Retention constitutes a fundamental phase of orthodontic treatment, of which the patient must be made aware from the outset. Retention, which can be fixed or movable, has the task of maintaining over time and stabilising the results obtained during treatment. This study assessed the efficacy of using removable restraints versus fixed solutions for maintaining long-term outcomes. A comprehensive search across major databases—Pubmed, Web of Science, Scopus—used ‘relapse’ and ‘orthodontic’ as keywords to gather articles on relapse discussions. The primary focus was relapsed cases in post-fixed orthodontic therapy. Both fixed and removable retainer systems prove effective in preserving orthodontic achievements. While fixed devices require regular wire integrity checks, mobile devices require patient compliance, proper usage, and a recommended wear time. Studies indicate that fixed retainers are generally successful, with relapse rates varying based on the retainer type. Full-time use of removable devices surpasses night-only wear. Vacuum-formed and Hawley retainers offer similar effectiveness. Fixed retainers excel in long-term alignment stability, whereas removable ones have higher failure rates yet remain beneficial.