Although no orthodontic retention method is without limitations, current evidence suggests that fixed retention is the most effective approach for maintaining treatment outcomes. Consequently, fixed orthodontic retainers are now used worldwide and are considered the standard of care. This lecture will address three key aspects of fixed retention: (1) clinical effectiveness, namely the ability of different types of bonded retainers to maintain anterior tooth alignment and prevent posttreatment changes, (2) incidence of retainer failures, an important factor influencing not only the long-term retentive function but also patient satisfaction and compliance, and (3) potential adverse effects of long-term fixed retention on periodontal tissues, an increasingly relevant topic in view of the growing trend toward lifelong retention. Particular focus will be given to unwanted tooth movements associated with flexible spiral-wire retainers. These movements typically manifest as progressive changes in tooth inclination and torque. Although orthodontic retreatment in these cases is generally feasible, severe root displacement beyond the alveolar bone envelop may result in irreversible complications, including bone dehiscence, gingival recession, and loss of tooth vitality, particularly when the changes are not detected at an early stage. The lecture will conclude with a discussion of how careful assessment of individual topographic and anatomical characteristics influences bone and soft tissue remodeling and regeneration following orthodontic repositioning of teeth into the alveolar bone.