The effect of lingual orthodontic appliances in the dimensional reduction of labial gingival recession and root prominence caused by the wire syndrome in the anterior mandible: a multicenter study.

Abstract

Background: The wire syndrome (WS) or X-effect/twist-effect describes undesired long-term tooth movements following fixed retainer placement. Since it includes root torque changes that might cause gingival recession, those situations often require periodontal, orthodontic and conservative treatment. Aim of this study was to assess the effectiveness of fixed orthodontic treatment with completely customized lingual appliances (CCLA) and continuous archwires for a clinically significant reduction in the dimensions of labial gingival recessions in the anterior mandible, caused by the wire syndrome (WS), in a group of consecutive patients treated with the same approach. Moreover, the reduction in root prominence (ROP) of the affected teeth relative to the two neighboring teeth was evaluated.

Subjects and methods: This retrospective cohort study from three centers included 20 consecutively recruited patients with labial gingival recession at lower incisors and canines due to WS. A total of 25 teeth were assessed. CCLA treatment with a standardized archwire sequence (0.012'/0.014' NiTi, 0.016'x0.022' NiTi, 0.018'x0.018' Beta-TMA with optional extra-torque) was identical in all three centers. Primary endpoints of recession depth (RD), recession width (RW), and recession surface (RS) were assessed on digital models at debonding (T1) and compared to baseline (T0) both as absolute differences (T0-T1), and as ratios ((T0-T1)/T0) by one-sample t-tests with p<0.05. As a secondary endpoint, the reduction of ROP relative to the gingival surface of the alveolar yoke of the two neighboring teeth was measured in millimeters.

Results: Treatment resulted in a significant reduction in all dimensions of gingival recession. The mean reduction in RD was 1.86 mm (44.9%) and in RW 0.70 mm (35.6%). The mean RS was reduced from 10.77 mm2 to 3.93 mm2, indicating a mean RS reduction of 61.4%. All changes were statistically significant (p<0.001). The range of RS reduction was from 25.4% to 100%, while 18 out of the 25 recessions showed a reduction of more than 50%. The maximum reduction in ROP amounted to more than three millimeters.

Conclusion: The use of completely customized lingual appliances to torque roots of the lower anterior teeth, exposed by the wire syndrome, towards the middle of the alveolar process reduces the area of subsequent labial gingival recession and reduces the root prominence of the affected teeth substantially. This is considered as a critical step in optimizing the predictability of the surgical recession coverage.