[Orthodontic treatment of overbite with an appliance for raising the anterior vertical dimension. Part 2]

If incisor overbite in the matter of orthodontic treatment entails difficulties with the appliances due to excessive overbite of the incisors, involving an anterior bite raiser to enable the unlocking of the occlusion and the bonding of the brackets on the anterior mandibular teeth poses the problem of the vertical behavior of the masticatory apparatus during treatment. A profile teleradiograph was therefore taken at the beginning of treatment and again once the occlusion had been lifted due to the presence of the bite raiser and within a period of three months. The sample was separated in two groups according to the value of FMA; a first group was composed of 44 cases exhibiting an FMA angle inferior to 25 degrees therefore similar to the cases analyzed by Dake and Sinclair in 1989, called "reference group" and a group of cases exhibiting an FMA angle superior to 25 degrees. The aim of this study is indeed to confront, as regards vertical behavior, the therapeutic approach of the authors with the one studied by Dake and Sinclair dealing with cases treated with Ricketts and Tweed technique (Schudy modified). Following Dake and Sinclair's approach, the authors managed to find out in cases with FMA inferior to 25 degrees that the vertical alterations in the study group were not different from those in the reference group. This means that in spite of the presence of an anterior bite raiser the mandibular plane angle had only increased by 1.8 degree, compared to 1.8 degree for the Ricketts group and 1.1 degree for the Tweed/Schudy group. As for the study sample with an FMA angle superior to 25 degrees, the vertical alterations in the study group show an increase of the angle of the mandibular plane equal to 1.2 degree, here again the increase is similar to the one observed in the reference group. It can thus be concluded that the use of an anterior bite raiser in conjunction with the Tip-Edge technique is not only advisable but strongly recommended both to unlock the occlusion but also to enable bracket bonding at the very beginning of treatment.