Treatment of large overjet in Angle Class II: division 1 malocclusion with Andresen activators versus prefabricated functional appliances—a multicenter, randomized, controlled trial

Objectives: The purpose of this study was to compare the clinical effectiveness in reducing large overjet between a prefabricated functional appliance (PFA) and a slightly modified Andresen activator (AA). Setting and sample population: Public Dental Service, Gothenburg, Sweden. Participants, study design, and methods: A multicentre, prospective randomized clinical trial was conducted with patients from 12 general dental practices. One hundred and five patients with an Angle Class II, division 1 malocclusion and an overjet of ≥6mm were eligible for the study. Eight patients were excluded due to various reasons and the sample consisted thus of 97 subjects (44 girls, 53 boys) with a mean age of 10.3 years. The study was designed as intention to treat and the patients were randomly allocated by lottery to treatment with either a PFA or an AA. The PFA and AA group consisted of 57 subjects (28 girls, 29 boys) and 40 subjects (16 girls, 24 boys), respectively. Overjet, overbite, lip seal, and sagittal molar relationship were recorded before, at the end of treatment and 1-year post-treatment. Blinding was not performed. The endpoint of treatment was set to overjet ≤3mm and after this a 6 months retention period followed. Results: No significant difference was found in overjet, overbite, sagittal relation, and lip seal between the two groups for the total observation period. The treatment of 40 (70 per cent) patients with PFA and 21 (53 per cent) with AA were considered unsuccessful mainly due to poor compliance. Limitations: No cephalometric records were taken as only patient-centred clinical outcome were used as an indicator for treatment success. The criteria of reduction of overjet to as low as 3mm could have affected the success rate. Conclusion: No difference in effectiveness could be shown between PFAs and AAs in correcting overjet, overbite, sagittal molar relation, and lip seal. The success rate in treatment with both appliances is, however, low. Registration: This trial was registered in “FoU i Sverige” ( ), registration number: 97131. Protocol: The protocol was not published before trial commencement.