Treatment effects of the Sander II appliance in class II therapy : A cephalometric, retrospective case-control study

To investigate the mechanism of class II correction using the Sander II (S-II) appliance.

In a retrospective case-control study, 102 class II patients (mean 10.46 years) treated with the S‑II appliance were compared to 64 untreated class II patients. Skeletal, dental, and occlusal parameters were evaluated using lateral cephalometric radiographs before (T0) and after treatment (T1). For the quantification of sagittal changes, the Pancherz sagittal occlusion analysis was applied. Statistical analysis was performed using SPSS (IBM, Armonk, NY, USA; significance level p < 0.05) and G*power (Heinrich-Heine University, Düsseldorf, Germany).

The annual treatment effects of the S‑II appliance (mean diff. of ∆ = T1 - T0 between both groups per year) were: a) sagittal correction of the skeletal class II relationship by -1.07 mm/year [(∆pog/OL_p) - (∆ss/OL_p)], achieved by anterior displacement of the mandible by 0.41 mm/year (∆pog/OL_p) and maxillary growth restriction by -0.66 mm/year (∆ss/OL_p). b) Retroinclination of the upper incisors by -0.75°/year (∆U1-NSL), -0.68°/year (∆U1-NA) and -0.68 mm/year [(∆is/OL_p) - (∆ss/OL_p)]. c) Maintenance of lower incisor inclination [(∆ii/OL_p) - ( ∆pog/OL_p): -0.18 mm/year]. d) Overjet correction by 1.58 mm/year (100%) as a result of 1.07 mm/year skeletal (68%) and 0.50 mm/year dental effects (32%). e) Molar correction of 0.90 mm/year (100%) mainly due to skeletal effects during mixed dentition.

In this study, the S‑II appliance effectively corrected overjet and class II molar relation by mainly skeletal effects (ventral displacement of the mandible, maxillary growth inhibition) and minimal dental effects (reclination of upper incisors). Functional treatment with the S‑II appliance may facilitate later orthodontic therapy as class II can be corrected without lower incisor proclination.