An evaluation of maxillary expansion after Phase I orthodontic treatment with clear aligners using model analysis and cone-beam computed tomography

The objective of this study was to utilize digital models and cone-beam computed tomography (CBCT) radiographs to quantify the skeletal and dentoalveolar maxillary expansion in Phase I orthodontic treatment using clear aligner therapy. Fifty-four patients (22 females and 32 males) had measurements taken on both the pre-treatment and post-treatment intraoral scans from the mesiolingual cusps of the maxillary permanent first molars and the cusp tips of the maxillary primary canines to perform model analysis of dentoalveolar expansion. The planned amount of expansion in the ClinCheck® setup was compared to the actual expansion. Twenty-nine patients (14 females and 15 males) out of 54 patients had both pre-treatment and post-treatment CBCT scans, which also allowed us to perform measurements between maxillary permanent first molars and between maxillary primary canines using CBCT data. Posterior expansion of 2.40 mm between maxillary permanent first molars and anterior expansion of 4.01 mm between maxillary primary canines was observed. A comparison with ClinCheck® showed percent yields of 51.15% for posterior expansion and 64.73% for anterior expansion. CBCT analysis displayed posterior expansion of 1.89 mm between the first molars, 1.87 mm between first molar cementoenamel junctions (CEJs), an angle change of −1.16° (buccal tipping) between first molars, anterior expansion of 3.64 mm between the primary canines, 1.78 mm between primary canine CEJs, and an angle change of 24.73° (facial tipping) between the primary canines. Our study highlights the potential capability of Phase I orthodontic treatment with clear aligners and shows that maxillary expansion does occur with the use of clear aligners.