In this retrospective study we aimed to evaluate the quality of treatment outcomes using the American Board of Orthodontics (ABO) scoring system with a completely customized lingual appliance used in combination with a Herbst appliance for Class II correction.

Patient selection criteria for this study were Class II division 1, II/2 or subdivision treated with a WIN® lingual appliance combined with an L-pin Herbst device. Thirty-two consecutively debonded cases were included in this retrospective case series. Pre- and post- treatment dental casts, dental set-ups, panoramic X-rays, cephalometric analysis, photographs and clinical files were available for data collection. The primary outcome was the ABO score based on the Discrepancy Index (ABO DI) including: overjet, overbite, anterior open bite, lateral open bite, crowding, occlusion (Angle class), lingual posterior crossbite, buccal posterior crossbite, ANB, IMPA and SN-GoGN angles and the Cast-Radiograph Evaluation (ABO CR-Eval) comprising of alignment/rotations, marginal ridges, buccolingual inclination, overjet, occlusal contacts, occlusal relationship (Angle class), interproximal contacts and root angulation. In addition, overjet, overbite and Class II correction were also evaluated on pre- and post-treatment models. The secondary outcome was bracket failure and complications related to the Herbst device.

The study cohort included 18 female and 12 male patients with a mean age of 15.8 (range 12, 6- 18, 5). Twenty patients were Class II division 1 and ten were Class II division 2. The mean pre-treatment value of ABO DI was 20.8 (range 10–39); more than two-thirds of the sample were rated as being either of moderate difficulty (ABO DI: 16–24) or severe (ABO DI: over 25). The average post-treatment ABO Cast-Radiograph Evaluation score was 15.0 (SD=4.4), which is considered a passing score. Twenty-six patients had a score equal or lower than 20 (undisputed passing score). The Class II discrepancy was effectively corrected from a score of 16.83 penalty points (SD: 3.65) pre-treatment to a score of 1.57 (SD: 1.70) post-treatment. No association was found between initial and final Class II occlusal relationships (P=0.42), indicating that regardless of the initial discrepancy, no difference in the success of Class II correction was observed. The mean bracket failure rate was 3.8 per patient. Herbst related complications were few: 1.6 per patient, with the majority of complications being of little consequence and with 43% of the patients having no breakages.

The completely customized lingual appliance assessed in this study combined with an L-pin Herbst led to effective Class II correction regardless of the initial severity of the sagittal discrepancy. The average ABO CR-Eval score for this sample was well below the undisputed passing score indicating a high quality of treatment outcomes.