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Published on: May 30, 2019
Clinical effectiveness of the prefabricated thermoplastic retainers using the virtual bracket removal technique: An
Jiarun Fu1, Yipeng Wang1, Yikai He1
1State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases & Department of Orthodontics, West China Hospital of Stomatology, Sichuan University Chengdu 610041, China.
Objectives:
To introduce an experience- and research-based approach for fabricating thermoplastic retainers through the virtual bracket removal (VBR) technique (VBR retainers) and evaluate their retention effectiveness compared to conventional retainers using a novel multi-dimensional measurement framework.
Methods:
Thirty-eight patients completing fixed orthodontic treatment were randomized to receive VBR retainers (the VBR group) or retainers constructed on stone models (the conventional group), respectively. Retention effectiveness over six months was evaluated via (1) surface deviations represented by root mean square (RMS); (2) arch form changes in width/length; (3) tooth movements in six dimensions. Outcomes were compared between groups and against clinical acceptable limits (CALs; 0.3 mm for RMS, 0.5 mm for arch form changes, and 0.5 mm/2° for linear/angular tooth movements). Statistical analyses included t-tests for normally distributed data and Wilcoxon signed-rank tests or Mann-Whitney U tests for non-normally distributed data, with statistical significance set at α = 0.05.
Results:
No significant inter-group differences were observed in RMS values or arch form changes, with all values significantly below CALs (P < 0.05). While most tooth movements showed no inter-group differences, the VBR group exhibited statistically significantly greater torque variations in upper canines (0.71 ± 0.91° vs. 0.40 ± 0.77°, P < 0.05), mesiodistal/occlusogingival translations in lower incisors (0.10 ± 0.19 mm vs. 0.06 ± 0.09 mm/0.26 ± 0.38 mm vs. 0.12 ± 0.25 mm, P < 0.05), and angulation/mesiodistal translations in lower posterior teeth (0.69 ± 0.95° vs. 0.49 ± 0.70°/0.11 ± 0.29 mm vs. 0.09 ± 0.16 mm, P < 0.05). Despite these statistical differences, all tooth movements remained significantly lower than CALs (P < 0.05). The VBR approach significantly reduced patient visit duration (7.91 ± 1.19 min vs. 64.98 ± 4.85 min, P < 0.05).
Conclusions:
VBR retainers demonstrate comparable retention effectiveness to conventionally fabricated retainers over six months and significantly reduce chairside time.
Clinical Significance:
The proposed criteria for VBR retainer fabrication offer practical suggestions for clinical and laboratory workflows. The findings from a multi-dimensional measurement framework support VBR retainers as an effective, efficient, and time-saving approach for orthodontic retention in routine clinical practice.
