Study stopped due to increased harm and slow progress in the intervention group.

Twin-Block treatment and Dynamax treatment for Class II division 1 malocclusion do not have different effects with regards to treatment duration, the quality of dento-occlusal outcome, skeletal and soft tissue profile, patient discomfort and gingival health.

The Dynamax appliance is a relatively new appliance for the treatment of Class II malocclusion and was introduced in 2003. The appliance has the theoretical advantages of incremental mandibular advancement without the need for bite registration, and the ability for the operator to simultaneously provide the functional and fixed appliance phases of treatment. Furthermore, the Dynamax appliance is designed to limit lower both lower incisor proclination and upper incisor retroclination without an increase in lower facial height. There has been limited research into this appliance and only one trial has been carried out. In this study the effects of the Dynamax were compared with the Twin-block, unfortunately, the trial was not carried out to contemporary standards and suffered from severe shortcomings. For example, the non compliance rate was not accounted for in the sample size calculation, the randomisation sequence was not clear, the investigators did not carry out an intention-to-treat analysis, the statistical analysis was simplistic and the study was carried out in a single dental school setting. This raises the question about the efficiency of the Dynamax appliance and whether or not they are effective in a 'real' world setting.

The aim of this study is to compare the effectiveness of the Dynamax appliance and the Twin-block appliance for the treatment of Class II Division 1 malocclusion.

Inclusion Criteria:

• Patients with a Class II malocclusion as defined by British Standards Institute classification.
• Overjet greater than 6mm
• Aged 10-14 years
• Clinical examination indicates a functional appliance is not contraindicated

Exclusion Criteria:

• Orthognathic treatment is required or there is a strong indication it will be required in the future
• Possession of a craniofacial anomaly
• Previous orthodontic treatment and/or premolar extraction
• Hypodontia of more than one teeth in any quadrant excluding third molars
• Inadequate oral hygiene