Cephalometric and occlusal changes following maxillary expansion and protraction

Abstract

A prospective clinical trial was conducted to determine the cephalometric and occlusal changes following maxillary expansion and protraction. Twenty Southern Chinese patients (eight males and 12 females with a mean age of 8.4 +/- 1.8 years) with skeletal Class III malocclusions were treated consecutively with maxillary expansion and a protraction facemask. Growth adaptation of these patients was followed for 2 years after removal of the appliances and compared with a control group of subjects with no treatment. Lateral cephalometric radiographs were used to quantify the skeletal and dental changes before treatment (T1), immediately after treatment (T2) and 2 years after removal of appliances (T3). With 8 months of treatment (T2-T1), overjet was overcorrected from a -2.0 to 3.5 mm. The maxilla moved forwards by an average of 2.1 mm and the molar relationship was improved to a Class I dental arch relationship. The palatal and occlusal planes were tilted upward 1.0 and 2.0 degrees, respectively. Two years following removal of the appliances (T3-T2), a positive overjet was maintained in 18 out of 20 patients. The maxilla continued to move forwards in the treated subjects similar to the controls. The mandible outgrew the maxilia. In most instances, dental compensation with proclination of the maxillary incisors was observed. The palatal plane returned to pre-treatment value. The occlusal plane continued to tilt upward due to eruption of the molars and proclination of the incisors. Analysis of dental casts showed a significant increase in maxillary intercanine (2.2 mm) and intermolar widths (2.3 mm) with 7 days of rapid palatal expansion followed by maxillary protraction. The percentage relapse in maxillary intermolar widths was 30-45 per cent after 1 year, in most cases with minimal retention. In the mandibular arch, the concurrent increase in intermolar width (2.3 mm) was primarily due to buccal uprighting of the posterior molars when the maxilla was protracted into a Class I skeletal relationship and was stable after 1 year. The results of this study indicate stability of orthopaedic treatment of Class III malocclusions directed at the maxilla. Despite some relapse, a net improvement in maxillomandibular relationship and a positive overjet was maintained in 18 out of 20 patients at the end of the follow-up period.

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

“…A direção do vetor de força para frente e para baixo apresentou inclinação mínima de 20 graus 16,20,39,41,43,44,45 e máxima de 45 graus 13,30 em relação ao Plano Oclusal. A inclinação média determinada neste trabalho foi de 27,5º em relação ao Plano Oclusal, semelhante com a recomendação da maioria dos estudos 15,19,22,23,25,27,28,29,[31][32][33][34][35] .…”

“…A força de 380g relatada por alguns autores 25,27,28,29 foi bem próxima da força de 395g usada por Saadia e Torres 34 e de 396g utilizada por Baccetti et al 4 e Franchi et al 11 Já Sung e Baik 38 variaram a força entre 300g e 400g (média 350g), como nos estudos que usaram a força de 400g 3,9,21,35 . 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 .…”

“…O vetor de força de 30º em relação ao Plano Oclusal foi o utilizado pelo maior número de estudos 15,19,22,23,25,27,28,29,[31][32][33][34][35] .…”

“…A instrução de uso diário de 10/12h (média 11h) e 12h foi preconizada por outros autores 6,15,21,23,27,28,29,35,38 .…”

Orthodontics. Part 7: Fact and fantasy in orthodontics

“…Several workers have shown that a small but significant anterior movement of the maxillae using protraction headgear during the mixed dentition is possible which has remained stable some 2 years after treatment. 29 In summary, orthodontic appliances that deliver an orthopaedic effect may induce a temporary improvement in the skeletal relationship. There is no evidence at present to show that orthodontic treatment can effectively restrain or enhance cranio-facial growth that is otherwise inherited by the individual.…”