were of non-significant magnitude (The changes during the 1-year post-retention period (T3–T2) were 1.1 mm in group A, 0.5 mm in group B, and 0.4 mm in group C. According to the Kruskal–Wallis test results, there was a statistically significant difference between the three groups (The maximum CPD (Max CPD) mean showed no statistically significant differences. At T3, Max CPD was 1.0 mm in group A, 0.9 mm in group B, and 1.0 mm in group C.Linear multiple regression analysis was used to test possible predictors. However, no good prediction model could be found using the maximum pre-treatment CPD, the maximum derotation during treatment, and the maximum CPD at debonding, age and gender.