Baseline positional asymmetry and its association with planned tooth movements in clear aligner therapy

BACKGROUND: Digital treatment planning software in clear aligner (CA) therapy incorporates virtual simulations to generate planned tooth movements. While baseline tooth positions constitute one of the geometric inputs to digital setups, limited information is available regarding the association between pre-treatment positional asymmetry and the magnitude of planned movements, and how these associations vary by tooth and movement type. METHODS: , while planned movements-including rotation, angulation, extrusion, and intrusion-were extracted from the corresponding digital treatment plans. Baseline asymmetry between contralateral teeth was calculated to quantify movement complexity. General Linear Model (GLM) regression analyses were employed to assess the relationship between initial asymmetry and the magnitude of planned movements. Descriptive statistics and normality assessments were also performed. RESULTS: In the 11-21 tooth pair, baseline asymmetry was significantly associated with planned extrusion (p = .002) and rotation (p < .001), but not intrusion (p = .190) or angulation (p = .270). For the 12-22 pair, significant associations were observed for intrusion (p = .008), angulation (p < .001), and rotation (p < .001), but not extrusion (p = .493). In the 13-23 pair, only extrusion was significantly associated with baseline differences (p < .001); no significant effects were observed for the other movement types. CONCLUSION: Baseline positional asymmetry was associated with variation in planned extrusion, intrusion, and rotation movements within digital CA setups. These findings should be interpreted as descriptive associations rather than evidence of software-imposed constraints or internal planning strategies, and underscore the relevance of baseline geometry when interpreting digitally planned tooth movements.