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.