The maintenance of a proper occlusion after orthodontic treament is a great challenge in clinical practice. As stated by Oppenheim, “Retention is the most difficult problem in Orthodontia; in fact, it is the problem” (1). Although relapses can be manifested by several occlusal traits, the alignment of mandibular anterior teeth is usually the main concern cited in the literature. To avoid this problem, fixed retainers made by flexible spiral wire have been shown to be effective (2).

The retainers must be installed passively in order to avoid uncontrolled movements. However, some complications may occur over time after treatment. The two main problems of posttreatment changes are torque difference between 2 adjacent mandibular incisors and increased buccal inclination of one or more teeth. In this post, we will illustrate one case from each type of these problems.


Case 1: Torque difference between 2 adjacent mandibular incisors

This female patient, visit our clinic with the chief complaint of a loose retainer. She also noted a change in position in the right lateral incisor. Surprisingly, her orthodontist and general dentist did not notice these problems, so she looked for a different opinion. Clinically, we could observe a significant buccal inclination of the lateral incisor. The root was almost visible from the lingual side. A cone-beam computed tomography of the region showed that the root was almost completely out of the cortical bone on its lingual side, including the apex. However, the tooth’s vitality was preserved, which means that the nerve and the vascular bundle had followed the apex. In this case, the patient also had some functional problems, such as the absence of appropriate anterior and lateral guides. The lack of a proper occlusion in the anterior area was due to a Bolton discrepancy, with excessive lower anterior tooth material. Therefore, this case was treated with conventional mechanics and individual and gradual torque control in order to reposition the lateral incisor root, at the same time that the anterior functional guides were reestablished after stripping of the lower incisors and anterior torque control.

Photos and cone-beam computed tomography images before retreatment  (A.) and at the end of retreatment (B). Look at the bone reconstruction around root surface and apex.


Case 2: Increased buccal inclination of one or more teeth

This male patient, came to our office complaining about a gradual but significant change in the position of his lower dentition. In fact, the lower anterior teeth on the left side were severely inclined to the buccal side, while the teeth on the right side were inclined to the lingual side. The patient reported difficulty in chewing, especially on the left side. After retreatment with conventional continuous archwire with emphasis on individual torque control of the left canine, adequate tooth positions and canine guidances were reestablished.

Photos before retreatment (up) and at the end of retreatment (down). Look at the oppostite inclinations when the right and left canines were compared before retreatment. After retreatment, these teeth were in correct positions.

Discussion and Clinical Tips

The two cases illustrated represent the most common complications of lingual retainers. In case 1, the cause was probably an unwanted activation of the wire due to functional overloading, such as biting on hard food. In the case presented, a standard leveling mechanics was used because the patient had other needs, such as the reestablishment of anterior and lateral guides, especially on the right side, in which the canines did not have a good intercuspation. As demonstrated on the CBCT images, the lateral incisor root was correctly repositioned to its alveolar envelope. If only one tooth should be moved, a custom-made appliance should be used, so it would be possible to distinguish the forces delivered to the active unit and the reactive unit. Some examples of these force driven appliances can be found on the article of Laursen et al. 2016 (3). On the second case presented, the problem was more severe than the first one, because all anterior teeth were malpositioned. Although an unwanted mechanical deformation due to overloading could have caused the problem, we cannot exclude that the operator might have induced elastic deflection of the wire during the bonding technique.


For the confecction of the retainers, we suggest the use of an .0215″ five-stranded spiral wire for the majority of cases. In patients requiring perfect control of the mandibular incisors torque, a rectangular .016″ X .022″ stainless steel bonded retainer is advisable. Moreover, vacuum formed retainers could also be prescribed in addition to bonded retention, since even small tooth displacements would be reflected in an improper fit and would be perceived by the patient. To conclude, it is important to emphasize that specialists must be involved through education in the interception of retainer complications. In adittion, patients and general dentists must be informed and instructed how to detect these complications, preferably at an early stage.



  1. Oppenheim, A.: The crisis in orthodontia, Part I: 2. Tissue changes during retention: Skogsborg’s septotomy, Int. J. Orthod. Dent. Child. 20:639-644, 1934
  2. Renkema, A.M.; Renkema, A.; Bronkhorst, E.; and Katsaros, C.: Long-term effectiveness of canine-to-canine bonded flexible spiral wire lingual retainers, Am. J. Orthod. 139:614-621, 2011.
  3. Laursen MG, Rylev M, Melsen B. Treatment of Complications after Unintentional Tooth Displacement by Active Bonded Retainers. J Clin Orthod. 50:290-7, 2016.