Quality of occlusal outcome in adult Class II patients treated with completely customized lingual appliances and Class II elastics compared to adult Class I patients

Abstract

Objectives: The aim of this investigation was to evaluate whether Class II malocclusion in adult patients can be successfully corrected using a completely customized lingual appliance (CCLA) in combination with Class II elastics.

Methods: In order to detect differences in the final treatment outcome, two groups were matched for age and gender. Treatment results of 40 adult orthodontic patients with a Class I malocclusion (Group 1) were compared to 40 adults with a Class II malocclusion (Group 2). All patients had completed treatment with a CCLA (WIN, DW Lingual Systems, Bad Essen, Germany) without known centric occlusion-centric relation discrepancies, issues of compliance, or overcorrection in the individual treatment plan which was defined by a target set-up. In order to compare the treatment results of the two groups, 7 measurements using the American Board of Orthodontics Model Grading System (ABO MGS) and linear measurements for anterior-posterior (AP) and vertical dimensions were assessed at the start of lingual treatment (T1), after debonding (T2B) and compared to the individual target set-up (T2A).

Results: A statistically significant AP correction was achieved in Group 2 which represented 95% of the planned amount. The planned overbite correction was fully achieved in the Class I and Class II group. In both groups, there was a statistically significant improvement in the ABO scores, with no significant difference between the two groups at T2. 100% of the patients in Group 2 and 92.5% in Group 1 would meet the ABO standards after CCLA treatment.

Limitations: The main limitation of this study is that only patients who were wearing the elastics as prescribed were retrospectively included. Therefore, the results of this study may have limited generalizability.

Conclusions: Completely customized lingual appliances in combination with Class II elastics can correct a Class II malocclusion successfully in adult patients. The final treatment outcome can be of a similar high quality in Class I and Class II patients.

Keywords: Angle Class II correction; Objective Grading System; adult orthodontics; completely customized lingual appliances; intermaxillary elastics; maxillomandibular elastics; orthodontic appliances.

Figure 1.

Canine bracket of the CCLA WIN with vertical insertion into the ribbonwise slot. The three-dimensional programming is performed with the help of the target set-up. To every individual inclination of the lingual surface, the hook can be adapted individually.

Figure 2.

One key feature of CCLAs is the computer-assisted fabrication of customized archwires. Every bracket slot is digitally identified (a) and the individual shape is calculated (b).

Figure 3.

Optional extra-torque bends of 13° or 21° can be incorporated in the anterior region (a). 2b shows a 0.016" × 0.024" stainless steel archwire with an extra-torque bend of 13° from canine to canine. The archwire orientation is ribbonwise.

Figure 4.

31-year-old male patient with Class I molar relationship, deep overbite, and severe crowding in the lower arch (a). The ABO MGS score at T1 was 64. The target set-up shows a corrected overbite with an improved interincisor angle and an ABO MGS score at T2A of 17 (b). After 25 months of fixed appliance treatment with a CCLA, the intended corrections were mostly achieved, with a final ABO MGS score of 24 (c).

Figure 5.

21-year-old female patient with Class II malocclusion of more than half a unit, deep overbite, and an initial total ABO MGS score of 68 at T1 (a). The target set-up shows a corrected molar relationship with a total ABO MGS score of 17 at T2A (b). After 24 months of fixed appliance treatment (T2B) with a CCLA and 7 months of Class II elastic wearing, the intended anterior-posterior correction of 5.0 mm was achieved (c).

Figure 6.

Situation in the patient from Fig. 5 after bonding of upper and lower completely customized lingual appliances (a). The deep overbite is raised immediately because of the contacts on the half-occlusal pads on the second molars. The mandible rotates downwards and backwards, which, as a consequence, worsens the Class II relationship and allows for a certain overcorrection. The archwire orientation ribbonwise is very helpful for levelling the lower curve of Spee. Slightly overcorrected molar relationship after dentoalveolar Class II compensation with Class II elastics for 7 months (b). Overcorrection especially is very beneficial, but not only in asymmetric distocclusions. One can notice that the actual bite correction amounted to much more than what was measured from T1 to T2B. Levelling of the mandibular curve of Spee before, and upper incisor torque control during, Class II correction are tooth movements indispensable for a successful bite correction of this kind. After the phase of levelling and aligning with 0.014" round and 0.016" × 0.022" superelastic NiTi wires, 0.016" × 0.024" stainless steel archwires are used for Class II correction with intermaxillary elastics. In the upper anterior segment (3-3), the wires have an extra-torque bend of 13°. In order to prevent space-opening mesial to the canines, the steel wire is bent vertically behind the second molar tubes (c). Also, in the lower arch 0.016" × 0.024" SS wires are inserted for anterior-posterior correction. In order to improve patient comfort, the wire is bent horizontally behind the second molars (d). The Class II elastics connect the hook of the upper canine brackets to a buccal button on the lower second molars.