A randomized controlled trial comparing retainers in bimaxillary proclination cases.

INTRODUCTION: There is currently no recommendation for retaining corrected bimaxillary proclination cases. This study aimed to compare retention protocols for maintaining stability of such cases. MATERIALS AND METHODS: In this single-center, single-blinded parallel control trial, 27 participants were assigned to three groups using block randomization with a 1:1:1 allocation ratio; fixed bonded retention (FBR), vacuum-formed retention (VFR), and dual retention (DR) comprising both types. Data were collected every 3-months from debond (T0) for 12 months (T4). The primary outcomes measured changes in soft and dental tissue parameters on traced lateral cephalograms. Secondary outcomes included intra-arch changes and the oral health impact profile (OHIP-14[M]). This trial was registered with Clinicaltrial.gov (NCT04578704). RESULTS: At T4, the upper lip, lower lip, and upper incisors moved anteriorly (mean difference (MD) of 1.63 mm (SD 3.7), 0.48 mm (SD 1.1), and 0.54 mm (SD 0.97), respectively). The upper and lower incisors were proclined by 0.96 degrees (SD 2.1) and 1.11 degrees (SD 2.63), respectively. The interincisal angle was reduced by 0.56 degrees (SD 1.23). Only the upper incisor inclination (UII) change showed significant differences between groups (eta(2) = 0.296; p = 0.015). Post-hoc comparisons revealed that the FBR and VFR groups exhibited greater proclination than the DR group (UII, MD = 3.33 degrees and 3.22 degrees, respectively). No differences were observed in OHIP-14[M] scores between the groups. CONCLUSION: All three retention protocols showed statistically small but clinically insignificant changes. CLINICAL RELEVANCE: Dual retention offers better control in preventing upper incisor proclination in bimaxillary proclination cases. TRIAL REGISTRATION: This trial was registered with Clinicaltrial.gov (NCT04578704).