Efficacy of the Sander bite-jumping appliance in growing patients with mandibular retrusion: a randomized controlled trial.

OBJECTIVES: The efficacy of functional appliances remains highly debated. This randomized controlled trial investigated the skeletal and dentoalveolar effects determined by the Sander bite-jumping appliance (BJA). The null hypothesis to be tested was that the appliance would not induce supplementary mandibular growth compared to untreated controls. SETTING AND SAMPLE POPULATION: This study was carried out at the Section of Orthodontics, University of Naples Federico II, Italy. Forty-six patients receiving a clinical diagnosis of skeletal and dental class II due to mandibular retrusion were either allocated to a treatment (23 patients;15 boys, 8 girls; mean age ± SD: 10.9 ± 1.3 years) or to an untreated control group (23 patients;11 boys, 12 girls; mean age ± SD: 10.5 ± 1.2 years), by using a balanced block randomization. METHODS: Lateral cephalograms were taken before and after treatment and used for comparisons. Measurements were analyzed by descriptive statistics, univariate and multivariate statistical tests. RESULTS: Treated individuals had a significant increase in mandibular length (6.4 ± 2.3 vs. 3.5 ± 2.5 mm; p < 0.001), overjet reduction (-5.0 ± 2.9 vs. 0.3 ± 1.2 mm; p < 0.001) and molar relationship improvement (-5.3 ± 2.4 vs. 0.1 ± 1.1 mm; p < 0.001) compared to controls. The use of the appliance did not significantly affect jaw divergence. Proclination of lower incisors was slightly greater (3.0°, p = 0.023) in treated patients than in controls. The increase in mandibular length was not significantly influenced by cervical stage (p = 0.40). CONCLUSION: The BJA can effectively correct class II malocclusions by a combination of dentoalveolar and skeletal effects. The long-term stability of the correction needs to be evaluated.