The document summarizes research on the impact of removable and fixed orthodontic retainers. Researchers reviewed 24 studies on factors like cost-effectiveness, failure rates, and periodontal health. For mandibular stainless steel fixed retainers fused from canine to canine, the mean failure risk was 0.29, while those fused to canines only showed a 0.25 risk. Another study found that while both removable and fixed lower lingual retainers can cause relapse in lower front tooth alignment after treatment, the extent of relapse was not significantly different between the two types. More high-quality research is still needed to fully understand the advantages of different orthodontic retainers.