Short-term morphological changes of vacuum-formed retainers with different gingival margin designs: a randomized clinical trial

Objectives: To investigate the morphological and dimensional changes in vacuum-formed retainers (VFRs) after intraoral aging of 3 months and 6 months and to compare changes between VFRs with conventional and modified gingival margin design. Materials and Methods: Forty-one patients were randomly assigned to two groups: conventional design (CD) and modified design (MD). Preuse and postuse digital models of each VFR were imported to Geomagic Control software to assess the morphological and dimensional changes. Results: In vivo, VFRs underwent significant changes over time. After 3 months, slight expan-sion of the VFRs was detected, while after 6 months, slight contraction was observed, despite not all parameters resulting in statistically significant differences. No statistically significant differences were found between the CD and MD groups. Conclusions: Intraoral aging affects the dimensional stability of VFRs. The gingival margin design did not impact the morphological and dimensional stability of VFRs over the observed period. (Angle Orthod. 2026;96:326–334.).