Comparison of Two Tooth-borne Expanders in Rapid Maxillary Expansion
Condition: Malocclusion; Posterior Crossbite
MeSH terms: Malocclusion
Study type: Interventional

Summary: 
      This study will assess the dentoalveolar effects and impact on quality of life of two types
      of maxillary expanders in orthodontic patients with permanent dentition, from 12 to 16 years
      old. Half of participants will be treated using the Hyrax expander, while the other half will
      use the mini Hyrax expander. The null hypothesis is that there is no difference between
      dentoalveolar effects and impact on quality of life of the two protocols.
    

Detailed description: 
      Transverse maxilla deficiency is characterized by narrowing of the maxillary arch with
      important functional and esthetic impact. In individuals which have not reached bone
      maturity, a rapid expansion of the maxilla by using tooth-borne expanders as Haas and Hyrax
      appliance are efficient and safe. A presentation of favorable results for the "mini-Hyrax
      inverted" expander with a small screw in the transversal correction of the maxilla in
      patients with cleft lip and palate, besides improving the comfort and the teeth cleaning,
      provoked an idea of application of this small screw to correct posterior crossbite in
      individuals without cleft lip and palate. The objective of this study is to compare the
      dentoalveolar effects and impact on quality of life of two types of maxillary expanders in
      adolescent patients with permanent dentition and active bone growth. The sample size
      calculation indicated a total sample of 28 individuals. Taking into account the loss of
      sample during the study, 34 subjects that have posterior crossbite and age from 12 to 16
      years, will be recruited at the Dental School, Pontifical University Catholic of Minas
      Gerais, Belo Horizonte, Minas Gerais, Brazil. These patients will be randomly divided into
      two groups, Hyrax and mini Hyrax, with 17 patients each. Digital models of both dental arches
      will be obtained by intraoral scanning precede the procedure (T0) and at the end of the
      retention period, after appliance removal (T2). OHIP-14 Oral Health Impact Profile
      Questionnaires, validated in Portuguese, will be applied before expansion (T0), after an
      expansion (T1) and at the end of the retention period (T2). In digital dental models,
      maxillary first and second bicuspids and first molar width, and rotation and inclination of
      maxillary first bicuspids and first molars will be assessed. After the normality test, the
      appropriate statistical test will be used in the intergroup comparison. A significance level
      of 5% will be regarded for all tests.
    

Intervention name(s): Hyrax; mini Hyrax
Intervention type(s): Device; Device
Intervention description(s): Rapid maxillary expansion using the Hyrax expander. Appliance anchorage will be performed by bands adapted to the first maxillary molars and arms of the screw contoured to adapt to palatal faces of the first and second maxillary bicuspids, in wich will be bonded by resin. The screw will be positioned perpendicularly to the palate sagittal midline, between second maxillary bicuspids and first maxillary molars, and 5 mm apically from marginal gingiva of palatal face of the first maxillary molars.The activation protocol will be 2 turns a day up to obtain transverse overcorrection. After the active period of RME, the screws will be fixed with ligature wire and the appliance will be kept as a retainer for 6 months.; Rapid maxillary expansion using the mini Hyrax expander. Appliance anchorage will be performed by bands adapted to the first maxillary molars and arms of the screw contoured to adapt to palatal faces of the first and second maxillary bicuspids, in wich will be bonded by resin. The screw will be positioned perpendicularly to the palate sagittal midline, between second maxillary bicuspids and first maxillary molars, and 5 mm apically from marginal gingiva of palatal face of the first maxillary molars. The activation protocol will be 2 turns a day up to obtain transverse overcorrection. After the active period of RME, the screws will be fixed with ligature wire and the appliance will be kept as a retainer for 6 months.
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: 2 groups: control group (Hyrax) and experimental group (mini Hyrax)
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: palatal expansion technique; adolescent; quality of life