RESUMO
INTRODUCTION: The objective of this research was to evaluate the buccal bone plate and root length of maxillary permanent first molars using cone-beam computed tomography after maxillary expansion with different activation protocols. METHODS: Cone-beam computed tomography images of growing patients were obtained from the orthodontic department of Pontifical Catholic University of Rio Grande do Sul in Brazil. The groups were Haas-type 2/4 turns, Haas-type 4/4 turns, hyrax-type 2/4 turns, and hyrax-type with alternate rapid maxillary expansions and constrictions (alt-RAMEC) 4/4 turns a day. Tooth length, periodontal insertion, alveolar bone thickness, and intermolar distances were evaluated. The data at the start of treatment and 6 months later were compared using generalized linear models. The intergroup differences were determined by univariate analysis of variance with the Bonferroni adjustment. RESULTS: Tooth length was significantly shortened after expansion in all groups (-0.28 to -0.51 mm), except for the alt-RAMEC group. Bone level variables (bone level and bone level at the tooth tip) changed statistically in all groups, except for the Haas 4/4 turns group. There was significant periodontal attachment loss after rapid maxillary expansion with the hyrax/alt-RAMEC (5.09 mm). The hyrax/alt-RAMEC and hyrax groups had more dehiscences, fenestrations, and exposures of the root. CONCLUSIONS: The consequence of rapid maxillary expansion using the hyrax was alveolar bone resorption, especially in the hyrax/alt-RAMEC group, whereas the Haas expander caused mild root resorption.
