Dentoskeletal Effects of the Expander With Differential Opening and the Fan-type Expander
Condition: Malocclusion; Crossbite (Posterior)
MeSH terms: Malocclusion
Study type: Interventional

Summary: 
      This study will assess the dentoskeletal effects of two types of maxillary expanders in
      orthodontic patients in the mixed dentition, from 7 to 11 years old. Half of participants
      will be treated using the expander with differential opening, while the other half will
      undergo rapid maxillary expansion using the fan-type expander. The null hypothesis is that
      there is no difference between dentoskeletal effects of the two protocols.
    

Detailed description: 
      Rapid maxillary expansion (RME) is the orthopedic procedure of choice to treat maxillary
      constriction and posterior crossbite, and the study of dental, skeletal and periodontal
      effects of this procedure has been widely discussed in the orthodontic literature. The
      conventional RME expanders promote a similar expansion in the anterior and posterior regions
      of the maxillary arch. On the other hand, the fan-type expander allows the expansion
      concentrated in the intercanine region with little effects the intermolar distance. Finally,
      the expander with differential opening has two palatal screws and the differential activation
      protocol promotes a different amount of expansion for the anterior and posterior regions of
      the maxilla. No clinical study compared dental and skeletal effects of the expander with
      differential opening with those of the fan-type expander, including a three-dimensional
      analysis using CBCT exams and digital dental models. So, the aim of the present randomized
      clinical trial is to compare the skeletal and dentoalveolar effects of the maxillary expander
      with differential opening and the fan-type expander in the mixed dentition.

      For this, patients will be recruited at the Orthodontic Clinic of Bauru Dental School,
      University of São Paulo, Brazil. A sample of 48 patients from 7 to 11 years old with
      transverse maxillary dental arch constriction will be prospectively and randomly allocated
      into two study groups. The first group will consist of 24 individuals treated with the
      expander with differential opening (DEG). The second group will consist of 24 individuals
      treated with the fan-type expander (FEG). In 12 patients from each group (immediate
      subgroups), a cone-beam computed tomography (CBCT) will be performed in the beginning of
      treatment (T1) and immediately after the rapid maxillary expansion (T2). In the other 24
      patients, 12 from DEG and 12 from FEG (late subgroups), a CBCT will be obtained at T1 and 6
      months after maxillary expansion (T3). Dental models will be obtained for all patients at T1
      and T3. In digital dental models, maxillary arch width, perimeter, length and shape will be
      assessed. Standardized CBCT coronal sections will be used for measuring maxillary transverse
      dimensions, nasal cavity width and posterior tooth inclinations. Segmentation and
      superimposition of T1 and T3 CBCT images at the cranial base will be also performed. The
      opening of the midpalatal suture at the anterior and posterior region and the geometry of the
      suture opening will be evaluated in axial reconstructions of the CBCT.Discomfort, pain and
      quality of life will be evaluated by questionnaires.

      After the normality test, the paired t test will be used in the intragroup comparison, and
      the independent t test will be used in the intergroup comparison. In the case of lost to
      follow-up patients, intention to treat analysis will be used. A significance level of 5% will
      be regarded for all tests.

      Possible harms that could appear are related to temporary discomfort during the first days
      after the installation of the expander. Patients and legal guardians will be carefully
      oriented and they will be able to stop the treatment at any moment.
    

Intervention name(s): Differential Expansion; Fan-Fype Expander
Intervention type(s): Device; Device
Intervention description(s): Twenty-four patients will be treated with a rapid maxillary expansion using the expander with differential opening. Appliance anchorage will be performed by bands adapted in the second maxillary deciduous molars and circumferential clamps will be bonded to the maxillary deciduous canines. The activation protocols will totalize an opening of 8mm in the anterior screw of the expander. After the active period of RME, the screws will be fixed with acrylic resin and the appliance will be kept as a retainer for 6 months.; Twenty-four patients will be treated with a rapid maxillary expansion using the fan-type expander. Appliance anchorage will be performed by bands adapted in the second maxillary deciduous molars and circumferential clamps will be bonded to the maxillary deciduous canines. The activation protocols will totalize an opening of 8mm screw of the expander. After the active period of RME, the screws will be fixed with acrylic resin and the appliance will be kept as a retainer for 6 months.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Palatal Expansion Technique; Cone-Beam Computed Tomography; Dental Models