Post-treatment Stability in Orthodontic Retention with Twistflex Retainers-Do Patients Benefit from Additional Removable Retainers?

OBJECTIVES

To evaluate post-treatment movements of lower anterior teeth during orthodontic retention in patients with fixed twistflex retainers versus those with combined fixed and removable retainers.

MATERIALS AND METHODS

This study was based on a retrospective data analysis of 57 adult patients during orthodontic retention. They were assigned to two groups: In group 1 (n = 30) the lower jaw was provided with twistflex retainers only and in group 2 (n = 27) with a twistflex combined with a removable retainer for night-time use. Orthodontic study models of the lower jaw were digitalized and superimposed. Tooth movements were analyzed at the retainer bonding (t0) and follow-up appointment ≥ six months later (t1). Rotational tooth movements (°) were measured around the x-axis (mesial/distal direction), the y-axis (buccal/lingual direction) and the z-axis (longitudinal direction, tooth axis). Translational tooth movements (mm) were registered along the x-axis (buccal/lingual direction), the y-axis (mesial/distal direction) and the z-axis (apical/coronal direction).

RESULTS

Canine and incisor position changes during orthodontic retention were more pronounced in group 1 compared to group 2 except for canine rotations around the z-axis. In both groups in most of the cases stable lower incisor alignment could be found, but the proportion was significant higher in group 2 (group 1: 56.7% vs. group 2: 81.5%). Severe misalignment was present in 13.3% of the participants of group 1 and only in 7.4% of group 2. The extent of canine tipping and movements along the x- and y-axis in severe misalignment cases was significantly lower in group 2 compared to 1.

CONCLUSIONS

Lower incisor alignment was more stable in patients with combined fixed and removable retainers compared to fixed retainers only.

CLINICAL RELEVANCE

Based on the present findings, the routinely application of supplementary removable retainers can be recommended to enhance anterior tooth alignment in patients with fixed twistflex retainers.