Skeletal and dental changes after microimplant-assisted rapid palatal expansion (MARPE) - a Cephalometric and Cone-Beam Computed Tomography (CBCT) study

Purpose The maxillary transverse discrepancy is common in orthodontic practice. Rapid palatal expansion has traditionally been used before puberty, but the skeletal effect is limited. Recently, micro-implant-assisted rapid palatal expansion (MARPE) has been proven to be effective in adolescents and adults. The purpose of this study is to assess the skeletal and dental 3-dimensional outcomes after MARPE. Materials and methods Nineteen subjects who presented with a maxillary transverse discrepancy and received MARPE treatment were included in this study. Cephalometric radiographs and Cone-Beam Computed Tomography (CBCT) images were obtained and analysed at the initial (T1) and the end of the expansion (T2). The Wilcoxon signed-rank test was used to evaluate the differences between the two time points. Results The results demonstrated anteroposterior correction. The SNA, ANB, FH-NA, N-A-Pog, A-Na perpendicular (mm) and U1-Nasion perpendicular (mm) all increased from T1 to T2, which explained the maxillary advancement after MARPE. The SN-MP, PP-MP and SNB changes indicated a mandible backward rotation followed expansion. In the CBCT analysis, the average expansion amount was 5.5 mm, of which 71.1% was due to a skeletal effect. In addition, the expansion pattern was almost parallel with a ratio of 83.2% from PNS to ANS. Conclusions MARPE treatment can provide successful transverse correction with near parallel expansion of the maxilla in the coronal and axial planes. Maxillary advancement and a mandibular backward rotation associated with MARPE can provide positive correction in the sagittal plane. As dentoalveolar tipping was limited, the expansion result was mainly skeletal.