Unexpected complications of bonded mandibular lingual retainers

Introduction: The flexible spiral wire (FSW) retainer is the most frequently used type of fixed retainer bonded on all 6 anterior teeth. Our aim in this article was to demonstrate unexpected posttreatment changes in the labiolingual position of the mandibular anterior teeth associated with the use of FSW retainers. Methods: During a 3-year period, patients attending the postgraduate orthodontic clinic of the Department of Orthodontics and Oral Biology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands, for regular, posttreatment follow-up appointments were screened for unexpected posttreatment changes in the mandibular anterior region. Results: Twenty-one patients with FSW retainers bonded on all 6 mandibular anterior teeth presented unexpected posttreatment changes in that region. Almost half of these patients were assessed as needing retreatment. Two patients are presented to illustrate the 2 distinct patterns of posttreatment changes: torque difference between 2 adjacent mandibular incisors and increased buccal inclination and movement of one mandibular canine. Conclusions: FSW retainers bonded on the 6 mandibular anterior teeth might cause unexpected movements of anterior teeth to such an extent that retreatment is necessary. Clinicians should consider this possibility when planning the retention strategy.