Dental Arch Expansion With In‐House Clear Aligners: An Exploratory Prospective Clinical Study on Torque, Vertical Control and Attachment Configuration

OBJECTIVE: To evaluate the short-term efficacy of transverse dental arch expansion with in-house aligners (IHA) by comparing planned and achieved buccolingual movements, and secondarily to explore torque expression, vertical control and the influence of attachment design/position using a contralateral within-subject approach. MATERIALS AND METHODS: In a prospective exploratory trial (n = 21; 12-30 y), six aligners were used over 6 weeks. INCLUSION CRITERIA: Class I dentoskeletal pattern and mild crowding. Digital models were planned in ArchForm; aligners were fabricated using 0.75 mm Polyethylene Terephthalate Glycol (PETG) sheets. Different attachments were bonded to canines and first molars. Programmed (AF), baseline (T0), and final (T1) models were oriented and registered in 3D Slicer; movements were referenced to global XYZ axes with Q3DC (torque = roll; rotation = yaw; buccolingual = ΔX; vertical = ΔZ). Paired t-tests compared planned vs. achieved movements and right vs. left attachment configurations. Equivalence (TOST, α = 0.05) was tested on planned-achieved differences using movement-scaled margins anchored to measurement error. RESULTS: Expansion effectiveness was highest in premolars (first/s: 59%/46%), moderate in canines (overall 42%; maxillary 51%, mandibular 33%), and lowest in first molars (overall 31%; maxillary 29%, mandibular 33%). Vertical control was maintained (several rows met TOST equivalence). Canine torque showed small, systematic buccal crown torque and did not meet equivalence under pre-specified margins. First-molar torque changes were < 1° with no significant differences between bevelled and horizontal-rectangular attachments. A slice attachment with an incisal base improved canine torque control versus a gingival base (p < 0.001). CONCLUSION: Short-term IHA expansion was more effective in premolars than in canines or molars and maintained vertical control. Under movement-scaled margins, canine torque did not reach equivalence, suggesting the potential relevance of attachment positioning; an incisal-base slice improved torque control. Observed effect sizes and variability from this prospective design can guide the planning of future adequately powered multicenter trials.