Background: Clear aligner therapy (CAT) is increasingly used for transverse dentoalveolar expansion of the maxillary arch; however, the extent to which digitally planned movements are clinically expressed remains uncertain. Objective: To evaluate the accuracy of maxillary transverse expansion achieved with clear aligners by comparing digitally predicted changes with clinically measured outcomes. Methods: Twelve skeletally mature adults with Class I malocclusion and maxillary constriction underwent 16 weeks of CAT. Transverse widths were recorded at pretreatment, digitally planned, and post-treatment stages using a standardized three-dimensional digital workflow with calibrated measurements on high-resolution printed models. Measurements included intercanine, inter-premolar, intermolar (mesial and distal cusp), and trans-palatal landmarks. Accuracy was calculated as the percentage of achieved relative to planned expansion. Paired-sample t -tests and repeated-measures ANOVA were performed (α = 0.05). Results: All transverse dimensions increased following treatment. Intercanine width increased by 1.59 mm, while first and second inter-premolar widths increased by approximately 1.21 mm. Posterior expansion was comparatively smaller, with first and second-molar widths increased by 0.7– 1.0 mm. Overall accuracy ranged from 45.1% to 63.0%, indicating partial expression of digitally planned movements. Predictability was higher in the anterior and premolar regions (approximately 56– 61%) than the posterior and trans-palatal sites (approximately 49– 52%). Expansion remained symmetrical, with no significant right-left differences in buccolingual inclination. No clinically detectable adverse effects were observed during the study period. Males demonstrated slightly greater second-molar transverse dimensions (p< 0.05). Conclusion: Clear aligner therapy produced measurable and symmetrical dentoalveolar maxillary expansion in skeletally mature adults, however the magnitude of transverse change was consistently lower than digitally planned values. Predictability decreased posteriorly, suggesting that calibrated digital overcorrection may improve alignment between virtual planning and clinical expression. Plain Language Summary: Clear aligners are popular orthodontic devices because they are comfortable, nearly invisible, and help patients maintain good oral hygiene. In addition to straightening teeth, orthodontists now use aligners to widen the upper dental arch in patients with a narrow upper jaw, a condition called maxillary constriction. A narrow upper jaw can lead to crowding, crossbites, breathing difficulties, and bite imbalance. Although digital software allows clinicians to plan expansion precisely, understanding how accurately aligners achieve these planned movements in real patients remains important. In this study, we followed 12 young adults who used clear aligners for 16 weeks to widen their upper jaws. We recorded digital scans before treatment, after digital planning, and after 16 weeks of aligner use. We measured several distances between the canines, premolars, and molars to compare the expansion predicted by the software with the expansion achieved clinically. All participants showed measurable widening of their upper teeth. Clear aligners produced measurable expansion, although the achieved widening was lower than digitally planned. On average, patients achieved 45%– 63% of the intended expansion. The front teeth (canines and premolars) responded more predictably than the back teeth (molars). Most of the widening occurred through controlled outward tipping of the teeth rather than full bodily movement within the bone. No clinically detectable adverse effects on the gums or teeth were observed during the study period. Keywords: clear aligner therapy, maxillary expansion, transverse dimension, expansion accuracy, digital orthodontics
Kumari et al. (Sun,) studied this question.