Fixed retainers are effective in maintaining the alignment of the anterior teeth more than 90% of the time, but they can produce inadvertent tooth movement that that in the most severe instances requires orthodontic retreatment managed with a periodontist. This type of unexpected and unwanted tooth movement is different from relapse into crowding when a fixed retainer is lost. These problems arise when a retainer breaks but remains bonded to some or all of the teeth, or when an intact retainer is distorted by function or was not passive when bonded. In both instances, torque of the affected teeth is the predominant outcome. Highly flexible twist wires bonded to all of the teeth appear to be the most likely to produce inadvertent tooth movement, but this also can occur with stiffer wires bonded only to the canines. Numerous examples of inadvertent tooth movement with fixed lingual retainers will be shown, along with a discussion of the most likely causes, suggestions for prevention, and supervision of patients during retention.
Distinguish the different types of inadvertant tooth movement that can be produced by the various fixed retainer designs and wire types.
Propose the most likely causes of inadvertant tooth movement with fixed ligual retainers.
Discuss the best methods for prevention of fixed retainer problems and supervision of patients during retention.