Class II malocclusion with excessive overjet is one of the most common malocclusions among children and adolescents. The overall goal of the project is to analyze orthodontic treatment of Class II malocclusion with excessive overjet when the treatment is started in different ages and treated with removable and/or fixed appliance.

Treatment initiated before the age of eleven is performed with a removable functional appliance, Headgear Activator (HGA). Treatment starting in early adolescence is performed with fixed orthodontic appliance (FA).

The hypotheses are:

• Treatment with HGA at the age of nine or eleven is effective. No spontaneous correction of the malocclusion is expected in the untreated control group.
• Patient experience, treatment effect and cost-effectiveness are equivalent whether the treatment with HGA is initiated at the age of nine or eleven.
• Treatment results, patient experience and treatment- and cost-effectiveness are equivalent whether treatment is initiated early with HGA or initiated in early adolescence with FA.
• The treatment of Class II malocclusion with excessive overjet renders long-term treatment stability and patient satisfaction.

Participants (children, 9 years of age) are recruited at the orthodontic specialist clinic in Norrköping, Sweden.

After informed consent participants are randomized into Group 1, 2 or 3. After randomization and registration, treatment with HGA is initiated for Group 1.

Group 2 and 3 serves as untreated control group. Two years after registration, Group 2 starts treatment with HGA at the age of eleven.

Group 3 serves as untreated control group to treatment with HGA.

Four years after registration, Group 3 starts treatment with FA (3M Victory brackets, .022 slot size, McLaughlin-Bennet-Trevesi prescription).

The patients in group 1 and 2 in need of a second phase of orthodontic treatment are treated with FA (3M Victory brackets, .022 slot size, McLaughlin-Bennet-Trevesi prescription) in early adolescence.

The following registrations are made:

Study models, photographs (extraoral, intraoral), Lateral head radiographs (T0, T2, T5, if required T1, T3), Child perceptions questionnaire.

T0: After randomization; before treatment start (Group 1), registration/control (Group 2,3).

T1: Two years after T0; after finished treatment for (Group 1), before treatment start (Group 2), control/registration for (Group 3).

T2: Two years after T1; follow up (Group 1), after finished treatment (Group 2), before treatment start (Group 3).

T3: Approx two years after T2 for patients not undergoing treatment with FA. For patients treated with FA, when treatment is finished.

T4: Approx two years after T3- follow up.

T5: Approx 8-10 years after T0 (Long term follow-up)

Inclusion Criteria:

• Eight to ten years of age at the start of the trial
• mixed dentition;
• Excessive overjet (≥ 6 mm) and first maxillary permanent molars in Class II malocclusion
• No sucking habits or ceased sucking habits should have been evident at least one year before the trial was started.

Exclusion Criteria:

• Craniofacial syndromes
• Previous orthodontic treatment
• Severe crowding of teeth, i.e. making the extraction of teeth necessary