Cifter M, et al. - The effects of vacuum-formed retainers (VFRs) on periodontal tissues and the retention efficiency of VFRs were evaluated in this study. The use of VFRs resulted in a slight periodontal attachment loss with regard to periodontal health. It appeared to be clinically insignificant, without gingival inflammation or recession. In orthodontic retention, VFRs were found to be effective in terms of stability.