This randomized clinical trial aims to compare the clinical performance of two types of three-dimensionally printed fixed retainers (Cobalt-Chromium and Titanium Grade 5) with the conventional multistranded stainless steel fixed retainer following orthodontic treatment. Thirty-six participants will be randomly allocated into three parallel groups with a 1:1:1 allocation ratio. The primary outcome is post-treatment stability assessed by Little's Irregularity Index and lower arch dimensions. Secondary outcomes include bond failure rate and periodontal parameters over a 12-month follow-up period.