Objective: The aim of this study was to test the null hypothesis that there is no difference at the midpalatal suture opening after rapid maxillary expansion (RME) using Expander with Differential Opening (EDO), Hyrax-type and Haas-type expanders. Methods: Occlusal radiographs of 52 patients (19 males and 33 females; average age= 9.46?1.20 years) treated with RME were divided into three groups, according to the expander used: EDO (n=17), Hyrax-type (n=21) and Haas-type (n=14). The evaluated variables were: A) Distance between the maxillary central incisors at the incisal edge; B) Distance between the alveolar ridges at the midpalatal suture; C) Suture opening at 10-mm distance from the crest to posterior, at the midpalatal suture; D) Suture opening at 20-mm distance from the crest to posterior, at the midpalatal suture; and E) Suture opening at 30-mm distance from the crest to posterior, at the midpalatal suture. To assess the normality of variables, the Shapiro-Wilk test was performed. For intergroup comparison, ANOVA with a significance level of 5% was used. Results: At the region A, Hyrax-type (4.66 mm) and EDO (4.87 mm) groups presented larger openings than the Haas-type group (3.43 mm). In regions B and C, EDO showed a statistically significant greater opening than the Haas-type group. In region D, a smaller opening of the midpalatal suture was observed in the Haas-type group, compared to the Hyrax-type and EDO groups. Conclusions: EDO and Hyrax-type produced greater immediate skeletal effects, compared with Haas-type, but these differences were about 1 mm and might not be clinically significant.

Objective Compare changes in arch form after RME achieved by Expander with Differential Opening (EDO), Hyrax‐type and Haas‐type expanders. Materials and Methods Dental models were obtained from 61 patients aged 7‐11 years before expansion (T1) and 6 months after the active phase when the appliances were removed (T2). The groups were formed according to the expander used: EDO (n = 18, mean age: 9.46 ± 0.82 years), Hyrax‐type (n = 22, mean age: 9.62 ± 1.57 years) and Haas‐type (n = 21, mean age: 9.29 ± 1.05 years). The expander`s activation protocol consisted of 7 mm, except for EDO`s anterior screw, which was 9 mm. The measurements of upper and lower intercanine distance, inter‐first permanent molar, arch perimeter and length, maxillary canine and first‐permanent molar inclination, and palatal depth were performed using the OrthoAnalyzer 3D software. Intergroup comparisons of T1 and between changes (T2‐T1) were performed using ANOVA followed by Tukey. Results In the upper intercanine distance EDO provided a greater increase than Haas‐type. In the distance between upper fist permanent molars EDO showed higher values than Haas‐type and Hyrax‐type. In the lower intercanine distance and maxillary arch length, Haas‐type promoted higher increase than EDO. Conclusions The EDO promoted greater transverse changes in anterior region than Haas‐type and greater transverse changes in posterior region of the maxilla than both conventional expanders. The appliance used for RME influences dental arch changes after treatment; therefore, it is recommended to individualize the choice of expander depending on the clinical necessity of each case.

Rapid maxillary expansion (RME) is the protocol of choice for early treatment of transverse malocclusions and it is achieved with fixed expanders that produce heavy forces to achieve midpalatal suture opening. One third of patients with maxillary constriction have a greater transversal deficiency at the intercanine width than at the intermolar. The aim of this article is to present a protocol for early treatment of posterior crossbite with the use of the expander with differential opening (EDO) for RME. It is a new appliance to perform RME and its main advantage would be to allow the expansion individualization. EDO was proposed aiming to promote greater expansion on the anterior rather than on the posterior region. A 9 year-old female sought treatment. The interceptive treatment plan was based on using EDO for RME. The post-expansion orthopedic response showed an opening of 7.5 mm between the maxillary central incisors, at the level of the incisal edge. It was observed an opening of 4.8mm in the midpalatal suture. The opening at a distance of 10 mm and 20 mm from the crest to posterior at the midpalatal suture were 3.9mm and 2.8mm. The upper intercanine distance showed an increase of 9.31 mm. The upper intermolar distance had increased 8.04 mm. The upper arch perimeter showed a difference from 74.02 mm to 80.11 mm . And the upper arch length, from 29.83 mm to 31.56 mm. The posterior crossbite was 2 mm overcorrected. Early diagnosis and treatment of posterior crossbite has a very favorable prognosis. Keywords: Palatal Expansion Technique. Interceptive Orthodontics. Malocclusion. Resumo A expansão rápida da maxila (ERM) é a técnica de escolha para o tratamento precoce das más oclusões transversais e é ativada com expansores fixos que produzem forças pesadas para possibilitar a abertura da sutura palatina mediana. Um terço dos pacientes com atresia maxilar apresenta uma maior deficiência transversal na região intercaninos do que na região intermolares. O objetivo desse artigo é apresentar um protocolo de tratamento precoce para a mordida cruzada posterior utilizando o expansor maxilar Diferencial (EMD) para realizar a ERM. EMD é um novo dispositivo que pode ser empregado para realização da ERM e sua principal vantagem seria permitir a individualização da expansão. EMD foi proposto para proporcionar maior expansão na região anterior do que na região posterior da maxila. Uma menina de 9 anos de idade buscou tratamento. O plano de tratamento interceptativo proposto foi ERM utilizando o dispositivo EMD. A resposta ortopédica pós-expansão mostrou uma abertura de 7,5 mm entre os incisivos centrais superiores, ao nível da borda incisal. Foi observada uma abertura de 4,8 mm na sutura palatina mediana. A abertura a uma distância de 10 mm e 20 mm da crista para posterior na sutura palatina mediana foi de 3,9 mm e 2,8 mm. A distância intercaninos superior apresentou aumento de 9,31 mm. A distância intermolares superiores aumentou 8,04 mm. O perímetro do arco superior apresentou diferença de 74,02 mm para 80,11 mm. E o comprimento do arco superior, de 29,83 mm para 31,56 mm. A mordida cruzada posterior foi sobrecorrigida em 2 mm. O diagnóstico precoce e o tratamento da mordida cruzada posterior tem um prognóstico muito favorável. Palavras-chave: Técnica de Expansão Palatina. Ortodontia Interceptora. Má Oclusão.