Evaluation of maxillary protraction and fixed appliance therapy in Class III patients

Abstract

The aim of this study was to examine the dentofacial changes in Class III patients treated with fixed appliances subsequent to rapid maxillary expansion (RME) and facemask therapy. The material consisted of the cephalograms and hand-wrist films of 14 (9 girls, 5 boys) skeletal Class III and 15 (10 girls, 5 boys) untreated subjects obtained at the beginning of treatment/observation T1, immediately after orthopaedic therapy T2, and at the end of the observation period T3. The mean pre-treatment/control ages were approximately 11.5 years and the observation period was 3 years T2-T1: 1 year, T3-T2: 2 years). The cephalometric films were analysed according to the structural superimposition method of Björk. All tracings were double-digitized and the measurements were calculated by a computer program. Intragroup changes and intergroup differences were statistically analysed. Forward movement of the maxilla (P < 0.01), backward movement and rotation of the mandible, an increase in the ANB angle (P < 0.001), lower face height and overjet (P < 0.001), a decrease of overbite, and an improvement in the sagittal lip relationship (P < 0.01) presented significant intergroup differences between T2 and T1. During the second phase of treatment T3-T2, although not statistically significant, forward movement of the maxilla was less than in the control subjects. Overall changes during the observation period T3-T1 revealed that correction was mainly due to favourable changes in the mandibular and dentoalveolar components of the discrepancy, while these in maxillary position were not different from the control group. The soft tissue profile improved significantly (P < 0.001) in the treatment group. Comparison with the Class I controls at the end of the observation period confirmed that some Class III characteristics still remained in the treated patients.

O tratamento da Classe III: revisão sistemática - Parte I. Magnitude, direção e duração das forças na protração maxilar

“…O tratamento da Classe III com protração maxilar tem sido bastante relatado na literatura 1,2,12,21,24,30,32,40,41,43 , porém a maioria dos trabalhos não identifica claramente a magnitude, a direção da força e o tempo de utilização do aparelho para obter-se a correção adequada desse problema. Nessa revisão sistemática, uma cuidadosa pesquisa da literatura foi realizada para encontrar estudos primários nos quais esses fatores fossem abordados.…”

“…MacDonald, Kapust e Turley 24 utilizaram uma força entre 200g e 450g (média 325g) e diversos autores afirmaram utilizar uma força entre 300g e 500g (média 400g) 5,6,10,41,43 , próxima da empregada nos estudos que usaram 500g de força 2,19,23,32,33 .…”

“…Outros trabalhos 2,3,5,9,10,34,[43][44][45][46] relataram o uso de, no mínimo, 14 horas por dia, semelhante à média de 14 horas relatada em outros estudos 8,13,30 . Para Pangrazio-Kulbersh, Berger, Kersten 32 e Pangrazio-Kulbersh et al 33 , as horas mínimas de uso variaram entre 14h e 16h (média 15h) por dia.…”

“…Todavia, a maioria dos autores são unâ-nimes em considerar a protração maxilar associada ou não à expansão palatina rápida como a melhor terapia para os pacientes em fase de crescimento 1,2,12,21,24,32,40,41,43 .…”

“…Diferentes tipos de dispositivos utilizados como ancoragem extrabucal para protração maxilar já foram descritos na literatura, como: máscara facial tipo Delaire, máscara facial tipo Petit, máscara facial de Turley e Sky Hook, entre outros 2,21 .…”