Immediate effects of rapid maxillary expansion with Haas-type and hyrax-type expanders: A randomized clinical trial

• Published in: American journal of orthodontics and dentofacial orthopedics Vol. 140; no. 3; pp. 366 - 376
• Main Authors: Weissheimer, André, de Menezes, Luciane Macedo, Mezomo, Mauricio, Dias, Daniela Marchiori, de Lima, Eduardo Martinelli Santayana, Rizzatto, Susana Maria Deon
• Format: Journal Article
• Language: English
• Published: New York, NY Mosby, Inc 01.09.2011; Elsevier
• Subjects: Adolescent; Analysis of Variance; Biological and medical sciences; Cephalometry; Child; Cone-Beam Computed Tomography; Dentistry; Female; Humans; Imaging, Three-Dimensional - methods; Male; Maxilla - diagnostic imaging; Medical sciences; Orthodontic Appliance Design; Otorhinolaryngology. Stomatology; Palatal Expansion Technique - instrumentation; Prospective Studies; Statistics, Nonparametric; Treatment Outcome; Clinical trial; Orthodontic procedures; Dentistry; Maxillary
• ISSN: 0889-5406; 1097-6752
• DOI: 10.1016/j.ajodo.2010.07.025

Introduction The purposes of this study were to evaluate and compare the immediate effects of rapid maxillary expansion (RME) in the transverse plane with Haas-type and hyrax-type expanders by using cone-beam computed tomography. Methods A sample of 33 subjects (mean age, 10.7 years; range, 7.2-14.5 years) with transverse maxillary deficiency were randomly divided into 2 groups: Haas (n = 18) and hyrax (n = 15). All patients had RME with an initial activation of 4 quarter turns followed by 2 quarter turns per day until the expansion reached 8 mm. Cone-beam computed tomography scans were taken before expansion and at the end of the RME phase. Maxillary transversal measurements were compared by using the mixed analysis of variance (ANOVA) model and the Tukey-Kramer method. Results RME increased all maxillary transverse dimensions ( P  <0.0001). There was less expansion at skeletal than dental levels. The hyrax group had greater statistically significant orthopedic effects and less tipping tendency of the maxillary first molars compared with the Haas group. Conclusions Both appliances were efficient in correcting a transverse maxillary deficiency. The pure skeletal expansion was greater than actual dental expansion. The hyrax-type expander produced greater orthopedic effects than did the Haas-type expander, but this effect was less than 0.5 mm per side and might not be clinically significant.