Quality of occlusal outcome following space closure in cases of lower second premolar aplasia using lingual orthodontic molar mesialization without maxillary counterbalancing extraction

Abstract

Background: Controlled space closure in cases of isolated lower second premolar aplasia (ILSPA) without maxillary counterbalancing extraction is challenging. Anterior anchorage loss may occur during space closure resulting in compromised occlusal results in terms of an absence of proper canine guidance during laterotrusive mandible movements. In order to evaluate the effectiveness of Herbst telescope anchorage in combination with double-cable, pull mechanics and a completely customized lingual appliance for orthodontic space management in cases of ILSPA, we tested the null hypothesis that there is a significant deterioration in the sagittal canine relationship towards an Angle-Class-II occlusion expressed as a loss of anterior anchorage following space closure with molar mesialization.

Methods: Twenty-five consecutively de-bonded subjects (female / male 17 / 8; aged at T0 (start of MB Tx) 12.3 to 20.6 years; mean age 15.0 / SD 1.7 years) were included in this retrospective analysis using the inclusion criteria of least of one lower second premolar aplasia; completed treatment with a totally customized lingual appliance (CCLA) in combination with Herbst telescopes. Exclusion criteria were the absence of counterbalancing maxillary extractions, as well as additional tooth aplasia other than lower second premolars. A total of 33 single, lower premolar aplasia space closures (right / left sided 17 / 16) were assessed using plaster casts and intra-oral photographs scaled to the plaster casts, at bonding (T0), Herbst insertion (T1), following gap closure (T2) and de-bonding (T3). Parallelism of roots was controlled by panoramic x-rays at T3.

Results: The mean aplasia space at T0 was 7.5 mm (SD 2.6). Complete space closure was achieved in all 33 situations. The null hypothesis was rejected. There was a significant improvement in the initial canine relationships (mean 3.5 mm distal occlusion at T0) to a mean 0.1 mm at T3. When evaluated against the individual treatment plan, the following amounts of planned improvements were achieved: space closure 100%, canine relationship 97.5%, overjet 93.9%, overbite 96.4%, parallel roots in space closure site 93.9%.

Conclusion: Herbst telescope anchorage in combination with double-cable pull mechanics and a CCLA for orthodontic space closure can deliver predictable, high-quality treatment results.

Conflict of interest statement

Ethics approval and consent to participate

This retrospective study received full approval from the ethics commission of Hannover Medical School (MHH; # 7727_BO_K_2018) prior to the commencement of data collection.

Consent for publication

All patients signed a written consent form.

Competing interests

DW is the inventor of the completely customized lingual appliance WIN and owner of the DW LingualSystems, Bad Essen, Germany. All other authors don’t have any competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Presentation of a case: Initial situation prior to bonding of the fixed lingual appliance at T0 (a, b, c); Figs. A and B were taken following pre-treatment with removable functional appliances, hence the mandible is seen in a protruded sagittal position. Following leveling and aligning and initiation of anchorage reinforcement by adding Herbst telescopes at T2 (d, e, f), and at T3 following de-bonding of the fixed lingual appliance. Posterior maxillary 6–7 retainers aid in maintaining the vertical relation until lower third molars are brought into occlusal contact, while mandibular 4–6 retainers prevent re-opening of aplasia spaces (g, h, i). Panoramic x-rays show an adequate root parallelism after completion of aplasia space closure (j, k)

Fig. 2

Canine relationship development during treatment at the site of aplasia. The deviation from a canine-Angle Class-I is given in mm. See text for details

Fig. 3

Success rate for canine relationship correction compared to the individual treatment plan (target set-up)

Fig. 4

Overjet development (in mm) during treatment. In cases with an initial Angle-Class II-malocclusion, the sagittal incisor relation has been temporarily over-corrected into an edge-to-edge relation at T2

Fig. 5

Overbite development (in mm) during treatment

Fig. 6

Treatment duration related to start of CCLA treatment: The learning curve as a trend line is indicated in red