Orthodontic retention is critical for maintaining post-treatment stability [1]. Among removable retention appliances, thermoplastic retainers are the most commonly used due to their aesthetic appeal and patient comfort [2]. However, conventional retainer fabrication workflow relies on physical impressions and stone models and has significant limitations such as the patient discomfort during impression-taking, time-consuming laboratory workflows leading to prolonged patient chairside visit, and risks of irreversible stone model breakage which necessitates revisit upon retainer loss or damage [[3], [4], [5]].

To address these limitations, Marsh K et al. proposed the virtual bracket removal (VBR) technique based on computer-aided design and manufacturing (CAD/CAM) process to prefabricate thermoplastic retainers [[5], [6], [7]]. This technique begins with an intraoral scan prior to clinical bracket removal, followed by virtual removal of brackets and reconstruction of buccal surfaces in the CAD systems [6]. The post-processed dentitions can then be three-dimensionally (3D) printed into resin models for further production of thermoplastic retainers, termed VBR retainers.

Although the VBR technique has been validated for surface reconstruction accuracy [7], with recommendations for optimal software settings [8] and proper ranges of relative bracket base areas [9], its clinical retention effectiveness remains uncertain. Several practical issues remain unresolved in chairside and laboratory workflows. For instance, residual adhesives around the brackets would obscure margins during virtual removal and complicate the determination of reconstruction boundaries. Moreover, cumulative errors from intraoral scanning, 3D printing, and thermoforming, such as potential digital model distortion, resin model deformation, and thermoplastic film shrinkage or over-thinning, may compromise the fit and integrity of thermoplastic retainers. These issues raise concerns about whether VBR retainers can reliably prevent post-treatment relapse, manifested as surface deviations, arch form changes, or unintended tooth movements [10,11].

Accordingly, this study aimed to propose criteria for VBR retainer fabrication and application, integrating optimized chairside and laboratory workflows, and to systematically evaluate — to our knowledge, for the first time in vivo — the retention effectiveness of the VBR retainers using a multi-dimensional framework. This framework includes surface deviations, arch form parameter changes, and 3D tooth movements. The hypothesis was that VBR retainers would demonstrate comparable retention effectiveness to the conventional ones, with all measurements clinically acceptable.