Comparison of Two Tooth-borne Expanders in Rapid Maxillary Expansion

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.